Sta command documentation

[dwRchyngqxs]

Hello, I am trying to extract static timing analysis results using the sta command but the documentation is missing some info.

What option does this command takes? Is it possible to get fewer information, only latest arrival time for instance? Is there an option to output it in a nice format like stat json output?

I assume the arrival times are computed using timing information provided in https://github.com/YosysHQ/yosys/blob/3ebc50dee4007f8cca4ffc0e850bc3e86f7641f4/techlibs/ecp5/cells_sim.v, am I right?

What is the unit for the arrival time?
(I know the timing analysis cannot be accurate before place and route)

[jix]

The sta command doesn't take any options at all, so it's not possible to adjust how the output is presented. It uses the timing information loaded into the current design, so to use ecp5/cells_sim.v you would precede sta with read_verilog -specify +/ecp5/cells_sim.v where -specify enables loading specify ... endspecify blocks.

I'm not sure about the units, as far as I can tell, it just uses the values in the specify blocks without ever performing any unit conversion.

(I haven't used the sta command, this is just what I got from a glance at the implementation, so I might have missed things)

[dwRchyngqxs]

Yosys 0.23+38 (git sha1 f9db7c0, clang 10.0.0-4ubuntu1 -fPIC -Os)
I will post the whole command sequence I used that generated this error because executing only this command does not produce any error, it does after synthesizing a design (EDIT: probably a bug in the design, see below).

[dwRchyngqxs]

I ran it on a smaller example, it did not produce any error. But now sta doesn't produce any useful result either: sta.log
The script I ran is:

read_verilog top.v;
synth_ecp5 -abc9 -nowidelut;
read_verilog -specify +/ecp5/cells_sim.v;
tee -o sta.log sta

[jix]

Ah, I think it wants you to use read_verilog -lib -specify +/ecp5/cells_sim.v; instead (i.e. adding -lib), so that it doesn't try to analyze the timing of the simulation model, but knows that the modules in cells_sim.v are primitives for which the specify data should be used instead.

[dwRchyngqxs]

Adding -lib did the trick. Thank you for your quick answer.

[Ravenslofty]

I'm not sure about the units, as far as I can tell, it just uses the values in the specify blocks without ever performing any unit conversion.

By convention, specify units are in picoseconds.