2016-01-28 00:05:00 +00:00
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__MAIN = $301
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.include "dos33.inc"
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2016-01-28 04:42:47 +00:00
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.include "ca65.inc"
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2016-01-28 00:05:00 +00:00
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; Listing 11
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HgrLo = $E5 ; Low byte Pointer to screen destination
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HgrHi = $E6 ; High byte Pointer to screen destination
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String = $F0
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TmpLo = $F5 ; Low byte Working pointer to screen byte
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TmpHi = $F6 ; High byte Working pointer to screen byte
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TopHi = $FD
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Font = $6000
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; ORG $0301 ; Listing 8
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DrawHexByte:
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PHA ; save low nibble
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ROR ; shift high nibble
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ROR ; to low nibble
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ROR ;
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ROR ;
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JSR DrawHexNib ; print high nib in hex
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PLA ; pritn low nib in hex
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DrawHexNib:
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AND #$F ; base 16
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TAX ;
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LDA NIB2HEX,X ; nibble to ASCII
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; ORG $0310 ; Listing 5
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DrawChar:
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JMP DrawCharCol
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; ORG $0313 ; Listing 9
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SetCursorRow:
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LDA HgrLoY,X ; HgrLoY[ row ]
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STA TmpLo
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LDA HgrHiY,X ; HgrHiY[ row ]
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CLC
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ADC HgrHi
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STA TmpHi
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RTS
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; ORG $0321 ; Listing 11
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SetCursorColRow:
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STX TmpLo
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LDA HgrLoY,Y ; HgrLoY[ row ]
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CLC
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ADC TmpLo ; add column
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STA TmpLo
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LDA HgrHiY,Y ; HgrHiY[ row ]
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CLC ; \ could optimize this into
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ADC HgrHi ; / single ORA HgrHi
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STA TmpHi
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RTS
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NOP ; pad
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; ORG $0335 ; Listing 6
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DrawCharColRow:
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PHA
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JSR SetCursorRow
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PLA
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; ORG $033A ; Listing 7
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DrawCharCol: ; A=%PQRstuvw
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ROL ; C=P A=%QRstuvw?
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ROL ; C=Q A=%Rstuvw?P
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ROL ; C=R A=%stuvw?PQ
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TAX ; X=%stuvw?PQ push glyph
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AND #$F8 ; A=%stuvw000
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STA _LoadFont+1; AddressLo = (c*8)
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TXA ; A=%stuvw?PQ pop glyph
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AND #3 ; Optimization: s=0 implicit CLC !
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ROL ; C=s A=%00000PQR and 1 last ROL to get R
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ADC #>Font ; += FontHi; Carry=0 since s=0 from above
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STA _LoadFont+2; AddressHi = FontHi + (c/32)
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; ORG $034C ; Listing 4a
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_DrawChar1:
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LDX TmpHi
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STX TopHi
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; ORG $0350 ; Listing 1
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_DrawChar:
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LDX #0
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_LoadFont: ; A = font[ offset ]
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LDA Font,X
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STA (TmpLo),Y ; screen[col] = A
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CLC
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LDA TmpHi ;
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ADC #4 ; screen += 0x400
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STA TmpHi
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INX
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CPX #8
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BNE _LoadFont
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; ORG $0363 ; Listing 4a
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IncCursorCol:
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INY
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LDX TopHi ; Move cursor back to top of scanline
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STX TmpHi
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RTS
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; ORG $0369 ; Listing 10
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SetCursorColRowYX:
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JSR SetCursorRow
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CLC
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TYA
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ADC TmpLo
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STA TmpLo
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RTS
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; ORG $037E ; Listing 12
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DrawString:
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STY String+0
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STX String+1
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LDY #0
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_ds1: LDA (String),Y
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BEQ _ds2 ; null byte? Done
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JSR DrawChar ; or DrawCharCol for speed
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CPY #40 ; col < 40?
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BCC _ds1
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_ds2: RTS
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; pad $0385 .. $38F
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.res $390 - *, $00
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; ORG $0390 ; Listing 8
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NIB2HEX:
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.byte "0123456789ABCDEF"
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; ORG $03A0 ; Listing 9a
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HgrLoY:
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.byte $00,$80,$00,$80,$00,$80,$00,$80
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.byte $28,$A8,$28,$A8,$28,$A8,$28,$A8
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.byte $50,$D0,$50,$D0,$50,$D0,$50,$D0
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HgrHiY:
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.byte $00,$00,$01,$01,$02,$02,$03,$03
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.byte $00,$00,$01,$01,$02,$02,$03,$03
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.byte $00,$00,$01,$01,$02,$02,$03,$03
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__END:
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