combinational logic in reference design

[Mike Treseler]

>
> I've started using your design methodology (init_regs etc.) some time

ago. I have got a question related to this. It is possible to describe
"pure" combinational logic in combination with this design method? I
tried to implement some amba arbiter and decoder in one process, decoder
is combinational, arbiter is not. I implemented it in 2 process, one
using (init_regs etc.) and second only combinational. I wonder if it is
possible to do this using only one process with structure that you
proposed. I've tried to describe some combinational logic in
update_ports procedure but (I think) it's not the good way.

>
> Marcin Wojcik
>

If the logic were purely combinational from device pin to device pin,
I would put it in a separate entity to be instanced in the top level.

If the output were a combinational function of register variables to
a device pin, I would put the assignment in the update_ports procedure
between the END IF and END PROCESS.

If the "output" were between two processes,
I would combine the processes into one.

-- Mike Treseler