Virtuoso AMS Environment User Guide

Netlisting

Ensuring that Floating Point Parameters Netlist Correctly

This section describes how to specify parameters for a cell so that floating point values appear as intended in netlists. The procedure described here prevents problems that can arise when whole number floating point values are simplified to integer values during netlisting. The solution is to use cell CDF parameters, overriding the values for specific instances by using object properties.

Defining the Parameter and Specifying a Default Value

You can use the following steps to define such a parameter and specify the default value for it.

1.In the CIW, choose Tools – CDF – Edit. The Edit Component CDF form appears.

2.Type in the Library Name and Cell Name of the component that specifies the parameter of interest.

3.Ensure that Base is selected in the CDF Type field.

4.In the Component Parameters section of the form, click Add. The Add CDF Parameter form appears.

Virtuoso AMS Environment User Guide

Netlisting

5.Select paramType string, parseAsNumber yes, and parseAsCEL yes and type the name of the parameter into the name field. For example, the form might look like this for a parameter named hiVolt.

6.Click OK, to close the Add CDF Parameter form.

The new component parameter appears in the Edit Component CDF form.

7.Type the default parameter value into the field labeled with the name of your parameter. Use the number format that you want to appear in the netlist. For example, to be compatible with text views coded in VHDL-AMS, which is a strongly typed language, you might need to enter a whole number as a number with a decimal point followed by zero.

Unless overridden on the instance (as described in “Overriding the Default Parameter for Specifi Instances” on page 145), this is the value of the parameter for this cell of the

Virtuoso AMS Environment User Guide

Netlisting

design whenever it is instantiated. For example, the form might look like this for the CDF parameters hiVolt and refVolt.

8. Click OK to close the form.

Overriding the Default Parameter for Specific Instances

Specifying a component parameter in the CDF as described in the previous section provides a default value for that parameter. If you need to specify a different parameter value for a specific instance, you can follow these steps.

Virtuoso AMS Environment User Guide

Netlisting

1.Select the instance in the schematic that is to use a non-default parameter value.

2.Open the Edit Object Properties form for the instance.

3.Change the value for the CDF parameter to the value you need for the instance.

4. Click OK.

Now when you netlist the schematic, the parameter appears in the netlist with the non-default value. Parameters that use the default value do not appear in the netlist. For example, with the Edit Component CDF and Edit Object Properties forms set up as in the previous illustrations, hiVolt appears in the netlist but refVolt does not.

Virtuoso AMS Environment User Guide

Netlisting

Virtuoso AMS Environment User Guide

Netlisting