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38 lines
984 B
Plaintext
38 lines
984 B
Plaintext
;Screen Control Assembly Lanuage Routines for VIC-20
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SUBROUTINE _SCREEN
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SMTEXT EQU $00 ;Default Text Screen
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SMWIDE EQU $FF ;Wide Text Screen (Undefined)
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;Set Screen Mode
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SETSCR: CMP SMTEXT ;If Default Text Screen
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BEQ GETSCR ;Return Return 0
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LDA #$FF ;Else Return ERROR
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RTS
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;Else Return 0
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;Get Screen Mode
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GETSCR: LDA #0 ;Return 0 (Default Text Mode)
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RTS
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;Clear the Screen
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CLRSCR EQU $E544 ;Aliased to CLSR Routine
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;Move Cursor To Home Position
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CRSRHM EQU $E566 ;Aliased to HOME Routine
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;Move Cursor to Specified Coordinates
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SETPOS: STA $D3 ;Save Cursor Column
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STY $D6 ;Save Cursor Row
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JMP $E56C ;Set Screen Poiners and Return
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;Get Cursor Position
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GETPOS: LDY $D6 ;Load Cursor Row
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LDA $D3 ;Load Cursor Column
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RTS
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;Get Screen Size
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GETSIZ: JSR $FFED ;Call SCREEN Kernal Routine
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TXA ;Transfer Width to Accumulator
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RTS
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