Virtuoso Schematic Composer User Guide

Creating Schematics

The Add Note Text form appears.

Add Note Text

You can type a note to document your design. You can also read in (or import) an ASCII file from disk.

~/fileName my_directory/fileName

2.In the Read File field, type the path to the file.

3.Click the Read File button.

Adding Patchcords

A patchcord is a special connection symbol. You use a patchcord to establish aliases between the signals of two different nets.

Unlike tap names, where you extract bits of a single net, you can use patchcords to copy one net to another. You can also use the patchcord to map bits from one net to different bits of another net.

The value (connection expression) of the NLP label describes how to map the bits of the net attached to the src (source) pin to the bits of the net attached to the dst (destination) pin.

Virtuoso Schematic Composer User Guide

Creating Schematics

The syntax you use for naming the vector expression is the same as the syntax for wires and multiple bits.

The number of bits in the src vector expression must equal the number of bits in the dst vector expression.

You can also use patchcords to connect multiple nets (merge two buses).

To add a patchcord to a schematic, do the following:

1.Choose Add – Instance.

The Add Instance form appears.

2.In the Library field, typebasic.

3.In the Cell field, typepatch.

The default connection expression is 0=0, which indicates that the nets are equal to or greater than 1 bit wide.

Virtuoso Schematic Composer User Guide

Creating Schematics

If the nets are more than 1 bit wide, you can update the connection expression value on the Edit Object Properties form.

4. Move the cursor into your design and click to add the patchcord.

To add the following properties to a patchcord symbol, do the following:

1.Choose Edit – Properties – Object. The Edit Object Properties form appears.

2.Click the Add button and add the following properties on the form that appears.

nlAction = ignore

pcbAction = ignore

schType = patchCord

These properties must exist on the patchcord symbol to ensure that the netlister ignores patchcord instances.

3.Make sure that the symbol view of the patchcord has two pins:

The source pin is named src.

The destination pin is named dst.

The system puts 0=0 in the Connection Expression field, which indicates that the nets are equal to or greater than 1 bit wide.

If the nets are more than 1 bit wide, you can update the connection expression value on the Add Instance form.

0=0

4. Click OK.

Note: The basic library contains the component cds_thru, which creates a pseudo-short for the situations where a patch does not suffice; for example, if you need a short between two terminals or a terminal and a global signal. The component is arranged to netlist in sensible ways for the following tools:

lvs/auLvs: the cds_thru component can be shorted using the Diva removeDevice function in your LVS rules

cdl/auCdl: a small value resistor which can be ignored with *.RESI