11 Commits

Author SHA1 Message Date
15ff8132f5 Tweak DTACK
On reads, DTACK will now come out 3 clocks after the READ command to the RAM
With a CAS latency of 2, the read data will be valid at READ+2

The A4091 latches data as soon as DTACK is seen, so this delay was needed to make sure the A4091 correctly latches data from GottaGoFaZt3r
2024-09-28 11:13:16 +12:00
c3d9513f81 Remove dirty speed hack
Previously the board would assert DTACK very early on reads for a speed
boost...
This usually isn't a problem because Buster is slow to notice but sometimes causes issues for the A4091

Thanks goes to dorken @ a1k.org for pointing this out
2023-06-28 08:14:35 +00:00
b0589a1632 Rewrite ram controller
Reduce macrocell usage from ~130 to 97
2022-08-29 22:28:48 +00:00
b2a5c3fa75 Minor updates:
* Set slew rate to slow
* SDRAM state engine: Don't wait for data strobes on reads
2022-06-20 15:03:32 +00:00
0a770dc2d6 Drive RAM and Autoconfig cycles with Z3 State machine
Previously ram_cycle would latch at FCSn asserted and not be cleared until another FCSn assertion happened

This caused issues because FCS_n_sync would lead ram_cycle_sync by 1 clock and this caused false memory cycles to start because ram_cycle_sync would still be true when it shouldn't be.
2022-06-13 15:27:55 +00:00
d1cbe28505 Remove burst stuff
Burst feature not working properly and probably not worth the pain
2022-06-07 17:59:50 +00:00
ae81ba2786 Add License + Documentation 2022-05-13 21:26:49 +00:00
6ca15ca666 Make state machine transitions explicit 2022-04-26 10:09:04 +00:00
c34c9c7f13 Fixup clock enable 2022-04-23 17:36:13 +00:00
bfd8223689 Tidy up code and add more comments 2022-04-23 15:12:29 +00:00
bc86047ed7 Initial Commit 2022-04-22 18:12:23 +00:00