[libre-riscv-dev] daily kan-ban update 17jul2020

[Luke Kenneth Casson Leighton]

On Saturday, July 18, 2020, Jacob Lifshay <programmerjake at gmail.com> wrote:

> today:
> started adding fsm div
> got a test where a whole bunch of the core fsm transition functions
> are strung together combinatorially to work
> (soc.fu.div.test.test_fsm.TestDivState.test_div_state_comb), so that
> means that the soc.fu.div.fsm.DivState* classes all work.


nice.


>
> However, when I try to wire them up in a simple synchronous fsm
> (soc.fu.div.test.test_fsm.TestDivState.test_div_state_fsm), it doesn't
> seem to work: I think the simulation process I made that checks
> outputs is somehow getting desynchronized from the process that
> toggles inputs -- I added some extra wires that the check process
> toggles.


ah.  we learned that even for synchronous signals it can be necessary to
use Settle().

this usually when a combinatorial block is generated *from* a synchronous
signal.


> it appears to me as though the check process is somehow
> delayed an entire divide operation (8 or 9 cycles, since I'm testing
> an 8-bit divider to make it easier).


ah that's a heck of a lot more :)


>
> Will try to fix that after tomorrow
>
> Jacob
>
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