You can use a Value Change Dump (VCD) file to capture simulation output. The Tcl commands are based on Verilog system tasks related to dumping values.
For the VCD feature, the Tcl commands listed in the table below model the Verilog system tasks.
Tcl Command | Description |
---|---|
open_vcd
|
Opens a VCD file for capturing simulation output. This Tcl command models the behavior of $dumpfile Verilog system task. |
checkpoint_vcd
|
Models the behavior of the $dumpall Verilog system task. |
start_vcd
|
Models the behavior of the $dumpon Verilog system task. |
log_vcd
|
Logs VCD for the specified HDL objects. This command models behavior of the $dumpvars Verilog system task. |
flush_vcd
|
Models behavior of the $dumpflush Verilog system task. |
limit_vcd
|
Models behavior of the $dumplimit Verilog system task. |
stop_vcd
|
Models behavior of the $dumpoff Verilog system task. |
close_vcd
|
Closes the VCD generation. |
See the Vivado Design Suite Tcl Command Reference Guide (UG835), or type the following in the Tcl Console:
<command> -help
Example:
open_vcd xsim_dump.vcd
log_vcd /tb/dut/*
run all
close_vcd
quit
See Verilog Language Support Exceptions for more information.
You can use the VCD data to validate the output of the simulator to debug simulation failures.