1RW1R support

[maliberty]

The message 1RW1R variants are temporarily disabled due to a bug. is two years old. Is there a plan to resolve this? I'd like to regenerate the RAMs for microwatt but they require this case that used to be supported.

[donn]

As I recall there's a pretty bad timing issue with it. We don't have anyone working on DFFRAM right now so I wouldn't count on it.

If your goal is recreating an older design, it may be your best bet to use a version of DFFRAM from the time...

[maliberty]

If only I knew what Anton did years ago...

[donn]

I wish I had the foresight to record in writing what bug it is…

Screw it, I'm bored today. I'll take a look.

[donn]

I… yeah 1RW1R appears to be routing fine…

Static timing's alright at a 20ns clock:

Still weary of recommending you use them for production because obviously 2022 me must have have had a good reason but if it's to recreate an old design, should be fine. I will however add a warning to dffram.py.