[Cryptech Tech] EIM: mostly working

[Bernd Paysan]

Am Freitag, 7. November 2014, 16:31:17 schrieb Paul Selkirk:
> novena_eim uses synch reset because that's how Bunnie wrote it (and I
> don't really understand the implications of changing it). My other
> novena projects just tie the reset line.

This is about timing of the reset. With a synchronous reset, you synchronize 
the reset line internally, and then you have a timing constraint of one clock 
cycle for the reset to work (especially reset deassertion has this one clock 
cycle constraint).

This can be tough, as the reset goes everywhere.

If you use an async reset, you do the synchronisation the other way round: you 
block the clock until after reset is gone, and then wait for some further 
clock cycles to release the clock.  This is in a central place, and the 
additional clock delay from the releas e time doesn't matter: Reset is already 
deasserted.

-- 
Bernd Paysan
"If you want it done right, you have to do it yourself"
http://bernd-paysan.de/