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gbdev
CHR_TRN can still be effective during border fade-out
CHR_TRN is normally buffered to SNES WRAM, and only gets transferred during a PCT_TRN. However, the transfer point is when the border finishes fading (so the transfer is seamless), so it's actually possible to send PCT_TRN, then CHR_TRN during the fade, and have it work.
Alfred Chicken apparently relies on this.
- [x] Investigate timing window
- [ ] Document all this
Note that this also means the border tiles do NOT update immediately upon CHR_TRN!
The Three Bears Test ROM lets the user specify a delay in frames between sending PCT_TRN and sending CHR_TRN
The acceptable timings are documented not in the README, but in docs/long_story.txt.
I propose recommending 61–63 frames, deferring directly to that document for more details, and noting that the acceptable range is likely to be poorly emulated (and therefore emulator testing may produce broken results).