Design Variables

You can use the following design variables with Layout XL.

Netlist Processor Expressions

Netlist Processor (NLP) expressions are properties that specify parameter values. These expressions are used by the Open Simulation System (OSS) in netlisting.

Layout XL evaluates CDF parameters that begin with the string '[@' as netlist processor (NLP) expressions regardless of the value of the parseAsCEL environment variable.

Analog Expression Language Expressions

Analog Expression Language (AEL) expressions, such as iPar and pPar, define the value of a parameter as a function of other instance parameters or parameters passed from other levels of hierarchy. If you specify the value of a parameter using an AEL expression, the parameter

Must be defined in the component description format (CDF) for the cell of which the symbol is a view.
Must be a string for which parseAsNumber and parseAsCEL properties are set to t.
Must not have a CDF callback (because the evaluation of the expression does not trigger the execution of the callback).

If Layout XL detects a parameter value defined with iPar, pPar, or other AEL expressions not defined in the CDF, you see a warning in a message box.

Netlisting Mode

To ensure that Layout XL always evaluates CDF parameters correctly, make sure that

The CDF parameters in question have the parseAsCEL option set to yes.
The CDS_Netlisting_Mode shell environment variable is set to Analog before you launch Layout XL.

You can also set CDS_Netlisting_Mode for the current session only. To do this,

Type the following commands in the CIW.

setShellEnvVar("CDS_Netlisting_Mode=Analog")
 
cdsSetNetlistMode()

To check which mode is currently set,

Type the following command in the CIW.
```
cdsGetNetlistMode()
 
```

If you have the CDS_Netlisting_Mode shell environment variable set to Digital, Layout XL will not evaluate the CDF parameters by default. But, you can set the dbSearchCDF SKILL function to t to cause CDF to be searched for parameter values.

For more information on AEL expressions, see Scope of Parameters in the Virtuoso ADE Explorer User Guide.

Simulation Design Variables

When you use simulation design variables to specify the value of a parameter in the circuit, Layout XL uses the value last saved during the simulation of the circuit as the value for the layout implementation.

For more information about simulation design variables, see Design Variables and Simulation in the Virtuoso ADE Explorer User Guide.

Virtuoso Layout Suite XL: Connectivity Driven Editing User Guide
Product Version IC23.1, November 2023