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Just found the very nice nestest.nes ROM, great stuff indeed. But I keep getting error 59 (STA (ind,x)) test. I am not sure how the test is performed as I haven't been able to locate the asm-source that nestest.txt refers to. I've browsed a few 6502 docs and some other NES sources but haven't found ...

I just thought of something else.. The counter is affected aswell when the PPU Address is auto-incremented when $2007 is written to?

Thanks for your reply! Most mapper-documentation today is alot more detailed than when I previously read them a few years ago, but they are not always that easy to understand if you're not highly skilled in eletronics. :) Oh of course, I remember seeing that message on Zelda2 and on more recent vers...

There's been alot of talk that the IRQ counter decreases when the "A12 on the PPU bus toggles from 0-1". What does this mean in plain english? Does it mean when bit 12 of the PPU address switches from 0 to 1 when for example setting an address via $2006? It only decreases on toggle? Assuming the pre...