On 2/26/2018 8:45 AM, Dr Jefyll wrote: > Jim Brain wrote >> I have no idea why I would not see a correct write on that >> cycle. > Hi, Jim. I'm having trouble following the context here. Is there a > reference for the code that's being run, and the cycle you're talking about, > please? The cycle is step 24, as shown in the PDF I linked to earlier. The code is the bootup code in the CBM B-128 (don't have a disassembly, but the code is at zimmers.net. $f9aa loads $06 into A $f9ac stores a into $0096 So, we can guarantee it's an $06 that should be stored. > But I'm guessing the write data on the STA differs because A itself > differs, as a result of an earlier /LDA/ which differed. Due to timing, > perhaps? Unfortunately, in this case, it was a direct load of the immediate value a line or two earlier in the code. > > I do feel timing is the central issue. Certainly there's a discrepancy from > being forced to use the Phi0 input (and thus suffer a slight delay) when an > '02 or 'C02 is in use. While I think timing is involved, I find it odd that the right value shows up on the bus for a bit of time, and then disappears. Jim Message was sent through the cbm-hackers mailing listReceived on 2018-02-26 15:01:56
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