Via Creation
To connect objects on different layers within a cellview, you can create vias by using the Create Via command. The various types of vias are OA standard, cds, syContact, Pcell, and fixed vias.
Vias are defined in the viaDefs section of the technology file. Via definitions (viaDefs) are of the following types:
-
Standard via definition (
standardViaDefs) -
Custom via definition (
customViaDefs) -
Standard via variant (
standardViaVariants) -
Custom via variant (
customViaVariants)
Vias must exist in the technology file in order for them to appear in the Via Definition field in the Create Via form. In both the Create Via and the Edit Via Properties forms, viaDefs are listed in the order as they are defined in the validVias list in the technology file.
Parameter Caching
When you first open the Create Via form, the parameter values for the respective viaDefs are seeded in the form from the technology database values, based on the values specified in the Create Via section in the Layout Editor Options form.
While creating a via or via stack, you can change the parameter values for a viaDef. If you successfully create a constraints-valid via or via stack using the updated parameters, the parameter set is cached for that viaDef. The next time you access the form in the same Virtuoso session with the same viaDef and layer/width values, the cached parameter set is used. Each time you create a via with a different viaDef or different parameter values, the cache is created or updated, respectively.
The cached parameter values are validated against existing constraints before you can use the parameter set to create a via or via stack. If the parameters are not valid, they are recalculated based on enclosure calculation settings.
Similarly, if while creating a via, you manually update the enclosure values in the Create Via form, the values are cached if they comply with the minimum rules. The manually specified enclosure values are not re-calculated when you update other viaDef parameters, as long as the enclosure values do not violate the minimum rules.
You cannot create a custom or standard via that creates an invalid geometry.
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