ModelSim PE (student ed.) vs. Xilinx ISE Simulator

Discussion in 'VHDL' started by Mihovil Frater, Mar 4, 2008.

  1. Hi!

    I have a synchronous design for Xilinx Spartan-3E FPGA and I'm comparing
    simulation results. For Behav. sim. everything is the same. For post-map
    simulation on ModelSim I get expected results. Problem is with
    post-place&route simulation.

    I'm asking myself which tool should I use?
    Is it 'enough' to 'trust' Xilinx ISE Simulator?

    Tools are installed with newest versions available & I've chose products
    which I get for free.

    For post-place&route simulation on Xilinx ISE Simulator I get expected
    results, the ones which I like. If I choose ModelSim PE, outputs have
    undefined value most of the time, I mean 'XXXXX' signals.
    But there is another cute stuff. My testbench lasts for 1400ns. Things
    which I described happen on first 1400ns. If I run it for another 1400ns
    (end on 2800ns), input signals repeat just as it starts from the beginning,
    but now I get 'good' results. Then if I do it again, for another 1400 ns, I
    get 'XXXXX' results again.

    Of course, I had to compile simulation libraries and I've done it in Xilinx
    ISE. I had a lot of warnings (hundreds) only for simprim library. These are
    the warnings:
    -- Compiling entity x_fdd
    -- Compiling architecture x_fdd_v of x_fdd
    -- Compiling entity x_fddrcpe
    ###### C:\Xilinx92i\vhdl\src\simprims\simprim_VITAL_mti.vhd(8220):
    tbpd_GSR_Q_C0 : VitalDelayType01 := (0.000 ns, 0.000 ns);
    ** Warning: [6] C:\Xilinx92i\vhdl\src\simprims\simprim_VITAL_mti.vhd(8220):
    VITAL timing generic missing port reference(s).
    (1076.4 section 4.3.2.1.2)
    ###### C:\Xilinx92i\vhdl\src\simprims\simprim_VITAL_mti.vhd(8241):
    tipd_GSR : VitalDelayType01 := (0.000 ns, 0.000 ns);
    ** Warning: [6] C:\Xilinx92i\vhdl\src\simprims\simprim_VITAL_mti.vhd(8241):
    VITAL timing generic missing port reference.
    (1076.4 section 4.3.2.1.2)
    ....

    I don't like this warnings, of course. On the other hand, post-map
    simulation worked fine on ModelSim. And after I run simulation for another
    1400ns (loop it again) I got results which I like :)

    Has anyone had similiar problems?

    I can post you my code, if you like, and testbench.

    Thnx for any help....
     
    Mihovil Frater, Mar 4, 2008
    #1
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