Value Change Dump
From Wikipedia, the free encyclopedia
VCD - Value Change Dump format - an ASCII file that contains the "Changes in Values of Signals". This is a STANDARD format and is compatible between different waveform viewers etc. Also most of the simulators can write out VCD files - both VHDL & Verilog versions.
A VCD file is an ASCII file that contains header information, variable definitions, and the value changes for all variables specified in the task calls.
Several system tasks can be inserted in the source description to create and control the VCD file.
Specifying the name of the dump file ($dumpfile)
In Verilog, the $dumpfile task is used to specify the name of the VCD file. The syntax for the task is as follows:
$dumpfile ( filename ) ;
The filename is optional.
Example:
initial
$dumpfile("module1.dump") ;
Specifying the variables to be dumped ($dumpvars)
In Verilog, the $dumpvars task is used to list which variables to dump into the file specified by $dumpfile . The $dumpvars task may be invoked as often as desired throughout the model (for example, within various blocks), but the execution of all the $dumpvars tasks must be at the same simulation time.
The $dumpvars task may be used with or without arguments. The syntax for the task without arguments is as follows:
$dumpvars ;
When invoked with no arguments, $dumpvars task dumps all the variables in the model to the VCD file.
[edit] See also
 |
This computer-related article is a stub. You can help Wikipedia by expanding it. |
