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The Process Rule Editor

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A process rule is a rule that constrains the implementation of a design based on the physical characteristics of the process technology being used. For example, a minSpacing rule specifies the minimum distance allowed between two shapes on a specified layer.

A constraint group is a collection of constraints and process rules created for a technology database or a specific design.

A process rule can exist only in a constraint group. Therefore, for a process rule to be applied to an object, design, or technology; it must be a member of a constraint group applied to that object, design, or technology.

The Process Rule Editor lets you create new process rules and constraint groups and apply them to objects, constraints, designs, or technology databases; and change or remove existing process rules and constraint groups.

The Process Rule Editor lets you create new process rules and constraint groups and apply them to objects, constraints, designs, or technology databases; and change or remove existing process rules and constraint groups. The Process Rule Editor supports the creation of process rules and constraint groups for:

• Design objects such as nets
• Certain constraints such as Diff Pair, Matched Length, Net Class, Shielding, Process Rule Overrides, Bus Net, and Symmetry
• Entire design
• Technology databases

Important Points to Remember

• • When dealing with Process Rule Override (PRO) on nets, you may encounter a mismatch between the representation on the schematic and the layout for the same PRO constraint. This may be due to an incorrect set up in the selected value for the Wire Editing constraint group (Layout: Options – Editor menu). The default value for this is the virtuosoDefaultSetup constraint group. To prevent the issue, ensure that the selected wire editing constraint group (default: virtuosoDefaultSetup) contains valid layers and valid vias.
  • To use table-based spacing rules in a PRO constraint, specify the rules in a Constraint Group along with other rules in the design using the Process Rule Editor or the technology file. Then, choose this Constraint Group from the drop-down list for the Default parameter (that specifies the default constraint group for the member object) of the PRO constraint in the Constraint Manager. All of these can be done procedurally using SKILL as well. For more information, see Creating a Constraint Group and Creating a New Process Rule.

For a complete list of process rules supported by the Process Rule Editor, see Process Rules Supported by the Process Rule Editor.

Starting the Process Rule Editor

To start the Process Rule Editor:

• On the Constraint Manager toolbar, click the Process Rule Editor button ( ).

Note:

• • Alternatively, right-click the design object in the layout canvas or the layout navigator and choose Process Rule Editor from the shortcut menu.
  • The Process Rule Editor command is available on the shortcut menu only for those objects that have a design issue and display a non-OK XL status.

The Process Rule Editor Graphical User Interface is displayed. The interface supports viewing multiple PRE windows simultaneously. Each PRE window responds to the changes in the design window from which it was opened.

For example, you have two designs open, design_A and design_B. Any changes you make to design_A will only update the Process Rule Editor you invoke from this design.

To make the Process Rule Editor respond to selections made in design_B:

• Open a new PRE window from the design_B Constraint Manager assistant.

Process Rules Supported by the Process Rule Editor

The table below lists the process rules and their corresponding Virtuoso constraint names. You can edit these rules by using the Process Rule Editor.

Process Rule Name	Virtuoso Constraint Name
Accepted Tolerance	msTolerance
Access Point	accessPoint
Access to Pin	accessShift
Allowed Layer Geometry Orientation	layerShapeAngle Techfile Name: allowedShapeAngles
Allowed Length Ranges	allowedLengthRanges
Allowed Neighbor Width Range	allowedNeighborWidthRanges (Two layers)
	allowedNeighborWidthRanges (One layer)
	allowedNeighborWidthRangesOver
Allowed Shape Angles	allowedShapeAngles (0-layer)
Allowed Spacing Ranges Different Layers	allowedSpacingRanges (Two layers)
Allowed Spacing Ranges Same Layer	allowedSpacingRanges (One layer)
Allowed Width Ranges Same Layer	allowedWidthRanges
allowedCutClass	allowedCutClass
allowedGateLengthRanges	allowedGateLengthRanges
allowedGateWidthRanges	allowedGateWidthRanges
allowedPRBoundaryDimensions	allowedPRBoundaryDimensions
allowedSpanLengthRanges	allowedSpanLengthRanges
Cluster Distance	clusterDistance
Corner Fill Spacing	cornerFillSpacing
Cut Class	cutClass Techfile Name: cutClasses
Default Horizontal Routing Offset	defaultHorizontalRoutingOffset Techfile Name: horizontalOffset
Default Horizontal Routing Pitch	defaultHorizontalRoutingPitch Techfile Name: horizontalPitch (One layer)
Default Left Diagonal Offset	defaultLeftDiagOffset Techfile Name: leftDiagOffset
Default Left Diagonal Pitch	defaultLeftDiagPitch Techfile Name: leftDiagPitch (0-layer)
Default Right Diagonal Offset	defaultRightDiagOffset Techfile Name: rightDiagOffset (0-layer)
Default Right Diagonal Pitch	defaultRightDiagPitch Techfile Name: rightDiagPitch
Default Vertical Routing Offset	defaultVerticalRoutingOffset Techfile Name: verticalOffset
Default Vertical Routing Pitch	defaultVerticalRoutingPitch Techfile Name: verticalPitch (One layer)
Diagonal Shapes Allowed	diagonalShapesAllowed
Dummy Extension	dummyExtension
edgeMustCoincide	edgeMustCoincide
edgeMustOverlap	edgeMustOverlap
Error on Derived Layer	errorLayer
forbiddenCutClassSpacingRange	forbiddenCutClassSpacingRange
forbiddenEdgePitchRange	forbiddenEdgePitchRange
forbiddenProximitySpacing	forbiddenProximitySpacing
Gate Orientation	gateOrientation
Gate Spacing Ranges	gateSpacingRanges
Generic Constraint	genericConstraint
Horizontal Offset	horizontalOffset Techfile Name: horizontalOffset
Horizontal Pitch	horizontalPitch Techfile Name: horizontalPitch
Horizontal Placement Offset	horizontalPlacementOffset Techfile Name: horizontalOffset
Horizontal Placement Pitch	horizontalPlacementPitch Techfile Name: horizontalPitch
Illegal H Gate Pattern	illegalHGatePattern
Keep PRBoundary Shared Edges	keepPRBoundarySharedEdges
Keep Shared Edges	keepSharedEdges
Ladder Frequency	ladderFrequency
Ladder Offset	ladderOffset
Ladder Style	ladderStyle
Large Rectangular Via Array Allowed	largeRectViaArrayAllowed
Left Diagonal Offset	leftDiagOffset Techfile Name: leftDiagOffset (1-layer)
Left Diagonal Pitch	leftDiagPitch Techfile Name: leftDiagPitch (1-layer)
Length Pattern Accordion	lengthPatternAccordion
Length Pattern End Run	lengthPatternEndRun
Length Pattern RW Accordion	lengthPatternRWAccordion
Length Pattern Trombone	lengthPatternTrombone
lengthPatternOff	lengthPatternOff
Match Per Layer	matchPerLayer
Match Tolerance	matchTolerance
maxDiffusionLength	maxDiffusionLength
Maximum Coupling Diff	maxCouplingDiff
Maximum Coupling Diff Percent	maxCouplingDiffPercent
Maximum Current Density	maxACCurrentDensity
Maximum Density	maxDensity
Maximum Diagonal Edge Length	maxDiagonalEdgeLength
Maximum Different Density	maxDiffDensity
Maximum Extension	maxExtension
Maximum Floating Area	maxFloatingArea
Maximum Ground Cap Diff	maxGroundCapDiff
Maximum Ground Cap Percent	maxGroundCapDiffPercent
Maximum Length	maxLength
Maximum Number of Minimum Edges	maxNumMinEdges
Maximum number of via cuts of a cluster	maxViaClusterNumCuts
Maximum Poly Length	maxPolyLength
Maximum Routing Distance	maxRoutingDistance
Maximum Single Coupling	maxSingleCoupling
Maximum Single Coupling Percent	maxSingleCouplingPercent
Maximum Spacing For Filling	maxFilling
Maximum Spacing Same Layer	maxSpacing
Maximum Tap Spacing	maxTapSpacing
Maximum Touching Direction Length	maxTouchingDirectionLength
Maximum Width	maxWidth
maxNumCorners	maxNumCorners
minCenterLineSpacing	minCenterLineSpacing Techfile Name: minCenterLineSpacing (Two layers)
minChamferLength	minChamferLength
minClusterSpacing	minClusterSpacing (One layer)
	minClusterSpacing (Two layers)
minCornerExtension	minCornerExtension
minCornerSpacing	minCornerSpacing (One layer)
	minCornerSpacing (Two layers)
minDirectionalOverlap	minDirectionalOverlap
minEndOfLineToNotchSpacing	minEndOfLineToNotchSpacing
minExtensionSpacing	minExtensionSpacing
minExtensionToCenterLine	minExtensionToCenterLine
minExtensionToCorner	minExtensionToCorner
Minimum Adjacent Via Spacing	viaSpacing
Minimum Area	minArea
Minimum Area With Exceptions	minAreaEdgeLength
Minimum Center To Center Spacing Same Layer	minCenterToCenterSpacing
Minimum Centerline Extension	minCenterlineExtension
Minimum Corner To Corner Width	minCornerToCornerDistance
Minimum Coupling	minCoupling
Minimum Coupling Percent	minCouplingPercent
Minimum Cut Class Spacing - Different Layers	minCutClassSpacing Techfile Name: minCutClassSpacing (Two layers)
Minimum Cut Class Spacing - Same Layer	minCutClassSpacing Techfile Name: minCutClassSpacing (One layer)
Minimum Cut Routing Clearance	minCutRoutingSpacing Techfile Name: minCutRoutingSpacing (Two layers)
Minimum Density	minDensity
Minimum Diagonal Edge Length	minDiagonalEdgeLength
Minimum Diagonal Spacing Same Layer	minDiagonalSpacing
Minimum Diagonal Width	minDiagonalWidth
Minimum Differential Potential Net Spacing	minDiffNetSpacing
Minimum Distance from The PRBoundary to Enclosed Shape	minPRBoundaryInteriorHalo
Minimum Distance from The PRBoundary to Outside Shape	minPRBoundaryExteriorHalo
Minimum Dual End of Line Extension	minOppEndOfLineExtension
Minimum Edge Adjacent Distance	minEdgeAdjacentDistance
Minimum Edge Adjacent Length	minEdgeAdjacentLength
Minimum Enclosure Edge	minExtensionEdge
Minimum End of Line Adjacent To Step	minEndOfLineAdjacentToStep
Minimum End of Line Cut Spacing	minEndOfLineCutSpacing
Minimum End Of Line Edge Extension	minEndOfLineEdgeExtension
Minimum End Of Line Extension	minEndOfLineExtension
Minimum End Of Line Extension Spacing	minEndOfLineExtensionSpacing
Minimum End of Line Keepout	endOfLineKeepout
Minimum End Of Line Perpendicular Spacing	minEndOfLinePerpSpacing
Minimum End Of Line Spacing	minEndOfLineSpacing
Minimum End of Line to Corner Spacing	minEndOfLineToConcaveCornerSpacing
Minimum Extension Distance	minExtensionDistance
Minimum Extension on Long Side	minExtensionOnLongSide
Minimum Fill to Fill Spacing	minFillToFillSpacing
Minimum Filler To Shape Spacing, Same Layer	minFillToShapeSpacing
Minimum Gate Extension	minGateExtension
Minimum Hole Area	minHoleArea
Minimum Hole Width	minHoleWidth
Minimum Inner Vertex Clearance	minInnerVertexSpacing Techfile Name: minInnerVertexSpacing (Two layers)
Minimum Inner Vertex Spacing	minInnerVertexSpacing
Minimum Inside Corner Edge Length	minInsideCornerEdgeLength
Minimum Inside Corner Extension	minInsideCornerExtension
Minimum Inside Corner Overlap	minInsideCornerOverlap
Minimum Large Via Array Cut Spacing	minLargeViaArrayCutSpacing
Minimum Large Via Array Spacing	minLargeViaArraySpacing
Minimum Large Via Array Width	minLargeViaArrayWidth
Minimum Length	minLength
Minimum Neighboring Via Spacing	minNeighborViaSpacing
Minimum Notch Spacing	minNotchSpacing
Minimum Notch Span Spacing	minNotchSpanSpacing
Minimum Number of Cuts	minNumCut
Minimum OneDimension Array Structure	minOneDArrayStructure
Minimum Opposite Extension	minOppExtension
Minimum Opposite Span Spacing	minOppSpanSpacing
Minimum Orthogonal Via Spacing	minOrthogonalViaSpacing
Minimum Orthogonal Spacing Between Corners Same Layer	minConvexCornerSpacing
Minimum Outer Vertex Spacing	minOuterVertexSpacing
Minimum Outside Corner Edge Length	minOutsideCornerEdgeLength
Minimum Overlap Distance	minOverlapDistance
Minimum Overlap in Length Direction	minWireOverlap
Minimum Parallel Span Spacing	minParallelSpanSpacing
Minimum Parallel Via Spacing	minParallelViaSpacing Techfile Name: minParallelViaSpacing (One layer)
Minimum Parallel Via Spacing (Layer Array)	minParallelViaSpacing Techfile Name: minParallelViaSpacing (Two layers plus metal)
Minimum Parallel Within Via Spacing	minParallelWithinViaSpacing
Minimum Perimeter	minPerimeter
Minimum PRBoundary Extension	minPRBoundaryExtension
Minimum Protruded Spacing, Same Layer, Within Influencing Shape	minStubInfluenceSpacing
Minimum Protrusion Number of Cuts	minProtrusionNumCut
Minimum Protrusion Spacing	minProtrusionSpacing
Minimum Protrusion Width	protrusionWidth
Minimum Rectangular Area	minRectArea
Minimum Redundant Via Setback	redundantViaSetback
Minimum Same Metal Share Edge Via Spacing	minSameMetalSharedEdgeViaSpacing
Minimum Same Net Clearance	minSameNetSpacing Techfile Name: minSameNetSpacing (Two layers)
Minimum Same Net Spacing	minSameNetSpacing Techfile Name: minSameNetSpacing (One layer)
Minimum Side Extension	minSideExtension
Minimum Size	minSize
Minimum Spacing Between Notch And Shapes	minEndOfNotchSpacing
Minimum Spacing Different Layers	minSpacing Techfile Name: minSpacing (Two layers)
Minimum Spacing Over Layer	minSpacingOver
Minimum Spacing Same Layer	minSpacing Techfile Name: minSpacing (One layer)
Minimum Spacing to Short Edges	minEdgeLengthSpacing
Minimum Spacing, Same Layer, Within Influencing Shape	minInfluenceSpacing
Minimum Step Edge Length	minStepEdgeLength
Minimum Touching Directional Extension	minTouchingDirEnclosure
Minimum Touching Directional Spacing	minTouchingDirSpacing
Minimum Via Clearance	minViaSpacing Techfile Name: minViaSpacing (Two layers)
Minimum Via Extension	minViaExtension
Minimum Via Joint Extension	minViaJointExtension
Minimum Via Spacing	minViaSpacing Techfile Name: minViaSpacing (One layer)
Minimum Voltage Clearance	minVoltageSpacing Techfile Name: minVoltageSpacing (Two layers)
Minimum Voltage Spacing	minVoltageSpacing Techfile Name: minVoltageSpacing (One layer)
Minimum Width	minWidth
Minimum Wire Extension	minWireExtension
minInnerVertexProximityExtension	minInnerVertexProximityExtension
minJointCornerSpacing	minJointCornerSpacing
minNeighborExtension	minNeighborExtension
minNeighboringShapesSpacing	minNeighboringShapesSpacing
minProtrusionWidthLength	minProtrusionWidthLength
minQuadrupleExtension	minQuadrupleExtension
minSideSpacing	minSideSpacing (One layer)
	minSideSpacing (Two layers)
minSpanLengthSpacing	minSpanLengthSpacing
minStitchOverlap	minStitchOverlap
Mixed Signal Shield Style	msShieldStyle
msConnectSupplyDistance	msConnectSupplyDistance
msMaxCap	msMaxCap
msMaxRes	msMaxRes
msMinCap	msMinCap
msMinRes	msMinRes
Number of Strands	numStrands
Pin Cover	pinCover
Pin Staple	pinStaple
Rectangular Shape Orientation	rectShapeDir
Right Diagonal Offset	rightDiagOffset Techfile Name: rightDiagOffset (One layer)
Right Diagonal Pitch	rightDiagPitch Techfile Name: rightDiagPitch (One layer)
Route Maximum Length	routeMaxLength
Route Minimum Length	routeMinLength
Routing Directions	routingDirections
Same mask	msSameMask
Shape Required Between Spacing	shapeRequiredBetweenSpacing
shapeRequiredSpacing	shapeRequiredSpacing
shareShields	shareShields
Shield Gap	shieldGap
Shield Width	shieldWidth
snapGridHorizontal	snapGridHorizontal
snapGridVertical	snapGridVertical
Strand Spacing	strandSpacing
Strand Width	strandWidth
Tandem Layer Above	tandemLayerAbove
Tandem Layer Below	tandemLayerBelow
Tandem Width	tandemWidth
Taper Halo	taperHalo
Track Pattern	trackPattern
Trunk Accessing Num Cuts	trunkAccessingNumCuts
Use Non Orthogonal Routing Rules	useNonOrthogonalRoutingRules
Valid Layers	validLayers
Valid LPPs	validLayers
Valid Vias**	validVias
Vertical Offset	verticalOffset
Vertical Pitch	verticalPitch Techfile Name: verticalPitch (One layer)
Vertical Placement Offset	verticalPlacementOffset Techfile Name: verticalOffset
Vertical Placement Pitch	verticalPlacementPitch Techfile Name: verticalPitch
Via Control	viaControl
Via Orient Shift	viaOrientShift
Via Percentage	viaPercent
Via Stacking Allowed	stackable
Via Stacking Limits	viaStackingLimits
viaEdgeType	viaEdgeType
viaRequiredWithin	viaRequiredWithin
Wire Percentage	wirePercent

Process Rule Editor Graphical User Interface

This section describes the seven different elements that comprise the Process Rule Editor graphical user interface. These GUI elements are:

• Toolbar
• Scope Selection Section
• Browser Pane
• Create Constraint Group Section
• Create Process Rule Section
• Dynamic Widget
• Apply Constraint Group Section

Before you explore the GUI elements, it will help to familiarize yourself with some useful features supported by the GUI:

• • Resizable form that allows controlling the various widget sizes independently, helps reduce the widget area to a minimal size.
  • Resizable Tree window widget that helps adjusting the height of the Tree and the Dynamic widget by moving the edge between the two areas.
  • Support for assigning purposes to layers for the selected constraint.
  • Attributes and Parameters tabs to specify the attribute and parameter values for the selected process rule.
  • Commands on the shortcut menu to expand and collapse the constraint tree in the browser pane.

Toolbar

The toolbar lets you access certain frequently-used functions.

For more information on the individual buttons on the toolbar, see the table below.

Icon	Button Name	Description
	Move Up	Increases the precedence of the selected constraint group or process rule by moving it up one position in the browser pane. This function is not available for objects at the top level of the browser tree, comprising the Constraint Groups. For more information, see Setting the Precedence of a Constraint Group or Process Rule.
	Move Down	Decreases the precedence of the selected constraint group or process rule by moving it down one position in the browser pane. This function is not available for objects at the top level of the browser tree, comprising the Constraint Groups. For more information, see Setting the Precedence of a Constraint Group or Process Rule.
	Remove	Removes the selected constraint group or process rule from the Process Rule Editor. For more information, see Removing a Constraint Group or Process Rule.
	Copy Rules	Copies the selected rules to the Process Rule Editor clipboard. For more information, see Copying an Existing Process Rule.
	Paste Rules	Pastes the process rules in the clipboard into the selected constraint group. For more information, see Copying an Existing Process Rule.
	Save Technology	Saves the changes made since the Process Rule Editor was opened or the last time the Save Technology button was pressed. For more information, see Saving Changes and Closing the Process Rule Editor.
	Help	Opens this document.

Scope Selection Section

The Process Rules on section lets you choose the scope for the changes you make in the Process Rule Editor. The section is also referred to as the Scope Selection section. In this section, choose:

Technology to define rules and overrides that apply to all the designs using the current technology databases.

Design to define rules and overrides that apply for the current design only.

Object to define rules and overrides for the selected objects or constraints in the design.

Browser Pane

The browser pane displays the current constraint groups, process rules, and a summary of the layers used for the selected process rule and the process rule values. The browser pane is divided into the following columns:

• The Browser column lists the constraint groups in all the technology databases applicable for the design. These are listed as the top level tree items and the constraint groups and process rules defined within the top level constraint groups appear at the appropriate sublevels in the tree.
• The Summary column displays a single concatenated string representing the layers used for the selected process rule and the current value of the constraint. For example, if the current layer and width values for a Minimum Width constraint are oxide and 0.0250 respectively, the string displayed in the Summary column is oxide 0.0250. This is displayed in the figure below.
  
  
  If the Summary column is highlighted brown, it indicates that the process rule was created using the default values. If you modify the default values, the concatenated string displays the new values and the Summary column is not highlighted.
• The contents of the browser pane are determined by the option selected in the Process Rules on section, which is also called the Scope Selection section.
  
  
  • When set to Technology, the browser pane lists all the rules defined in the constraint groups across all the technology databases applicable to the current design.
    The top level of the tree lists the name of the constraint group along with the technology database in which it resides. Expanding a constraint group reveals the rules defined within it. Provided the technology database is writable, you can override the setting for the current rules or create new rules in the selected constraint group.
  • When set to Design, the browser pane lists the constraint groups and process rules defined only for the current design. Here too, provided the design is writable, you can override the setting for the current rules or create new rules that apply only to the current design.
    
    
  • When set to Object, the browser pane lists only the rules and constraint groups that apply for the selected object or constraint. For example, if you select a net, you see only the technology categories relevant for a net: Default, Input Taper, and Output Taper. In addition, you will see the rules associated with any constraints applied to the net (for example, a Shielding constraint).
    
    
  Selecting one of these categories populates the Create Process Rule section with the rules you can define in that particular category. For more information, see Creating a New Process Rule for a Selected Object.

Process Rule Editor Context Menu

The Process Rule Editor shortcut menu provides a number of context-specific options that you can apply on a constraint group or a process rule. To display the menu, right-click a constraint group or a process rule in the browser pane.

For example, when you are at the top-most level of the Constraint Group tree, the Move Up command appears inactive.

The various commands in the context menu are tabulated below along with their description.

Command Name	Description
Copy Rules	Copies the selected process rules to the clipboard. This feature only copies the supported process rules. Any unsupported process rules are ignored by the command. For more information, see Copying an Existing Process Rule.
Paste Rules	Pastes the selected process rules from the clipboard to the specified location. You can paste the rules in the clipboard into as many locations as you want by repeatedly clicking the Paste Rules button. For more information, see Copying an Existing Process Rule.
Remove	Removes the selected constraint groups or process rules from the Process Rule Editor. If you delete a process rule in the browser in between copying and pasting, the deleted rule is also removed from the clipboard and is not subsequently pasted.For more information, see Removing a Constraint Group or Process Rule.
Move Up Move Down	Increases or decreases the precedence of the selected constraint group or process rule by moving it up or down one position in the browser pane. The commands are not available for the objects at the top level of the browser tree. For more information, see Setting the Precedence of a Constraint Group or Process Rule.

Create Constraint Group Section

You can use this section to create a new constraint group that contains process rules. For information about how to perform the task, see Creating a Constraint Group.

Create Process Rule Section

You can use this section to create a new process rule in the selected constraint group. The Create Process Rule section includes:

• The drop-down list box at the top that enables you to specify the type of rule you want to create. The list contains only those rules that are valid for the selected constraint group or object.
• The drop-down list box at the bottom that enables you to choose an appropriate data value format for defining a particular rule. For example, you can define a Minimum Spacing Same Layer rule in terms of distance or as a 1D Table or a 2D Table, as displayed in the figure below.
  
  
  The most common data value formats are:
  • distance
  • 1D table
  • 2D table
  
  Some other supported formats are:
  • 2 layers, distance
  • 2 layers, 2D table
  • 2layers, dual distance
  • dual distance table
  • Layer Array
  • Via Array
  • direction
  • BooleanValue
  • voltage, spacing
  • IntFltTblValue
  • FltValue
  
  The type of process rule you choose from the drop-down list at the top governs the data value formats that are available in the Dynamic Widget.
• The plus (+) button that creates a new process rule and displays the process rule Description and the Attributes, Value, and Parameters, if applicable.

IntFltTblValue

This data format value represents a 1D integer lookup table value where the value is a float.

FltValue

This data format value represents a float value.

Dynamic Widget

You can use this widget to set the values for a new process rule.The widget comprises the following tabs:

• Description Tab
• Attributes Tab
• Value Tab
• Parameters Tab

You can also use these tabs to edit the values for an existing process rule. However, only relevant tabs are available for each rule.

Description Tab

This tab provides a pictorial and a textual description of the selected process rule, as displayed in the figure below.

The textual description is a generic definition of the process rule and the associated picture elaborates on this definition. The contents of the tab cannot be edited.

Attributes Tab

You can use this tab to specify the process rule attributes, such as name, ID, and description. In addition, you can use the tab to specify if the process constraint is hard or soft.

• Name : A unique, default name is displayed in this field for every process rule that you add. You can replace this name with a new name, if needed.
  
  The new name that you specify for a process rule must be unique. Otherwise, an error message is displayed in the CIW stating that the name could not be changed because a process rule by that name already exists.
• Hard : Select the Hard check box for a process rule if you do not want another process constraint to over-ride this rule.
• ID : Use the ID field to assign an ID to the process rule.
• Description : Use the Description field to provide a brief description of the process rule in the context of its current scope (Tech. Design, or Object) or the constraint group to which the rule is applied.

Value Tab

You can use this tab to select a layer such as Metal2, a constraint value such as 0.03, and an appropriate layer purpose, such as drawing, for the process rule you are creating. You can use the layer-purpose widget provided by the Value tab to create layer-purpose pairs, as required. For more information about creating layer-purpose pairs, see Creating a Layer-Purpose Pair.

Some process rules, such as Minimum Spacing Different Layers, may require you to select two layers and specify the associated purposes.

Parameters Tab

You can use this tab to specify the parameters, such as distance, width, and endOfLineSpace, that define the conditions governing when or how a process rule can be applied.

Depending on the process rule you select, the parameters displayed on this tab vary.

• If a process rule has no associated parameters, the Parameters tab is unavailable.
• If a process rule has several associated parameters, default values are displayed for all the constraint parameters. You can modify these default values, as required.
• If a process rule has several parameters of which some are currently not supported, these parameters display “UNSUPPORTED” next to their name. The supported parameters display a default value that you can modify.

If you modify the default value of a parameter, the Restore Default Value ( ) button appears next to the new parameter value. You can click this button to revert to the default value for this parameter.

• The value you enter for a parameter is validated against the data types allowed for that parameter, such as integer or string. An unsupported data type is not accepted.

Apply Constraint Group Section

This section lets you apply a constraint group from the same or different scope to the selected constraint group in your current scope. In other words, the Apply Constraint Group section acts as a link, making all the applicable Constraint Groups available in the current scope.

For example, you can select a constraint group from the Tech scope and apply it to a custom constraint in the Design scope. However, you can apply a constraint group to a selected constraint only once. For information on how to perform the tasks, see Applying a Constraint Group.

For more information about using the Apply Constraint Group section, see Applying a Constraint Group.

For information on the tasks you can perform in the Process Rule Editor, see the topics listed below.

• Creating a Constraint Group
• Customizing a Constraint Group
• Creating a New Process Rule
  • Creating a New Process Rule in the Technology or Design Mode
  • Creating a New Process Rule for a Selected Object
  • Creating a New Process Rule for a Constraint
  • Copying an Existing Process Rule
  • Creating a Layer-Purpose Pair
  • Applying Valid LPPs Process Rule
  • Creating a Voltage Dependent Process Rule
  • Editing Existing Process Rule Values
• Applying a Constraint Group
• Setting the Precedence of a Constraint Group or Process Rule
• Virtuoso Generated Constraint Groups
• Applying an Existing Constraint Group to a Selected Object
• Removing a Constraint Group or Process Rule
• Saving Changes and Closing the Process Rule Editor

Creating a Constraint Group

You can create a new constraint group only in the Technology or Design mode by using the Create Constraint Group field. In the Object mode, the field is inactive.

To create a new constraint group:

1. On the Constraint Manager toolbar, click the Process Rule Editor button ( ).
   
   Alternatively, right-click the design object in the layout canvas or the layout navigator and choose Process Rule Editor from the shortcut menu.
   The Process Rule Editor Graphical User Interface is displayed.
2. In the Process Rules on section, choose one of the following:
   • Technology to create a constraint group applicable for all the designs that use the current process technology.
   • Design to create a constraint group applicable only for the current design.
   • Object to create a constraint group for the selected object or constraint in the design.
3. Type a name for the new constraint group in the Create Constraint Group section.
   
   
   You cannot prefix a constraint group name with an underscore ( _ ). This convention is reserved for Cadence internal use.
4. Click the plus (+) button in the Create Constraint Group section to add the new group to the database you selected.

The constraint group you created is added to the browser pane as displayed in the figure above.

The new constraint group is created as an empty floating constraint group for the selected mode (technology or design).

Customizing a Constraint Group

There can be constraints that are specified by adding information with the PRE. This information can be directly added or viewed in the constraint manager when you want to apply a single pre-existing constraint group to the available fields in the PRE. However, there are cases where you may not have any available constraint groups that meet your requirement. Therefore, you can generate customized constraint groups that are specific to your naming convention and as per the required design or style.

This customization can be provided in the form of the following SKILL functions:

isConstraintGroupApplicable( 
    ciCon, CGDefName, CG
) 

=> t|nil

listGroupsThatCanBeGenerated( 
    ciCon, CGDefName
) 

=> a list of strings)

generateConstraintGroup( 
    ciCon, CGDefName, CGName 
) 

=> a SKILL Constraint Group Object 

where:

• ciCon is the SKILL object representing the current constraint in the constraint manager.
• cgDefName is the name of the CI constraint group's definition that you are trying to fill. For example, shielding, transReflexive, reflexive, default, taper, inputTaper, and outputTaper.
• CG is the SKILL object representing a constraint group that you want to test.
• CGName is the string name of the constraint group that you want to generate.

In addition, you can override the built-in functions by:

• Creating replacement functions with arguments and return values as shown above.
• Calling the ciSetCMCGSKILLCallbacks SKILL function.

You can use nil for any of these values if you want to reset them to default.

Creating a Custom Constraint Group and Defining Default Parameter Values

Alternatively, you can also create a custom constraint group and define default parameter values using the SKILL commands ciAddRuleGroup and ciAddProcessRules in the CIW. For example,

1. In the CIW, create a new constraint group called myRG1, using the ciAddRuleGroup command:
   

   cv=geGetEditCellView()

   myRG1=ciAddRuleGroup(cv "myRG1")

2. Define default values for the top and bottom layers of the constraint group myRG1 using the ciAddProcessRules command:
   

   ciAddProcessRules(myRG1 '( ("minWidth" "Metal1" 1.0) ("minWidth" "Metal2" 1.2) ("validLayers" nil ("Metal1" "Metal2" "Metal3"))))

   The new constraint group can now be selected as the Default Group (Constraint Group) on the Constraint Parameter Editor.

Creating a New Process Rule

You can create new process rules for the entire technology or design, for one or more selected objects, or for a constraint applied to an object in your design. You can also copy process rules from one or more constraint groups to another constraint group. In addition, you can edit an existing process rule and specify layer purposes. You can also create and apply rules that are voltage dependent.

• Creating a New Process Rule in the Technology or Design Mode
• Creating a New Process Rule for a Selected Object
• Creating a New Process Rule for a Constraint
• Copying an Existing Process Rule
• Creating a Layer-Purpose Pair
• Applying Valid LPPs Process Rule
• Creating a Voltage Dependent Process Rule
• Editing Existing Process Rule Values

Creating a New Process Rule in the Technology or Design Mode

To create a new process rule in a constraint group using the Technology or Design mode:

1. In the browser pane, choose the constraint group in which you want to create the new rule.
2. In the Create Process Rule section, choose
   • The type of rule to create from the first drop-down list.
   • The value type, where appropriate, from the second drop-down list.
     
     Each list is seeded appropriately depending on what is selected in the browser pane.
     
3. Click the plus (+) button in the Create Process Rule section to add a new process rule to the selected constraint group.
   
   Alternatively, press the Enter key.
   The process rule is added to the list. The Summary field in the browser pane is highlighted brown to indicate that the rule was created using the default values. You can modify the rule by changing the default values. This also removes the highlight from the Summary column.
4. Modify the rule by specifying appropriate data on the Attributes, Value, and Parameters tabs.
   
   Only relevant tabs are available for a process rule.
5. Click Update to apply the value you set in the Value tab.
   
   The changes you make on the Attributes and Parameters tabs are automatically saved. Therefore, you do not need to click the Update button to save these changes.
   The new values that you specify on the Value tab appear in the Summary column of the browser pane.
   
   To quickly add more process rules of the same type, click the Add button instead of Update. Each click adds a new rule with the same values displaying in the Summary column as the last one you added. The Summary column appears brown to indicate that the process rule values might need to be changed.
6. Select each new rule you added and edit the values, as required.

Creating a New Process Rule for a Selected Object

You can use the Process Rule Editor to create process rules for the selected objects in your design. In this mode, the browser pane shows only the categories that are applicable for the selected objects. For example, if you select a net object, you see only the Default, Input Taper, and Output Taper categories.

Selecting one of the categories populates the Create Process Rule section with the rules you can define in that particular category. For example, for Input Taper, as displayed in the figure above, you can define the following rules only:

• Minimum Spacing Same Layer
• Minimum Width
• Taper Halo
• Valid LPPs
• Valid Layers
• Valid Vias
  
  

To create a process rule in the Object mode:

1. Use the Navigator assistant or the design window to select the object to which you want to add a process rule.
2. In the browser pane, choose the category for which you want to create the rule.
3. In the Create Process Rule section, choose
   • The type of process rule to create from the first drop-down list.
   • The value type, where appropriate, from the second drop-down list.
     
     Each list is seeded appropriately depending on what is selected in the browser pane.
     
4. Click the plus (+) button in the Create Process Rule section to add the new process rule to the selected constraint group.
   
   Alternatively, press the Enter key.
   The process rule is added to the list. The Summary field in the browser pane is highlighted brown to indicate that the rule was created using the default values.
5. Modify the rule by changing the default data on the Attributes, Value, and Parameters tabs.
   
   Only relevant tabs are available for a process rule.
6. Click Update to apply the new values you set in the Value tab.
   
   The changes you make on the Attributes and Parameters tabs are automatically saved. Therefore, you do not need to click the Update button to save these changes.
   The new values that you specify on the Value tab appear in the Summary column of the browser pane. The brown highlight disappears indicating that the rule has been modified.
   
   To quickly add more process rules of the same type, click the Add button instead of Update. Each click adds a new rule with the same values displaying in the Summary column as the last one you added. The Summary column appears brown to indicate that the process rule values might need to be changed.
7. Select each new rule you added and edit the values, as required.
   
   You can also create an appropriate Virtuoso-generated constraint group or apply an existing constraint group to a selected object. For more information, see Applying a Virtuoso Generated Constraint Group and Applying an Existing Constraint Group to a Selected Object.

Creating a New Process Rule for a Constraint

You can use the Process Rule Editor to create process rules for constraints selected in the Constraint Manager assistant. The following constraints are supported.

• Diff Pair
• Matched Length
• Net Class
• Shielding
• Symmetry
• Bus Net
• Process Rule Overrides

When you define process rules for constraints, the browser pane displays only the process rule categories that apply to the selected constraint. For example, for a Diff Pair constraint, you can see the Group to Outside Group, Within Group, and Default categories.

Note:

• Group to Outside Group refers to rules that apply between the members of the current constraint and the objects outside the current constraint.
• Within Group refers to rules that apply between the members of a constraint.
• Default refers to the default set of constraints that apply to the members of the current constraint.

Selecting one of these categories populates the Create Process Rule section with the rules you can define in that particular category. For example, for Group to Outside Group, you can define the Minimum Spacing Different Layers and Minimum Spacing Same Layer rules.

To create a process rule for a constraint;

1. Select the constraint for which the rule is to be created in the Constraint Manager assistant.
2. If the Process Rule Editor is not displayed, click the Process Rule Editor button ( ) on the Constraint Manager toolbar.
   
   Alternatively, right-click the design object in the layout canvas or the layout navigator and choose Process Rule Editor from the shortcut menu.
3. In the Process Rule Editor browser pane, select the category for which you want to create the rule. For this example, let us select the Group to Outside Group category.
4. In the Create Process Rule section, choose
   • The type of process rule to create from the first drop-down list.
   • The value type, where appropriate, from the second drop-down list.
     
     Each list is seeded appropriately depending on what is selected in the browser pane.
5. Click the plus (+) button in the Create Process Rule section to add the new process rule to the selected constraint group.
   
   Alternatively, press the Enter key.
   
   The process rule is added to the list. The Summary field in the browser pane is highlighted brown to indicate that the rule was created using the default values. You can modify the rule by changing the default values. This also removes the highlight from the Summary column.
6. Modify the rule by specifying appropriate data on the Attributes, Value, and Parameters tabs.
   
   Only relevant tabs are available for a process rule.
7. Click Update to apply the values you set in the Value tab.
   
   The changes you make on the Attributes and Parameters tabs are automatically saved. Therefore, you do not need to click the Update button to save these changes.
   The new values that you specify on the Value tab appear in the Summary column of the browser pane.
   
   To quickly add more process rules of the same type, click the Add button instead of Update. Each click adds a new rule with the same values displaying in the Summary column as the last one you added. The Summary column appears brown to indicate that the process rule values might need to be changed.
8. Select each new rule you added and edit the values, as required.

Copying an Existing Process Rule

You can quickly create new process rules by copying the existing ones.

To copy some existing process rules to a new location:

1. In the browser pane, select one or more process rules you want to copy.
   Note:
   
   • Hold the Shift key while you select multiple items in the tree.
   • The selected set can contain multiple process rules from different constraint groups.
2. Click the Copy Rules button on the toolbar.
   
   Alternatively, right-click the process rule that you want to copy and choose Copy Rules.
   The selected rules are copied to the clipboard.
3. Select the constraint group to which you want to copy the selected rules and click the Paste Rules button on the toolbar.
   
   Alternatively, right-click the target constraint group and choose Paste Rules.
   The process rules are pasted into the new location as displayed in the figure below.
   
   
   Note:
   
   • You can paste the copied rules to a single constraint group at a time. The tool does not support selecting multiple target destinations for pasting the copied rules.
   • To copy a rule to different target destinations, select each target at a time and click the Paste Rules button on the toolbar. Alternatively, you can use the Paste Rules command from the shortcut menu.
   
   If you delete a process rule in the browser in between copying and pasting, the deleted rule is also removed from the clipboard and is not subsequently pasted.

Creating a Layer-Purpose Pair

To create a layer-purpose pair in PRE:

1. Select a layer from the drop-down list box and click the arrow ( ) button to the right of the list.
   A new purpose drop-down list box appears, as displayed in the figure below.
   
   
   The default value for layer purpose is NONE. This indicates that a purpose is currently not defined for the layer.
2. Select an appropriate purpose, such as drawing, for the selected layer.
   
   
   Currently, PRE supports default purposes for most of the layer constraints. However, other Virtuoso applications fully support purposes only for the following constraints: Minimum Spacing, Minimum Width, and Minimum Clearance. Therefore, the default state of the Purpose cyclic field for the constraints that are not “purpose-supported” by other Virtuoso applications is NONE. For more information about the layer-purpose pairs supported by the Virtuoso technology file, see Purpose-Aware Derived Layers and techPurposes in the Virtuoso Technology Data ASCII Files Reference User Guide.
3. Specify an appropriate data format value for the selected layer. For example, when creating a Minimum Spacing Different Layers rule, you need to specify a minimum spacing value, such as 0.0250, between the two selected layers.
   
   
4. Click Update to apply the new values you set on the Value tab.

The Summary column displays a single concatenated string representing the layers used for the selected process rule and the current value of the constraint. The brown color indicates that the process rule has been created using default values, which might need to be changed.

Applying Valid LPPs Process Rule

In addition to allowing purposes to be defined for the selected layer when creating a process rule, the Process Rule Editor supports the Valid LPPs (Valid Layer Purpose Pairs) process rule. This rule defines the valid layer-purpose pairs that can be used for routing. Like most other process rules, you can add this process rule to a constraint group in the Technology or Design scopes or to an Object. You can also modify or delete the process rule, as required.

To select a valid layer-purpose pair from the Valid LPPs process rule:

1. Select the Valid LPPs process rule in the browser pane and click the Value tab.
2. From the list of layer-purpose pairs displayed on the Value tab, select the check box next to the layer name in the row that carries the required layer-purpose combination.
3. Click Update to apply the layer-purpose values you selected.
   The layer-purpose pair that you selected displays as a single, hyphenated string in the Summary column of the browser pane.

For information about creating a layer-purpose pair in PRE, see Creating a Layer-Purpose Pair.

Creating a Voltage Dependent Process Rule

Voltage dependent rules are the ones that define a process constraint in terms of a voltage level. Currently, PRE supports two such rules—minVoltageSpacing and minVoltageClearance. Both these rules define the separation constraint between two devices in terms of voltage levels. The data value format supported by both the rules is voltage, spacing.

minVoltageSpacing defines the spacing between devices along a single layer, whereas minVoltageClearance defines the spacing between devices on two layers. You can define the required voltage values and the corresponding spacing for both the process rules using the VOLTAGE-Spacing table in the Value tab, as displayed below.

To specify the required voltage and spacing values for a selected layer:

1. Type an appropriate value for the voltage in the VOLTAGE field.
2. Double-click the Spacing field and type in an appropriate value.
3. To add another voltage-spacing column to the table, click the Insert new column (+) button on the right.
   A new VOLTAGE-Spacing column is added as displayed below.
   
   
   
   If you click the Insert new column (+) button multiple times, multiple columns are added. By default, the voltage in each column increments by 1. You can select each column and modify the voltage and spacing values, as required.
4. Click Update to apply the values you set.
   The new values that you specify on the Value tab appear in the Summary column of the browser pane.

For minVoltageClearance, you need to select two layers instead of one and perform the steps as described above.

Editing Existing Process Rule Values

To edit the layer-specific values for an existing process rule:

1. In the browser pane, select the process rule you want to change.
   A dynamic widget is displayed. The widget comprises the following tabs:
   • Description Tab
   • Attributes Tab
   • Value Tab
   • Parameters Tab
   
   Each tab displays the current values for the selected process rule.
2. To edit the existing process rule values, change the values in each of the tabs, as required.
   
   The Description tab is not editable.
   
3. Click the Update button to save the values you changed on the Value tab.
   
   The changes you make on the Attributes and Parameters tabs are automatically saved. Therefore, you do not need to click the Update button to save these changes.
   The process rule is updated to reflect the new settings.
   
   To quickly add more process rules of the same type, click the Add button instead of Update. Each click adds a new rule with the same values displaying in the Summary column as the last one you added. The Summary column appears brown to indicate that the process rule values might need to be changed.

Applying a Constraint Group

For a process rule to be applied to a technology, design, or object; it must be a member of a constraint group that supports the rule. Likewise, when applying a constraint group, the target constraint should support the applied constraint group.

For example, when applying a Constraint Group in the Technology scope, you can only select the Constraint Groups that are supported by the Technology database. The supported items are the ones that appear in the Constraint Group drop-down menu for each database.

To apply a constraint group to another constraint group, use the data value formats in the Apply Constraint Group section. The Constraint Group drop-down menu reflects the associated database as a tag (Tech or Design). This helps avoid confusion when selecting the constraint groups.

Let us now apply a constraint group to the virtuosoDefaultExtractorSetup constraint group in the browser.

1. Select the virtuosoDefaultExtractorSetup constraint group in the browser pane.
   
   
2. Choose the constraint group you want to apply from the drop-down list box in the Apply Constraint Group section.
   
   
3. Click the arrow button on the right of the list box to apply the constraint group.

The constraint group is inserted into the virtuosoDefaultExtractorSetup constraint group in the browser pane. Any process rules defined in the DefaultRouteSpec constraint will now be applied to any design referencing the virtuosoDefaultExtractorSetup constraint group.

The constraint group is still also listed on the main branch of the browser pane.

To make any changes to the Constraint Group, you must update the source Constraint Group and not the one linked in. Applied constraint groups are not available for editing. In fact, any changes you make to the source automatically reflect at instances where the constraint group is linked.

For example, to update the process rules for LEFDefaultRouteSpec, you must update the constraint group in the main browser pane instead of trying to update the instance appearing under virtuosoDefaultExtractorSetup.

Setting the Precedence of a Constraint Group or Process Rule

Process rules are applied in the order in which they are listed inside a constraint group. However, you can change the precedence of an applied constraint group or individual process rule by using the Move Up and Move Down arrow buttons on the toolbar.

To change the precedence of an applied constraint group or process rule:

1. Select the constraint group or process rule you want to move.
   
   
2. Do one of the following:
   • Hold down the left mouse button to drag the constraint group to its new location. This method lets you move the selected constraint group or process rule more than one position at a time.
   • Right-click the constraint group or process rule and choose Move Up to increase or Move Down to decrease the precedence. This moves the selected object up or down the list one position at a time.
     
     These functions are not available for objects at the top level of the browser tree comprising the Constraint Groups.
   • Click the Move Up or Move Down button on the Process Rule Editor toolbar. This moves the selected object up or down the list one position at a time.
     
     
   The browser pane updates to show the constraint group or process rule at its new location.
   
   

Virtuoso Generated Constraint Groups

Virtuoso ships with a number of predefined constraint groups, which you can generate and apply to selected objects or constraints in your design.

These constraint groups are generated with a predefined set of rules set to values that are based on the available technology information. A generated constraint group is stored in the design when you apply it to a selected object or constraint in that design. The constraint group can also be applied to other objects and constraints. This lets you quickly generate and reuse constraints groups without having to manually enter the long list of common process rules. Furthermore, this allows the users to create their own Constraint Groups and modify them, as required, in less time.You can generate a predefined constraint group from the Constraint Manager parameters pane. To do this, select the object or constraint to be constrained, generate the type of constraint group you need, and then add, modify, or remove the process rules, as required.

For example, the picture below shows the constraint groups you can generate for a Shielding constraint – Parallel, Tandem, and Coaxial.

The label Generate at the end of each constraint group name indicates that this is a predefined constraint group that has not yet been generated for the current design. When you choose a constraint group from the Shielding drop-down list box, that group is generated with its default rules in the Process Rule Editor browser pane. This causes the Generate entry to be removed from the list box and is replaced by a Design entry of the same name. This indicates that the constraint group has been generated and stored in the design.

The table below lists the predefined constraint groups you can generate for each constraint type.

Constraint Type	Parameter Name	Constraint Group	Contents
Diff Pair	Within Group	2x Spacing thru 10x Spacing	Varying multiples of the minimum spacing defined for each layer in the reference technology file.
	Group to Outside Group	2x Spacing thru 10x Spacing	Varying multiples of the minimum spacing defined for each layer in the reference technology file.
Matched Length	Group to Outside Group	2x Spacing thru 10x Spacing	Varying multiples of the minimum spacing defined for each layer in the reference technology file.
Bus Net	Within Group	2x Spacing thru 10x Spacing	Varying multiples of the minimum spacing defined for each layer in the reference technology file.
	Group to Outside Group	2x Spacing thru 10x Spacing	Varying multiples of the minimum spacing defined for each layer in the reference technology file.
Process Rule Override	Default	2x Width thru 10x Width	Varying multiples of the minimum width specified for each layer in the reference technology file.
	Input Taper	1UU Taper Halo	Taper halo set to 1u. Allowed layers are the same as those defined in the reference technology file plus all polysilicon materials.
	Output Taper	1UU Taper Halo	Taper halo set to 1u. Allowed layers are the same as those defined in the reference technology file plus all polysilicon materials.
Shielding	Shielding	Parallel	minWidth (shieldWidth) and minSpacing (shieldSpacing) for all the layers defined in the reference technology file. Width and spacings taken from the reference technology file.
		Tandem	Tandem Layer Above specifies the layer above the given signal wire layer to use as a shielding (Layer#1= signal Layer#2 = Shielding) Tandem Width specifies the width for the layer in the shielding constraint.
		Coaxial	Parallel rules created as above, tandem rules created as above but wider to cover both the signal and parallel shields.
Symmetry	Group to Outside Group	2x Spacing thru 10x Spacing	Varying multiples of the minimum spacing defined for each layer in the reference technology file.
Net Class	Within Group	2x Spacing thru 10x Spacing	Varying multiples of the minimum spacing defined for each layer in the reference technology file.
	Group to Outside Group	2x Spacing thru 10x Spacing	Varying multiples of the minimum spacing defined for each layer in the reference technology file.

Applying a Virtuoso Generated Constraint Group

You have a design which you want to route with a minimum width that is double the width defined in the technology files. You need to create and apply a constraint group that contains process rules re-specifying the minimum width for all the valid routing layers in your design.

You can either create this constraint group manually and add and set the value for each rule individually, or you can have Virtuoso generate a constraint group containing the rules you need. To do this,

1. On the Constraint Manager toolbar, click the Process Rule Editor button.
   
   
   The Process Rule Editor Graphical User Interface is displayed.
2. From the Navigator assistant, select an object in the design.
3. In the Constraint Manager assistant, create a Process Rule Override constraint for that object.
   
   
4. Pull down the list next to the Default parameter and choose the 2x Width generated constraint group.
   
   
   The 2x Width constraint group contains rules that redefine the minimum width for each routing layer to be double the value defined in the technology files.

The predefined constraint group is added to the Design scope of the Process Rule Editor.

You can edit the constraint group directly or use the copy and paste functions to make the predefined constraint group more specific for your design.

For more information, see

• • Creating a New Process Rule in the Technology or Design Mode
  • Copying an Existing Process Rule
  • Editing Existing Process Rule Values

If you now check the Default parameter drop-down list box in the Constraint Manager, you will see that the Generate entry has changed to the corresponding Design entry. This indicates the constraint group has been generated and added to the Design library. You can add this constraint group to any net in the Design or Object scope other than net102 in the example.

Applying an Existing Constraint Group to a Selected Object

In addition to generating a new constraint group for an object, you can reapply an existing constraint group to another object. The parameters pane in the Constraint Manager assistant allows you this feature.

Assume that you have nets in your design.You want to route these nets using double-cut vias and with a minimum width larger than that defined in the technology files. To do this,

1. On the Constraint Manager toolbar, click the Process Rule Editor button ( ).
   The Process Rule Editor Graphical User Interface is displayed.
2. Create a constraint group containing the individual constraints you need.
   1. Choose Design in the Process Rules on section.
   2. Create a constraint group to contain the process rules you require. See Creating a Constraint Group.
   3. Add the process rules you require. See Creating a New Process Rule.
   
   You have created a constraint group definition such as the 2xDoubleCut constraint group shown below, which specifies the list of valid layers, double cuts for each via and a larger width than the minimum specified in the technology file.
   
   
   You could generate a constraint group like the one above more quickly by using one of the Virtuoso generated constraint groups as a starting point and adding the specific rules you need. For example, you could start with the 2xWidth constraint group and then edit the generated group to limit the layers and create double cuts for all the vias. For more information, see Applying a Virtuoso Generated Constraint Group.
3. From the Navigator assistant, select the first net to which you want to apply this constraint group.
4. In the Constraint Manager assistant, create a Process Rule Override constraint for the selected net.
5. Pull down the list next to the Default parameter and choose the 2xDoubleCut constraint group you created previously.
   
   
6. Repeat steps 3 through 5 for each net to which you want to apply these constraints.
   This lets you apply the same process rule overrides to different objects without having to re-enter the same process rules manually every time.
   
   

For example, assume the Default field in the Constraint Manager shows Empty. You open the Process Rule Editor and apply the 2xDoubleCut constraint group. The Default field in the Constraint Manager now updates to show 2xDoubleCut (Design).

• If the Process Rule Editor is empty, the Default field shows Empty.
• If the Process Rule Editor contains a single group, the Default field always shows the name of that group.
• If you apply some process rules to the Default Constraint Group in the Object scope, the Default field in the Process Rule Editor shows Custom. If you then apply a constraint group to the Default constraint group, the value of the Default field changes to a constraint group string. The string includes the name of the new constraint you added. In addition, it displays Custom to indicate you have also added some custom Process Rules to the Default constraint group. The constraint string is displayed by both, the Constraint Manager and the Constraint Editor.
  
  
• When you try to change the setting of the Default field from Custom to a different value, you see a warning that doing so will replace all the custom edits you have made. This prevents you from inadvertently replacing a large amount of custom work with a single reference to a constraint group.

Removing a Constraint Group or Process Rule

You can remove a constraint group or an individual process rule from the Process Rule Editor to prevent it from being applied to the current design or object. The behavior is different depending on what you are removing.

If the selected object is:

• A process rule, the rule is deleted from the technology database.
  
  
• A constraint group applied to another constraint group, the reference is removed from the browser pane but the constraint group is not deleted from the technology database.
  
  
  • After the constraint group is removed, it still appears in the technology scope.
    
    
• A constraint group definition on the main branch of the browser pane, the constraint group is deleted from the technology database, is removed from the main branch, and removed from any constraint group that references it.
  
  

To remove a constraint group or process rule from the browser pane:

1. Select the constraint group or process rule you want to remove.
2. Do one of the following:
   • Click the right mouse button and choose Remove.
   • Click the Remove Selected button in the toolbar.
     
     

Saving Changes and Closing the Process Rule Editor

To save the changes you have made at any time:

• Click the Save Technology button in the Process Rule Editor toolbar.
  
  
  The changes are saved but the Process Rule Editor is not closed. Use this to save your work periodically as you define process rules.

To close the Process Rule Editor:

• Click the Exit button in the bottom right corner of the Process Rule Editor window.
  Any unsaved changes are saved and the Process Rule Editor window closes.

Related Topics

For a list of process rules supported by the Process Rule Editor, see

• Process Rules Supported by the Process Rule Editor

For more information on the Process Rule Editor graphical user interface, see

• Process Rule Editor Graphical User Interface
  

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