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Expand on DTACK generation comments

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Matt Harlum 2021-08-23 20:47:18 +00:00
parent e71284424d
commit 3adac9eae0
1 changed files with 5 additions and 1 deletions
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RTL/gottagofast2000.v
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@ -253,7 +253,11 @@ assign LCASn = !(access_lcas | refresh_cas);
assign OEn = !(!RWn | ((autoconfig_cycle | ram_cycle) & !ASn & DOE & BERRn) & RESETn);
// DOE doesn't get asserted by Buster until the access cycle is in the correct phase with C1/Custom chips
// So we need to hold off DTACK until that is the case by using ASq instead of ASn for DTACK generation
// For some reason this seems to sometimes assert late into S6 which doesn't give enough time to
// propogate from the RAM through the buffers
// So we need hold off DTACK using ASq (internally generated DOE) instead of ASn.
//
// This is known to solve issues GadgetUK164 was experiencing with this card, and the odd crash I experienced.
//
// ASNq valid from middle of S3 which means no waitstates.
// Using DOE instead of ASNq would cause a waitstate as DOE is not active until S4 rise