Re: co-simuation

On 8/31/2015 12:25 PM, Edward Vidal wrote:
> Hello All,
> I am testing VHD2VL and trying to test the outputted file ifchain.v with MyHDL & Iverilog
> co-simulation on a Raspberry Pi 2 B.
>
> I created the files and folder vcd
> https://github.com/develone/raspberrypi2_yocto/tree/master/vhd2vl/examples/tb
>
> ifchain  myhdl.vpi  tb_ifchain.v  test_ifchain.py  vcd
>
<snip>
> If in stimlus section of test_ifchain.py.
> I comment the lines 25 & 26 I get the results below.
>
>      python test_ifchain.py
>      Running test...
>       0
>        *{'a': Signal(intbv(0L)), 'status': Signal(False), 'b': Signal(intbv(0L)),
>      compiling ...
>        iverilog -o ifchain ../ifchain.v ./tb_ifchain.v
>      cosimulation setup ...
>        vvp -m ./myhdl.vpi ifchain
>      VCD info: dumpfile vcd/ifchain1.vcd opened for output.
>        <myhdl._Cosimulation.Cosimulation object at 0x769f6870>
>      back from prep cosim
>      start (co)simulation ...
>
> This appears to work okay but when I gtkwave vcd/ifchain1.vcd
> The signals a,b and clk red and status is yellow.
>
> When the I uncomment lines 25 & 26 try send values to the co-simulation.
> The program does not run to completion but crashes with the following error.
>    File "/usr/lib/python2.7/site-packages/myhdl-1.0dev-py2.7.egg/myhdl/_Waiter.py", line 142, in next
>      clause = next(self.generator)
>    File "test_ifchain.py", line 25, in stimlus
>      a.next = 10
>

This actually is not a cosimulation error.  I ran your
code and the resulting error is:

     ValueError: intbv value 10 >= maximum 8

In your code your `a` and `b` are:

     a = Signal(intbv(0)[3:])
     b = Signal(intbv(0)[3:])

Now remember, in Python the upper limit is exclusive,
you created 3bit bit-vectors.  The max value that can
be used is 7.  You probably intended it to be:

     a = Signal(intbv(0)[4:])
     b = Signal(intbv(0)[4:])

When I make the changes, you code executes without
error.

Regards,
Chris


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