Talk:Errata: Difference between revisions
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Rainwarrior (talk | contribs) (→NMI enable mid-vblank: or is $4210 the answer?) |
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: 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? - [[User:Rainwarrior|Rainwarrior]] ([[User talk:Rainwarrior|talk]]) | : 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? - [[User:Rainwarrior|Rainwarrior]] ([[User talk:Rainwarrior|talk]]) | ||
: Yes, it has the same behavior as on the NES —[[User:Lidnariq|Lidnariq]] ([[User talk:Lidnariq|talk]]) 08:10, 25 May 2022 (UTC) | |||
Latest revision as of 08:10, 25 May 2022
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)
