Posted By
Luca
on 2011-07-04
08:22:01
 |  Re: FLD and $FFFF
Heh, probably I should use a weird version of your first hint: I'll keep the 2x music with a couple of simple $FF1D checks, and when the FLD ends, the IRQs will be performed instead of those simple checks (in order to keep the 2x perfectly equidistant by 312/2 lines).
Of course i've just tried to force $FF06 with the blank screen's bit 4 turned off, but incredible to say it does still show the $FFFF value. I used values like #$2B.
And then, the miracle: I used ORA #$78 for $FF06 FLD (even though it work also with #$68 of course) and a simple AND #$BF in order to reset the bitmap at the end of the FLD itself. Yes, #$78. screen on!
Dunno if YAPE is cheating me or not, I wanna test it on Istvan's emulator too and on the real iron once at home, but the result is perfect! ECM is the answer, but I dunno why. Moreover, the upper screen is black, even if I fill the $FF14-corresponding color infos, even if I change $FF15/16/17/18/19 toward other different colors! Maybe I cutoff badlines by FLD keeping the first charline's color for all the upper area?
Waiting for a verify of all this, here come some questions:
- why $FFFF value is displayed as gfx during a bitmap FLD?
- why ECM+blank mask it and not blankscreen only?
- where has that black color been assigned? (Sort of) DMA delay?
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