Re: [stella] asymmetrical playfields

Subject: Re: [stella] asymmetrical playfields
From: "Roger Williams" <mer02@xxxxxxxxxxxxx>
Date: Thu, 20 Sep 2001 18:03:59 -0700
> It doesn't look like you can do any meaningful processing at the head of
> any scanline and guarantee any sort of accurate cycle count which I would
> need when rewriting PF2, which makes using the added cycles of my desired
> kernel hard to exploit.
> Any advice?

When loading the second set of playfield registers you still want to load
PF0 first, since it disappears first, but reverse the order of PF1 and PF2.
You will have a real problem getting the timing exactly right since you
transition instantly from PF2A to PF2B; if you don't bang it on the exact
cycle you will get an artifact.  Other than this it should not take any
than the duplicate version; you should be able to get the new playfield
regs set up by shortly after the middle of the screen, after which you will
have 30 or 40 cycles until you have to WSYNC.  Since you have to do
it every line there is basically very little time left for anything else,
you could probably run a software UART or other quick table lookup
for sound or something.

--Roger Williams

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