Chapter 3 Review Introduction to Drawing and Editing

Chapter 3. Layout Editing

3.1. Schematic and Schematic Layout Interaction

When building a schematic, the layout for the schematic is also started. This section presents various ways of working between the Schematic View and the Layout View of a design.

3.1.1. Element Symbol Color

When building a schematic, the default element symbol color is blue (or the color specified for Element on the Environment Options dialog box Colors tab). This color indicates that a layout for the element does not yet exist.

After you open a layout window for the schematic, the layout for the element is initialized and placed in an optimal location. The element symbol color changes to purple by default (or the color specified for Ele with Lay on the Environment Options dialog box Colors tab) unless you assign the symbol a custom color, in which case it retains that color.

See "Environment Options Dialog Box: Colors Tab " for more information about changing these colors.

3.1.2. Initial Layout Shape Placement

When you first view a schematic layout, the layout attempts to arrange the shapes so that they are connected (no rat lines). As you add new elements (not copy and paste of existing elements), the layout attempts to connect the shapes. The following figure shows a single element on a schematic, and its layout.

If you add an MLIN to the schematic and connect it directly to the adjacent MLIN, the schematic and layout display as follows, with one MLIN element connected to the other.

If you add an MLIN as above without connecting the nodes, the schematic and layout display as follows.

If you move the element after placing it or draw a wire to connect the nodes, the layout does not attempt to arrange the elements to remove rat lines, as shown in the following figure.

This occurs because the layout object was already placed, and the Cadence® AWR Design Environment® platform software does not automatically move items or snap them together.

After initial element placement, there are several options for changing shape location without manually moving a shape in layout, including using snapping and placement commands.

3.1.3. Snapping Layout Cells

A snapping function attempts to move shapes so the shapes are all connected. In some schematics it is not possible to connect every shape in the layout, so the layout contains rat lines.

The Snap Together button (command) is available on the Schematic Layout toolbar

or by choosing . The Layout Options dialog box Layout tab Snap Together option allows you to set the snapping mode. See "Layout Options Dialog Box: Layout Tab " for more information on this dialog box, including:

• Auto snap on parameter changes: All the layout objects in the active window snap together when using the snap command or when a parameter is changed for that schematic. This command is always active.

• Manual snap for all objects: All the layout objects in the active window snap together when using the snap command. This command is always active.

• Manual snap for selected objects only: Only the items selected in the layout attempt to move when using the snap command. This command is only active upon selection of a layout object.

The snap command only works on layout objects in the current level of hierarchy. You can choose to snap the layouts for the current level of hierarchy and lower levels.

Some models can change their length during the snapping process. You can choose or click the Snap to Fit button (command) on the Schematic Layout toolbar to make the shapes attempt to change the length of the element.

The following example of a simple layout where the left line is an MTRACE2 element and the right line is an MLIN element shows use of this command. The MTRACE2 can add bends in the layout while the MLIN cannot.

If you select the MTRACE2 element and click the Snap to Fit button on the toolbar, the layout does not move the left-most location of the cell, but the shape is adjusted to connect the layout.

If you select the MLIN element and click the Snap to Fit button on the toolbar, the layout displays as shown in the following figure. This model cannot add bends so it does its best to connect the shape by adding length and moving the location.

3.1.4. Freezing and Anchoring Shapes

Freeze and anchor options are also available to assist in the snapping process. To access these options, select a shape in layout, right-click and choose Shape Properties to display the Cell Options dialog box. On the Layout tab, select the Freeze check box to prevent a shape from moving during the snapping process. In the layout, the shape displays with a blue circle on it to indicate that it is frozen.

Select the Use for anchor check box to specify that the snapping process starts with that layout object, which means it should not move. In the layout, the shape displays with a red circle on it to indicate that it is an anchor and will remain in a fixed location.

If more than one connected shape is anchored, one of the anchors is used and the others are ignored.

3.1.5. Layout Placement Commands

The following commands assist with placing layout objects, including:

• : Select items in the schematic and choose this command to open the layout window. The selected shapes are in placement mode. Move the cursor around and then click to place the layout objects at the selected location.

• : From a Layout View, this command opens the Place All dialog box.

  

  After specifying the spacing and clicking OK, all the layout objects are arranged based on their schematic location, as well as the spacing specified. A layout options control in the layout objects also matches the schematic rotation. See "Layout Options Dialog Box: Placement Tab " for more information.

• : From a Layout View, this command reverts any layout edits and displays the layout as if it has not been created. A warning message displays to remind you that you cannot undo this operation and you can lose your layout edits.

  

  This is not a common command and should only be used when the layout is not repairable (for example, you cannot find items).

3.1.6. Cross-selecting in Views

When working in one view (schematic or layout), you can easily identify and select the same object in the opposite view. When you select an item in the schematic, it is highlighted in the layout as shown in the following figure.

Similarly, when you select an item in the layout, it is highlighted in the schematic, as shown in the following figure.

You can also select the object in the opposite view. Select one or more objects in the current view, right-click and choose if in the schematic or if in the layout. The opposite view opens in a new window if not already opened, and those objects are selected in that view. You can right-click the selected objects to access their properties.

3.2. Layout Manager

The Layout tab located on the main window opens the Layout Manager.

The Layout Manager has the following components:

• Layer Setup: Right-click this node to import process definition files (*.lpf). You can also import LPFs by choosing Project > Process Library > Import LPF. The *.lpf files display as subnodes.

  Double-click a file to display the drawing layer Options dialog box which controls all functions associated with drawing layers in the Layout View. Right-click a file to display additional commands available for that file.

• Layout Options: Double-click this node to open the Layout Options dialog box with options for layout, paths, dimension lines, rulers, the layout font, and the GDS Cell Stretcher.

• Cell Libraries: Right-click this node for options to create or import artwork cell libraries. You can import artwork cell libraries in GDSII or DXF format or create new cells in a drawing editor activated from this node.

• Layout Cells: Generates a list of all parameterized cells loaded in a project. You can add these cells to any layout (schematic, artwork cell, or EM) and the parameters of the cells are edited on the Cell Options dialog box Parameters tab.

• Drawing Layer pane: Shows or hides layers, and activates layers for drawing or editing. Toggle between drawing a drawing layer-based shape or a line type-based shape.

• Line Types pane: Activates a line type for drawing or editing line type-based shapes. Toggle between drawing a drawing layer-based shape or a line type-based shape.

The Layout Manager is used for the following functions:

• In the Drawing Layer pane, displays the set of drawing layers (or model layers if an Artwork Cell Editor is active) that are being used in the Layout View Editor. You can select the active drawing layer and hide or view drawing layers. See "Layout Editing" for information about the differences between the Artwork Cell Editor and the Layout View Editor.

• Managing the libraries of artwork cells you can use in a layout.

• Configuring the layer properties (color, 3D heights, etc) for layers in each .lpf files.

• When an artwork cell library name node is selected in the top pane, displays the artwork cells in that library in a Cell Library pane in place of the Drawing Layer pane, and you can drag-and-drop cells into any open layout window to allow any layout cell to be used or combined to make new cells.

  

• When the Layout Cells node is selected in the top pane, displays the parameterized cells loaded in the project in a Layout Cells pane in place of the Drawing Layer pane. You can drag-and-drop parameterized cells into any schematic layout window to use the parameterized cell standalone in layout without a corresponding schematic element.

  

• In the Line Types pane, displays the line types defined in the LPF. You can select a line type to draw line type-based shapes instead of drawing layer-based shapes in the layout. Line type shapes draw with all the layers and layer offsets set in the Line Type definition in the LPF (see "Line Type Definitions" for information).

• Double-clicking a layout cell in the upper pane opens the layout cell in the Layout View Editor. Right-clicking the nodes in the upper pane displays menus for adding new libraries and cells. You can also merge, delete, rename, and perform other operations on cells and libraries using the right-click context menus.

3.2.1. Drawing Layer Pane

The Drawing Layer pane has many controls to help work with layout.

The title bar displays the .lpf file used for the active window in the project. This is useful when using multi-technology projects (multiple .lpf files in a project) or when switching from schematic layout to EM layout.

The Layout Manager toolbar includes various buttons to manage the pane and access additional controls. For more information about a button, hover the mouse cursor over it for a tooltip. See "Using Property Grids" for details on common toolbar buttons. The following buttons are specific to the Layout Manager.

Hiding Non-active Layers

The Hide non-active layers button changes the visibility so only the active layer is visible.

The following figure shows the Hide non-active layers option Off, with all checked layers visible.

The following figure shows the Hide non-active layers option On, so only the selected (active) layer is visible.

The following figure shows the selection of a new (active) layer that is now the only layer visible.

Selecting a Configuration

The Select configuration button allows you to change configurations or save a new configuration.

Configurations are different default settings for the properties for each layer such as fill pattern, visibility, or cloaking. This control allows you to select an existing configuration or to save the current settings as a new configuration. For additional controls to manage the configurations you can double-click the .lpf name in the Layout Manager or click the Edit Drawing Layers button to the right of this button.

Editing Drawing Layers

This button displays the drawing layer Options dialog box with options for the active .lpf file.

3.2.2. Artwork Cell Libraries

The Layout Manager displays all of the layout artwork cell libraries that are loaded into the project. Each artwork cell library is stored as either GDSII (the default) or DXF. When GDSII format is used, the library can contain any number of layout cells that can also be hierarchical. DXF format also supports hierarchical cells.

GDSII cell libraries in the Layout Manager are connected to a file on the computer that allows linking to libraries and updating cell libraries. You can view this link as shown in the following figure by pointing to the library name in the Layout Manager.

Moving a project with a GDSII cell library to a different directory can break the link, as indicated by a red X on the cell library icon as shown in the following figure.

When an artwork cell within the library is used in a project layout, a copy of the artwork cell is stored in the project. Until this occurs, the contents of the GDSII file stored on the computer are used by the project to update the cell library.

To display the Cell Library Properties dialog box, select the library name in the Layout Manager, right-click and choose Cell Library Properties.

See "Cell Library Properties Dialog Box " for a picture and details on this dialog box.

After an artwork cell is used in a schematic layout, the stored copy of the artwork does not automatically update when the *.gds cell library file changes unless you select the Always read newest or Replace all cells (even modified cells) check box in the Cell Library Properties dialog box. Replace all cells (even modified cells) ignores all cells stored in the project and reads directly from the *.gds file. Always read newest checks the date of the cell file stored in the project, compares it with the same cell file in the *.gds file on the hard disk, and uses the newest version.

3.2.3. Navigating the Libraries in the Layout Manager

The Layout Manager displays a list of all libraries loaded into the project. The library icons indicate the state of the libraries. The following figure shows the different icons.

Each artwork cell in a layout library displays in the Layout Manager with an icon that indicates the state of the cell. The following figure shows the various icons and a description of the state each represents. Artwork cells that are used in the current layout display with a red and blue rectangle; those that are not used display with gray rectangles.

3.3. Layout Editing

There are two different layout editors in Cadence® AWR® Microwave Office® software:

• Schematic Layout/EM Layout Editor : Edits the schematic layout and EM layout. This editor opens when you create a Layout View from a schematic or create an EM structure. All the layout cell properties apply to layout objects when the editor is opened for schematic layout. The slight difference in schematic and EM layout is that in the EM Layout Editor the drawing layers correspond to the physically different z-positions in the dielectric stack. The extent of the physical enclosure is shown for the EM structure.

• Artwork Cell Editor : Creates custom artwork cells or edits cells imported from GDSII or DXF files. This editor opens when you double-click a cell in the Layout Manager.

Although most of the functionality and drawing tools are the same for both of the editors, the following are some differences:

• The Artwork Cell Editor draws shapes on model layers, while the Layout View Editor draws shapes on draw layers. When the Layout Manager is active, the layers that are being used in the Layout View Editor or the Artwork Cell Editor are visible in the lower pane of the Layout Manager window. If a Layout View Editor is active, the displayed layers are drawing layers. If an Artwork Cell Editor is active, the displayed layers are model layers. See "Drawing Layers and Model Layer Mapping" for a complete description of model layers and drawing layers.

• The Artwork Cell Editor has an extra drawing tool for drawing connection faces onto the artwork cells.

• You can only use the Artwork Cell Editor to create and edit static shape objects (polygons, ellipses, text objects, faces, etc.). The Layout View Editor can include static shape objects and also layout cell objects that are linked to schematic elements (such as parameterized layout cells).

• The geometry created within the Artwork Cell Editor is saved in standard geometry formats (either GDSII or DXF). This can lead to some subtle differences between the two editors. For example, in GDSII, there are no ellipse objects, so if an ellipse is created in the Artwork Cell Editor and saved, it is converted to a polygon when the file is re-opened.

• Groups can be used to help construct the geometry in the Artwork Cell Editor, but the grouping is lost when the artwork cell is saved (all the correct geometry is saved though). Groups are not saved in the artwork cell because there are no group objects in GDSII.

3.3.1. Schematic Layout/EM Layout Editor

The Schematic Layout Editor is the primary layout editor in the AWR Design Environment platform, opened by activating a schematic window and clicking the View Layout button on the toolbar or choosing View > View Layout.

The EM Layout Editor is opened when you create an EM structure or double-click an existing EM structure in the Project Browser. See "Creating EM Structures without Extraction" for information about creating, importing, and exporting shapes in EM structures.

3.3.2. Artwork Cell Editor

The Artwork Cell Editor supports the main Layout View Editor by providing a method to import or create custom cell libraries. You can create GDSII or DXF cells or import GDSII (.gds) and DXF (.dxf) library file formats into AWR Microwave Office software through the Artwork Cell Editor. There are three ways to bring an artwork cell object into a Layout View Editor window:

• Drag and Drop: You can drag cell objects in an artwork cell library into a Layout View Editor or Artwork Cell Editor window by selecting the name of the library in the Layout Manager window and dragging the object from the lower pane of the Layout Manager window. If you drop it into an Artwork Cell Editor, the resulting artwork cell is hierarchical (when constructed this way). Each artwork cell you drag into the artwork cell being edited is placed as a reference to the dragged-in instance. If the dragged-in instance is not part of the same library, the resulting library will have a dependency on another library. Also, when you save the library through the Layout Manager, any cells referenced from other libraries are not written as part of the library.

• Copy and Paste: You can copy and paste objects in an artwork cell library into a Layout View Editor window by choosing Edit > Copy and Edit > Paste.

• Associate Artwork Cell with Schematic Element: From a schematic window, select an element or subcircuit, right-click, and choose Properties. In the Element Options dialog box Layout tab, the names of all cell objects with the specified number of nodes displays. Select the desired cell object and click OK.

There are two types of artwork cell objects that you can create in the Artwork Cell Editor:

• Artwork Cell Object: An artwork cell object consists of one or more polygons. You can create artwork cell objects in the Artwork Cell Editor or you can import them from a GDSII or DXF file. You can use the Layout menu or Schematic Draw Tools toolbar to access the drawing functions in the Artwork Cell Editor.

• Artwork Cell Object with Ports: You can create artwork cells with ports from any artwork cell by adding ports to the polygons to define the connection points. The connection points correspond to the schematic element or subcircuit nodes.

3.4. Schematic/EM Layout Draw Tools

There are many drawing tools in the Draw menu that you can use in the Schematic Layout and EM Layout Editor.

You can also use the drawing tools by clicking the corresponding toolbar buttons. To display the Draw Tools toolbar, right-click the toolbar and choose Draw Tools.

You can customize toolbars by specifying which tool buttons display on them, either individually or as part of a split button. Choose Tools > Customize to open the Customize dialog box, then click the Toolbars tab to specify buttons for each toolbar type.

3.4.1. Drawing Tools

The following is a brief description of some of the most common drawing tools. A more detailed explanation of some of these drawing tools is provided in the following sections.

Circle

To draw a circle, choose Draw > Circle. Click and drag to draw the circle, and then release the mouse button.

You can also change the size of a circle after it is drawn. Select the circle in the layout window, right-click and choose Shape Properties to open a Properties dialog box with a Circle tab.

Ellipse (Ctrl+E)

To draw an ellipse, choose Draw > Ellipse. Click and drag to draw the ellipse, and then release the mouse button.

You can also change the size of an ellipse after it is drawn. Select the ellipse in the layout window, right-click and choose Shape Properties to open a Properties dialog box with an Ellipse tab.

Path (Ctrl+L)

To draw a path, choose Draw > Path. Click to place the points and double-click to complete the path. To change the default path width, bend type, or end type choose Options > Layout Options or double-click Layout Options in the Layout Manager. In the Layout Options dialog box Paths tab, you can specify path properties.

You can also change the path width, end type and bend type after the path is drawn. Select the path in the layout window, right-click and choose Shape Properties to open a Properties dialog box with a Path tab.

Polygon (Ctrl+P)

To draw a polygon, choose Draw > Polygon. Click to place each point, and right-click to erase a point. Double-click to close the polygon. For more information on polygon editing, see "Polygon Editing".

Rectangle (Ctrl+B)

To draw a rectangle, choose Draw > Rectangle. Click and drag to draw the rectangle, then release the mouse button.

You can also change the size of a rectangle after it is drawn. Select the rectangle in the layout window, right-click and choose Shape Properties to open a Properties dialog box with a Rectangle tab.

Text (Ctrl+T)

You can add text to the layout by choosing Draw > Text, and then clicking in the location where the text is to be added. An edit box displays for text entry. To finish the text drawing command, press Enter or click outside of the edit box. The initial properties of the added text are based on the default font settings. To change the default settings, choose Options > Layout Options and click the Layout Font tab to make your changes.

You can edit existing text properties by selecting the text, right-clicking, and choosing Shape Properties. A Properties dialog box displays with a Font tab that contains the font properties to set.

You can set the following additional properties on the Properties dialog box Layout tab.

• Draw Layers: The layer that the text is to be drawn on. If the text is being added to the Artwork Cell Editor you must specify the model layer.

• Orientation: The angle that the text is drawn with respect to the vertical baseline, along with an option to flip the text.

• Freeze: The text object can be frozen to prevent the object from being accidentally moved.

The layout text is drawn as polygons on the specified drawing layer (or model layer in the Artwork Cell Editor) if the Draw as Polygons check box is selected. The polygons are automatically generated from the TrueType font definition. If there is not a suitable font available, you can use any commercial font creation software to create a font that you can use within the AWR Microwave Office layout. If the text is in the Artwork Cell Editor, it is converted to polygons when the artwork cell is saved in the artwork cell library.

In the EM Layout editor, if a layout text is drawn using an EM mapped layer, the Draw as polygons check box must be cleared, otherwise the text is included in the simulation. Right-click the layout text and choose Shape Properties, click the Font tab and clear the Draw as polygons check box. Another option is to draw the layout text with a Drawing Layer that does not have an EM Mapping configured, although this text is not displayed in a 3D view.

As shown in the following example text, the text polygons are drawn with cuts to avoid donuts in the polygons.

3D Clip Area

The 3D clip area is used to create a rectangular area in the layout that can be used to clip the 3D drawing of the layout. This is useful for viewing sections of a layout in 3D, and can be drawn by choosing Draw > 3D Clip Area. Only one clip area can be drawn in a Layout View.

Drill Hole

To draw a drill hole, choose Draw > Drill Hole. Place the cross cursor at any point within the drawing window and click. The drill hole placed is the default size specified in the *.lpf process file. To change the drill size, select the drill hole, right-click, and choose Shape Properties. A Properties dialog box with a Drill Hole tab displays with an option for selecting various drill tools that are specified in the Options - Drill Hole Layers dialog box. Select a drill tool to automatically change to that drill size.

To add a new drill tool, choose Options > Drawing Layers to display the drawing layer Options dialog box. Click Drill Hole Layers and type in the name, diameter, and tool number of the new drill tool.

3.4.2. Layout Shapes Editing

The following options are used by many of the drawing tools and commands.

Grid Snap (Ctrl+G)

To toggle on/off the grid snap you can choose Draw > Grid Snap. When the grid snap is on, the drawing tools snap to the grid. Editing operations (such as moving a shape) also use the grid snap. For example, if the grid snap is set to 5 um, when moving an object it can only be moved in multiples of 5 um. You can dynamically change the snap grid by fixed multiples by selecting the snap multiple from the Grid Spacing button on the toolbar. For example, if the grid snap is 5 um and the Grid Spacing button on the toolbar specifies 2x, the grid snap is 10 um for the layout.

Orthogonal (Ctrl+O)

The orthogonal option can be toggled on or off by choosing Draw > Orthogonal. This option is primarily used with polygon editing. When the Orthogonal option is on, it restricts the stretching of edges and vertices to an orthogonal direction.

Shape Selection

You select an object in the layout by clicking on it. Selected objects display with selection highlighting. There are three system layers for selection highlighting. The layer 'FirstSelected' is used to highlight the first selected object, which is used as the reference for commands like alignment and sizing. The layer 'Selection' is used to highlight the second and subsequent objects in a selection set. Finally, there's a system layer named 'Subselection' that is used to highlight selected sub-objects like segments on an iNet. When performing a polygon selection on overlapping layers, the default selection picks the smallest polygon. This is useful for editing complex drawings such as FET cells. You can Ctrl+Shift -click on overlapping objects to cycle through the objects under the click point. There are additional settings to control selection behavior available in the Layout Editor Mode Settings dialog box.

Multiple Selection

You can select multiple objects in any of the layout editors using any of the following techniques:

• Shift-click on each object one at a time to select objects. Shift-click on an object again to deselect it.

• Alt-click on an area of the screen and then drag a rectangular selection area over the objects you want to select. All objects that are completely within the selection area are selected. Objects that are only partially within the selection area are not selected.

• Press the Shift key while dragging the selection area to select any object that touches (is only partially within) the selection area.

• Press Ctrl + Shift for a selection method similar to the normal area selection, except that the first click can be on top of an existing object. This is useful for area selection in dense layouts where there is no empty space to start the area selection. If the first object clicked on is already selected, it remains selected and all objects within the selection area are also selected.

Multiple Selection Editing

You can simultaneously change the properties of multiple layout objects. Select a group of objects in the Layout View using any of the multiple selection methods. Right-click and choose Shape Properties, and change the properties. All applicable changes are made to each of the selected objects.

Move with Reference

You can move a shape or shapes with reference:

1. Select the shape(s) you want to move, then choose or press Ctrl+Shift+M.

2. Click the location to establish the reference.

   

3. Move the mouse to move the shape(s) with the reference, and click to place it.

   

Copy with Reference

You can copy a shape or shapes with reference:

1. Select the shape(s) you want to copy, then choose or press Ctrl+Shift+C.

2. Click the location to establish the reference

   

3. Move the mouse to copy the shape(s) with the reference, and click to place it.

   

Shape Edge Selection

AWR Design Environment platform layout supports sub-selecting multiple edges of a shape, or multiple edges of a shape within a multi-layer shape. This allows you to select specific edges on two shapes and align the two edges with specified spacing between them. In some cases, it may be useful to select more than one edge to perform a custom operation on the selected shapes. Multi-edge selection allows you to select and highlight multiple edges of a shape or multiple edges of a shape within a multi-layer shape.

To select an edge, Alt -click on it and hold down the Alt key while moving the cursor to the edge of one of the selected shapes. When the cursor changes from a multi-directional move arrow to a standard cursor arrow you are over the edge and can click. Hold down the Alt key again while moving the cursor to the upper edge of the rectangle. When the cursor displays as a standard arrow over the shape edge, click to select the upper rectangle edge. When the edge is selected it is highlighted.

Multi-edge selection extends edge selection to allow you to select multiple edges on the same shape. Operations such as the Align command work on shapes with multiple selected edges, however since you can only align one edge on each shape with the other shape, only the first edge selected is used. Multi-edge selection is most beneficial for custom solutions where you want to select multiple edges of a shape and then run a script that uses these selections to create additional structures relative to the selected edges.

Command Repeat Mode

You can use command repeat mode to keep any edit mode active until you cancel it. For example, click the Command Repeat Mode button on the toolbar , choose Draw > Rectangle, and draw a rectangle. Note that the Draw Rectangle command remains active, allowing you to continue to draw shapes without repeating the menu command. To exit command repeat mode press the Esc key. Alternatively, choose to toggle this command on and off.

Gravity Points

Gravity points provide a quick and easy method for creating, positioning and aligning shapes within the layout. Gravity points are activated by pressing the Ctrl key while moving the cursor over objects in the layout. If no drawing operation is in progress, pressing the Ctrl key while moving the cursor causes the cursor to snap to vertices, edges, intersections, midpoints or control points of selected objects. The different types of gravity points have different strengths. Stronger gravity points are preferred over weaker gravity points. For example, while pressing the Ctrl key, the cursor snaps to the edges of a selected polygon, but if the cursor is moved towards a corner, the cursor snaps to the corner even though it is already snapped to an edge. The following figure shows the typical control points for a few different shapes. Note that the intersections of the shape edges are also control points.

Gravity points can be used in many different situations. Pressing the Ctrl key when no drawing operation is in progress is useful for setting the base point for an operation. For example, when moving a shape, if you first snap the cursor to a corner of the shape, it is very easy to move the shape such that the corner aligns with a corner, midpoint, edge, or intersection of another shape. Setting the initial base position using the Ctrl key only works with selected shapes, while all the other uses of the gravity points operate on any shape (selected or deselected).

The following are useful applications for gravity points:

• Moving Objects: When moving a shape in the layout, press the Ctrl key and move the cursor to a gravity point on a selected shape and then click and drag the shape. The cursor is now locked to the exact gravity point on the selected shape. If you press the Ctrl key during the drag operation, the cursor snaps to any gravity point on any other object (selected or deselected). If you move the cursor to a gravity point on another object and release the mouse (ending the drag operation), the gravity points on the moved object and the other object are at the same point. For example, if the gravity point on the moved object is the corner of the rectangle, and the gravity point on the other object is also the corner (and it is a rectangle) then the corners of the two rectangles are aligned.

• Aligning Edges: You can make the edges of shapes coincident by moving the shapes and using the edges for the gravity points.

• Centering Ellipses: You can center a circle or ellipse on another gravity point.

• Drawing Polygons: You can use gravity points while drawing a polygon. To use gravity points, press the Ctrl key while clicking on gravity points to add the new points to the polygon. This allows you to quickly draw polygons that are coincident with the corners, edges, midpoints or intersections of any existing shapes.

• Drawing Rectangles: You can use gravity points to define the two opposing corners of a rectangle during a drawing operation.

• Drawing Paths: When using gravity points with the Path drawing tool, you can make the path center line points snap to gravity points if you press the Ctrl key while drawing the path.

• Rotating Objects: To rotate a shape about an exact point (for example, to rotate it about one of its corners), select the shape, right-click it and choose Rotate. If you press the Ctrl key while the cursor is moved, the cursor snaps to any gravity point on itself or any other shape. Once the cursor has snapped to a gravity point, click and drag the rotation line to rotate the object about the gravity point.

• Flipping Objects: To flip a shape about an exact point or edge (for example, to flip a shape so that one of its edges in the same position), select the shape, right-click it and choose Flip. If you press the Ctrl key while moving the cursor, the cursor snaps to any gravity point on itself or any other shape. Once the cursor has snapped to a gravity point, click and drag the flip line to flip the object about the flip line.

• Measuring: The measurement tool always uses gravity points (you do not need to press the Ctrl key), making it easier to make precise measurements on different shapes in the layout.

• Adding Cell Ports: When adding cell ports to artwork cells in the Artwork Cell Editor, you must ensure that the cell port is coincident with the edges of the connecting shapes in the artwork cell, otherwise there may be small gaps in the final layout. The gravity points can be used to define the two end points of the cell port during the port drawing operation.

Rotation and Flipping

To arbitrarily rotate objects in layout, select the objects, right-click, choose Rotate, and move the mouse in the desired direction. The rotation uses the Rotation Snap angle set in the Layout Options dialog box Layout tab. An alternate method for rotating is to select the object, right-click, choose Shape Properties, and then specify an Angle in the Orientation area of the Cell Options dialog box. The layout system allows arbitrary angle rotation down to 0.1 deg increments.

To flip an object in the layout, select the object, right-click, choose Flip, and then click and drag. The line defined by the endpoints of the click and drag operation defines the line that the layout object is flipped about.

Gravity points or coordinate entry can also be used during rotation and flipping for more precise control of the positioning.

Restricted Object Selection

Restricted object selection is added in schematic Layout Views to prevent objects from being selected. To use this feature, right-click in the layout window, choose Restrict Selection and then select the item types to restrict. Selecting a layout item type prohibits it from being selected in the layout. If you find you cannot select certain items in a layout, you should verify that they have not been restricted for selection. See "Restrict Selection (Layouts) Dialog Box " for more information.

3.4.3. Polygon Editing

Adding Polygons

You can draw polygons in the layout by using the mouse or by coordinate entry. To draw a polygon, choose Draw > Polygon. You enter the first point by clicking and releasing the mouse at the desired position. For the next point in the polygon, you can add the point graphically by clicking (gravity points can be used to graphically enter exact coordinates). If you press the Shift key while adding new points, you can add segments at other than vertical, horizontal, or 45-degree angles. You can remove previously placed points by right-clicking during the drawing operation. You can enter the last point by double-clicking (that point is added to the polygon and the polygon is closed) or by clicking on the first point to close the polygon.

To draw a polygon using coordinates entry, see "Coordinate Entry".

Editing Points and Edges

You can move a shape point or edge, or use the Edit Points command to modify its vertices.

To move a point or edge of a polygon, double-click the polygon to activate edit mode (in edit mode, the polygon displays selection squares on each vertex and selection diamonds at each midpoint). To move an edge, click and drag one of the selection diamonds at one of the midpoints. To move a point, click and drag one of the selection squares on a vertex. Rectangles, paths, and ellipses can be modified in a similar way.

To move points or edges of a polygon using coordinates entry, see "Coordinate Entry".

The Edit Points command in the Layout Editor allows you to add, remove and edit the vertices of shapes, or add/remove fillets and chamfers. You can add new points to an existing polygon and then move them to change the polygon shape, or you can delete points to remove vertices from the polygon. In point edit mode, you can select and move single or multiple vertices of the shape to introduce new sides to an existing polygon and new segments to an existing path.

To use the Edit Points command, select the shape you want to edit, then choose , or right-click the shape and choose . The shape displays in edit mode.

Clicking on the shape or its vertices, or clicking and dragging to select an area maintains edit mode. In edit mode you can:

• Stretch vertices by clicking on a vertex and dragging while holding down the mouse button

• Select highlighted vertices by clicking on them singly or by Shift -clicking to select multiples. Selected vertices display a selection square as shown in the following figure.

  

• Select multiple vertices by clicking and dragging a selection box to enclose them, as shown in the following figure.

  

• Delete selected vertices by pressing the Delete key or Backspace key

• Add vertices by clicking on an edge between existing vertices

• Add a fillet or chamfer by selecting one or more vertices, then right-clicking and choosing

• Remove a fillet or chamfer by selecting two or more vertices which make up the fillet or chamfer, then right-clicking and choosing

To end edit mode and keep your changes, click in an open space to end the command, or press the Esc key to cancel the command and revert any changes.

For the Edit Points command, an edge is defined as the line connecting two existing vertices, as shown in the following figure.

Deleting Shape Vertices

You can remove a selected vertex from the shape by pressing the Delete key. When deleting vertices, if the number of remaining vertices is not sufficient to create a viable shape, the shape is removed. Polygons must have at least three points, and paths must have at least two points.

Stretching Shape Vertices

You can select and move multiple vertices to stretch the shape. To stretch the selected vertices, click on one of them and drag it while holding down the mouse button, then release the mouse to end the stretch operation. The following figure shows the top two vertices selected and dragged upward to increase the height of the polygon.

You can stretch a single vertex without first selecting it, similar to point editing (outside of Edit Points command mode) by simply clicking a vertex and dragging it to stretch the shape, as shown in the following figure.

Adding Shape Vertices

You can add vertex points to a shape by clicking on a shape edge between two existing vertices. For a polygon, the vertices are along the outer edge of the shape. For path objects, the edges are along the centerline of the path. When the cursor is close to an edge at a location and away from existing vertices where a point can be added, it changes from an arrow to a plus sign "+". You can click in this location to add a point. For example, clicking the middle of the top of the polygon near the edge adds a point in the center of the top, as shown in the following figure.

After adding a vertex you may want to stretch the polygon around the newly added vertex. Since editing involving single vertex stretching attempts to maintain the angles into and out of each vertex, selecting the new center vertex and dragging up moves the two adjacent vertices as well.

Often the reason for inserting a vertex is to create a split in the polygon to introduce a new edge at the location of the inserted point. You can do so by stretching either the point before or after the newly inserted vertex. For example, stretching the upper left vertex introduces a new edge at the location of the newly added point, as shown in the following figure.

This often has the desired effect of splitting the edge at the location of the new point and introducing a new side. You can again stretch the point after the newly inserted point to insert a new side in the polygon.

You can also insert points into path objects along the centerline. The following figure shows insertion of a point in the middle section of a path.

After inserting a point you can use the same process of stretching the point before or after the inserted point to introduce a new path segment, as shown in the following figure.

As with polygons, when modifying paths you can also click and drag the point before the newly inserted point to create a new path segment.

It is often useful to create a trombone-like segment in a section of straight path to allow adjustment of the length by adjusting the length of the U-shaped segment in the trombone. The Edit Points command can introduce a trombone segment into a straight segment of path by inserting two points and then stretching one of the two newly inserted points. For example, you can first introduce two new points into a straight segment as shown in the following figure.

Next you drag down the two outside points, which introduces new segments at the inserted point locations. You use the outside points because stretching the collinear points in the middle brings the path segment with them.

An alternative is to use a combination of the Edit Points command to insert the points and a standard Stretch Area command to create the trombone section. After the points are inserted you can create the trombone by using a mid-point selection handle in the middle of the middle segment. After introducing two new points as shown in the previous figure, you click in an open space to exit Edit Points mode. Next you double-click the path to enter normal path editing mode and stretch the middle handle, as shown in the following figure.

This method has the advantage of not needing to move the path end-points. If the path is connected at the ends, this is the best method for adding a trombone without changing the connection points.

Filleting or Chamfering Vertices

You can modify corners by selecting one or more vertices, then right-clicking and choosing .

In the Modify Selected Vertices dialog box, you can specify how to modify the selected vertices, the radius of inside and outside corners, and what to do when not enough room is available for the specified radius. When you select the Layout Options dialog box Layout tab setting is used:

You can also create fillets with Arc segments

or create chamfers.

In addition you can specify what to do with vertices when not enough room is available to create the desired fillet. In choose to not fillet the vertex. In the following figure, the edge between the selected vertices needs to be 120um to support two of the desired 60um fillets, so no fillet is added.

Choosing reduces the fillets to 40um to fit the available 80um width:

Removing Fillets or Chamfers

You can remove filleted or chamfered corners by selecting two or more vertices, then right-clicking and choosing .

Adding/Editing Cutouts and Arcs

Polygons in the AWR Design Environment platform support cutouts without the need for cutlines or arc segments (arcs described by a center point and radius rather than vertices at certain degree intervals). This allows for simplified layout creation and editing of more complex shapes. Polygons with cutouts or arc segments are referred to as generalized polygons and polygons without cutouts or arc segments are referred to as simple polygons.

The following sections show the basics for adding cutouts to shapes, editing those cutouts, and editing the segments of a polygon to turn them into an arc. There are more advanced use cases for these constructs as well. For example, generalized polygons can have cutouts as well as arc segments, and even cutouts can have their own arc segments. Used independently or together these two layout constructs can simplify creating complex board layouts.

Adding Cutouts

You add cutouts to existing polygon shapes in layout. To add a cutout to an existing polygon, select the polygon and choose and , , , or , then draw the cutout on the polygon in the same way the shape type is drawn when creating a new object in layout.

Editing Cutouts

To reposition a cutout, double-click the parent polygon to enter edit mode. Each cutout has a drag handle in the middle for repositioning. Simply click and drag the drag handle to reposition the cutout.

To reposition multiple cutouts at the same time, double-click the parent polygon to enter edit mode, then press the Shift key while selecting the cutouts you want to reposition. Click and drag the center drag handle of a cutout to move all the selected cutouts the same distance.

You can also edit the size or shape of a cutout. To edit a cutout, double-click the parent polygon to enter edit mode. With the drag handles displayed, press the Shift key and click in the cutout region. Drag handles for the cutout display to allow you to edit the size or shape of the cutout.

You can remove a cutout from a polygon by double-clicking the parent polygon to enter edit mode. With the drag handles displayed, press the Shift key and then select the cutout(s) to delete. Next press the Delete key or choose .

Adding Cutlines

In some cases you may need to revert a generalized polygon with cutouts back to a simple polygon with cutlines. To do so, select the polygon and then right-click the shape and choose or choose . When you execute this command, a cutline is added for each cutout present in the polygon converting the generalized polygon back to a simple polygon (if no arc segments are present). The following figure shows an example of an added cutline.

Editing Arc Segments

Generalized polygons also support the notion of an arc segment, which is a side segment that can be bent into an arc between the two segment end points. This can be convenient for creating rounded portions of a polygon object without having to enter all the arc points individually. Any polygon in the AWR Design Environment platform Layout Editor can have arc segments added to the polygon by editing the polygon sides.

To edit arc segments, select the polygon for which you want to edit the segments, then choose .

When the command executes, edit handles display in the middle of each of the polygon side segments. Dragging these handles perpendicular to the segment side causes the segment to bend into an arc. The farther you drag the handle, the greater the curvature in the arc.

The following figure shows the addition of solder pads to the end of the trace.

Array Copy

The Array Copy command is used to create multiple copies of single or multi-layered shapes and artwork cells by giving the number of rows and columns and separation for each dimension. To access this command choose .

Area Stretching (Stretch Area)

You can use the Stretch Area command to stretch parts of one or more selected shapes. To start the operation, choose Draw > Modify Shapes > Stretch Area. When the command is active, clicking and dragging the mouse over an area selects the points on selected shapes that are inside the area. The selected points are indicated by being drawn in the selection color (usually a dark color). You can click and drag over an area repeatedly to add more points. You can also select points by clicking directly on the shape vertices. As points are selected, previously selected points remain selected. If you press the Shift key while dragging over an area, the points within the area are deselected. Similarly, if you press the Shift key and click on a shape vertex that is already selected, that point is deselected. Once all the desired points have been selected, click (and hold down) the mouse on one of the selected points by moving the square in the upper left hand corner of the cursor over a vertex. When the cursor square turns into four arrowheads, click and drag the vertex to move all the selected points. If you drag and release the mouse, all of the selected points are shifted by the amount the mouse moved.

To stretch by entering coordinates, see "Coordinate Entry".

Slicing Polygons (Slice Shape)

You can slice multilayer (layout shapes) polygons. Polygon slicing is useful for isolating the portion of a cell you want to reuse, or for breaking up a polygon that exceeds a maximum number of vertices.

To access Polygon Slicing, in Layout View, select the desired shapes. Click the Slice Shape button on the Draw Tools toolbar or choose Draw > Modify Shapes > Slice Shape. Click to start a line segment through the shape where you want to split it, and then click to set the line segment. The slice operation uses the segment to define an infinite line, and any selected shape that intersects the infinite line is sliced.

To slice layout shapes using coordinate entry, see "Coordinate Entry".

Creating Notches (Notch Shape)

You can add an intruding or protruding notch to a polygon shape using the Notch tool.

To access Notching, in Layout View, select the desired shape. Click the Notch Shape button on the Draw Tools toolbar or choose Draw > Modify Shapes > Notch Shape. Click and drag the mouse over the shape to create an intruding notch of the desired size, or click and drag the mouse outward from the edge of the shape to create a protruding notch of the desired size, then release the mouse button to complete the notch.

To add a notch using coordinate entry, see "Coordinate Entry".

Merge Shapes

The Merge Shapes command is used to combine positive, negative, and normal layers without requiring an export to apply these shape modifications. To merge shapes, choose Draw > Modify Shapes > Merge Shapes. If you are not familiar with these layer concepts, see "Negative Layers " for details. Note that this operation cannot change shapes assigned to schematic items. You may want to copy and paste an entire layout into a new schematic layout to remove all layout association from schematic elements. This command works only on selected layers, so a common use is to select all shapes on the positive and negative layers only to perform the subtraction of the cut-out layers.

Fracturing Polygons (Fracture Shapes)

The Fracture Shapes command is used to break up complex polygons with a large number of vertices into multiple polygons with limited vertices. You specify the maximum number of vertices for the resulting polygons when you run the command. To use this command, first select the polygon, and then choose Draw > Modify Shapes > Fracture Shapes.

Shape Mirroring (Mirror)

You can create mirrored images of shapes in a layout (or elements in a schematic).

To access Mirroring, in Layout View, select the desired shape and choose Edit > Mirror. The cursor changes to reflect the mirroring operation. Click in the layout to position the new shape. The following example shows the results of a mirroring operation:

Shape Modification Operations

The shape modifier commands modify a polygon or groups of polygons. The commands are dependent on the order in which you select the polygons. You can use Ctrl + click, Shift + click, and drag-and-click mouse commands to select multiple polygons. See "Multiple Selection" for more information about multiple selection.

There are additional settings on the Layout Options dialog box Boolean tab to control shape modifier operations. You can specify whether modified polygons contain cutlines, and whether resized acute corners are rounded. See "Layout Options Dialog Box: Boolean Tab" for details.

To execute the shape modification commands choose Draw > Modify Shapes and then choose the appropriate option, or you can click the corresponding toolbar button. The following operations are available (for commands that require the selection of two or more shapes, this assumes that the "A" shape is selected before the "B" shape). These operations only function for shapes on the same layer. For example, if you select shape 1 on layer A and shape 2 on layer B, merging of the shapes cannot occur.

• Union: Select two different overlapping or touching polygons and this command merges the areas into a single polygon, as shown in the following figure.

• Intersection: Select two different overlapping polygons and this command eliminates all areas that do not intersect. The result is a single polygon, as shown in the following figure.

• Subtraction: Select two different overlapping polygons and this command subtracts the overlapping area from the first polygon selected. The second polygon selected disappears completely, as shown in the following figure.

• Resize: Select a polygon and this command allows you to resize it by adding an offset to the (x, y) dimension of each vertex, as shown in the following figure. Positive numbers make it larger; negative numbers make it smaller.

• Resize Copy: Select a polygon and this command allows you to create a resized copy of the polygon by adding an offset to the (x, y) dimension of each vertex. The copy displays directly on top of the original of each vertex, as shown in the following figure.

• Exclusive Or (Xor): Select two different overlapping polygons and this command deletes the areas that overlap, as shown in the following figure.

• Make Ring: This command turns a solid polygon into a ring with a width that you specify, as shown in the following figure.

• Smooth: This command removes collinear vertices in polygons. It does not apply to shapes drawn in the Layout Editor, which do not contain excess collinear points. It is intended for use with imported layouts that may contain shapes with excess collinear vertices.

3.4.4. Coordinate Entry

You can use coordinate entry for most of the drawing entry and editing you do using the mouse. The layout system uses a uniform approach for coordinate entry. To perform an operation with coordinate entry, press the Tab key or Space bar during any operation that requires a mouse movement. The following dialog box displays to allow you to enter (x, y) coordinates as absolute or relative coordinates. You can also enter (mag, angle) by selecting the Polar check box.

If you select Snap, the cursor moves to the closest grid location to start drawing. Coordinate entry can be intermixed with normal mouse editing. For example, when drawing a polygon, you can add some of the points with the mouse and other points using coordinate entry.

The following are some of the more useful applications of coordinate entry:

• Drawing Polygons: You can use coordinate entry to type in the exact coordinates of a polygon as you draw the polygon. To use coordinate entry, choose Draw > Polygon. You can enter the first point by either clicking and releasing the mouse at the desired position, or you can press the Tab key or Space bar to directly enter the coordinates of the first point. Do not select Rel in the Enter Coordinates dialog box for the first point since a relative position does not apply for the first point entered. After entering the coordinates in the dialog box, click OK (or press Enter). For the next point in the polygon, again you can add the point graphically by clicking (you can use gravity points to graphically enter exact coordinates) or by pressing the Tab key or Space bar to display the Enter Coordinates dialog box. You can then enter the coordinates as relative coordinates (the default; relative to the previous point) or as absolute coordinates. This procedure is continued for all points in the polygon. You can enter the last point (close the polygon) using the techniques discussed in "Adding Polygons" or if using coordinate entry, by entering a relative value of (0,0). The default relative value in the Enter Coordinates dialog box is (0,0), so you can close the polygon by pressing the Tab key or Space bar to display this dialog box, then press Enter. If you enter the coordinates such that the last point coincides with the first point, the polygon is closed also. The coordinate entry mode is designed to make it possible to enter the entire polygon without needing to use the mouse. To enter the polygon without using the mouse, press Ctrl+P to start the polygon tool, press the Tab key or Space bar, then type in the absolute x coordinate, press the Tab key or Space bar, then type in the absolute y coordinate, press Enter to accept the point, press the Tab key or Space bar to start the next point, and so on, then press the Tab key or Space bar followed by Enter to close the polygon.

• Drawing Rectangles: You can also use coordinate entry to specify either or both of the opposing points that define the rectangle. The first point is entered in absolute coordinates (or with the mouse) and the second point is entered in either relative or absolute coordinates (or with the mouse). As with the polygon entry, you can use gravity points to define either point with the mouse. Start the command by choosing Draw > Rectangle.

• Drawing Ellipses: You draw ellipses by specifying the rectangular bounding box of the ellipse, so coordinate entry is the same as that of the rectangle. You start this command by choosing Draw > Ellipse.

• Drawing Paths: Adding a path using coordinate entry is almost the same as adding a polygon using coordinate entry. Start the command by choosing Draw > Path. The center line of the path is drawn like a polygon. The main difference is that the polygon defining the center line is not closed when the command is finished. You can complete the path drawing command by entering a relative (0,0) point for the last point when using coordinate entry.

• Placing Drill Holes: You can use coordinate entry to place a drill hole object. To place the object, choose Draw > Drill Hole, then press the Tab key or Space bar to display the Enter Coordinates dialog box. The absolute coordinates you enter are the position of the center of the drill hole object.

• Moving Objects: Coordinate entry provides a couple of options for moving objects in the layout. To move an object, click (and hold down) on the object with the mouse. Instead of moving the object by dragging the mouse, press the Tab key or Space bar. The coordinate entry dialog box opens to allow you to enter relative or absolute coordinates. If you use relative coordinates, the object is shifted by the specified amount. If you use absolute coordinates, the object is placed at the specified point. The base point of the object is the click point when using absolute coordinates. If you enter absolute coordinates, you should usually have the base position snapped to one of the gravity points on the object. For example, to move a rectangle so that it has a corner at (100,100), select the rectangle, press the Ctrl key and snap the cursor to the desired corner, then click. While pressing the mouse button, release the Ctrl key, then press the Tab key or Space bar to display the Enter Coordinates dialog box. Clear the Rel check box and enter (100,100) as the coordinates, then press Enter. The specified corner of the rectangle is now at (100,100).

• Stretching Shape Edges: You can easily move an edge (or point) of a polygon or other shape by a specified amount using coordinate entry. To move an edge of a polygon, double-click the polygon to activate edit mode (selection squares display on each vertex and selection diamonds display at each midpoint), then click on one of the selection diamonds and hold down the mouse button. Next, press the Tab key or Space bar to display the Enter Coordinates dialog box. If you enter the coordinates as relative, the edge moves by the specified amount. If you enter absolute coordinates, the edge is moved to fall on the specified point. You can stretch the corners of the polygons in the same way. You can also similarly modify rectangles, paths, and ellipses.

• Stretching Areas: You can use the Stretch Area command to stretch parts of one or more selected shapes. You can use coordinate entry to specify the distance that the area is stretched. To use coordinate entry, press the Tab key or Space bar while holding down the mouse button on one of the selected points during the area stretch. The Enter Coordinates dialog box displays to allow you to specify the shift in relative or absolute coordinates. For more information on stretching areas, see "Area Stretching (Stretch Area)".

• Adding Notches: You can use the Notch command to add intruding or protruding notches to a shape. You can use coordinate entry to specify the coordinates of the added notch. To use coordinate entry, select the shape, then click the Notch Shape button on the toolbar and press the Tab key or Space bar to open the Enter Coordinates dialog box. Click OK to display a crosshair cursor with a dx/dy coordinates display. Position the cursor at the desired coordinates and click to draw the notch. For more information on notches, see "Creating Notches (Notch Shape)".

• Splitting Polygons: You can use the Slice Shape command to split polygons. You can use coordinate entry to specify the coordinates of the line that splits the shape. To use coordinate entry, select the shape, then click the Slice Shape button on the toolbar and press the Tab key or Space bar to open the Enter Coordinates dialog box. Specify the x and y coordinates for the starting point of the line you draw to slice the shape. Drag the cursor to the coordinates at which you want to end the line and click OK to create the split. You can separate the shape halves by selecting them and dragging them apart. For more information on splitting polygons, see "Slicing Polygons (Slice Shape)".

• Copied Object Placement: You can use coordinate entry to precisely place objects when you copy and paste them into the layout. For example, to make a copy of a rectangle 100 units to the right of the original rectangle, select the rectangle, then copy and paste it. When you paste the rectangle it moves with the cursor. To place it exactly, press the Tab key or Space bar to open the Enter Coordinates dialog box. Next, enter a relative coordinate of (100,0) and press Enter. The copied rectangle is offset from the original by exactly 100 units in the x direction. If you do not select Rel in the Enter Coordinates dialog box, the copy is placed at the absolute coordinate you entered. The reference point for absolute placement is always the center of the shape.

• TRACE Element Routing: You can reroute TRACE layout objects (for example, MTRACE) by drawing the center line of the TRACE in the same way that a path is entered. To indicate the end of an MTRACE or MCTRACE routing command, enter a relative coordinate of (0,0) to end the command. Press the Tab key followed directly by the Enter key to end the command when entering relative coordinates, because the default relative coordinates are always (0,0). For more information on routing the TRACE element, see "TRACE Elements".

• Rotating about Points: You can use coordinate entry to specify the point about which an object is to rotate. To rotate a shape about an exact point, select the shape, right-click the selected object and choose Rotate. If you press the Tab key or Space bar the Enter Coordinates dialog box displays and you can enter the point to rotate about in absolute coordinates. The rest of the rotation command proceeds as normal.

• Flipping about Points: You can use coordinate entry to specify the line about which an object is to flip. To flip a shape about an exact line, select the shape, right-click the selected object and choose Flip. If you press the Tab key or Space bar, the Enter Coordinates dialog box displays and you can enter the first point of the flip line in absolute coordinates. The rest of the flip command proceeds as normal.

3.4.5. Measuring Tools

The following measuring tools are available in a Layout View.

Standard Ruler

The Ruler measures the distance between two points, and is visible only during the measuring operation.

To access the ruler press Ctrl + D or choose Draw > Measure. To measure the distance between two points, click on the starting point for the measurement, then drag the mouse to the point to which you want to measure. The ruler automatically snaps to grid points in the layout as you move the mouse, to make measuring exact distances easier. If there is a shape vertex, midpoint, edge, intersection or other grid point near the cursor, the cursor automatically snaps to the exact point. If both the first point and the second point are snapped to grid points, the displayed distance is the exact distance between the two points. The cursor displays dx, dy and the total distance. To force the measurement to an exact vertical, horizontal or 45-degree angle, press Shift while measuring. When you release the mouse button the measurement no longer displays.

Layout Ruler

The Layout Ruler also precisely measures the distance between two points by displaying a ruler with specified increments and unit of measure. Unlike the standard ruler activated by choosing Draw > Measure, the Layout Ruler remains visible after you measure.

To access the Layout Ruler, choose Draw > Layout Ruler. Using the ruler crosshair to set the measurement origin, click and drag the ruler beside the element you want to measure. Release the mouse to set the length of the measurement and click again to end the measurement. Hold down the Ctrl key to snap to shape vertices. The following figure illustrates a measurement using the Layout ruler.

To set default ruler properties, choose Options > Layout Options and click the Ruler tab on the Layout Options dialog box. You can specify properties such as the ruler increments, the gap from the measured object, the ruler tick mark height, and measurement precision in number of decimal places. See "Layout Options Dialog Box: Ruler Tab " for dialog box details.

To modify individual ruler properties, right-click the applied ruler and choose Shape Properties.

Dimension Line

The Dimension Line feature measures and displays the distance between two points.

To access the Dimension Line, choose Draw > Dimension Line. Using the ruler crosshair to set the measurement origin, click and drag the line between the points you want to measure. Release the mouse to set the desired length, then move the mouse to move the dimensioning line away from any objects. Click again to place the line and end the measurement. Hold down the Ctrl key to snap to shape vertices. The following figure illustrates a measurement using a dimension line.

To set default dimension line properties, choose Options > Layout Options and click the Dimension Lines tab on the Layout Options dialog box. You can specify properties such as the line's arrow location (inside or outside), text direction in relation to the line, the arrow size, the gap between the line and measured objects, the measurement precision in number of decimal places, and the measurement accuracy tolerance. See "Layout Options Dialog Box: Dimension Lines Tab " for dialog box details.

To modify individual dimension line properties, right-click the applied line and choose Shape Properties.

3.4.6. Zooming and Panning

The following are techniques for zooming in and out of, and panning in a Layout View.

View All

Press the Home key or choose View > View All to display the entire layout in the window.

View Area

Choose View > View Area to start the view area command. When the cursor changes to a magnifying glass, click and drag the cursor over the desired area and then release the mouse button to zoom in on that area.

Zoom Previous

Press the End key or choose View > Zoom Previous to return the view area to its previous state before the last View All, View Area, Zoom In, Zoom Out or Zoom Previous command was executed.

Zoom In

Press the "+" key, choose View > Zoom In, or hold Ctrl while scrolling the mouse wheel to zoom in on the current view. If you press and hold the mouse button at a point in the layout, the zoomed area is centered on that point. Otherwise, the zoomed in area is centered around the center of the view. You can also use Zoom In, Zoom Out, and panning while executing other editing operations. For example, when moving a shape in layout by dragging it, you can press the "-" key (or Ctrl + the mouse wheel) while dragging to zoom out and display more of the layout. You can move the shape to another point in the layout by continuing the drag operation. If you press the "+" key while dragging a shape, the view area zooms in on the shape that you are moving. This is useful for moving shapes in large layouts when the placement of the shapes requires the Layout View to be zoomed. You can maintain the same zoom level while panning.

Zoom Out

Press the "-" key, choose View > Zoom Out, or press Ctrl while scrolling with the mouse wheel to zoom out of the view.

Panning

Press the up, down, left, or right arrows on the keyboard to pan the view in the specified direction. You can also scroll the mouse wheel with no keys selected to pan up and down. To pan right and left, press Shift while scrolling the mouse wheel. Alternatively, hold down the middle mouse button (or wheel) and when the cursor changes to a hand, drag to reposition the view in the window.

3.4.7. Grouping

The Group command locks together the relative positions of multiple layout objects. The Ungroup command separates grouped objects. To access these commands click the Group or Ungroup buttons on the Draw Tools toolbar. Groups can be used to help construct the geometry in the Artwork Cell Editor, but the grouping is lost when the artwork cell is saved (all the correct geometry is saved however). Groups are not saved in the artwork cell because there are no group objects in GDSII.

3.4.8. Alignment Tools

To access polygon alignment functions, select two or more polygons to align and choose Draw > Align Shapes or display the Alignment Tools toolbar by right-clicking the toolbar and choosing Align.

The alignment tools align the selected shapes as follows:

• Align Top : Aligns all shapes to the top edge of the first shape selected.

• Align Bottom : Aligns all shapes to the bottom edge of the first shape selected.

• Align Middle : Aligns all shapes vertically with the mid-point of the first shape selected.

• Space Evenly Down : Aligns all shapes using the vertical spacing you specify in the Spacing dialog box that displays. The first shape selected is the "virtual anchor".

• Align Left : Aligns all shapes to the left edge of the first shape selected.

• Align Right : Aligns all shapes to the right edge of the first shape selected.

• Align Center : Aligns all shapes horizontally with the mid-point of the first shape selected.

• Space Evenly Across : Aligns all shapes using the horizontal spacing you specify in the Spacing dialog box that displays. The first shape selected is the "virtual anchor".

• Make Same Width : Makes all shapes the same width as that of the first shape selected.

• Make Same Height : Makes all shapes the same height as that of the first shape selected.

• Make Same Both : Makes all shapes the same width and height as that of the first shape selected.

• Space and Size as Array : Displays the Align Shapes to Array dialog box and aligns and resizes shapes in an array.

Note that a frozen polygon does not move. You can unfreeze a shape by right-clicking it and choosing Shape Properties, then on the Layout tab, clear the Freeze check box.

3.5. Intelligent Cells (iCells)

iCells make the use of many elements much simpler and less error-prone. With iCells, the parameter values from one element can be associated with the parameter values of another element. For example, AWR Microwave Office software does not require parameters for both interconnecting transmission lines and discontinuity models. iCells dynamically adapt, based on their electrical connections, effectively inheriting their properties from the connections and thus eliminating synchronization errors and increasing designer productivity.

3.5.1. Standard iCells

There are many iCells that are already set up within AWR Microwave Office software. The standard iCell elements have names that end with a "$". The rest of the name is the same as the non-iCell version of the element. For example, the MTEEX iCell is MTEEX$. The schematic in the following figure shows an iCell version of the MTEEX element that is connected to three MLIN elements. The MTEEX$ element does not require any parameters for any of the widths of the MTEEX. All the required width values are automatically obtained from the elements that are connected to the MTEEX$ iCell.

The following layout is the Layout View of the previous schematic. Note that the three widths required to draw the center MTEEX element are correctly assuming the values of the connected lines.

Standard iCells require that the elements they connect to have the parameter the iCells are looking for. For example, the MTEEX$ element must have elements connected at each node that have W parameters. If one of the connected elements does not have a W parameter, the iCell reports an error. You can edit the iCells to allow them to connect to different parameter names if needed. For example, you can change MTEEX$ so that its W1 parameter connects to a connected element's W1 parameter instead of the default W parameter. To do so, double-click the iCell element in the schematic window or right-click the selected element and choose Edit Element. You can view and edit the W1, W2, and W3 parameters of the MTEEX$ in the Element Options dialog box (you can also make them visible on the schematic by deselecting Hide for the parameter on the Display tab). If the W1 parameter is selected in the Parameters list, you can see that it has a value of W@1. This syntax indicates that W1 should be assigned to the value of the W parameter from the element connected to node 1 of the MTEEX$ element. If you change this to W1@1, the MTEEX$ tries to connect to a W1 parameter from the element connected to its node 1.

3.5.2. User-Defined iCells

Any element can be made to act as an iCell by using the correct iCell syntax for the element's parameter values. For example, if you place a MTEEX element on the schematic and its W1, W2, and W3 parameter values are set as follows,

W1 = W@1 W2 = W@2 W3 = W@3

the MTEEX instance is the same as a MTEEX$ element (except the W1, W2, and W3 parameters are visible on the schematic).

The iCells are created by assigning parameter values X using the syntax X=P@N. This syntax indicates that X should be assigned to the value of the parameter P from the element connected to node N of the iCell element.

NOTE: When creating user-defined iCells, it is possible to connect elements together that form a circular reference. This causes errors in the circuit and should be avoided.

3.5.3. Generalized iCells

Generalized iCells are an extension of normal iCells. Normal iCells allow you to assign parameter values to the parameter values of elements connected to the iCell. Generalized iCells allow you to assign parameters to the parameter values of any other element in the schematic. The generalized iCells are created by assigning parameter values X using the syntax X=P@ELEMENT.NAME. This syntax indicates that parameter X should be assigned to the value of the parameter P from the element of type ELEMENT with an ID parameter equal to NAME. For example, W1=W@MLIN.TL1 indicates that the parameter W1 should be assigned to the value of the W parameter of a MLIN element with an ID parameter named TL1.

3.6. TRACE Elements

There are several different TRACE elements. The MTRACE is a microstrip line that can have zero or more bends. The MCTRACE is a variation of the MTRACE that uses curves instead of bends. The SCTRACE is the same as MCTRACE, except it is used for stripline.

3.6.1. TRACE Editing

In general, you perform graphical editing of the TRACE layout cells using mouse commands. Double-clicking the layout object activates edit mode and displays the black diamonds that you use to edit the bends and lines.

On one straight segment there are three diamonds. The outside diamonds control the length of the segment while the middle diamond controls bend manipulation. The diamonds are manipulated by placing the mouse over the diamond to activate an arrow cursor.

To move the diamond, click and drag the arrow cursor to another position and then release the mouse button.

Adding a Bend

To add a bend, select the MTRACE element in the Layout View. To move the middle diamond, click and drag the arrow cursor to another position and then release the mouse button. Before the mouse button is released, an outline of the new MTRACE displays, as shown in the following figure.

The following figure shows the completed bend.

Moving Bend Position with Overall Length Constant

There are three options when moving a bend to a new position. The first two options refer to moving a bend on one of the end segments. The third option refers to moving a middle segment between two bends.

Option 1: When moving an end segment, the two segments attached to the bend being moved take up the slack in length while the other segment remains constant. To move the middle diamond of an end segment, click and drag the arrow cursor to another position and then release the mouse button. An outline of the new bend position displays as shown in the following figure.

The following figure shows the new bend position with overall length constant.

Option 2: To move the middle diamond of an end segment, press Ctrl + Shift while clicking and dragging the arrow cursor to another position, then release the mouse button. This option is the opposite of option 1. The slack in the length is taken up by the segments that are not being moved. Observe that the end segment that is moving is constant in length while the other two segments change, as shown in the following figure.

The following figures shows the new bend position for option 2.

Option 3: When moving a middle segment between two bends, the middle segment remains constant while the end segments vary in length, as shown in the following figure. Use the same commands as in option 1 to move a middle segment.

Moving the Bend Position and Changing the Overall Length

To move a bend position while changing the overall length, you move the end segments of the TRACE when there are two bends or less in the layout. When changing the length of a TRACE and moving a bend position, the segment being moved remains at a constant length while the segment attached to the bend varies in length. To move a bend and change the length, hold down the Shift key. To move the middle diamond of the end segment, click and drag the arrow cursor to another position and then release the mouse button. The length of the middle segment changes, while the end segment remains a constant length, as shown in the following figure.

The following figure shows the new change in length and bend position.

When there are more than two bends in the TRACE you can change the bend position and the length in a "trombone" action by holding down the Shift key. To move the diamond, click and drag an interior segment of the TRACE to another position and then release the mouse button. Notice that the middle section's length remains constant while the other two segments vary in length, as shown in the following figure.

Adding a Bend After Initial Bend

To add a bend after the initial bend is added, hold down the Ctrl key, and click and drag the middle diamond between the two bends to another position and then release the mouse button. The following figure shows the outline of the new bend.

The following figure shows the final TRACE with the new bend.

Rotating a Segment

To rotate the end segment of a TRACE, press the Ctrl key and click and drag the end of an MTRACE that has at least one bend in it to another position, and then release the mouse button.

NOTE: When grid snap is on, the angle of rotation is only placed on a snap angle increment specified in the Layout Options dialog box (choose Options > Layout Options and click the Layout tab).

3.6.2. TRACE Routing

You can route the TRACE layout cell using the TRACE routing command. The TRACE is routed from the start end which is indicated by an arrow.

The TRACE routing command routes the TRACE from a center line path that is drawn with the mouse (or using coordinate entry). You start TRACE routing by double-clicking the TRACE to put it into edit mode, where its grab diamonds are visible. To start TRACE routing you double-click one of the diamonds on either end of the TRACE.

After you start the TRACE routing command, you can draw a center line path as shown in the following figure. If you press the Tab key or Space bar while drawing, a Coordinate Entry dialog box displays to allow coordinate entry of the center line points. You can also use gravity points when drawing the center line. You draw the center line by clicking at each of the desired vertex points. To complete the center line drawing, double-click for the last point or click on the same point twice.

Hold the Shift key during trace routing to route with no orthogonal restraints on the route.

After the center line path drawing is completed, the MTRACE element routes itself to the center line path. The routing is not always exactly on the center line because there are other constraints that may need to be satisfied. For example, when routing the MTRACE, there is a minimum allowable length for each segment.

Maintaining the Line Length

During TRACE routing, the length of the TRACE is based on the length of the drawn center line. If you want to route an MTRACE while maintaining its length, press the Shift key when double-clicking to end the route. This action causes the MTRACE to be scaled such that the general shape of the MTRACE is the same as the drawn center line, but the length is the same as the length of the original line.

NOTE: Avoid pressing the Shift key during intermediate routing points; it makes it difficult to drag orthogonal routes.

3.6.3. Snap to Fit

There are several elements that have layout cells that can automatically resize themselves to Snap to Fit between two points. The TRACE elements and iNet all support this feature, as do many of the transmission line cells (for example, the MLIN cell). The use of Snap to Fit is shown in the following figure.

The following figure shows the result of applying Snap to Fit on the center MTRACE cell in the previous figure.

When it is not possible for the layout cell to resize itself to fit exactly, it resizes as closely as it can. For example, an MLIN cell can only stretch in one dimension, so if Snap to Fit is applied to an MLIN, the MLIN may still be disconnected in the direction perpendicular to the MLIN.

3.6.4. Symmetric Circuits

You can use generalized Intelligent Cells (iCells) to simplify the creation of layouts that have symmetric components. The generalized iCell syntax allows an element parameter to be assigned the same value as a parameter on any other element in the schematic. For example, you can assign the W parameter on an MLIN (instance TL1) to have the same W parameter as another MLIN (instance TL2) using the syntax W=W@MLIN.TL2 for the W parameter of TL1. The instance name TL1, is the value of the ID parameter for the schematic element.

For the schematic shown in the previous figure, the MTRACE element with ID=X2 uses the generalized iCell syntax to assign most of its parameter values to the same values as the corresponding parameters in the MTRACE instance with ID=X1. Normally, the DB and RB parameters for the MTRACE element are hidden (they can be made visible or edited in the Element Options dialog box). The DB parameter specifies a vector of segment lengths, and the RB parameter specifies the angle of each bend. If the RB and DB parameters are assigned as equal to the RB and DB parameters of another MTRACE, the resulting TRACE will have the same bends. It is important to also set the length of the MTRACE to the same as the other MTRACE so that the line is drawn symmetrically. You can also assign the other parameters of the MTRACE (such as width) to the other MTRACE parameters, but this is not required. The following figure shows the resulting layout for the previous circuit. If the upper TRACE is re-routed, or edited, then the lower TRACE automatically re-routes itself to match. In the following figure, the MTRACE that uses the generalized iCell syntax is also flipped so that the circuit is completely symmetric.

3.7. Electrical Net (iNet) Elements

Electrical Nets (iNets) are advanced schematic and layout objects in the AWR Design Environment platform that are only available with the most advanced feature set. If you are unsure if your current license includes iNets, please contact your regional sales representative.

Like all models in the AWR Design Environment platform, iNets have both a schematic and layout representation. In the schematic, an iNet is a single node that connects two or more element nodes together. This node is created by wires or by named connectors (the NCONN element), or by directly connecting the element nodes. In the layout, an iNet is a collection of routes and shapes drawn to physically complete the connections specified in the schematic. When incomplete, these connections display as rat lines in the layout. Routing is the process of drawing the routes that complete the connections and eliminate the rat lines.

Once an iNet is routed, you can use it in simulation through the AWR extraction process. This means the iNet geometry is used as the input to one of many physical simulators that can determine the characteristics of the iNet based on its geometry and physical stackup. For silicon designs, this is typically an RLCK parasitic extractor. For microwave designs (MMIC or PCB), this is typically the ACE extractor or EM simulators (EMSight, Cadence® AWR® AXIEM® 3D planar EM analysis simulator, Cadence® AWR® Analyst™ 3D FEM EM analysis software, or EM simulators from vendors who use the EM Socket). See "EM: Creating EM Structures with Extraction" for more information.

iNets must be properly configured for each process. This section discusses how to properly use iNets after the technology is configured. For silicon and MMIC design, the PDKs are configured for iNets. For PCB, you should contact your regional sales representative to get support configuring your PCB process for iNets.

3.7.1. Defining iNets

The following sections define iNets in a schematic and in a layout.

Defining iNets in a Schematic

Each iNet is one electrical node connecting two or more model connections.

Defining iNets in a Layout

iNet - A collection of routes and/or shapes that complete the physical connection of cell faces in layout.

Route - A collection of segments (and vias, if needed) that connect two points in a layout. Double-click a ratline in the layout to start adding a route.

Segment - One rectangle, the simplest part of an iNet.

An iNet can have different combinations of routes to make it complete.

You can also associate an existing arbitrary shape (dumb shape) with an iNet.

You can use dumb shapes to complete the connections of an iNet.

Finally, you can use a combination of routes and shapes to complete an iNet.

Note that iNet shapes can only be extracted and simulated by EM simulators such as AXIEM, because an arbitrary shape cannot always be mapped to an available distributed element model. For maximum simulation flexibility, use iNet routes wherever possible, and use shapes only when necessary.

3.7.2. Preparing to Route

The following sections discuss routing configuration.

Default Vias and Discontinuities

If connected segments in an iNet are on different layers, their connection includes vias. Depending on your technology, you may need to configure default via and discontinuity settings for your iNets. Choose Options > Layout Options to display the Layout Options dialog box, then click the iNet tab. See "Layout Options Dialog Box: iNet Tab " for more information.

Minimal 2 iNet Route Via Mode

Minimal 2 via mode provides support for constructing complex multi-layer self-overlapping iNet route structures. This option provides a mode where the via insertion location is more predictable than the standard Minimal via mode when working on these types of structures.

In the Minimal 2 vias mode a via is only inserted under two conditions:

1. If two consecutive line segments along the iNet route change layers a via is inserted at the junction between the two line segments.

2. If an end of the iNet Route terminates over an area pin on a different layer a via is inserted to connect the end to the pin.

This is more restrictive, so more predictable than the standard Minimal via mode. It only inserts vias in the junctions of a single iNet route or between a route and end points and overlapped area pins. It does not insert vias when the route overlaps itself or if two independent routes overlap each other.

The following figure shows an example of how the new Minimal 2 via mode works for a multi-level self-overlapping route.

This figure shows that the Minimal 2 via mode only inserts vias at the junctions where the line changes layers. In this layout many corners overlap but the vias are only placed where the line transitions from one layer to another. At the lower end there is an area pin which overlaps the route end point so a via is inserted to connect that area pin to the route.

Minimal 2 via mode provides support for predictable via insertion when constructing complex multi-level self-overlapping iNet route structures.

Default Widths and Line Types

Choose Layout > Show Routing Properties or click the Show Routing Properties button on the toolbar to open the iNet Routing dialog box and set the initial iNet properties when routing.

Use HV routing: When this check box is cleared, horizontal and vertical routing use the same defaults. When you select this check box, you can specify different options for horizontal and vertical routing.

When you are routing a net, you cannot change the settings in this dialog box; you can only change iNet widths during routing if you press the Tab key or Space bar.

Default width: Specify an iNet width (in the project unit for length). Previous widths are remembered.

Line type: Select a line type available in your process.

3.7.3. Starting Routes

Double-click a rat line in the layout or select a rat line or completed route, right-click and choose Select Draw Route. The following figure shows a layout with two iNets, with the left iNet in routing mode.

The cursor changes to a routing symbol that also includes dx, dy and Line displays. dx and dy display the amount moved in either direction for the current segment, and Line displays the line type used for the current segment.

All faces or area pins to be connected by the iNet are highlighted in blue.

All rats lines from different iNets are gray to help identify only the iNet being routed.

3.7.4. Entering Routes

Once you start a route, click to set the start/end points of each segment.

Press Ctrl + Shift and use the mouse wheel to change the line type for the current segment. The Line name changes on the cursor display.

Right-click to undo the last iNet segment.

While in routing mode, press the Tab key or Space bar to set iNet segment locations with coordinate entry. You can enter coordinates relative to the previous point or absolute x,y coordinates.

Also while in routing mode, press Shift + V to cycle through valid via types between the layers being connected. The last via added becomes the current (default) via.

Double-click or press Enter to finish the current route.

Minimum Spacing Routing Guides

The Minimum Spacing Routing Guides provide assistance for entering iNet routes, which allows you to place the route lines as close as possible to other structures in the design without violating the design rules. The guides use the separation entries from the DRC file to create guides which help when tracing out routes consistent with the rules in the DRC file. The Minimum Spacing Routing Guides show a guiding line to guide the route trace centerline at a distance that results in the route trace being as close as possible to the other structures, while still satisfying the DRC minimum spacing separation rules. An option to reject points within the minimum spacing range of a structure prevents placing routing points inside the minimum spacing guides. The guides provide gravity assistance to guide the entry, but do not rigidly constrain entry to the guide. The route entry can move off the guide at any point if needed to continue a route. The route gravity specifies how strongly the mouse is attracted to the guide and how far away from the guide it needs to be moved before gravity is released.

Design Rule Specifications

To provide these guides, the process library needs to include a set of DRC rules for the process with separation specifications for all important layer spacings. For the route spacing guides the important rules are the "SEPARATION" entries which specify the minimum separation spacing required between specific design layers, as shown in the following example:

SEPARATION "Metal 2" "Metal 2" 3000 SEPARATION "Metal 1" "Metal 1" 3000 SEPARATION "Metal 1" "Metal 2" 3000

For example, the following rule

SEPARATION "Metal 2" "Metal 2" 3000

specifies that two structures on the layer "Metal 2" must have at least 3 µm minimum separation between them. These values from the DRC rules are used in the calculation of where to place the guide so that the resulting trace has this minimum spacing between the layers in the route line and other structures in the design.

Activating the Separation Rules

After loading into the project the DRC rule files with minimum spacing rules, choose . Under Routing options select the following options.

• Minimum spacing guides enables the use of minimum spacing guides when drawing routes.

• Reject clicks inside min spacing rejects single mouse clicks inside the regions around shapes that are inside the minimum spacing guides. You can override this behavior by holding down the Alt key to allow a route connection to a desired shape.

• Constrain to outside min spacing attempts to restrict routing to outside of the minimum spacing guides. While routing, if the current segment approaches a shape, the progress is constrained when the route reaches the minimum spacing guide. You can override this behavior by holding down the Alt key to allow a route connection to a desired shape.

  • To override this behavior you can hold down the Alt -key to allow a route connection to a desired shape.

• Disable self avoidance guides disables guides normally placed around segments of the current route as they are entered.

The Alignment gravity setting also pertains to the routing guides. It affects how strongly the cursor is pulled to stay in alignment with the guides during routing. The stronger the gravity, the farther away from the guide you must move the cursor in order to pull it off alignment with the guides.

The following example shows some wired elements in a schematic.

Their layout view shows two elements are already connected using iNet routes.

After the separation rules in "Design Rule Specifications" are included in the DRC file and activated, the Minimum Spacing Route Guide displays with a dotted red line when starting the iNet routing on the remaining rat line.

Route the second line as close to the initial line as possible without violating the DRC rules regarding the separation between the line layers. When you start on Metal 1 and move toward the left, as you approach the existing route a dotted red line displays to the right of it as shown in the following figure. If you try to click inside the red dotted line and the existing route to place the route, route placement is not permitted.

Continuing to route displays the route guide as shown in the following figure. A closer look at the spacing between the traces resulting from the minimum spacing guides indicates that the separation between the Metal 2 - Metal 2 and Metal 1- Metal 2 is as defined in the SEPARATION rules in the previous section.

Horizontal/Vertical Routing with Minimum Spacing Guides

For H/V routing, guides are placed at the maximum of the spacing values for the two line types used. This is to try to ensure that neither line type is placed at a position that is too close to an existing structure, resulting in DRC violations. For example if the separation rules are as follows,

SEPARATION "Metal 2" "Metal 2" 5000 SEPARATION "Metal 1" "Metal 1" 3000                

and the H/V routing is set to use Metal 1 for horizontal and Metal 2 for vertical.

If routed along Metal 2 shapes, the guides display and guide both the horizontal lines and the vertical lines at a distance of 5um from the structure.

iNet Status

When all pins of the models connected to an iNet are connected with routes, the iNet is complete. For simple iNets, you can see visually if the iNet is complete or not.

With an iNet selected, you can view the Status bar along the bottom of the AWR Design Environment platform main window to see whether or not an iNet is complete.

Connecting to Non-orthogonal Faces and Area Pin Sides

When starting an iNet route segment from the side of a non-orthogonal area pin or from a non-orthogonal face, the Layout Editor provides alignment lines and alignment gravity to help guide the iNet route segment direction to maintain a perpendicular connection to the area pin side or cell face so that the resulting connection is flush. This alignment help is also useful when attempting to finish a route by connecting the last segment of an iNet route to a non-orthogonal area pin side or cell face.

For example, in the following figure, there are two pins which have non-orthogonal faces that need to be connected together to complete the circuit and replace the flight line.

To replace the flight line with an iNet route, double-click on the flight line, then starting from the connection point on one of the pins, click and drag to begin a new iNet route segment. As the segment is drawn away from the non-orthogonal pin face, alignment gravity guides its direction to maintain a perpendicular end connection with the pin face. A dotted line drawn down the middle of the route segment shows the perpendicular direction out from the pin face. The following figure shows this directional support and centerline while drawing the line outward from the pin.

Since the pins are not directly aligned for connection with a single segment, you need to create a horizontal segment that is just long enough to assure alignment with a third (diagonal) segment which is perpendicular to the second pin's non-orthogonal face. It can be difficult to determine how long the horizontal segment should be so that the final diagonal segment is perpendicular to the pin face and results in a flush connection.

A guide line and alignment gravity display when the horizontal segment is at the correct length to create the final segment and make it align perpendicular with the pin face. The following figure shows the point at which the alignment gravity provides a slight resistance and the alignment line is drawn along the flight line, indicating that starting the final segment at this point aligns correctly.

Click and begin the final segment leading into the second pin. As the cursor gets close to the pin, alignment gravity attempts to guide the connection of the iNet route end segment to the pin face connection point providing a clean flush connection. The following figure shows the final position where the alignment gravity assisted in connecting to the pin face.

Double-click to end the route, and both the start and end connections should provide flush connections to the pin faces. The following figure shows a magnified look at the resulting segment connection.

The alignment guides and gravity help create clean flush start and end connections to pins with non-orthogonal faces of any angle, helping to provide clean connections to these hard-to-align faces.

Coordinate Entry

When entering iNet route objects through coordinate entry, the Enter Segment Coordinates and Properties dialog box allows you to specify coordinates, line type, and line width. When starting entry of a route using coordinate entry, the initial width and line type are the defaults specified in the iNet Routing dialog box (with a layout window active, choose ), as shown in the following figure.

To use coordinate entry when starting a new route, double-click on a flight line and then press the Tab key to display the Enter Segment Coordinates and Properties dialog box. The first time you display this dialog box, its values match those of the iNet Routing dialog box.

Once you change these values, the new line type and width become the default value for the next route entry.

3.7.5. Editing Routes

After you enter iNet routes, there are several editing techniques for editing the end points of each route's segments and editing the line types and vias for each route.

End Points

Double-click any route to enter editing mode. In editing mode, diamonds display along the middle of the route.

Click and drag the edit diamond in the middle of a segment to move that segment. The length of any segments on either side is adjusted.

Click and drag the edit diamond on the end of a segment to move the end point of the two connecting segments. The length of segments on either side are adjusted.

Click and drag the end point of any route to move the end point. The length of the attached segment and one segment behind are adjusted.

During any segment movement the cursor displays the distance the segment(s) has moved in the x and y directions.

You can also use the Tab key or Space bar to move segments specific amounts.

Line Types

After you finish a route, you can change the line type used for each segment, for multiple segments, or for all segments of the route.

Select a route, right-click, and then choose Route Segment Properties to display the Segment Properties dialog box.

In this dialog box you can change the Line Type and Width for all selected segments.

You can select individual segments of a route. Shift+right-click a segment to draw a line through the center of the segment. Using the same technique, you can select more segments or click again on selected segments to deselect them.

Vias

You can add vias while in routing mode. Pressing Shift + V during routing allows you to cycle through valid via types between the layers being connected. The last via added is shown as the current (default) via.

After you finish a route, you can change the via properties that connect segments on different layers.

Double-click over the via area to display the edit diamonds for the via region only.

Click and drag the edit diamonds to resize the via area graphically.

Right-click over the via and choose Route Via Properties to display the Via Properties dialog box and edit the via properties.

Select multiple vias for editing by Shift+right-clicking the vias.

Note that for different iNet configurations, via editing changes. Some processes have fixed via sizes, so dragging the edit diamonds does not apply. Instead you change the Via Type in the Via Properties dialog box.

To offset vias, select the via(s) to offset, right-click and choose Route Via Properties. In the Via Properties dialog box, clear the Auto Size check box and enter the desired offset. Note that the LPF must have the DRAW_VIA_ON_SEGMENT_END property unset.

Alternatively, you can offset vias directly in the layout by double-clicking on a via and dragging it by its center drag handle, as shown in the following figure.

Shape Properties

To specify all iNet route properties, select an iNet, right-click, and choose Shape Properties to display the Properties dialog box. See "Properties Dialog Box: Layout Tab " for information on layout options.

The Route tab controls the discontinuity types for the route. Typically, silicon designs use square discontinuities and microwave designs use any of the types available. See "Properties Dialog Box: Route Tab " for information on route options.

The Segments tab controls the properties for each segment of the route. When you select a segment in this dialog box it is also highlighted on the route with a line through the center of the segment. See "Properties Dialog Box: Segments Tab " for information on segment options.

The Vias tab controls the properties for each via of the route. When you select a via in this dialog box, it is also highlighted on the route with an "X" through the center of the via. See "Properties Dialog Box: Vias Tab " for information on via options.

Bend Styles

iNets can have square, mitered, curved, chamfered or rounded bends.

The following figure shows a section of iNet route with four default square style bends.

Rounded bends provide an alternative to square bends, decreasing radiation at the corner points, similar to mitered corners. Rounded corners are also preferable in some processes such as Printed Circuit Boards (PCBs). Implementation of a rounded bend is similar to a square bend, but with the outer edge corners rounded off with a radius that is half the line width.

To use rounded bends, select the route, then right-click and choose to display the Properties dialog box.

On the Properties dialog box Route tab, select Rounded as the Bend style, as shown in the following figure.

Chamfered bends are useful for maintaining a fixed diagonal segment length while adjusting the route segments. Chamfered provides an intermediate step between a square bend and a rounded bend, providing one diagonal segment that cuts off the corner, as compared with the square bend. You can control the length of the diagonal segment by setting the chamfer amount, similar to the way the amount of curvature for a rounded bend is controlled by adjusting the radius.

On the Properties dialog box Route tab, select Chamfered as the Bend style, as shown in the following figure.

The amount of chamfer in a bend is relative to the route width or specified by an absolute size. When the lengths of the incoming and outgoing segments to a bend become too small to fit the full-size chamfer segment, the length of the chamfer segment is automatically reduced to fit a shorter segment by default. To prevent automatic resizing, select the Curves use fixed radius check box in the Properties dialog box. If selected, incoming or outgoing segments that become too short cause the bend to revert to a rounded style.

The following figure shows the route segment with chamfered bends, with the amount of chamfer relative to the width and Amount set to 1, so the chamfer length is equal to the width.

Reroute Mode

After a route is complete, you can continue editing the segments of the route. Select the route, right-click, and choose Extend Route. You can enter new segments to the route or right-click to remove the last segment.

The location in which you right-click to enter this mode is important. The end of the route you are closest to is the end of the route you will edit.

Snap to Fit

iNets can slightly auto-correct to complete a route, such as when a model to which the iNet is connected moves or is resized. While iNets function with the Snap to fit command it is important to note that they do not work with the snap command.

Select the iNet and choose Edit > Snap to fit or click the Snap to fit button on the toolbar to complete a route.

Snap to Fit should not be confused with routing capability. Snap to Fit only attempts to adjust the two segments of the route back from the end of the route that has a rats line. If you want more extensive iNet changes you should use Reroute mode.

Reshaping Routes

You may need to change an existing route to accommodate new design elements, specifically to reshape the route around obstacles. The Route Reshape feature allows you to make the necessary modifications without deleting and redrawing the entire route. Instead, by picking a point along the route and entering a new sequence of segments that connect back to the route, you can cut out and replace a section of the route.

The following figure shows an example of an iNet route line running over the top of a FET device in a design. It is best to reshape the existing route around the device, rather than deleting and replacing the entire route.

To reshape the existing route, select the iNet route, right-click and choose Reshape Route.

Select a point on the route centerline where you want to begin the reroute. In the following figure, a point above the FET is selected, along the existing iNet route centerline. After the first click, the reshaped section is started to the right by dragging the mouse away from the centerline.

Click to add new segments to the reshape portion, the same as creating a new route. To finish the reshape segment, double-click the original route where the reshape section should connect back to it. The following figure shows the reconnection back to the original iNet Route, after drawing the reshaped section.

After you double-click, the region of the original iNet route between the start of the reshape and the end is removed, and the reshaped section replaces it, as shown in the following figure.

Similarly, you can replace multiple route segments. The following example shows a three-segment route that passes over the top of a FET.

To reshape this route, select the iNet route, right-click and choose Reshape Route, then click on the centerline of an existing route segment. Draw the reshape section and double-click on the centerline of another existing segment to end the reshape section. The following figure shows the process of drawing the reshaped route around the FET.

When you complete the reshaped section by double-clicking on the existing segment centerline, the segments between the start and finish points are removed and replaced by the reshaped section, as shown in the following figure.

Snap Cell Connections

Often when developing a design, you need to shift a cell a small amount to accommodate additional design elements. If the cell also has iNet route connections to its faces, shifting the cell results in flight lines from the location off the cell with the previous iNet connections to the new location of the cell. The following figure shows an example of a FET cell shifting to connect with a couple of connections, where doing so opened up two other connections.

The Snap Cell Connections command can adjust iNet routes with remaining flight lines to close the connections and connect to the cell faces. To use this command, select the cell, right-click and choose Snap Cell Connections as shown here.

This command attempts to adjust the iNet routes which have flight lines close the connection and attach the lines to the middle of the cell faces. The following figure shows the result of running the command for this example.

3.7.6. Selecting iNets in Layout

You can select more than one route or shape of an iNet by Shift-clicking to add or remove them from the current selection set. This technique is difficult for complex iNets, however.

To select all routes and shapes associated with an iNet, select the corresponding wire in the schematic, then right-click and choose Select in Layout.

Alternatively, you can select a route in the layout, right-click and choose Select net routes to add all routes (not shapes) to the current selection.

3.7.7. Deleting an iNet

You can delete routes and shapes of an iNet by selecting them and pressing the Delete key or choosing Edit > Delete.

Since an iNet is an object in both schematics and layouts, you can also delete an iNet from the schematic by deleting the wire connecting model nodes or by renaming or removing named connectors. If you delete a schematic iNet the layout iNet remains in layout in a disassociated state.

You can identify an iNet in a disassociated state in several ways. The Status bar with the iNet selected shows a disassociated status. The iNet also draws on the Error Highlight drawing layer, so the routes of the iNet differ visually. The rat lines for the iNet no longer draw to the routes or shapes.

3.7.8. Associating and Disassociating iNets

In this section, the term "route" applies to both routes and shapes of an iNet. You can correct a disassociated iNet by associating the route in layout with the correct iNet by first selecting the rat line for the proper iNet, then pressing the Shift key, selecting the disassociated routes, right-clicking, and choosing Associate Net Routes. The following figure shows the route associated back to the iNet.

To disassociate associated iNet routes, select the routes, right-click, and choose Disassociate Net Routes.

You can automatically associate and disassociate all iNets in a layout based on connectivity by choosing Layout > Connect Net Shapes. Any routes in contact with the pins on which the "x" of the rat lines display are associated with the corresponding iNet(s). Additionally, any other routes that contact such an associated route are also associated with the same iNet. Finally, this command disassociates any routes that do not connect to an iNet through contiguous metal. Connect Net Shapes uses connectivity rules to determine connections between different layers. See "Connectivity Rules" for details.

The following figure shows examples of Connect Net Shapes working. Disassociated routes and shapes, which directly or indirectly connect to one or more ends of an iNet, become associated with that iNet.

The following figure shows an example of Connect Net Shapes disassociating a route and a shape from an iNet because they are not connected to it. The second example shows a route being disassociated from one iNet and associated with another, again based on connectivity.

3.7.9. iNet Cleanup

The Net Cleanup command provides editing features for iNet route objects in addition to the normal routing editing commands. This command supports the following optional operations that you can perform on a selected set of iNet route objects:

• Merge end-connected routes

• Insert route crossovers

Invoking the Command

To enable the menu a layout window must be active, and to enable the command you must select at least one route object in the layout window. Choose Layout > Net Cleanup to display the Net Cleanup dialog box with options for merging end connected routes and inserting crossovers, as shown in the following figure.

Merging End-Connected Routes

This option does not require any additions to the Layer Process Definition (LPF). In the design, it is possible for several routes to be associated with a line of single connection, and a single route might be separated into two Route objects using the Slice command. The Merge end-connected routes option can clean this up.

The following figure shows how to merge end-connected routes. Here the route is sliced and needs be merged together.

If you select the two routes and choose the Merge end-connected routes option, the two routes are joined to form one route, as shown in the following figure.

Inserting Crossovers

You can also insert crossovers to perform Net Cleanup. The Insert crossovers option attempts to automate the process of inserting a new crossover segment on a different layer, and keeping the route as one object, making it easier to edit and manipulate.

For the Net Cleanup command to handle the intersection of two line types, some process rules must be defined in the LPF. These rules tell the command when it encounters an intersection of specific line types, what layers each line type should be transitioned to, to form the crossover. The rules can also describe how far back from the other lines the intersection must be to be valid for the process. The following is a typical rule:

$CROSSOVER_RULES_BEGIN ! LT1:LT2   LTUnder     LTOver     OffUnder     OffOver     Flags M1:M1     M1          M2         5e-6         5e-6        1 $CROSSOVER_RULES_END              

This rule indicates that when you see an intersection between line type M1 and line type M1, the first line type should stay on M1 and the second line type should be transitioned to M2 at the intersection. In both cases the pullback should be 5 um from the lines at the intersection. Note that the flags are set to 1. This indicates that an extra half of a line width should be included in the pullback to make room for things like the addition of an inline via. If the flag is set to 0, only the fixed pullback is used for the lines at the intersection.

The following example uses the rules supplied for the example AWR MMIC process.

!--- Used for automatic crossover insertion ---- $CROSSOVER_RULES_BEGIN ! -> LT1:LT2                            LTUnder              LTOver            OffUnder OffOver   flags "Thick Metal Line:Thick Metal Line"     "Thick Metal Line"  "Cap Bottom Line"    5e-06   5e-06    1 "Cap Bottom Line:Cap Bottom Line"       "Thick Metal Line"  "Cap Bottom Line"    5e-06   5e-06    1 "Plated Metal Line:Plated Metal Line"   "Thick Metal Line"  "Cap Bottom Line"    5e-06   5e-06    1 "Thick Metal Line:Plated Metal Line"    "Thick Metal Line"  "Cap Bottom Line"    5e-06   5e-06    1 "Cap Bottom Line:Plated Metal Line"     "Cap Bottom Line"   "Thick Metal Line"   5e-06   5e-06    1 $CROSSOVER_RULES_END              

You only need to specify crossover rules when layers are in conflict. For the MMIC process, an intersection between Thick Metal Line and Cap Bottom Line is fine because these line types are on different layers. Note however that an intersection between a Plated Metal Line and either a Cap Bottom Line or Thick Metal Line requires crossover rules since the Plated Metal Line includes the layers used by the Cap Bottom Line and the Thick Metal Line.

The following example shows how the rule is implemented, starting with a figure of the lines with their routes before the net cleanup is performed.

Assuming there is sufficient space to insert the crossover segments and perform the pullbacks, you can insert the crossover segment shown in the following figure.

A feature of the command when working with just two lines is the ability to control by selection order, which line is selected as the over and under line. Changing the selection order for the lines allows you to control which line gets the crossover inserted. In this case, the vertical line is selected first and then the horizontal line. If this were reversed, the crossover is inserted in the horizontal line as shown in the following figure.

You can insert multiple crossovers if the line crosses a number of other lines, as shown in the following figure.

If there is sufficient space to insert crossover segments and perform pullbacks, then you can insert multiple crossover segments as shown in the following figure:

If the lines are too close, you can manually extend one to have two separate crossovers inserted.

Frequently with crossovers, one of the lines needs to be moved to retain connections or to make room for additional circuitry. If the move is not too significant, you can run the Net Cleanup command again on some routes to try to update the crossover location.

After shifting the lines, the crossover bridge is in the wrong location. If you select the two routes again and run the Net Cleanup command using the Insert crossovers option, the location of the crossover is updated to be at the intersection between the lines, as shown in the following figure:

Inserting Crossovers Incrementally

Incrementally adding crossovers provides a mechanism for suppressing the automatic update of existing crossovers when adding additional crossovers. Crossover updating is a useful feature, however sometimes it is better not to have any of the existing crossovers updated when attempting to insert additional crossovers. For example, the following figure shows a scenario where you are attempting to insert multiple crossovers between some lines and you want a specific orientation for each crossover.

For example, if you want to insert a crossover in the vertical line at the top intersection and a horizontal crossover in the lower intersection, because these are different orientations, you cannot select all the lines and precisely control the orientations at the intersections. You need to insert the crossovers by selecting the lines in pairs and running the Net Cleanup command for each intersection. To perform the insertion at the top intersection, you select the vertical line first and then the horizontal line, as shown in the following figure:

Next you run the Net Cleanup command, selecting Insert crossovers. This applies the crossover rules so that the crossover segment is inserted into the vertical line at the top intersection, as shown in the following figure.

In the next step you need to select the two lines that form the lower intersection, and because you want the crossover inserted horizontally, you select the horizontal line first. This may be a problem because the Net Cleanup command only considers intersections in the lines that are selected to be candidates for crossovers; the update behavior may remove the top crossover. For this step, you suppress the update behavior by telling the Net Cleanup command to add the crossover incrementally. Existing crossovers are not disturbed, and only the selected lines are considered for adding new crossovers. Here you select the lower horizontal line first, the vertical line second, and when running the Net Cleanup command, you also select the Add Crossovers Incrementally check box, as shown in the following figure:

When you run the Net Cleanup command, the crossover at the top is not disturbed and a new horizontal crossover is added to the bottom intersection, as shown in the following figure:

Here the lower crossover is inserted with a horizontal orientation, and the top one with a vertical orientation. This was accomplished by selecting the lines in pairs in a specific order, and when inserting the second one, by selecting the Add Crossovers Incrementally check box to suppress the update behavior on the vertical line.

3.7.10. Copying iNets

You can copy and paste routes. Select the routes to copy, choose Edit > Copy (or press Ctrl+C), or choose Edit > Paste (or press Ctrl+V) and then click where you want to paste the route.

When you paste a route, it belongs to the same iNet as the route from which you copied.

To associate the copied route with a different iNet, you can use either method previously described in "Associating and Disassociating iNets":

1. Position each copied route so it overlaps a connection of the new iNet with which you want to associate it, and choose Layout > Connect Net Shapes to associate all of them.

2. Select a route or rat line from the different iNet, Shift -select the copied route, and then right-click and choose Associate Net Route.

3.7.11. Simulating with iNets

iNets are included with electrical simulation through the extraction process in the AWR Design Environment platform. See "EM: Creating EM Structures with Extraction" for details on the extraction process.

The portion of the extraction process specific to iNets is their enablement for extraction. In a schematic, select the wire for an iNet, right-click and choose Edit Net Properties. In a layout, select any route of the iNet, right-click and choose Element Properties. Both of these commands open the Element Options dialog box. Click the Model Options tab and note the EM Extraction Options section. See "Element Options Dialog Box: (Distributed Line) Model Options Tab" for more information.

In this dialog box you can enable or disable iNets for extraction and also specify the extraction group to which they belong.

3.7.12. Additional iNet Commands and Options

The following sections describe additional iNet commands and options.

Net Highlight

Net highlight is a means to easily identify (in both the schematic and layout) all of the objects that exist for a single iNet, by using different colors to draw schematic wires and iNet routes.

In a schematic, select the wire for an iNet, right-click and choose Highlight On. In a layout, select any route of the iNet, right-click and choose Highlight On to open a Color dialog box and choose a highlight color.

The following figure shows the iNets in schematic and layout with the highlight color specified as orange.

Turn off the net highlight using the same mouse clicks on a schematic or layout, and choose Highlight Off.

Selecting All iNets

To select all iNets at one level of hierarchy:

1. View the entire layout by right-clicking and choosing View All.

2. Right-click and choose Restrict Selection.

3. Click the Check All button.

4. Clear the iNets check box.

5. Press Ctrl+A to select the entire layout.

Note that you need to view the entire layout because one of the selection filters is for "Object bounds exceeds view". If you want to zoom in and then select all, you should deselect this filter and then select all.

Repeat Command

When routing a complex net, the repeat command allows you to continue adding routes to an iNet after you finish a route. For example, if you route the iNet shown by the rat lines in the following figure,

the finished routing displays as follows:

Without the repeat command, you could add one horizontal route over the squares, then add five vertical routes hooking up to the horizontal route. For each vertical route, you would need to double-click the rat line to start the route. To route this example without the repeat command would take 29 mouse clicks.

With the repeat command, once you finish the horizontal route you can immediately start entering the vertical routes. To route this example using the repeat command takes only 20 mouse clicks.

The repeat command is not available by default, so you must configure it as a hotkey, toolbar item, or menu item. To configure this command as a toolbar or menu item, see "Customizing Toolbars and Menus". To configure this command as a hotkey, choose Tools > Hotkeys to display the Customize dialog box. In Categories, select Miscellaneous and in Commands choose CommandRepeatMode. In Press the new hotkeys, press the key or key-combo you want to use as the hotkey. The following example uses the R key for this command and applies the hotkey to the SchematicLayout group after you click Assign.

When you create iNet routes you can invoke this repeat command using the hotkey you set up. To exit repeat mode press the Esc key.

Colinear Points

iNets can easily connect to many layout pins with one segment. Colinear points refers to three or more points that are along a single line. For example, you can route the following layout objects with a single segment route.

Hierarchy

When using iNets in hierarchy, you must define your connection points in the schematic layout you are building. The best way to do this is to assign the RECT_PIN layout cell to your PORT or PORT_NAME elements, then you can route iNets to the port. The RECT_PIN layout cell can draw on any of the line types in your process. In the layout, you can edit the size of this layout cell by selecting the RECT_PIN, right-clicking, and choosing Shape Properties. Click the Parameters tab of the dialog box that displays.

Verifying Connectivity

Connectivity errors can occur for various reasons, including different iNets being routed across one another on the same layer, erroneously positioned polygon vertices that short iNets, completed nets or elements accidentally moved to cause open circuits. See "Connectivity Checking " for information on how to check for connectivity errors.

Current Density

Since iNets are both schematic and layout objects, the program can easily display the current and/or current density for each iNet. From your top level design, right-click the schematic name in the Project Browser and choose Add Annotation. In Measurement Type, choose Annotate and in Measurement, choose INET_I or INET_J. See AWR Microwave Office Measurement Catalog for setting details. The following figure shows a resistor between two iNets with the current density annotation turned on. Each iNet segment is 0.5 um wide.

The different colors of the annotation denote if an iNet is below (blue), near (purple), over (red) or extremely over (yellow) the current density limit set by the annotation. The annotation can also show the width of the iNet needed to pass the current density limit.

RC Equivalent

If the process you are using is properly configured, you can also display the total resistance and capacitance of each iNet. In the Project Browser, right-click the name of the schematic that contains iNets and choose Add Annotation to display the Add Annotation to the Schematic dialog box. In Measurement Type, choose Annotate and in Measurement choose INET_RC. See "Add/Edit Schematic/System Diagram/EM Structure Annotation Dialog Box "for more information about the options in this dialog box. The following figure shows an iNet with this annotation turned on.

These values are determined through calculations based on the stackup of the process, not from simulation results.

3.8. Routes

The "Electrical Net (iNet) Elements" section covered the details of creating and working with intelligent nets. There is a corresponding layout object called a route. It is similar in how you add and edit the route, but different in that it is not associated with a net from the schematic. Routes are layout objects only, and therefore have no electrical model when added to a schematic layout. You can set up routes with extraction so they can be EM simulated. Additionally, routes can be added directly in EM layout.

3.8.1. Adding Routes

You can add a route to a schematic or EM layout by choosing . The commands you use are the same as those used to draw iNets. Click to add a point of the route. Press Shift + Ctrl and scroll the mouse wheel to change the line type of the current route segment. Right-click to undo the last segment added. Double-click to end adding the route.

3.8.2. Adding Vias

Routes do not add vias between line types automatically, as shown in the following example. This layout is drawn as a simple route.

The 3D layout view shows clearly that there is no via between the different segments of the route.

To add the via, select the route, right-click and choose . An outline follows the cursor along the route segments. Cadence recommends adding vias only at the intersections where the line types change. Otherwise, the via can be difficult to select, because both the start and stop linetypes would be the same.

Click to place the via in the desired location. After adding the via to the intersection of the two segments, the 3D layout shows that the segments are connected.

After adding the via, double-click it to display drag handles that you can use to change its size.

Additionally, right-click on the via and choose to display the Via Properties dialog box where you can specify the size of the via as well as control the line types on each end of the via.

3.8.3. Preparing To Route

The default discontinuities and line widths are identical to using iNet routing. See "Preparing to Route" for details.

3.9. Placement Mirroring

Placement Mirroring allows mirroring of elements in both schematic and layout. When mirroring elements in a schematic, select the elements you want to mirror by choosing , then click inside the schematic window.

Mirroring of layout elements and iNets requires a vertical or horizontal symmetry line. For mirror placement in layout, all the layout elements and iNets must have identifiable pairs, and for each pair the corresponding schematic elements' ID must follow the naming convention. The required element ID naming convention for each pair is deviceName a, deviceName b. For example, in the following figure, one nmos is assigned ID=M1a and the other nmos is assigned ID=M1b. Similarly, one pmos is assigned ID=M2a and the other pmos is assigned ID=M2b. The ID must be unique to each pair and cannot be used more than once.

After the pair is identified, draw a symmetry line in the layout window by choosing .

Select the mirror devices, iNets, and symmetry line, and choose . The mirror pair along with the iNet is placed as shown in the following figure.

3.10. Shape/Layer Modifiers

Shape modifiers are layout objects that can manipulate shapes by various methods such as edge length, spacing, and Boolean operations. A shape modifier applies to one or more shapes in a layout. A layer modifier applies to all shapes on the selected layers. Typical applications for these modifiers include:

• Parameterizing an EM layout so the geometry can be swept to create a parameterized EM model (reference section) or parameterized EM layout such that when used in a subcircuit, it gets EM simulation for geometries requested (reference section). In this mode, these modifiers are used in EM layout. See "Parameterizing EM Structures" for details on parameterizing EM structures.

• Changing all shapes on specific layers that can be used with extraction and yield analysis to study effects of layers shifting or resizing during the manufacturing processes. In this mode, these modifiers are used in schematic layout. See "Extraction and Shape/Layer Modifiers" for more information

• Aligning or spacing shapes in a schematic layout when using layout items not associated with schematic models, which cannot snap together like layouts with schematic models.

NOTE: While shape modifiers act immediately on the layout they are operating on, to see the effects of layer modifiers you need to place the document in hierarchy and view it from the top level. If it is an EM layout, the geometry preview also shows the effects of the layer modifiers.

The available shape modifiers include:

• Edge

• Point Stretch

• Width

• Radius

• Ellipse Size

• Array Modifier

• Spacing Modifier

• Polar Spacing Modifier

• Stretch Area Modifier

• Control Point Modifier

The available layer modifiers include:

• Layer Offset

• Layer Resize

• Layer Boolean

• Layer Corner

• Shape Pre-processing

3.10.1. Adding Modifiers

From an EM layout or a schematic layout, choose . The enabled modifiers depend on the type(s) of layout object(s) currently selected. Shape modifiers are not available in the Artwork Cell Editor. The following sections provide detailed information about each modifier.

The layout for the shape/layer modifiers uses the Dimension line layer for the shape and the text.

The default modifier size and font size are determined by the Height specified on the Layout Options dialog box Layout Font tab (choose ). See "Layout Options Dialog Box: Layout Font Tab " for details.

Edge Modifier

To add an Edge modifier:

1. Select one or more shapes in your layout and choose .

2. Move the cursor over the edge of any selected shape. The modifier displays on the edge closest to the cursor position. You can only add this modifier to shapes not associated with a schematic element. For example, if you have an MLIN in a schematic, you cannot add this modifier to the layout for this element.

3. Click to add the modifier to that edge.

4. Move the cursor to the initial location of the text and click again to finish adding the modifier, as shown in the following figure.

   

   The edge of the modifier that draws a square is the end that remains fixed if the edge length changes.

5. Right-click the modifier (not the modifier text) and choose to display the Properties dialog box (see "Properties Dialog Box: Edge Modifier " for details).

6. Change the FE (Fixed End) parameter to "Left", "Right", or "Center".

Point Stretch Modifier

To add a Point Stretch modifier:

1. Select one or more shapes in your layout and choose .

2. Move the cursor over the edge of any selected shape. The modifier displays on the edge closest to the cursor position. You can only add this modifier to shapes not associated with a schematic element. For example, if you have an MLIN in a schematic, you cannot add this modifier to the layout for this element.

3. Click to add the modifier to that edge.

4. Move the cursor to the initial location of the text and click again to finish adding the modifier, as shown in the following figure.

   

   The edge of the modifier that draws a square is the end that remains fixed if the spacing changes.

5. Right-click the modifier (not the modifier text) and choose to display the Properties dialog box (see "Properties Dialog Box: Point Stretch Modifier " for details).

6. Change the FE (Fixed End) parameter to "Left", "Right", or "Center".

Width Modifier

To add a Width modifier:

1. Select one or more paths or iNets in your layout and choose .

2. Move the cursor over any of the selected paths or iNets. The modifier displays at the location closest to the cursor position.

3. Click to add the modifier to that location of the path.

4. Move the cursor to the initial location of the text and click again to finish adding the modifier, as shown in the following figure.

   

   When adding a path modifier to an iNet, you can control the width of each individual segment.

5. Right-click the modifier (not the modifier text) and choose to display the Properties dialog box (see "Properties Dialog Box: Width Modifier " for details).

6. Change the WT (Width Type) parameter to "Segment". If each modifier on an iNet is set to "Segment", then you can specify different widths. If any path modifiers are set to "Path", then all modifiers use the width of that modifier. The following figure shows a multi-segment iNet with different widths.

   

Radius Modifier

To add a Radius modifier:

1. Select one or more perfect circles in your layout and choose .

2. Move the cursor over any of the selected circles. The modifier displays at the location closest to the cursor position.

3. Click to add the modifier to that circle.

4. Move the cursor to the initial location of the text and click again to finish adding the modifier, as shown in the following figure.

   

   See "Properties Dialog Box: Radius Modifier " for details on the settings for this shape modifier.

Ellipse Size Modifier

To add an Ellipse Size modifier:

1. Select one or more ellipses in your layout and choose .

2. Move the cursor over any of the selected ellipses. The modifier displays at the location closest to the cursor position.

3. Click to add the modifier to that ellipse.

4. Move the cursor to the initial location of the text and click again to finish adding the modifier, as shown in the following figure.

   

   See "Properties Dialog Box: Ellipse Size Modifier " for details on the settings for this shape modifier.

Array Modifier

To add an Array modifier:

1. Select one or more shapes in your layout and choose .

2. Click to add the modifier to any location in the layout, as shown in the following figure. This modifier does not snap to any shapes, and the text displays above the modifier.

   

   See "Properties Dialog Box: Array Modifier " for details on the settings for this shape modifier.

Spacing Modifier

To add a Spacing modifier:

1. Select two or more shapes in your layout and choose .

2. Move the cursor over any of the selected shapes. The modifier displays at the location closest to the cursor position.

3. Click to add the first point of the spacing modifier.

4. Move the cursor over another of the selected shapes. The modifier displays at the location closest to the cursor position. By default the modifier draws in orthogonal mode and the furthest distance (x or y). Press the Ctrl key to toggle from horizontal to vertical or vertical to horizontal, and the Shift key to allow any angle.

5. Click to add the second point of the spacing modifier.

6. Move the cursor to the initial location of the text and click again to finish adding the modifier, as shown in the following figure.

   

   The edge of the modifier that draws a square is the end that remains fixed if the spacing changes.

7. Right-click the modifier (not the modifier text) and choose to display the Properties dialog box (see "Properties Dialog Box: Spacing Modifier " for details).

8. Change the FE (Fixed End) parameter to "Left", "Right", or "Center".

Polar Spacing Modifier

To add a Polar Spacing modifier:

1. Select two or more shapes in your layout and choose .

2. Move the cursor over any of the selected shapes. The modifier displays at the location closest to the cursor position.

3. Click to add the first point of the spacing modifier.

4. Move the cursor over another of the selected shapes. The modifier displays at the location closest to the cursor position.

5. Click to add the second point of the spacing modifier.

6. Move the cursor to the initial location of the text and click again to finish adding the modifier, as shown in the following figure.

   

   The edge of the modifier that draws an angle indicator is the end that remains fixed if the spacing or angle parameter change.

7. Right-click the modifier (not the modifier text) and choose to display the Properties dialog box (see "Properties Dialog Box: Polar Spacing Modifier " for details).

Stretch Area Modifier

To add a Stretch Area modifier:

1. Choose .

2. Click on the layout to draw a polygon, one click per point. Double-click to finish drawing the polygon.

3. Move the cursor to the initial location of the text and click again to finish adding the modifier, as shown in the following figure.

   

   See "Properties Dialog Box: Stretch Area Modifier " for details on the settings for this shape modifier.

Control Point Modifier

To add a Control Point modifier:

1. Choose .

2. Click on the layout to draw a polygon, one click per point. Double-click to finish drawing the polygon.

3. Move the cursor to the initial location of the text and click again to finish adding the modifier, as shown in the following figure.

   

   See "Properties Dialog Box: Control Point Modifier " for details on the settings for this shape modifier.

Layer Offset Modifier

To add a Layer Offset modifier:

1. Choose .

2. Click to add the modifier to any location in the layout, as shown in the following figure. This modifier does not snap to any shapes, and the text displays above the modifier.

   

   See "Properties Dialog Box: Layer Offset Modifier " for details on the settings for this shape modifier.

Layer Resize Modifier

To add a Layer Resize modifier:

1. Choose .

2. Click to add the modifier to any location in the layout, as shown in the following figure. This modifier does not snap to any shapes and the text displays above the modifier.

   

   See "Properties Dialog Box: Layer Resize Modifier " for details on the settings for this shape modifier.

Layer Boolean Modifier

To add a Layer Boolean modifier:

1. Choose .

2. Click to add the modifier to any location in the layout, as shown in the following figure. This modifier does not snap to any shapes and the text displays above the modifier.

   

   See "Properties Dialog Box: Layer Boolean Modifier " for details on the settings for this shape modifier.

Layer Corner Modifier

To add a Layer Corner modifier:

1. Choose .

2. Click to add the modifier to any location in the layout, as shown in the following figure. This modifier does not snap to any shapes and the text displays above the modifier.

   

   See "Properties Dialog Box: Layer Corner Modifier " for details on the settings for this shape modifier.

Shape Preprocessor (SPP) Modifier

To add an SPP modifier:

1. Choose .

2. Click to add the modifier to any location in the layout, as shown in the following figure. This modifier does not snap to any shapes and the text displays above the modifier.

   

   See "Properties Dialog Box: Shape Preprocessor (SPP) Modifier " for details on the settings for this shape modifier.

3.10.2. Layout Modifier Order

The order in which layout modifiers operate can change how a structure's parameterization is performed. Each modifier type has a given priority as well as an order. In general, the order is determined by the order in which you add the modifiers, and the priority of the modifier. You can modify the order of operation in the Layer Modifiers dialog box by choosing . See "Layer Modifiers Dialog Box: Shape Modifiers tab " for dialog box details. You should only re-order modifiers within a given priority. Moving a lower priority modifier above a higher priority modifier may lead to an incorrect layout and prompt a warning message to display.

Layout modifiers are categorized by three priorities, listed as follows from high to low priority.

• Priority 1: Simple shape modifiers (Edge, Width, Circle Radius, Ellipse Size, Array, Spacing)

• Priority 2: Shape Modification modifiers (Stretch Area)

• Priority 3: Global Layer Modifiers (Layer Offset, Layer Resize, Layer Boolean)

You should always order Priority 1 modifiers before priority 2 modifiers. Priority 3 modifiers are always applied last because priority 2 and priority 3 modifiers flatten shapes. Once a shape is flattened, priority 1 modifiers may not have a shape on which to operate. For example, if the Stretch Area modifier is applied to a path before a Width modifier, the path is flattened into a polygon, so it no longer exists for the Width modifier to operate on.

3.10.3. Editing Modifiers

You can edit individual modifiers just as you do model parameters. You can set up each parameter for optimization and yield analysis, and set values to variables. For individual modifier details, see "Adding Modifiers".

To enable or disable a single modifier, right-click the modifier and choose . To change the enable state of several modifiers at once you can select or clear the Enabled column check box for each in the Layer Modifiers dialog box (choose ). See "Layer Modifiers Dialog Box: Shape Modifiers tab " for dialog box details.

Click and drag a modifier to move it in a schematic. Moving modifiers that are attached to shapes may not be desirable. You can right-click an edge modifier and choose to move the modifier back to its associated shape.

3.10.4. Debugging Modifiers

You can identify which shapes belong to a modifier in a layout. Attributes of the shapes that are directly connected to the modifier (such as a shape, a vertex, or an edge) display in light blue, and any additional associated shapes are outlined in a dotted green shape. The following figure shows a simple Spacing modifier with the modifier selected.

The text and arrows of the modifier are yellow because they are selected. The vertices of the two shapes that are being spaced display with a light blue square, and the remaining shapes being spaced are outlined in a dotted green shape.

When building up a parameterized layout, you will want to view the results of the modifiers. All of the shape modifiers directly change the layout except the Stretch Area modifier. None of the layer modifiers directly change the layout. For the shape modifiers and the Stretch Area modifiers, you need to use another technique to see the effects of the modifiers. If you are working in an EM layout, right-click the EM document and choose to see the modified geometry. If you are working in a schematic layout, you should use the schematic you are working on as a subcircuit in another schematic, then view the layout for the schematic that is using the parameterized layout through hierarchy.

When a parameterized subcircuit schematic or EM document utilizes many modifiers, it can be difficult to understand the interactions between the modifiers. To see the effects of each modifier one by one, select the subcircuit instance in the Layout editor, right-click and choose to display the Debug Cell Instance dialog box. See "Debug Cell Instance Dialog Box" for details on using the interactive debugger.

3.11. Via Fill and Via Fence

The Via Fill feature provides support for via stitching in a layout design. Via stitching is used to tie together layers in specific areas with a large number of vias arranged in a grid to provide a strong vertical connection between layers. The Via Fencing feature allows the creation of lines of vias to separate different regions and provide isolation between parts of the design.

3.11.1. Setting Up the Via Fill/Fence Operation

To use the Via Fill and Via Fencing features you must include a cell library that defines the via cells to use in the Fill or Fence operation. For information on importing a cell library, see "Loading Artwork Cell Libraries". For information on creating a cell library, see "Creating Artwork Cell Libraries".

3.11.2. Via Fill

After you import the via cells you can begin using the Via Fill operation to add vias to shapes in layout designs. Open a design that contains the regions you want to fill. To perform the operation you must first define the region to fill by creating a polygon that covers the region. For many designs this region may already exist. To fill a region in the layout, select the polygon(s) to fill with vias and choose Draw > Add Shapes > Via Fill to display the Via Fill dialog box used for defining the fill.

Running the Via Fill Operation

Select the shapes to fill and then choose Draw > Add Shapes > Via Fill to open the Via Fill dialog box. For more information on Via Fill options, see "Via Fill Dialog Box ".

After specifying spacing, offset, and clearance values, click OK to fill the regions with the selected via cell.

If the resulting fill pattern is not what you want, you can Undo (press Ctrl + Z) the operation and remove the inserted vias. Next, reselect the polygon and restart the Via Fill command by choosing Draw > Add Shapes > Via Fill. The Via Fill dialog box remembers all the settings, allowing you to adjust the values for a more favorable outcome.

Via Fill Presets

You can use process defaults or presets for the Via Fill command. By adding entries to the Layer Process File (LPF), you can establish default settings for Via Fill operations so that the spacing values are auto-filled with values that are correct for a particular process. If the process file has these entries, you can enter standard Via Fill settings in the Via Fill dialog box by selecting one entry in the Process Defaults drop-down list.

For Via Fill, the entries in the LPF are defined as follows:

!--- Via Fill Entries Process Presets ---- $VIA_FILL_ENTRIES_BEGIN      <Entry Name> <Lib Name> <Cell Name> <Spacing Type> <Spacing X> <Spacing Y> <Offset X> <Offset Y> <Clearance> <Stagger>  $VIA_FILL_ENTRIES_END

An example entry would be as follows:

!--- Via Fill Entries Process Presets ---- $VIA_FILL_ENTRIES_BEGIN  "Via1" "ViaLib"      "ViaCell"     0      15e-6  15e-6  0.0           0.0           5e-6       0  "Via2"  "ViaLib2"    "ViaCell2"    0      10e-6 10e-6  0.0           0.0           15e-6       0  $VIA_FILL_ENTRIES_END

After the LPF with the Via Fill entries is imported into the project, the settings are available for use in the Via Fill dialog box.

3.11.3. Via Fence

After you import the via cells you can begin using the Via Fence operation to add vias to shapes in layout designs. Open a design that contains the regions you want to fill. To perform the operation you must first define the region to fill by creating a polygon that covers the region. For many designs this region may already exist. To fence a region in the layout, select the polygon(s) to fill with vias and choose Draw > Add Shapes > Via Fence to display the Via Fence dialog box used for defining the fence.

Running the Via Fence Operation

Select the shapes to fence and then choose Draw> Add Shapes > Via Fence to open the Via Fence dialog box. For more information on Via Fence options, see "Via Fence Dialog Box ".

After the Via Fence settings are correct, click OK to fence the shape with the selected via cell.

If the resulting fence pattern is not what you want, you can Undo (press Ctrl + Z) the operation and remove the inserted vias. Next, reselect the polygon and restart the Via Fence command by choosing Draw > Add Shapes > Via Fence. The Via Fence dialog box remembers all the settings, allowing you to adjust the values for a more favorable outcome.

Via Fence Presets

Like Via Fill, Via Fence can use process defaults or presets specified in the LPF. By adding entries to the LPF, you can establish default settings for Via Fence operations so that the fence option values are auto-filled with values that are correct for a particular process. If the process file has these entries, you can enter standard Via Fence settings into the Via Fence dialog box by selecting one entry in the top Process Defaults drop-down list.

For Via Fence, the entries in the LPF are defined as follows:

!--- Via Fence Entries Process Presets ---- $VIA_FENCE_ENTRIES_BEGIN      <Entry Name> <Lib Name> <Cell Name> Spacing Type> <Spacing> <Offset X> <Offset Y> <Merge Perimeters> <Perimeter Oversize> <Open Ends>  $VIA_FENCE_ENTRIES_END

An example entry would be as follows:

!--- Via Fence Entries Process Presets ---- $VIA_FENCE_ENTRIES_BEGIN      "Via1" "ViaLib"      "ViaCell"     0      15e-6  0.0           0.0         0          0.0        1      "Via2"  "ViaLib2"    "ViaCell2"    0      10e-6  0.0           0.0         0          0.0        1  $VIA_FENCE_ENTRIES_END

After the LPF with the Via Fence entries is imported into the project, the settings are available for use in the Via Fence dialog box.

3.12. Artwork Cells

Artwork cells are layout cells that read in as standard CAD drawing cells or are created from scratch using the Artwork Cell Editor. AWR Microwave Office software can read in GDSII-based or DXF-based drawing cells. The GDSII- and DXF-based layout cells are stored as native GDSII or DXF, so any layout cells created in the AWR Microwave Office program can be read and edited in any layout software that supports GDSII or DXF.

An artwork cell needs to have connection points defined that correspond to the nodes of the electrical component. These connection points are called "faces" in AWR Microwave Office software. The orientation of the face is used to determine to which side of the face adjacent layout cells snap.

To draw an artwork cell with new layers you must first add the drawing layers and the model layer mapping (see "Drawing Layers and Model Layer Mapping"). To use the layers in GDSII artwork cells, make sure you use proper GDSII layer convention (see"Drawing Layers and Model Layer Mapping").

3.12.1. Editing Artwork Cells

You can edit artwork cells by double-clicking the artwork cell in the upper pane of the Layout Manager. The artwork cell opens in the Artwork Cell Editor. You can use the Cell Port tool to add a face to the cell by choosing Draw > Cell Port or by clicking the Cell Port button on the Draw Tools toolbar. You can snap a cell port to a polygon edge by pressing the Ctrl key while placing the port. You can create artwork cells with multiple faces for each connection point by assigning the same port number to two or more faces in the Artwork Cell Editor. To change the port numbers, select the cell port in the editor, right-click, and choose Shape Properties. The Properties dialog box displays with a Cell Port tab and allows you to enter the Port Number and port Connection Type.

You must ensure that there is at least one port for each consecutive number starting from 1. For example, it is not valid to have a port 1 and a port 3 without having a port 2. For more information, see "Face and Snap to".

If you make any edits to the artwork cell, you must save the cell into the library before any of the references to the layout cell are updated in the project. Unsaved edits are lost when you close the project. Choose Layout > Update Cell Edits to save modified artwork cells.

Creating an Area Pin

Cell ports allow connections only along a linear face and over a specified area. To create an area pin, select a structure in the Artwork Cell Editor and choose Draw > Create Pin. The entire area of the shape selected becomes the area pin. You can also choose Draw > Cell Pin to free-hand draw the area for a pin. The pin has a default side for connections shown by the arrow of the pin. To move the location of the default side of the area pin, double-click the area pin and click on the drag handle on the tip of the default side arrow to drag it to the desired default side.

3.12.2. Stretching Artwork Cells

The Cell Stretcher allows you to create parameterized cells graphically by stretching cells instead of creating them by programming in C++.

To access Cell Stretcher properties, double-click a cell in the GDS library to display it, then click the Cell Stretcher button on the Draw Tools toolbar or choose Draw > Cell Stretcher. Draw a horizontal or vertical break line at the point you want to stretch the cell, then click to set the line. Select the line and then right-click to display the Properties dialog box.

In the Layout Options dialog box on the Gds Cell Stretcher tab, you can specify the Multiplier, the Parameter in the element to which the manipulated cell connects, and the Offset value to create an equation that solves for the distance the Delta point moves in the specified Direction. You can also specify the Minimum and Maximum distances a point may move and the Arrow height of the displayed arrow. The parameter property is the name of the element's electrical parameter used in the stretching equation. For example, the parameter for a resistor is R, a capacitor C, or the electrical length of an ideal transmission line EL.

Consider a resistor whose length is varied to adjust the resistance. The general relation for the resistance of a thin-film resistor is

R=RsL/W

(3.1)

where R_s is the resistance in ohms per square, L is the length, and W is the width. For a stretched resistor, this is simply

R=Rs(ΔL+L0)/W

(3.2)

where L₀ is the unstretched length and ΔL is the extension. You need ΔL, however, as a function of resistance, R; this is easily determined from the above equation:

ΔL=(W/Rs)R-L0

(3.3)

The Multiplier value is W/Rs and the Offset value is L ₀. If both sides are stretched (Both is the Direction), this value of ΔL is applied to both halves of the stretched cell. Thus, the values entered for the multiplier and offset should be halved.

Note that quantities in the above equations must use MKS units, in this case meters and ohms. If a capacitor is stretched, the units are meters and Farads. Also, the cell must be associated with a specific circuit element in either a circuit or a library for the Cell Stretcher to work.

3.12.3. Saving Artwork Cells

Saving the project or closing the artwork cell window prompts you to save the artwork cell.

When saving GDSII cell library edits, the GDSII file is saved directly using the GDSII layers used in the artwork cell library.

When saving DXF cell library edits, the DXF file is saved through the first DXF export mapping table defined in the software. See "Exporting the Layout " for more information. If you do not have a DXF export mapping table defined, an "Unable to find export mapping" error message displays.

To correct this, add a DXF export mapping table, ensure all of the layers are selected for Write Layer, and then save the cell edits again.

Generally, you only need to add a DXF export mapping table. There are special cases where you may be using special model layer names (see "Drawing Layers and Model Layer Mapping" for more information). In this case, when you add a DXF export mapping table, you must set up the Drawing Layers used to display the layers in the DXF artwork cell to export to the right model layer names (the same model layers used in the artwork cell), or the cell updates do not work correctly.

3.12.4. Flattening Parameterized Layout Cells

The Cell Flattening feature allows you to flatten a parameterized layout cell to access and change it at the polygon level. You can use this feature to change a single instance of a library cell or make minor changes to an existing cell without recreating it entirely.

To flatten a cell, in the Layout View, select a cell and choose Draw > Modify Shapes > Flatten Shape. Select the shape you want to alter and then change its properties, position, or dimensions.

3.12.5. Creating Artwork Cell Libraries

You can create artwork cell libraries in a project by selecting Cell Libraries in the upper pane of the Layout Manager, right-clicking, and choosing New GDSII Library or New DXF Library. After you create a library you can create a new artwork cell by right-clicking the library in the Layout Manager and choosing New Layout Cell. The artwork cell name must be unique across all of the libraries open in the project.

You can also create a new layout cell by copying an existing artwork cell. Right-click the artwork cell and choose Copy Layout Cell to display the Copy Cell dialog box. If the cell is hierarchical you can choose Copy Hierarchy or Flatten new cell. Specify the Library name to which you want to copy the cell.

3.12.6. Saving Artwork Cell Libraries

You can save an artwork cell library as a GDSII file by right-clicking the library in the upper pane of the Layout Manager and choosing Export Cell Library. If there are any cell references in the library that reference cells from other libraries, these cells are not written out from the library.

GDSII libraries are saved directly to the GDSII model layer names used in the artwork cell library.

There are a couple of different ways to save a DXF library. If there is a DXF export mapping table defined, the layers are exported to the DXF layer name in the mapping table whether the Write Layer field is selected or not. If more than one DXF table is defined, the software uses only the first one. If there is no DXF export mapping table defined, the layers are written to the drawing layers used to display the layers in the artwork cell.

3.12.7. Loading Artwork Cell Libraries

You can import artwork cell libraries from a GDSII file or DXF file (DXF libraries can only contain one layout cell per library) by selecting the Cell Libraries node in the upper pane of the Layout Manager window, right-clicking, and choosing Import GDSII Library or Import DXF Library. You can also link to the libraries by choosing Link To GDSII library. When the library is linked, any changes made to cells are saved in the original location of the library. For imported libraries, the changes made to cells are saved in the project only, unless the library is exported. After you load a library, you can add new artwork cells to it by right-clicking the library in the Layout Manager and choosing New Layout Cell.

Typically, layout cells for parameterized electrical elements are created from the element's electrical parameters (a microstrip's length and width determine the layout of the element). It is possible to set the layout for a non-parameterized element (for example, a capacitor) to have a layout representation of a parameterized cell (for example, a microstrip layout representation). In this case, there is missing information in the electrical element's parameters to create the layout cell (the capacitor only has a capacitance value as its electrical parameter, therefore the layout cell does not have the length and width parameters needed to draw the layout). When this occurs, the length and width of the layout cell become a property of the layout cell. You can view and edit the value of the layout cell parameters on the Parameters tab of the Cell Properties dialog box by selecting the layout cell in the Layout View and choosing Layout > Edit Shape Properties, or right-clicking the layout cell and choosing Shape Properties.

When importing a GDSII or DXF library, the following message may display. This warning commonly displays when placing a part from a vendor library into a schematic.

It indicates that the project does not have corresponding drawing layer names for the layer names in the file, so the program automatically creates these drawing layers. Click OK to accept this auto-generation.

3.12.8. Assigning Artwork Cells to Layout of Schematic Elements

Artwork cells are created to give a user-specified layout to any element. After an artwork cell is created and its cell ports are attached, you can assign it to an electrical element. You can change the layout for any element by right-clicking the element in the schematic window and choosing Properties. Click the Layout tab on the Element Options dialog box and select the library name in Library Name. A list of all available layout cells with the same number of ports as the specified Number of nodes displays. Clicking on one of the available cells shows a preview of the layout. A compatible cell with an "*" at the end of its name specifies a layout cell built into AWR Microwave Office software.

After disassociating a layout cell with an element in a schematic's layout (right-click the cell in the layout and choose ) you can re-associate the cell with the same or another element in the schematic by right-clicking the cell in the layout and choosing . The "Associate Cell Dialog Box " displays with a list of the elements in the schematic that are not associated and that have the correct number of ports to be associated with the cell. After selecting the desired element, click OK. The color of the element in the schematic changes from blue to purple to indicate that it has an associated layout cell.

3.13. Layout Cell Properties

Circuit components that are connected in the schematic are connected in the Layout View. The schematic connectivity controls the connectivity in the layout. All new circuit components or connections must be added in the Schematic View. Circuit components that do not have layout cells result in disconnected layout objects as shown in the following figure. When you move layout objects, the connections to other layout objects are shown as connection lines between the objects. To "snap" the shapes together (eliminate the connection lines by moving the shapes) choose or click the Snap Together button on the toolbar. Snap Together snaps together all selected objects and objects that are connected to them.

The AWR Microwave Office layout tool provides options to specify what each layout cell looks like and how cells connect together. These options are stored in the properties of each layout cell. The properties are edited by selecting the layout cell in the layout window and choosing Layout > Edit Shape Properties or by right-clicking on the layout cell and choosing Shape Properties to display the "Cell Options Dialog Box: Layout Tab ".

3.13.1. Cell Options

The Cell Options dialog box Layout tab allows you to configure how parameterized cells are drawn, the orientation of every layout cell, and how layout cells interact spatially with other layout cells. You can also create user-defined parameterized cells which support configuration from the LPF files. The following sections provide details about the options available in the "Cell Options Dialog Box: Layout Tab ".

Line Type

When layout cells have configurable layers, you can specify the line type. Each of the line types created in the LPF file are available options. Selecting the line type for the layout cell causes the cell to use that line type when drawing the cell.

• Configurable layers: The configurable cells support multi-layer processes (such as when a transmission line is created from two layers of metal with an etch layer between the metal layers).

• Multi-layer layout cell definition: The following example is for a multi-layer transmission line. The W and L dimensions represent the width and length of the transmission line that is used to model the electrical behavior of the component. Any shapes that are drawn larger or smaller than the L x W transmission line are for layout only and do not affect the electrical simulation.

  

• Multiple line type definition: The LPF file allows the definition of multiple line types. A line type describes the layers used for a single transmission line. For example, a plated metal line that requires two metal layers and an etch layer can be configured as a line type in the LPF file. The following shows an LPF entry for four different line types:

                $LINE_TYPE_BEGIN "Plated Line"        !Name is to identify the line 	!Layer     Layer_offset  minWidth   flags 	"Metal1"       0          2e-6      0  0 	"Via2"         -0.5e-6    3e-6      0  0 	"Metal2"       0.5e-6     2e-6      0  0 	$LINE_TYPE_END  	$LINE_TYPE_BEGIN "Metal0 Line" 	"Metal0"       0          2e-6      0  0 	$LINE_TYPE_END  	$LINE_TYPE_BEGIN "Metal1 Line" 	"Metal1"       0          2e-6      0  0 	$LINE_TYPE_END  	$LINE_TYPE_BEGIN "Metal2 Line" 	"Metal2"       0          2e-6      0  0 	$LINE_TYPE_END

"Layer" is the name of the model layer. "Layer_offset" is the offset used for drawing the layer as shown previously. The "minWidth" value is used for checking design rule violations. The flags can be used to pass specialized information to the layout cells.

The previous LPF file defines four different types of lines (Plated, Metal0, Metal1 and Metal 2). A configurable cell (such as a microstrip line cell) can select which line type is used to draw the cell in the layout. If the "Plated Line" type is selected, then the microstrip line is drawn using three layers (Metal1, Via2 and Metal2) where Via2 is drawn inset by 0.5um and Metal2 is drawn outset by 0.5um. If the "Metal0 Line" type is selected, the line draws on a single layer (Metal0). The following figure shows a plated line.

The multi-layer layout cells are designed to interlock so that the shapes on each layer join correctly. The following figure shows a layout cell for a microstrip tee. The tee on the top is pulled apart to show how the interlocked cells are drawn.

Line Type Definitions

Line type definitions are automatically linked with an identically named substrate definition element (for example, MSUB). When the line type of an element is changed, its MSUB in the schematic automatically updates to the linked MSUB. When an element's MSUB parameter changes, if the name of the MSUB element is identical to the line type name defined in the LPF, the element layout is automatically updated to the linked line type. Since MSUB names cannot include spaces, you cannot link to a substrate a line type that has spaces in its name. To use existing line types with spaces in their names, you must export the LPF, edit it to change the line type names (remove or replace the spaces and match the substrate names), and import it again. NOTE: Do not change the order of the line types when modifying the LPF of an existing project. Older projects do not change automatically. When you open a project older than v12, elements retain their MSUB and line type, even if they are mismatched, and matching versions are available. The change occurs when an element's substrate or line type is changed.

Layer Mapping

Layer mapping lists all of the mapping tables available for the layout cell to use. The available layer mappings are read from the LPF file or added from the drawing layer Options dialog box (choose Options > Drawing Layers). For more information on layer mapping, see "Drawing Layers and Model Layer Mapping".

Flip Cell

You can flip cells about the horizontal axis by selecting the Flipped check box.

Orientation Angle

You can set the rotation of a cell by specifying the Angle in degrees. You can also change the orientation angle by rotating the cell with the mouse, however when doing so only angles allowed by the current rotation snap are allowed. When entering the rotation angle manually, the rotation snap is overridden.

Freeze Position

You can freeze the cell position to prevent it from being moved with the mouse or by coordinate entry. Frozen cells, like anchored cells, do not move when the layout is snapped together, but are editable when you double-click them. Frozen cells exhibit a weaker form of snapping than other cells, which leads to somewhat different behaviors than anchored cells. With anchored cells, adjacent layout cells attempt to re-adjust so that they snap to the anchored cell. With frozen cells, the adjacent cells do not always try to snap to the frozen cell when the layout is snapped together. To make another layout cell snap to a frozen cell, try selecting the frozen cell and then snap the layout together. There can be multiple frozen cells within a layout.

Use For Anchor

You can "anchor" one cell within a layout. The anchored cell stays in a fixed location, and all other cells adjust themselves accordingly when circuit parameters are changed and objects are resized. You can anchor multiple objects per schematic. Each anchored object stays in a fixed position when the layout is snapped together. Unlike the Freeze operation, you can move anchored cells with the mouse (or with coordinate entry). Selecting both the Use for anchor and Freeze check boxes causes the cell to be used as an unmovable anchored cell. Only the anchored layout objects at the top level of a hierarchy are used to anchor the layout cells.

Stretch to Fit

You can use this option with LINE elements (for example, MLIN and SLIN), the TRACE elements (for example MTRACE or MCTRACE), and iNets to automatically stretch the elements to fit between two other cells when the layout is snapped together.

3.13.2. Face Properties

The connections between the layout cells in the Layout View are defined by faces. A layout cell face is a line segment that defines how other cells should connect to the cell when they are snapped together.

The Cell Options dialog box Faces tab allows you to configure how faces of layout cells snap together (including multi-layer layout cells), assign layout face connectivity for cells that have multiple layout faces, and specify offsets when faces connect together. This section provides details about the options available in the "Cell Options Dialog Box: Faces Tab ".

The following figure shows the faces for two simple transmission lines. When the two layout shapes are snapped together, the centers of the two faces coincide.

The layout cell faces have properties you can set to specify how the faces connect to each other. The default is for all faces to connect "center to center". Other options include top- or bottom-justified connections. The following figure shows two transmission lines snapped together with the face properties set to "top" justification.

The "variable" justification setting allows elements to connect anywhere along the face (rather than the center, top, bottom, or specified offset from center). If any part of this face overlaps the adjacent face, the elements are considered connected. You can specify all face settings as "variable" by default by selecting Variable alignment as the Default Face Justification on the Layout tab of the Environment Options dialog box. Note that this setting only applies to elements placed in a schematic after this setting is made.

Face and Snap to

For most layout cells, there is a connection face for each node of the electrical component with which the cell is associated. Layout cells can also be created with multiple physical connection points (faces) for a single electrical node by adding additional faces using the same node number for more than one face. For multiple faces with the same node number, the first face added is the default connection point. The following schematic illustrates multiple faces using a single node. Transmission line TL1 and transmission line TL2 are both connected to the FET node 3.

As shown in the following figure, an artwork cell is used for the layout cell of the FET in this schematic. The layout cell for the FET has four faces that correspond to three nodes. You can modify the layout face node numbers by selecting an element connected to that node, right-clicking, and choosing Shape Properties. The Properties dialog box displays with a Cell Port tab and allows you to enter the Port Number and port Connection Type. The node numbers are shown on the face objects in the following figure.

The Layout View for the FET schematic is shown in the following figure. The transmission lines connected to the FET are pulled away from the FET to make the connections easier to see. When there is more than one face for a node, the face is identified in the Cell Property dialog box using a letter after the number. For the FET example, there is a face 3a and a face 3b. The transmission line TL1 is connected to face 3a and transmission line TL2 is connected to 3b.

When there are three items connected to a single node as shown (and there are two layout faces for one of the nodes) then there are several different possible connections that can be made between the connected layout cells. In the example shown, either transmission line could be connected to either face, or the two transmission lines could have their faces connected to each other. Since it is generally impossible to detect what the correct connection should be, you must specify the desired connection using the Snap to operation on the Faces tab of the Cell Options dialog box (unless the default gives the desired connection). Snap to is used to specify which face snaps to which other face. You first select in Face the face for which you want to set properties. The selected face displays in blue in the layout window. After selecting the desired face, you select a Snap to face. The Snap to face displays in red in the layout window. You should do this for both faces with the same node number. In the following example the face on TL1 is snapped to 3a and 3b is snapped to TL2.

An alternate method of element connection is to just move the elements around in layout and allow the software to find the closest face connection. To disable this ability you can clear the Default connection to closest face check box in the Layout Options dialog box. Instead of completing all of the face assignments as previously described, you could move TL1 and TL2 to opposite sides of the device artwork to allow the connection points to be automatically determined.

Cells that have multiple faces with the same node number are also used to provide alternate connection points for a layout cell. An example for a thin film capacitor is shown in the following figure. Node 1 has faces 1a and 1b that can be used as connection points.

Snap To Adjacent

This feature enables the snapping feature for the connected faces. When the layout is snapped together, the two faces line up with no space between them. If the faces are separated and this feature is active, a connection line (typically red) displays between them. When the layout is snapped together the faces line up and the connection line disappears. If this feature is not active, the line between the faces is gray. When the layout is snapped together the faces do not snap together and the gray line remains.

Multi-layer Drawing

• There are several options used to configure how the multi-layer cells draw at the connection faces. The following figure illustrates the options where the left ends of the lines are drawn using "Inside", "Outside", and "Flush".

  

• Air bridge: This feature specifies that a line face attaches to an air bridge. Many times in MMIC designs, line ends attach to air bridge elements. When this occurs, the various layers to build the line need to be stretched and spaced for attachment. Air bridges are user-defined parameterized cells that must be defined for a particular MMIC process to work. The name of the air bridge that is created is entered into the LPF file so it is available for use in the project.

• Default: This feature ensures continuity of all the layers in a multi-layer drawing. The default specifies how the multi-layer face properties are drawn. The line elements are drawn as specified in the LPF file. The discontinuities are drawn so that all of the layers are connected. The "T" element has the layers inside the outermost layer extended so they touch the same layers in the line elements.

• Bridge type: The LPF file allows specification of as many bridges as needed. All of the bridge types in the LPF file are available. You can specify which air bridge definition you want to use when specifying Airbridge as the multi-layer drawing type.

Face Justification

For more control over the relative positions of the faces, you can define a variable offset that allows a delta X, delta Y, and a rotation angle to be set for the faces. The variable offset has the effect of shifting the face to an offset position. When the layout shapes are snapped together, the connected layout shapes snap to the offset face as shown in the following figure.

3.13.3. Local Cell Parameters

Usually the parameters needed to draw a layout cell are provided by the schematic component with which the layout cell is associated. You can add additional "local" parameters to the layout cell definition to allow the layout cell instance to store information that can be used to draw the layout cell. This is typically used when there are dimensional parameters needed to draw the layout cell that are not part of the electrical model. You can set the values of the local parameters on the Parameters tab of the Cell Properties dialog box.

Local parameters are also automatically created when a layout cell is connected to a schematic element that does not have the parameters that the layout cell needs. This allows you to use any layout cell with any electrical element (regardless of the number of nodes). For example, you can assign a layout cell for a spiral inductor to a subcircuit that uses measured S-parameters. The physical dimensions of the spiral are then entered as local parameters to allow the spiral to draw correctly.

3.14. Dynamic Voiding

Dynamic voiding is a layout mode that automatically adds clearance between layout shapes and signal traces, such as signal traces embedded in ground or power planes. You can also apply clearance between layout shapes such as a power and ground plane. Additional features include rounding of layout shape corners and the removal of small features that could potentially cause DRC violations or manufacturing issues.

Dynamic voiding applies only to schematic layouts, not to EM documents or artwork cells. However, you can apply it in a schematic layout and then extract to an EM document.

Dynamic voiding can be enabled or disabled in a Layout view by choosing or by clicking the button on the Draw Tools toolbar:.

With dynamic voiding disabled, clearance cutouts are not applied. When dynamic voiding is enabled, clearance is applied to the layout shape surrounding the signal trace, and the outside corners of the layout shape are rounded.

3.14.1. Dynamic Voiding Setup

As shown in the following figure, signal shapes are the routed traces of the design. These can be either layout representation of elements from a schematic, iNet routes, or layout shapes that are associated with a schematic net. Dynamic shapes are drawn as shapes such as rectangles or polygons, and they represent layout items such as ground planes and power planes. The following example shows signal shapes including the MLIN microstrip elements at the ends as well as an iNet route between the two elements.

Signal and dynamic shapes use the positive and negative layer naming convention. Dynamic shapes are drawn on the positive layer and signal shapes are drawn on the normal layer. You can apply additional cutouts by drawing a layout shape on the negative layer as shown.

If a line type is defined so that it includes a negative layer with offset defined, the clearance is set by either the negative layer offset value or the dynamic voiding rules, whichever is larger. See "Negative Layers " for details on positive and negative layers.

Signal shapes that are associated with schematic elements or iNet routes require a defined line type. For more information on line types, see "Line Type ". To configure line types, the "Process Definition Wizard" is available.

Layout shapes can be associated with net routes by selecting the layout shape and the net rat line or an iNet route, right clicking, and choosing . These shapes must be drawn on the normal layer. Associating net routes can also be performed automatically, see "Automatic Net Connectivity Extraction".

3.14.2. Utilizing Constraint Rules

Constraint rules are defined in the layout process file (LPF). See "Options - Voiding Constraint Sets Dialog Box " for details on configuring the constraint rules.

Two main groups define the dynamic voiding constraint rules: Spacing and Same Net Spacing. Spacing rules apply to signal shapes and dynamic shapes that have different net names. Same Net Spacing rules apply to signal shapes and dynamic shapes that use the same net name. The following figure shows the Same Net Spacing rules set to 10 mils, and the Spacing rules set to 5 mils.

In the following Layout View, the upper dynamic shape has the same net name as the route, yielding a clearance of 10 mils in accordance with the Same Net Spacing rules. The lower dynamic shape has a different net name than the route, so its clearance conforms to the Spacing rule of 5 mils.

The LPF Voiding Options control the rounding of dynamic shape corners and the removal of small dynamic shape features. See "Options - Voiding Options Dialog Box " for details on setting these parameters. The on the Circuit Options dialog box Nets/Voiding tab is related to the Voiding Options settings. With set to Disabled, the dynamic shape corner rounding and small feature removal are not applied as shown:

With set to Standard, all outside corners are rounded and small features are removed as shown:

When is set to Allegro compatibility (the default), small features are removed and corners around the perimeter of the dynamic shape are not rounded. Interior corners are not rounded if the adjacent signal shape is a square corner. In the following figure, the two interior corners are rounded due to the clearance spacing rules that void the dynamic shape between the signal route and the rectangular signal shapes. The other interior corners are not rounded because the dynamic shape fully surrounds the adjacent signal shapes.

You can assign priority to overlapping dynamic shapes so that the clearance operation is only applied to the lower priority shape. For example, in the following figure, dynamic shapes A and B overlap when dynamic voiding is disabled. Dynamic shape A is assigned a higher priority than dynamic shape B. When dynamic voiding is enabled, dynamic shape A is left intact, while dynamic shape B has the clearance applied.

When dynamic shapes have the same priority value, the shapes overlap without clearances being applied.

To assign a priority, right-click the layout shape and choose . On the Properties dialog box , set the . See "Properties Dialog Box: Net Properties Tab " for details.

3.14.3. Dynamic Voiding Across Hierarchy

For hierarchical schematics, the Show top level dynamic only option on the Options dialog box Nets/Voiding tab controls whether dynamic shapes in lower levels of the hierarchy are included in the top level.

The following figure shows two layouts in a hierarchy with Show top level dynamic only enabled (default selection). The dynamic shape in child schematic Level_2 layout is not included in the parent schematic TopLevel layout. This allows dynamic shapes to be defined only at the top level in the hierarchy.

The following figures shows the same structure with Show top level dynamic only disabled. In this configuration, the dynamic shape in schematic layout Level_2 is included in the TopLevel schematic layout.

3.14.4. Assigning Net Names and Constraint Rules

Net names are associated with both signal shapes and dynamic shapes. Layout shapes without a net name are not included in dynamic voiding. These shapes are still included in the layout; however, clearance extraction, corner rounding, and small feature removal are not applied when dynamic voiding is enabled.

To assign a net name to a dynamic shape, right-click the layout shape and choose . On the Properties dialog box , specify the . See "Properties Dialog Box: Net Properties Tab " for details.

After signal shapes and dynamic shapes are added to the schematic layout, you can modify the net names and apply the constraint rules to a particular net using the Net and Constraint View window. See "Net and Constraint View Window " for details.

Net Name Restrictions:

1. The following characters are not allowed in a net name: ) ( , = \ " ' ` / { } ! *

2. Net names cannot be longer than 31 characters.

3. Net names are not case sensitive and must be unique. For example you cannot use NetA and NETA for two different net names.

3.14.5. Net Connectivity

A net is defined by two or more schematic element pins that are connected together. Net connection can be made by connecting schematic elements together with a wire, by joining the schematic elements together, or by using a Named Connector between schematic element pins as shown in the following figure.

Unique net names are automatically assigned to each net as shown in the following figure. Once assigned, you can reassign the net name in the "Properties Dialog Box: Net Properties Tab " for iNet routes, or in the "Net and Constraint View Window " for all signal shapes.

The one exception to unique name assignment pertains to supernets. A supernet is a collection of separate nets that are assigned the same net name. The one supernet structure supported is separate nets connected through schematic vias as shown in the following figure.

When nets are connected through vias, all the nets as well as the vias in the collection are automatically assigned the same net name. If the net name is changed on any one item in the supernet structure, then all net names in the supernet structure also change. The schematic vias that are supported with supernet structures are: VIA, VIAM, VIAM2 and TVia.

To assist with net management, choose to access the "Net and Constraint View Window ". This dialog box allows you to browse and filter net objects and assign net names and constraint sets to signal shapes and dynamic shapes. You can also toggle on/off highlighting of shapes and instances associated with selected nets.

3.14.6. Automatic Net Connectivity Extraction

To manually associate layout shapes with a net, select the layout shape and the net rat line, right-click and choose Associate Net Routes. Automatic net extraction allows layout shapes that overlay signal shapes to inherit the net name of the signal shape without performing the Associate Net Routes procedure. Automatic net extraction behavior is set globally on the "Circuit Options Dialog Box: Nets/Voiding Tab", accessed by choosing . These settings can also be set per schematic on the schematic Options dialog box Nets/Voiding tab. The selections for Connectivity mode are:

• Disable

• Extract before voiding

• Auto extract

Each of the setting affects layout shapes that are drawn on the normal layer and overlap with signal shapes such as iNet routes or schematic instances.

With set to Disable, the layout shape does not get connected to the net and is not assigned a net name. In the following example, the rat line drawn across the layout shape indicates that this shape is not connected to the net. In addition, the layout shape is not highlighted when the net is selected in the Net and Constraint View window.

When is set to Auto Extract, layout shapes that overlay with signal shapes are automatically connected to the net. In the following example, the rat line ends at the layout shape edge, indicating that the layout shape is now part of the net. In addition, the layout shape is now highlighted when the net is selected in the Net and Constraint View window.

When Shapes sticky to nets is selected, if the layout shape is moved such that is does not overlap with any other signal shape on the net, the layout shape retains the original net name, as shown in the following example. The rat lines connecting to the layout shape indicate that it is still connected to the net.

If the layout shape is moved such that it overlaps with a signal shape on another net, that layout shape inherits the new net name and becomes part of the new net if is set to Auto Extract.

When the is set to Extract before voiding, the automatic net extraction behavior depends on whether or not dynamic voiding is enabled. In this mode, if voiding is disabled the behavior is the same as set to Disable. Under these conditions (voiding disabled and set to Extract before voiding), layout shapes that overlap signal shapes do not automatically become part of the net. In this mode, if voiding is enabled, the behavior is the same as set to Auto Extract. Under these conditions (voiding enabled and set to Extract before voiding), layout shapes that overlap signal shapes automatically become part of the net.

Chapter 3 Review Introduction to Drawing and Editing

Source: https://awrcorp.com/download/faq/english/docs/Layout/layout_editing.html

Share :