Virtuoso AMS Environment User Guide

Designing for Virtuoso AMS Compliance

declaration of busname<15:0:2>, so you lose the ability to cross-probe the net that includes the bus.

Component Description Format

Do not use library component description format (CDF) information. In the AMS environment, library CDF information has no effect on netlisting.

(You can, however, use cell CDF. For information, see “UsingCell Parameters” on page 609.)

Parameters

This section describes the guidelines for using inherited parameters, cell parameters, and parameter formats in the AMS environment.

Using Inherited Parameters

If your design uses inherited parameters, comply with the following guidelines to ensure that you get the results you expect. (For background information, see the Analog Expression Language Reference Manual and the Component Description Format User Guide.)

■Do not use atPar ( [@ ) or dotPar ( [. ) expressions. If you ignore this guideline, atPar expressions are interpreted as pPar expressions, and dotPar expressions are interpreted as iPar expressions.

■Ensure that the parameters for any iPar ( [~ ) expressions are defined, with defaults, in the CDF for the master of the instance. Ensure that the parameters for any pPar ( [+ ) expressions are defined, with defaults, in the CDF for the instantiating cell.

■Define all parameters used as the argument of a pPar expression in the CDF.

If a parameter that is used as the argument of a pPar expression on an instance is not declared in the CDF, the parameter statement is written near the instantiation statement in the netlist file rather than at the top of the module. This behavior makes the netlist less readable.

■Do not use the { param } expression to pass parameters between levels of hierarchy. This form is not supported by the AMS environment. Parameters can be passed from one level of the design hierarchy to a lower level by using pPar expressions.