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46 lines
1.1 KiB
Plaintext
46 lines
1.1 KiB
Plaintext
;Screen Control Assembly Lanuage Routines for VIC-20
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;SUBROUTINE
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SMTEXT EQU $00 ;Default Text Screen
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SMWIDE EQU $02 ;Wide Text Screen (Undefined)
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;Set Screen Mode
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SETSCR: SEC ;Set Carry
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JSR $FF5F ;Call SCRMOD
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LDA #0 ;Set Return Value to Zero
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BCC .RETURN ;If Carry Set
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DEC ; Return 255 (Error)
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.RETURN RTS
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;Get Screen Mode
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GETSCR: CLC ;Clear Carry
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JMP $FF5F ;Execute SCRMOD
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RTS
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;Clear the Screen
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CLRSCR LDA #$93 ;Load CLR/HOME Character
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JMP PUTCHR ;and Print to Screen
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;Move Cursor To Home Position
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CRSRHM LDA #$13 ;Load HOME Character
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JMP PUTCHR ;and Print to Screen
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;Move Cursor to Specified Coordinates
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SETPOS: .DC $5A ;PHY Copy Row
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.DC $FA ;PLX to X Register,
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TAY ;Column to Y Register
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CLC ;Set Carry
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JMP $FFF0 ;and Execute Plot
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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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