Re: [myhdl-list] Calling regular python code during simulation

[Christopher F. <chr...@gm...>]

On 1/18/12 6:35 AM, Matti wrote:
> I want to do something like this:
>
> def myfunc(data):
>      return float(data)
>
> def Int2Float(inval, outval, clock):
>      @always(clock.posedge)
>      def Int2FloatLogic():
>          out.next = myfunc(data)
>      return instances
>
> Of course this will not pass the convertor. But I would like to use it in
> simulation, and at a later date replace the float() call with an appropriate
> vendor-supplied library. In the real example myfunc is more complicated.
> Questions:
> - How can I get the simulator to just execute the python code without trying to
> convert it to myhdl primitives?
> - How do I tell the simulator that myfunc requires 28 clock cycles?
>
> Thanks,
> Matti
>


As you elude, you can use any valid Python in simulation (this is why 
any other HDL language is extinct for verification!).  In Python speak 
you want to create a generator that can be passed to the MyHDL 
simulation engine.

Your example would be valid other than it does not have the 28 clock 
cycle delay.  You could add a counter to count clock cycles or you could 
use the delay (@always(delay(28*CLK_SIM_STEPS))).  By using the delay in 
the @always decorator your generator will only execute the specified 
number of simulation steps.

Another, slightly more flexible, way to write generators is like the 
following.

def mod():

    @instance
    def tb_model():
       # Init variables
       while(True):
          out.next = myfunc(data)
          yield delay(28*CLK_SIM_STEPS)
          # can do some more
          # ...

In the above form, you have a little more flexibility but you have to be 
more explicit.  It doesn't "feel" as hardware description as the 
decorators (@always, @always_comb).  In the above you can use the delay 
or you can use a "variable" as a counter.

Hope that helps,
Chris