Displaying text: Difference between revisions
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<pre> | <pre> | ||
;Displays text pointed by A0 at the VRAM address in D1. $FF:Next line, $00:End of text. | ;Displays text pointed by A0 at the VRAM address in D1. $FF:Next line, $00:End of text. | ||
;Uses A0, D0 and REG_VRAMMOD | ;Uses A0, D0 and REG_VRAMMOD. ASCIISTART is the character 0 fix tile. | ||
Write8Text: | Write8Text: | ||
move.w d1,VRAM_ADDR | move.w d1,VRAM_ADDR | ||
move.w #$20,VRAM_MOD | move.w #$20,VRAM_MOD | ||
.textmaplp: | |||
clr.w d0 | clr.w d0 | ||
move.b (a0)+,d0 | move.b (a0)+,d0 | ||
tst.b d0 | tst.b d0 | ||
beq textmapend | beq .textmapend | ||
cmp.b #$FF,d0 | cmp.b #$FF,d0 | ||
bne nolinejump | bne .nolinejump | ||
addq.w #1,d1 | addq.w #1,d1 | ||
move.w d1,VRAM_ADDR | move.w d1,VRAM_ADDR | ||
bra textmaplp | bra .textmaplp | ||
nolinejump: | .nolinejump: | ||
addq.w ASCIISTART,d0 | addq.w ASCIISTART,d0 | ||
move.w d0,VRAM_RW | move.w d0,VRAM_RW | ||
bra textmaplp | bra textmaplp | ||
textmapend: | .textmapend: | ||
rts | rts | ||
</pre> | </pre> | ||
Revision as of 05:06, 23 May 2011
ASM routine for displaying text with a 8x8 pixel font on the fix layer:
;Displays text pointed by A0 at the VRAM address in D1. $FF:Next line, $00:End of text.
;Uses A0, D0 and REG_VRAMMOD. ASCIISTART is the character 0 fix tile.
Write8Text:
move.w d1,VRAM_ADDR
move.w #$20,VRAM_MOD
.textmaplp:
clr.w d0
move.b (a0)+,d0
tst.b d0
beq .textmapend
cmp.b #$FF,d0
bne .nolinejump
addq.w #1,d1
move.w d1,VRAM_ADDR
bra .textmaplp
.nolinejump:
addq.w ASCIISTART,d0
move.w d0,VRAM_RW
bra textmaplp
.textmapend:
rts
"ASCIISTART" should be the fix tile number corresponding to ASCII value 0. This depends on what tileset you are using. Usually, onboard fix tilesets have a full 8x8 font starting at tile #0.
The VRAM address is calculated from the desired text position: D1=#FIXMAP+(Y+2+((X+1)*32))
"FIXMAP" being #$7000.