Difference between revisions of "Displaying text"

From NeoGeo Development Wiki
Jump to: navigation, search
m
m
 
(2 intermediate revisions by 2 users not shown)
Line 5: Line 5:
 
;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,VRAM_ADDR
+
     move.w  d1,REG_VRAMADDR
     move.w  #$20,VRAM_MOD
+
     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,VRAM_ADDR
+
     move.w  d1,REG_VRAMADDR
 
     bra    .textmaplp
 
     bra    .textmaplp
 
.nolinejump:
 
.nolinejump:
 
     addq.w  ASCIISTART,d0
 
     addq.w  ASCIISTART,d0
     move.w  d0,VRAM_RW
+
     move.w  d0,REG_VRAMRW
     bra    textmaplp
+
     bra    .textmaplp
 
.textmapend:
 
.textmapend:
 
     rts
 
     rts
Line 30: Line 30:
  
 
[[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.