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There is a rare type of flip-flop that has only one output. It is used on pages 12 and 32 only.
On page 12 (CH1 Sweep) there are two columns with these flip-flops: DOLY...GALO and DEVA...HORA.
On page 32 these are all the flip-flops that have a !RESET input but no !SET input, like RAWU.
The schematics show those flip-flops with a connected !Q output and an unused Q output. However, for APU channel 1 to work, this must be the other way around: Q output used, !Q unused (or better not drawn at all). When CH1 gets restarted, it first resets all of those flip-flops. Their outputs are connected to some full-adders. The carry output of the full-adder of the highest bit acts as a stop trigger for CH1 (it goes through CORU->BYLE->ATYS->BONE->BERY and then into the RESET input of CYTO (see #29)). So if those flip-flops had !Q outputs, then they immediately cause all carry outputs of those adders to be 1, including CORU, which causes CH1 to stop before it even has started.
This is why I think that they must have Q outputs instead. I'm not 100% sure, because I haven't simulated the PPU yet.
@rgalland, in #53 I asked about MEGU before, which was a different type (it doesn't have !RESET), so I'm not sure now if you meant all single-output flip-flops on that page when you said, that they have Q outputs?
The text was updated successfully, but these errors were encountered:
There is a rare type of flip-flop that has only one output. It is used on pages 12 and 32 only.
On page 12 (CH1 Sweep) there are two columns with these flip-flops:
DOLY
...GALO
andDEVA
...HORA
.On page 32 these are all the flip-flops that have a !RESET input but no !SET input, like
RAWU
.The schematics show those flip-flops with a connected !Q output and an unused Q output. However, for APU channel 1 to work, this must be the other way around: Q output used, !Q unused (or better not drawn at all). When CH1 gets restarted, it first resets all of those flip-flops. Their outputs are connected to some full-adders. The carry output of the full-adder of the highest bit acts as a stop trigger for CH1 (it goes through
CORU
->BYLE
->ATYS
->BONE
->BERY
and then into the RESET input ofCYTO
(see #29)). So if those flip-flops had !Q outputs, then they immediately cause all carry outputs of those adders to be 1, includingCORU
, which causes CH1 to stop before it even has started.This is why I think that they must have Q outputs instead. I'm not 100% sure, because I haven't simulated the PPU yet.
@rgalland, in #53 I asked about
MEGU
before, which was a different type (it doesn't have !RESET), so I'm not sure now if you meant all single-output flip-flops on that page when you said, that they have Q outputs?The text was updated successfully, but these errors were encountered: