Verilog-A read file separated by delays

 Anyone with experience in reading stimuli files through Verilog-A at all?

More general the question can be stated as:

How can I make a delay (in a transient simulation) dependent on the content of a read file?

I'd like to investigate, but the day job has been getting in the way... maybe somebody else has the time.

Andrew.

kennethbrun said:

More general the question can be stated as:

How can I make a delay (in a transient simulation) dependent on the content of a read file?

I take it this isn't possible?

I started on something similar, but it sounds like it isn't going to work.

RobinCommander said:

I take it this isn't possible?

I started on something similar, but it sounds like it isn't going to work.

Hi Robin,

I succeeded with the task the last time. I'm currently busy, but will post you ideas within a couple of days. Don't remember the details, but I can look them up...

/Kenneth

 OK thanks.

I was also trying to make the file name a parameter but couldn't get it to run in Spectre when I included the path.

In VerilogA:    parameter string read_file="/path/SPI_commands.txt";

In spectre.out:      Error found by spectre during circuit read-in.
    ERROR (SFE-874): "input.scs" 12: Unexpected operator "/".

Line 12 of input.scs:      I0 (net3 net4 net1 net5) SPI_stim read_file=/path/SPI_commands.txt

If I could persuade the netlister to put quotes around the string maybe this would work, but I haven't found a way to do this.

Robin

  Did you try escaping either quotes or slashes?

 E.g.

parameter string read_file="\/path\/file.txt"

or

parameter string read_file="\"/path/file.txt\""

I do it by:

parameter string simId = "default";

and then open the file with:

    fd = $fopen({{"$PROJECTSDIR/",simId}, ".txt"}, "r");

 /Kenneth

 Escaping the quotes or slashes didn't help, I also tried "\042/path\/file.txt\042" (042 is octal ").

But this feature was just plus, maybe something like your method will work.

Robin

Robin,

There's a bug in correctly setting the view-specific CDF for string parameters in VerilogA views, it seems.

To solve this, if you do:

almGetParameterList("mylib" "mycell" ?view "veriloga")

to find out what parameters you have - in your case you have one called read_file (maybe others too). Set the parameterList to not include read_file, but include all the other parameters (I called them param1 param2) - if there are no others, you can just pass nil instead of '(param1 param2):

almSetParameterList("mylib" "mycell" '(param1 param2) ?view "veriloga") 

Then tell it that read_file is a string parameter:

almSetStringParameterList("mylib" "mycell" '(read_file) ?view "veriloga")

Having done this, it should netlist it with quotes around the fileName.

I am filing a CCR on your behalf to correct the VerilogA parser/CDF creation to do this automatically.

As for implementing the delay in the original question, I would do it not by setting a timer every 1ps - because that will hurt simulation performance - but instead keep track of the time of the next "event" and set a non-periodic timer to start then and read the next data from the file).

Regards,

Andrew.

Robin,

Turns out that you don't need to do the almSetParameterList removing the read_file parameter; all you have to do is call almSetStringParameterList().

I filed CCR  1230515 to get the VerilogA parsing fixed.

Regards,

Andrew.

Robin,

Here is the important part of my solution to the problem.

--

   analog
     begin
        @(initial_step)
          begin
             timeOfNextStep = 0;
             simTimeStep=0;
          end
        @(cross($abstime-timeOfNextStep*1e-9,1) or initial_step)
          begin
             fileTimeStep=0;
             fd = $fopen({{"/path/inputcounter/",simId}, ".txt"}, "r");
             while($fscanf(fd, "%s = %s", signalName, signalVal)>0)
               begin
                  if(fileTimeStep==simTimeStep)
                    begin
                       case(signalName)
                         "#":
                         begin
                            timeOfNextStep=timeOfNextStep+signalVal.atoi();
                            $display("INFO: (%m) (time:%g) Delay read from file %s ns",$abstime,signalVal);
                         end
                         "CdrLocked":
                           begin
                              case(signalVal)
                                "0": CdrLockedVar = 0;
                                "1": CdrLockedVar = 1.2;
                                "X": CdrLockedVar = 0.6;
                                "Z": CdrLockedVar = 0.6;
                                "z": CdrLockedVar = 0.6;
                                "x": CdrLockedVar = 0.6;
                                default: $strobe("ERROR: (%m) (time:%g) Unsupported signal value for signal CdrLocked: %s",$abstime,signalVal);
                              endcase
                              $display("INFO: (%m) (time:%g) Stimuli read: CdrLocked = %s",$abstime,signalVal);
                           end
                           end
                         default $strobe("ERROR: (%m) (time:%g) Unknown signal name: %s",$abstime, signalName);
                       endcase // case(signalName)
                    end // if (fileTimeStep==simTimeStep)
                  if(signalName=="#")
                    begin
                       // keep track of the number of "timesteps" in file
                       fileTimeStep=fileTimeStep+1;
                    end
               end
             simTimeStep=simTimeStep+1;
             $fclose(fd);
          end
        V(CdrLocked) <+ transition(CdrLockedVar,0,1e-12);
end
--

The example is not self-contained, but let me know if you need further details.

/Kenneth

PS: the performance of this forum is horrible today. Just had three timeouts :(