#27 Digital simulation with more than few inputs


Simulation a component with f.e. 20 inputs 1 output does not work (in more or less real time):
1) Truth table simulation:
1.1) hangs in step "running VCD conversion... " with qucsconv.exe running. Aborting the simulation does not stop qucsconv.exe.
1.2) or stops after simulation with an error message about "out of memory" in log.
2) TimeList simulation stops with an error message "Unknown time unit .04858e+07
Unknown command 'ns'. Type h for help." in log.


  • Nobody/Anonymous

    TimeList simulation netlist

  • Stefan Jahn

    Stefan Jahn - 2009-10-21

    Hello! Can you please provide the schematic for easier bug finding? Also: which version of qucs and freehdl are you using?

  •  gatisg

    gatisg - 2009-11-03

    QUCS v0.0.15 (Win). FreeHDL latest (IMHO v0.0.7?) - seems like FreeHDL has no command line option to get version info.
    On adding a comment there is no way to add attach - see previously attached netlist.txt

  • Stefan Jahn

    Stefan Jahn - 2010-03-29

    Hello! I was now able to reproduce the problem. Let's see what I can do about it.

  • Stefan Jahn

    Stefan Jahn - 2010-03-29
    • assigned_to: nobody --> ela
  • Stefan Jahn

    Stefan Jahn - 2010-04-14

    Hello there!

    I just changed the VCD converter in CVS. The VCD processing is now much faster. I tested with 18 and 19 bit truthtables and this is working now fine. It is a bit unusual with so many inputs for a truthtable. Technically speaking it is difficult with so many inputs; just consider with 18 inputs you have 256k table entries with 19 samples even 512k table entries. Is this number of table entries (or even more) still useful?

    Nevertheless I'll be checking if I can reduce memory consumption (speed is not a problem anymore) a little. Now, with 2^19 truthtable entries, approx. 1GB is required...

    Best regards, Stefan.

  •  gatisg

    gatisg - 2010-04-19

    Should be fine. Every tool has its limits, so truth table too. Nice enough to have it more than 17 bits :)
    Thank You!

  • Stefan Jahn

    Stefan Jahn - 2010-05-10
    • status: open --> closed
  • Stefan Jahn

    Stefan Jahn - 2010-05-10

    Hello! For now I consider this issue fixed, agreed?


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