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ASM routine for displaying text with a 8x8 pixel font on the [[fix layer]]: | ASM routine for displaying text with a 8x8 pixel font on the [[fix layer]]: | ||
< | <syntaxhighlight> | ||
;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. ASCIISTART is the character 0 fix tile. | ;Uses A0, D0 and REG_VRAMMOD. ASCIISTART is the character 0 fix tile. | ||
| Line 23: | Line 23: | ||
.textmapend: | .textmapend: | ||
rts | rts | ||
</ | </syntaxhighlight> | ||
"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. | "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. | ||
Revision as of 13:41, 14 March 2012
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.