Re: [stella] MultiSpriteDemo update (source+binary)

Subject: Re: [stella] MultiSpriteDemo update (source+binary)
From: emooney@xxxxxxxxxxxxxxxx (Erik Mooney)
Date: Mon, 07 Apr 1997 07:05:24 GMT
>fed 0 to the FC-convert routine.  I suspect that even though STA RESP0
>takes three cycles, the write hits Stella at the end of the second cycle
>and it responds accordingly.  I'll experiment further tonight.

argh, stupid me didn't realize that if Y=0, a DEY/BNE loop doesn't work
right and that screwed up what I was saying there (as well as what I was
trying to display.)  A DEY/BPL loop will work, though (thanks again Nick
for the help on the flags).. using Piero's posted Air-Sea Battle X to FC_X
conversion routine, objects display correctly with a WSYNC, 14 cycle wait,
DEY/BPL loop with the coarse value, and then hit RESxx, and make sure to
write HMxx and HMOVE somewhere in there.

Also, since no one responded to one earlier question, I experimented on my
own.. STA WSYNC can begin no later than cycle 71 to catch the end of the
current line.  On PC Atari, though, a STA WSYNC beginning at cycle 74 or
earlier syncs to the end of the current line.. that difference caused me a
headache for a while (why won't this thing work on the TV but it works on
the emulator?!)

One more question: anyone know exactly what the vertical-delay registers
do?  I couldn't make sense of the circuit diagram in the "big file"
STELLA.PDF regarding them.  The registers sound like they're supposed to
delay any writes to GRP0 or GRP1 by one scanline, and experimentation would
let me delay Player 1 by one line but not Player 0.  ?

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