No, you cannot use ideal delay in PSS.

-Ken

Hi, Ken,

Is timer() function valid for PSS simulation? I used real RC delay to implement the 256 delayed clocks. It's fine but the simulation time is two long.

So I want to implement 256 clock source in veriloga. I used timer() to implement the clock. It's fine for tran. But there no clock for PSS plot. Is timer() valid for PSS? If it's not, any suggestion?

Hi Ken,
I am trying to create a new delay cell that does not have hidden states so that I can use to run PSS shooting method.  Here is my code.

module delay_trans (out, in);

output out; voltage out;
input in1; voltage in;

parameter real vh = 1;                  // output voltage in high state
parameter real vl = 0;                  // output voltage in low state
parameter real vth = (vh + vl)/2;      // threshold voltage at inputs
parameter real td = 0 from [0:inf);      // delay to start of output transition
parameter real tt = 0 from [0:inf);      // transition time of output signals

analog begin
   @(cross(V(in) - vth));
   V(out) <+ transition( V(in), td, tt );
end
endmodule

Please suggest.

Hi Ken,
Thanks for your input.
I found a workaround for running PSS with a "delay" cell.
I ended up using an ahdlLib inverter for which we can specify the delay value. I also specified non-zero tr and tf for the ahdlLib inverter.

With this, PSS  analysis does not give me an error about "distributed element" or "hidden state". However, PSS does not converge !!!

Is it possible that the ideal ahdlLib inverter transfer function is not smooth causing PSS convergence errors?


The log file shows the following. "PSS failed to converge PSS will adjust tstab a little and try again".
finally, "Even after adjusting tstab value, PSS failed to converge"

I checked the transient waveforms at the end of "tstab" time, they look periodic and correct.

Thanks
-CMOSA

Hi Ken,
Thanks, Will try CV/I kind of delay element.
Thanks
Marshnil