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Correct usage of PPUSTATUS
http://forums.nesdev.com/viewtopic.php?f=2&t=16289
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Author:  rainwarrior [ Thu Aug 03, 2017 12:39 pm ]
Post subject:  Re: Correct usage of PPUSTATUS

tokumaru wrote:
GradualGames wrote:
What could cause an unpaired write except for improper locking of nmi vs. main thread?

I can't think of many things...

If you restrict the possibilities to things you intend your code to do, there's no accounting for bugs at all. ;P

STA (pointer), Y can write anywhere depending on what's in the pointer. Accidental execution of data or RAM as can end up writing anywhere as well. Don't forget the PPU registers aren't just at $2000-2007, they are mirrored, so the target for a stray write is fairly wide.


It's true that a lot of bugs will simply crash the game or otherwise leave it totally failed, but I find (maybe surprisingly?) that quite a lot are relatively benign and often totally recoverable.

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