Zeropage copy of current mode's sync polarity
Posted: Tue May 14, 2013 10:33 pm
Just to document this somewhere useful I'll post this here.
In my efforts to fix the wrap-around bug seen by the folks on stardot, I've made an interesting discovery. By complete accident I've discovered a zeropage location which appears to store the *current* Sync polarity setting! If I'm right, this could be really useful for AutoVIDC (and you'll be able to do away with my sync-polarity 'guess' routine).
The current mode's sync polarity is actually stored in unused bits 11&12 of the VIDC control register copy at &1584
Or if you read the just the byte itself (probably best?), it's the byte at &1585, bits 3&4... Mask: %00011000
At least I'm 99% confident that's what it is...
Steve
In my efforts to fix the wrap-around bug seen by the folks on stardot, I've made an interesting discovery. By complete accident I've discovered a zeropage location which appears to store the *current* Sync polarity setting! If I'm right, this could be really useful for AutoVIDC (and you'll be able to do away with my sync-polarity 'guess' routine).
The current mode's sync polarity is actually stored in unused bits 11&12 of the VIDC control register copy at &1584
Or if you read the just the byte itself (probably best?), it's the byte at &1585, bits 3&4... Mask: %00011000
At least I'm 99% confident that's what it is...
Steve