Pulse counter verification in vhdl

Discussion in 'VHDL' started by JSreeniv, Jun 16, 2009.

  1. JSreeniv

    JSreeniv Guest

    Hi all,

    I am presently working on verification and validation of pulse counter
    (where i am having such 8 counters)
    When i wrote a testbench in VHDL and checking the results in Modelsim
    i am not getting desired results.
    Here are the steps for vhdl code for simulation.

    1.setting the por_n = 0 for 100 ns and release to por_n =1 (power on
    2. Setting up bit 20 of inhibit_1 register to which enables the
    functionality of Pulse_counter_0_results register/counter
    3. checking the all registers before setting up the values: READ
    operation for ZERO values
    4. wait for 10 ns
    5.Set up register for software defined period for first two bits
    6.set up same register for Time base 100 ns on other two bits
    6.Load the count value to 10 in a register
    7.set the register for start measurement
    8. wait for 1000 ns

    9. Read the pulse_counter_0_results register after waiting above time
    10. As well read the loadable count register after this waiting time
    (where i am giving a continues pulse_din signal as a clock of 40 ns,
    so i need to get total pulse count in results register as : 1000 ns/40
    ns = 25 = 19(Hex)
    11 after waiting for 100 ns time also i should get same desired values
    which leads holding correct values in correspond results registers.
    12. Stop measurement

    But i am not getting that desired value instead i am getting only 14

    The whole simulation also depends on two clocks : fpga_clk = 50 MHz,
    and dsp_clk = 100 MHz,....

    So if anyone give me some exposure on this simulation desired
    results ....it will be very helpful.


    MITC - Bangalore
    JSreeniv, Jun 16, 2009
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  2. JSreeniv

    Shannon Guest

    My guess would be a thrown Johnson Rod or bad timing on the Spitzer

    But seriously, I think I can speak for the group. There is little
    chance we are going to be able to help with out some indication the
    problem code or something. We can't possibly guess at where the
    missing semicolon is otherwise.

    Shannon, Jun 16, 2009
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  3. JSreeniv

    JimLewis Guest

    Add all signals to simulation waveform window.
    Run simulation. Watch what did happen.
    Start watching from the beginning. What went
    right. What did not go right.
    Postulate as to why. Add more signals if necessary
    to prove your postulation.

    Your counter may start running with an old value and not
    load the new value until it rolls over. This would cause
    a difference in startup than you may expect, but it may produce
    correct steady state system behavior if it is tolerable
    at the beginning to act this way. Often it is tolerable
    because the software does not get to your programmable
    counters right away anyway.

    I usually make my programmable counters to have two
    features. 1: Write counter, but do not reload until
    roll over. 2: Write counter and reload immediately.
    That way I have both possible features covered.

    JimLewis, Jun 17, 2009
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