I tried to write the word "NOT" to the BIOS screen from my game's code (to make it read "NOT PRODUCED BY OR UNDER LICENSE FROM SEGA ENTERPRISES LTD."); I've already tried to do something similar with the Sega CD's BIOS before, with success. But now, trying with the MD BIOS, seems like the VDP doesn't work, because even if I write the new map data in the wrong location in VRAM, I should see that data somewhere with the VDP debugger.
Right after the entry point, I wrote this code:
Code: Select all
;Escribir sobre la pantalla de la BIOS
move.l #PlaneA_WOff,(VDP_Control)
;move.w #$8144,(VDP_Control)
move.w #$6E,(VDP_Data) ; N
move.w #$6F,(VDP_Data) ; O
move.w #$74,(VDP_Data) ; T
move.l #$FFFF,d7
@l1: moveq #$7F,d6
dbf d6,*
dbf d7,@l1