Video mode switching
Posted: Sat Jul 07, 2012 10:53 pm
I've written a little tool to help determine the effects of mid-scanline mode switching. It's called "stripe" and is available from http://www.6809.org.uk/tmp/da/tests/ as assembly source, .cas and .wav.
From the source:
There's still stuff to figure out (in particular what determines which data and colours get used when a mode change happens mid-byte), but I've done some preliminary work in getting XRoar to do the right thing in the latest snapshot here: http://www.6809.org.uk/tmp/xroar/.
PAL CoCo timings are still generally out, but it does finally render the opening screen of the PAL DragonFire hack correctly!
From the source:
Code: Select all
; Controls:
; Up, Down, Left, Right - move stripe around by changing timings.
; 1, Q - Set/reset !A/G, GM2, GM1
; 2, W - Set/reset GM0 (and !INT/EXT)
; 3, E - Set/reset GM2, GM1 (switch between 32- and 16-byte graphic modes)
; 4, R - Set/reset CSS
; Enter - Cycle through different screen patterns
; Break - Return to BASIC
PAL CoCo timings are still generally out, but it does finally render the opening screen of the PAL DragonFire hack correctly!
