Talk:Errata

The stuff on this page definitely needs to be double-checked, and ideally tested on a SNES where applicable. These issues don't seem to be documented very well online, and I've had to rely on forum posts and bits of documentation here and there about problems. - NovaSquirrel (talk) 05:54, 21 May 2022 (UTC)

NMI enable mid-vblank

"If NMI is enabled during vblank, NMI will trigger immediately."

It seems this should be easy to mitigate with HVBJOY/$4212. My question is whether reading $4212 flips off the vblank flag like NES $2002, or if instead the correct thing to do is keep reading it until the vblank flag reads clear? - Rainwarrior (talk) 05:24, 22 May 2022 (UTC)

Or does reading RDNMI/$4210 have the NES-like behaviour of clearing it? Can't quite tell from the description if that's only when NMI is already enabled. So... at least bit $4012 / bmi should be sufficient before enabling NMI, but possibly bit $4210 would do it in one instruction and skip the wait? - Rainwarrior (talk)