Re: [myhdl-list] always_comb from a change in Signal list does not get triggered

[Thomas T. <tho...@de...>]

Günter Dannoritzer wrote:

> This is my code:
> 
> def pipe(clk,en,din, dout, N,width):
> 
>   pipe = [Signal(intbvSigned(width)) for i in range(N)]
> 
>   print "N: ", N
> 
>   @always(clk.posedge)
>   def rtl1():
>     if en:
>       for i in downrange(N,1):
>         print "i: %d"% i
>         pipe[i].next = pipe[i-1]
>       pipe[0].next = din
>     print "pipe: %s"% pipe
> 
> 
>   @always_comb
>   def rtl2():
>     print "pipe[N-1]: %d"% pipe[N-1]
>     dout.next = pipe[N-1]
> 
> 
>   return instances()
> 
> I changed the code so that the pipe memory has only N-1 entries and dout 
> being the Nth register, which worked fine. I just would like to know 
> what I am doing wrong so that the always_comb gets not triggered anymore?

I think this is a bug in myhdl.

BTW, some related comments/questions:

 >       for i in downrange(N,1):
 >         pipe[i].next = pipe[i-1]

The following should also work:

	for i in range(1,N):
           pipe[i].next = pipe[i-1]

It will not override, the current value because you write to the 
next-attribute.


In your simple example you could put the
	dout.next = pipe[N-1]
inside the rtl1 generator so you don't need rtl2 (you probably know it, 
your code might be a simplification).


Also in this simple case. Is there something bad about the following 
code, using a @always instead of @always_comb ?

   @always(clk.posedge)
   def rtl2():


Have a nice weekend,

Thomas

-- 

Thomas Traber
DESY, MDI
Notkestrasse 85
D-22603 Hamburg, Germany
email:	tho...@de...
phone:	+49 40 8998 4246