Re: Mantis 850: final step

Graham,

In a Verilog-AMS environment, one could use the final block next to the 
analog block; there would be no need to do the same thing in @final_step. 
In pure Verilog-A on the other hand, the combination $finish and 
@final_step have currently different semantics than in pure digital SV the 
combination $finish and final block.

It would break a lot of existing code to change the current Verilog-A 
behavior. Even though it is not possible to change the values of analog 
port variables anymore in the @final_step, one can still read them, and 
write them out to file - a file that is not necessarily open if $finish is 
called early (say in the @initial_step).

analog begin
  @(initial_step) begin
    if (Vx < 0) begin
      $strobe("Vx is smaller than 0, aborting ...");
      $finish;
    end
    fp = $fopen("output.tbl");
  end

  @(final_step)
    $fstrobe(fp, "Vout = %g, V(out));

end

final begin
  $strobe("$finish called ...");
end

As the final block and the @final_step event are different animals, I do 
not see a reason to make their behaviors equivalent - one is handled by a 
continuous-time solver, the other by a discrete event handler.

In summary: if you need postprocessing after a $finish, you can add a 
final block (in SV-AMS), if you want the simulation to stop immediately, 
use a @final_step event.

Regards,
Marq


Marq Kole
Competence Leader Analog Simulation, Philips ED&T










Helwig Graham-A11558 <Graham.Helwig@freescale.com> 
Sent by:
owner-verilog-ams@eda.org
26-10-2005 02:51

To
Chandrasekaran Srikanth-A12788 <Srikanth.Chandrasekaran@freescale.com>
cc
verilog-ams <verilog-ams@eda.org>
Subject
Mantis 850: final step
Classification







Hello Sri,
 
There was some discussion about how @final_step should behave w.r.t. $stop 
and $finish system tasks. System Verilog v3.1a has defined a final block 
(similar to initial blocks). For example:
 
    final begin
        $display("$finish has been called.");
    end
 
It would reasonable to make digital final block and analog @final_step 
event behave the same way. 
 
Regards
Graham