Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Jump to bottom

CHR_TRN can still be effective during border fade-out #199

Open
1 of 2 tasks
ISSOtm opened this issue Mar 2, 2021 · 2 comments · May be fixed by #494
Open
1 of 2 tasks

CHR_TRN can still be effective during border fade-out #199

ISSOtm opened this issue Mar 2, 2021 · 2 comments · May be fixed by #494
Labels
content Improvements or additions to documentation research

Comments

@ISSOtm
Copy link
Member

ISSOtm commented Mar 2, 2021 •
edited
Loading

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.

  • Investigate timing window
  • Document all this

Note that this also means the border tiles do NOT update immediately upon CHR_TRN!
@ISSOtm ISSOtm added content Improvements or additions to documentation research labels Mar 2, 2021
@pinobatch
Copy link
Member

The Three Bears
Test ROM lets the user specify a delay in frames between sending PCT_TRN and sending CHR_TRN

@ISSOtm
Copy link
Member Author

ISSOtm commented May 20, 2023 •
edited by avivace
Loading

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).

ISSOtm added a commit to ISSOtm/pandocs that referenced this issue Jul 4, 2023
@ISSOtm
Explain SGB border at a high level, and document "CHR_TRN after PCT_TRN"
6ae4c9e 
Fixes gbdev#199
@ISSOtm ISSOtm linked a pull request Jul 4, 2023 that will close this issue
Draft
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment
Assignees
No one assigned
Labels
content Improvements or additions to documentation research
Projects
None yet
Milestone
No milestone
Development

Successfully merging a pull request may close this issue.

Improve SGB border documentation ISSOtm/pandocs
2 participants
@pinobatch @ISSOtm