Yet another modelsim problem

Discussion in 'VHDL' started by Thomas, Aug 12, 2003.

  1. Thomas

    Thomas Guest

    Completed process "Generate Post-Translate Simulation Model".

    ERROR: Hidden remap failed

    Launching Application for process "Simulate Post-Translate VHDL Model".

    not only the software's stupid enough to launch the GUI after the error,
    but there is not a single entry about this error in the xilinx database, on
    the modelsim server or even in google (but me complaining about the same
    problem a month ago)
    The 'reason' field is as useful as usual :) this time they just didn't
    bother typing a message that makes no sense, they just left it empty.

    here's the code:

    process(Reset, MasterClock) is
    variable counter : std_logic_vector(2 downto 0);
    if(Reset = '1') then
    counter := "000";
    elsif(rising_edge(MasterClock)) then
    dividedclock <= counter(2);
    counter := counter + 1;
    end if;
    end process;

    so, all the calls to modelsim, regardless of the type (post translate, post
    map, etc) fail the same way.

    then 'generated expected simulation results' yields another interesting

    if, in the timing constraints, I select the clock to be rising edge only,
    it works; if I pick dual edge, it just 'skips' cycles every 30 or so in the
    display and everything gets out of sync...

    Any ideas?
    Thomas, Aug 12, 2003
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  2. Thomas

    K Mussatt Guest

    The FPGAs I have worked and do work with do not allow for a dual edged CLK.
    Assuming your does and /or assuming the
    synthesizer does some neat trick to allow this for your FPGA, maybe you
    could specifiy rising clock edge if in the layer above
    this entity, you had a faster clock divide by 2 to make this clock that you
    are using here. I dont' know if that is a possibility, but
    I do remember running into some odd synthesis problems once trying to make a
    dual edged clock.

    Also, it has been my experience to 'not' do a divided clock by using one of
    the bits, but rather to use it as an enable to drive
    something maintaining sync with the one and only true clock.


    DIV_2_EN <= COUNTER(2); -- pick the bit off you want to use
    DIV_2_EN_R <= DIV_2_EN; -- make another signal delayed by one (true) clk
    --outside of the CLK do this:
    DIV2CLK <= '1' when DIV_2_EN ='1' and DIV_2_EN_R = '0' else '0'; -- this is
    not a 50% duty cycle clock, but it has the correct freq. of CLK/2

    K Mussatt, Aug 14, 2003
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