Scripting in Vivado

Question

I am using Vivado for running my Verilog codes. Even though I do not see any errors while running synthesis and implementation, bitstream cannot be built.

This is the error I get:

ERROR: [Drc 23-20] Rule violation (NSTD-1) Unspecified I/O Standard - 12 out of 12 logical ports use I/O standard (IOSTANDARD) value 'DEFAULT', instead of a user assigned specific value. This may cause I/O contention or incompatibility with the board power or connectivity affecting performance, signal integrity or in extreme cases cause damage to the device or the components to which it is connected.

Which also suggests:

To correct this violation, specify all I/O standards. This design will fail to generate a bitstream unless all logical ports have a user specified I/O standard value defined. To allow bitstream creation with unspecified I/O standard values (not recommended), use this command:

set_property SEVERITY {Warning} [get_drc_checks NSTD-1]

NOTE: When using the Vivado Runs infrastructure (e.g. launch_runs Tcl command), add this command to a .tcl file and add that file as a pre-hook for write_bitstream step for the implementation run.

Which comes down to how can I script in Tcl using Vivado? I added the suggested command to the tcl console but I still get the same error.

Answer 1

I sugest you do what the tool is telling to do, which is specify IO standard for your top level ports, for example, if you have sys_rst_n top level port you may add the following line to your .xdc constraint file:

set_property IOSTANDARD LVCMOS18 [get_ports sys_rst_n]

of course you should change LVCMOS18 to match IO standard of you port.

The error you get is really not a Tcl issue.

Answer 2

YOU WANT to fix these IOs, otherwise you may damage your hardware.

• open the routed checkpoint (dcp)
• using the IO port window fix the IOs that have default IO standard (one by one if needed)
• create the bitstream from the tcl window

Here's how to create a .tcl to fix this without having to re-implement the whole project:

• copy the commands that ran to fix the IOs from above (from the tcl console) and put the commands in a tcl file
• add this tcl file as a hook to "post route physopt" so the tcl runs automatically when this last step in the implementation flow.
• if you'll be rerunning implementation in the future, you should just place the commands in the project xdc file instead.