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???
11/13/06 17:10
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 		 #127887 - test bench
Responding to: ???'s previous message
Russ Cooper said:
Thanks, Jez. I think that's what I thought. When programming in C, if I write a function like this:

int Add(int a, int b) { return a + b; }
then I can also write a throw-away function like this to test Add() in isolation from all the rest of my functions:

void main() { printf("3 + 5 = %dn", Add(3, 5)); }
If I understand you correctly, this second function is vaguely equivalent to your "test bench", and by the time I finally get it to print out "3 + 5 = 8", I have a fair degree of confidence that both the test bench and the function under test (FUT) are correct. Correct?


Very vaguely equivalent.

A proper test bench will compare the response to the given stimulus to the known correct value and tell you if you fail. (This way, you don't have to search through a lot of waveforms looking for the failure.) So, to use your C example,
Save This Code
void main()
{
    int x = 3;
    int y = 5;
    int expected_sum = 8;
    int Add_result;

    Add_result = Add(x,y);
    if (Add_result != expected_sum)
        printf("failure! Add_result %d didn't match expected %d\n", Add_result, expected_sum);
}


Again, the beauty of this is that you're told when you fail, not that you've passed a million tests.

-a

List of 81 messages in thread
TopicAuthorDate
Getting Started With FPGAs            01/01/70 00:00      
   A Book            01/01/70 00:00      
   Proceed with caution!            01/01/70 00:00      
   This is quite a nice deveolpment board            01/01/70 00:00      
   I like this board            01/01/70 00:00      
      I\'ve got one of these and can\'t recommend it            01/01/70 00:00      
         What are you talking about            01/01/70 00:00      
            Let me explain ...            01/01/70 00:00      
   generaly speaking            01/01/70 00:00      
      Damn, Jez, you need a spell-checker!            01/01/70 00:00      
         HDL-based design needs TEST BENCHES            01/01/70 00:00      
            I use 'em all the time, but ...            01/01/70 00:00      
               If your design is so simple            01/01/70 00:00      
                  What\'s important is the entry effort            01/01/70 00:00      
                     I dunno where you get these ideas from Richard            01/01/70 00:00      
                        Can you say ModelSim?            01/01/70 00:00      
                     Wrong            01/01/70 00:00      
                        Well, the schematic needs a little work            01/01/70 00:00      
                           more work?            01/01/70 00:00      
                              a few points ...            01/01/70 00:00      
                           ...            01/01/70 00:00      
                     HDL vs Schematics, take 1E6            01/01/70 00:00      
                        Thta may be great comfort to you ...            01/01/70 00:00      
                           Schematics? You're kidding!            01/01/70 00:00      
                              No, nor is my customer.            01/01/70 00:00      
                              both are a 'representation of Boole'            01/01/70 00:00      
                                 Yep, you're right...            01/01/70 00:00      
                                    To Clarify            01/01/70 00:00      
                                       schematic as equivalence check            01/01/70 00:00      
                                          Manual verification impossible because ...            01/01/70 00:00      
                                             schematic verification            01/01/70 00:00      
                                       Some more clarification            01/01/70 00:00      
                                          hanging problem            01/01/70 00:00      
                                             so will your post be            01/01/70 00:00      
                                    it's not fear of the unknown, but fear of its cost            01/01/70 00:00      
                           Static Timing Analysis and those "young engineers"            01/01/70 00:00      
                              It's a sign of the times, I suppose            01/01/70 00:00      
                                 And times change            01/01/70 00:00      
                                 senior?            01/01/70 00:00      
                                    That's because you've been avoiding the subject            01/01/70 00:00      
            I agree entirely. test benches are a pain but            01/01/70 00:00      
   Update from the OP            01/01/70 00:00      
      It's true ... we see things differently            01/01/70 00:00      
      the first buuk for any such venture            01/01/70 00:00      
      FPGA boards and that Cypress book            01/01/70 00:00      
         This may answer your question(s)            01/01/70 00:00      
   some of the references in the fpga faq            01/01/70 00:00      
      Good attitude            01/01/70 00:00      
   Also remeber to look at webistes like www.xilinx.c            01/01/70 00:00      
   My recommendation and opinions            01/01/70 00:00      
      I would stay away from Virtex-II            01/01/70 00:00      
         If you're going to fiddle with the 805x core ...            01/01/70 00:00      
            Something about life-cycles            01/01/70 00:00      
               No doubt about it.            01/01/70 00:00      
                  useful work            01/01/70 00:00      
                     Well, I beg to differ.            01/01/70 00:00      
                        salient point            01/01/70 00:00      
                           There's an area where that's not necessarily true            01/01/70 00:00      
                           FPGA Editor            01/01/70 00:00      
            Not necessarily            01/01/70 00:00      
               It's still too costly            01/01/70 00:00      
   Thanks to all            01/01/70 00:00      
   Update #2 from the OP            01/01/70 00:00      
   A testbench is...            01/01/70 00:00      
      I C            01/01/70 00:00      
         test bench            01/01/70 00:00      
            Makes sense            01/01/70 00:00      
   Yeah but...            01/01/70 00:00      
   Tristate buffer with propagation delays            01/01/70 00:00      
   Schematics vs. HDL            01/01/70 00:00      
      In a nutshell            01/01/70 00:00      
         it\'s been a while            01/01/70 00:00      
      Yes, but ... and there's always a but ...            01/01/70 00:00      
   Yep you can its called gate level design            01/01/70 00:00      
   Its really nothing to do with showing off            01/01/70 00:00      
      did you paraphrase this?            01/01/70 00:00      
      Jez, It\'s not \"sea of gates\" design, you know ...            01/01/70 00:00      
         Richards, it is there philosophy            01/01/70 00:00      
         Viewlogic            01/01/70 00:00      
   it is true            01/01/70 00:00      
   Here you go Richard graphical design exploration            01/01/70 00:00      

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