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)

Yes, it has the same behavior as on the NES —Lidnariq (talk) 08:10, 25 May 2022 (UTC)

White noise generator

"The hardware noise unit uses the contents of an LFSR to generate a signed noise sample. Because the LFSR only shifts 1 bit per sample, the correlated lower bits end up producing a strong highpass filter effect on the noise.[8] Especially in the high and low ranges, this will differ from the more typical 1-bit LFSR noise sound seen in other sound chips."

Despite being familiar with sound synthetis and electronics, this is not understandable to me. Is there a way to rephrase this to point out what is specific on the SPC700's white noise generator ? Bregalad (talk) 10:59, 28 November 2024 (UTC)