[stella] 6502 hardware register writes

Subject: [stella] 6502 hardware register writes
From: "TwoHeaded Software" <adavie@xxxxxxxxxxxxx>
Date: Fri, 2 Nov 2001 19:57:50 +1100
Being somewhat interested in working on a '2600 emulator, I thought I'd
start by asking if writes to hardware (ie: graphics) registers occur on the
last cycle of the instruction.  That is, in, say, a 3-cycle store, does the
effect of writing to the register become visible on the first pixel
immediately drawn after the end of the 3rd cycle?  Or is it apparent at the
start of the 3rd cycle (ie: end of 2nd cycle)?
In general, I'm interested in discussing '2600 emulation - perhaps those on
the list who have tackled this, and can help when tricky problems show up,
might hold up their hands.
Andrew Davie, TwoHeaded Software

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