Displaying text: Difference between revisions
Jump to navigation
Jump to search
m (4 revisions: Import from wikkii) |
mNo edit summary |
||
| (4 intermediate revisions by 4 users not shown) | |||
| Line 1: | Line 1: | ||
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. | ||
Write8Text: | Write8Text: | ||
move.w d1, | move.w d1,REG_VRAMADDR | ||
move.w #$20, | move.w #$20,REG_VRAMMOD | ||
.textmaplp: | .textmaplp: | ||
clr.w d0 | clr.w d0 | ||
| Line 15: | Line 15: | ||
bne .nolinejump | bne .nolinejump | ||
addq.w #1,d1 | addq.w #1,d1 | ||
move.w d1, | move.w d1,REG_VRAMADDR | ||
bra .textmaplp | bra .textmaplp | ||
.nolinejump: | .nolinejump: | ||
addq.w ASCIISTART,d0 | addq.w ASCIISTART,d0 | ||
move.w d0, | move.w d0,REG_VRAMRW | ||
bra textmaplp | bra .textmaplp | ||
.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. | ||
The VRAM address is calculated from the desired text position: D1=#FIXMAP+(Y+2+((X+1)*32)) | The VRAM address is calculated from the desired text position: D1=#FIXMAP+(Y+2+((X+1)*32)), [[68k ASM defines|"FIXMAP"]] being #$7000. | ||
[[ASM | |||
[[Category:Code]] | [[Category:Code]] | ||
[[Category:Graphics Code]] | |||
Latest revision as of 09:54, 3 October 2017
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,REG_VRAMADDR
move.w #$20,REG_VRAMMOD
.textmaplp:
clr.w d0
move.b (a0)+,d0
tst.b d0
beq .textmapend
cmp.b #$FF,d0
bne .nolinejump
addq.w #1,d1
move.w d1,REG_VRAMADDR
bra .textmaplp
.nolinejump:
addq.w ASCIISTART,d0
move.w d0,REG_VRAMRW
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.