User guide

7-3

VCD and VPD File Utilities

$var wire 8 ! out1 [7:0] $end

Therefore all the value changes and simulation times for signal out1

are for the entire signal and not just for the 0 bit.

The vcdpost utility can create an alternative VCD file that defines a

separate $var section for each bit of the vector signal. The results

are as follows:

$var wire 8 ! out1 [7] $end

$var wire 8

" out1 [6] $end

$var wire 8 # out1 [5] $end

$var wire 8 $ out1 [4] $end

$var wire 8 % out1 [3] $end

$var wire 8 & out1 [2] $end

$var wire 8 ’ out1 [1] $end

$var wire 8 ( out1 [0] $end

What this means is that the new VCD file contains value changes and

simulation times for each bit.

Uniquifying the Identifier Codes

In certain circumstances, to enable better performance, VCS assigns

the same VCD file identifier code to more than one net or register, if

these nets or registers have the same value throughout the

simulation. For example:

$var wire 1 ! ramsel_0_0 $end

$var wire 1 ! ramsel_0_1 $end

$var wire 1 ! ramsel_1_0 $end

$var wire 1 ! ramsel_1_1 $end

Here VCS assigns the ! identifier code to more than one net.