Constraint Group Definitions

The following values are supported for t_defName:

• foundry
  The foundry constraint group specifies process rules typically provided by the foundry or manufacturer. It is stored in the technology database. Define in this constraint group the absolute minimum set of process rules required to manufacture a design.
  The foundry constraint group is checked last in the constraint precedence lookup hierarchy. If a constraint override is not defined elsewhere, various applications use the values defined in the foundry constraint group.
  All applications recognize the foundry constraint group. Constraints specified in the foundry constraint group must always be satisfied.
  • Creating the foundry constraint group: The foundry constraint group is created and populated with information during lef2oa translation. The translators get the information from sections within the LEF file. Alternatively, you can create the foundry constraint group by loading an ASCII technology file containing the foundry constraint group information by using the Tools – Technology File Manager option in CIW.
  • Information in the foundry constraint group: The foundry constraint group contains all the information necessary to manufacture the design. Everything from minSpacing/minWidth for layers, minEnclosure, minStep, to via rules, to electrical constraints such as antenna rules.
  • Using the foundry constraint group in Virtuoso: The foundry constraint group is the final stop along the constraint precedence lookup trail. If a constraint override is not defined elsewhere, the tools use the value(s) in the foundry constraint group.
  
  The foundry constraint group is usually not writable for most users, but can be viewed by using the Process Rule Editor or by taking an ASCII dump. You can launch the Process Rule Editor by clicking the RMB in the Constraint Manager assistant or by clicking the PRE icon from the toolbar in the Constraint Manager assistant. You can set the scope to Technology and view the foundry constraint group in this dialog box. See Process Rule Editor.
• alternateFoundry
  (Virtuoso Advanced Node for Layout Only) The alternateFoundry constraint group contains one or more foundry constraint groups.
  To enable the name of the constraint group that contains the foundry constraints, use the AlternateFoundryCG environment variable.
• virtuosoDefaultExtractorSetup: Specifies that it is used by default by the extractor for connectivity extraction. This constraint group can be stored within the technology database or directly on the design itself, that is, lib/cell/view.
  • Information in the virtuosoDefaultExtractorSetup Constraint Group: The virtuosoDefaultExtractorSetup constraint group includes layers needed for extracting connectivity, plus poly, all metal layers, and cut layers in the valid layers section.
  • Using the virtuosoDefaultExtractorSetup Constraint Group in Virtuoso: A constraint group for extraction is required to specify the extractable layers.
  
  Connectivity extraction gets the constraint group name from the value of the setupConstraintGroup variable in your .cdsenv file. The default value is virtuosoDefaultExtractorSetup. You can change the name of the constraint group by resetting the value. If the setupConstraintGroup variable has no value set, the extractor prompts you for a constraint group to use for extraction.
• virtuosoDefaultSetup: Supplies a default set of constraints for both interactive and automatic routing.
  • Information in the virtuosoDefaultSetup Constraint Group: The virtuosoDefaultSetup constraint group contains validVias and validLayers for routing (no cut layers), and possibly other rules such as minWidth and minSpacing for the layers, overriding the foundry rules.
  • Using the virtuosoDefaultSetup Constraint Group in Virtuoso: The virtuosoDefaultSetup constraint group is typically used to define a full set of validLayers and validVias for the purpose of default interactive and automatic routing.
  
  For example, if any particular signal is selected for routing and does not have a constraint group assigned to it, the constraints in the virtuosoDefaultSetup constraint group apply. The contents of validLayers in virtuosoDefaultSetup are usually a subset of those defined in the virtuosoDefaultExtractorSetup constraint group because, while you may want to extract connectivity for non-metal layers, you do not want interactive and automatic routing to use the non-metal layers.
• virtuosoExtractorSetup
• virtuosoMPTSetup
• LEFDefaultRouteSpec: Stores routing information, such as information about layers and vias. This constraint group contains rule definitions typically used in digital standard cell applications or custom and mixed-signal applications that require metal layers only.
  • Creating the LEFDefaultRouteSpec Constraint Group: The LEFDefaultRouteSpec constraint group is specific to a LEF or DEF design flow and is created during lef2oa translation. Since a LEF file serves as the library source for technology information, the lef2oa translator puts all the technology information into the LEFDefaultRouteSpec constraint group. The valid layers, valid via definitions, and valid rules also become part of the LEFDefaultRouteSpec constraint group.
  
  The lef2oa translator translates any NONDEFAULTRULES in LEF as constraint groups in the OpenAccess tech database.
  • Information in the LEFDefaultRouteSpec Constraint Group: The LEFDefaultRouteSpec contains valid layer and valid via definitions. The via definitions are typically standard vias and several custom vias used by other routers such as NanoRoute in the Innovus environment. The LEFDefaultRouteSpec also contains any other non-default rules such as wide metal rules.
  • Using the LEFDefaultRouteSpec Constraint Group in Virtuoso: You can select the LEFDefaultRouteSpec as the default constraint group for interactive or automatic routing in the Wire Editing section of the Layout Editor Options form (Options — Editor).
• LEFSpecialRouteSpec: Stores information about power routing vias.
• taper
• inputTaper
• outputTaper
• shielding

Application-specific constraint groups, including all of the above barring foundry and alternateFoundry, influence the behavior of a particular application. You can also create application-specific constraint groups with user-defined names. To designate such constraint groups as application-specific, assign to them an appropriate constraint group definition, which determines the type of objects to which the constraint group applies.

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