Re: [myhdl-list] Generating 160 bit signal

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

On 3/7/2015 4:12 PM, Edward Vidal wrote:
> Hello All,
> Trying to take 16 values from an image to generate 160 bit signal
>
Here is an example that might help.  Differs from yours
in that it uses ShadowSignals and elaboration to build
the "flat" representation.  The example uses an 8x5
matrix of 8bit signals and creates a 160 bit flat
version of the 4 lsb from each matrix element.

     def m_flatten(matrix, flat):
         _flat = ConcatSignal(*[col(4,0) for row in matrix
                                         for col in row])
         @always_comb
         def rtl():
             flat.next = _flat
         return rtl


     def test_flatten():
         matrix = [[Signal(intbv(0)[8:]) for col in range(5)]
                                         for row in range(8)]
         flat = Signal(intbv(0)[160:])
         tbdut = m_flatten(matrix, flat)
         @instance
         def tbstim():
             yield delay(1)
             print(bin(flat, 160))
             assert flat == 0
             matrix[0][0].next = 0x8
             yield delay(1)
             print(bin(flat, 160))
             assert flat[160-1] == 1
         return tbdut, tbstim
     Simulation(test_flatten()).run()

https://gist.github.com/cfelton/d52fc4abe8d50b73c13c

<snip>

> Most of the time it works
> working okay generates a signal of 160
<snip>
> ValueError: intbv value -4 < minimum 0

I believe the error you are seeing can be explained
with this little example:

     x = intbv(0)[16:]
     y = intbv(0, min=-128, max=128)
     z = intbv(0, min=0, max=256)

     # this will work
     x[:] = (y << 8) | z
     print(x)


     # this will fail
     y[:] = -8
     x[:] = (y << 8) | z
     print(x)


     # this will work
     y[:] = 118
     x[:] = (y << 8) | z
     print(x)


Regards,
Chris