generate_vcd_ports - 2024.1 English

Vivado Design Suite Tcl Command Reference Guide (UG835)

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2024.1 English

Generate VCD ports for the instance


generate_vcd_ports [‑quiet] [‑verbose] <scope>


Name Description
[-quiet] Ignore command errors
[-verbose] Suspend message limits during command execution
<scope> Instance scope hierarchy




Open a VCD file handle for writing the port activity of the design unit instance. The VCD file is read by create_testbench Tcl command to read the port activity for writing stimuli source. The instance can be selected from the scope window in XSim simulator IDE or by specifying the hierarchical path to the instance when executing this command from Tcl console.

The command creates dummports.vcd file that will get populated when running simulation for the selected instance scope.

Note: The XSim simulator must be up and running in order to generate this file for the selected instance.

If running this command from Vivado™ IDE, then the dumpports.vcd file will be created in the simulation run directory. If running this command from XSim standalone GUI, then the dumpports.vcd file will be created in vcd2tb sub-directory in the current directory.


-scope <arg> - (Required) Specify the instance scope hierarchy name.

-quiet - (Optional) Execute the command quietly, returning no messages from the command. The command also returns TCL_OK regardless of any errors encountered during execution.

Note: Any errors encountered on the command-line, while launching the command will be returned. Only errors occurring inside the command will be trapped.

-verbose- (Optional) Temporarily override any message limits and return all messages from this command.

Note: Message limits can be defined with the set_msg_config command.


The following commands will create VCD file for /top/DUT/fifo/buf_1 instance of type buf module, record waveform activity for 2000ns, and close the VCD file handle:

generate_vcd_ports {/top/DUT/fifo/buf_1}
    run 2000ns
    close_vcd -ports