asmgen/drawfont.s
Rob McMullen 527cd2226c Since I now have an approved fork rather than contributing back to Quinn, changing to more PEP-8 python style
* changed some assembly variables and categorized them by address to hopefully make debugging easier
2017-07-05 12:50:22 -07:00

114 lines
3.0 KiB
ArmAsm

DrawHexByte
PHA ; save low nibble
ROR ; shift high nibble
ROR ; to low nibble
ROR ;
ROR ;
JSR DrawHexNib ; print high nib in hex
PLA ; pritn low nib in hex
DrawHexNib
AND #$F ; base 16
TAX ;
LDA NIB2HEX,X ; nibble to ASCII
; ORG $0310 ; Listing 5
DrawChar
JMP DrawCharCol
; ORG $0313 ; Listing 9
SetCursorRow
LDA TEXTROW_L,X ; TEXTROW_L[ row ]
STA hgrptr
LDA TEXTROW_H,X ; TEXTROW_H[ row ]
ORA HgrHi
STA hgrptr+1
RTS
; ORG $0321 ; Listing 11
SetCursorColRow
STX hgrptr
LDA TEXTROW_L,Y ; TEXTROW_L[ row ]
CLC
ADC hgrptr ; add column
STA hgrptr
LDA TEXTROW_H,Y ; TEXTROW_H[ row ]
ORA HgrHi
STA hgrptr+1
RTS
NOP ; pad
; ORG $0335 ; Listing 6
DrawCharColRow
PHA
JSR SetCursorRow
PLA
; ORG $033A ; Listing 7
DrawCharCol ; A=%PQRstuvw
ROL ; C=P A=%QRstuvw?
ROL ; C=Q A=%Rstuvw?P
ROL ; C=R A=%stuvw?PQ
TAX ; X=%stuvw?PQ push glyph
AND #$F8 ; A=%stuvw000
STA _LoadFont+1; AddressLo = (c*8)
TXA ; A=%stuvw?PQ pop glyph
AND #3 ; Optimization: s=0 implicit CLC !
ROL ; C=s A=%00000PQR and 1 last ROL to get R
ADC #>FatFont ; += FontHi; Carry=0 since s=0 from above
STA _LoadFont+2; AddressHi = FontHi + (c/32)
; ORG $034C ; Listing 4a
_DrawChar1
LDX hgrptr+1
STX scratch_0
; ORG $0350 ; Listing 1
_DrawChar
LDX #7
_LoadFont ; A = font[ offset ]
LDA FatFont,X
STA (hgrptr),Y ; screen[col] = A
CLC
LDA hgrptr+1 ;
ADC #4 ; screen += 0x400
STA hgrptr+1
DEX
BPL _LoadFont
; ORG $0363 ; Listing 4a
IncCursorCol
INY
LDX scratch_0 ; Move cursor back to top of scanline
STX hgrptr+1
RTS
; ORG $0369 ; Listing 10
SetCursorColRowYX
JSR SetCursorRow
CLC
TYA
ADC hgrptr
STA hgrptr
RTS
; ORG $037E ; Listing 12
DrawString
STY tempaddr+0
STX tempaddr+1
LDY #0
_ds1 LDA (tempaddr),Y
BEQ _ds2 ; null byte? Done
SEC
SBC #$20
JSR DrawChar ; or DrawCharCol for speed
CPY #40 ; col < 40?
BCC _ds1
_ds2 RTS
; ORG $0390 ; Listing 8
NIB2HEX
.byte "0123456789ABCDEF"
; ORG $03A0 ; Listing 9a
TEXTROW_L
.byte $00,$80,$00,$80,$00,$80,$00,$80
.byte $28,$A8,$28,$A8,$28,$A8,$28,$A8
.byte $50,$D0,$50,$D0,$50,$D0,$50,$D0
TEXTROW_H
.byte $00,$00,$01,$01,$02,$02,$03,$03
.byte $00,$00,$01,$01,$02,$02,$03,$03
.byte $00,$00,$01,$01,$02,$02,$03,$03