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40 lines
1.0 KiB
Plaintext
40 lines
1.0 KiB
Plaintext
;Screen Control Assembly Lanuage Routines for C02
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;Skeleton Code for Systems with no Screen Control
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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: LDA #$0C ;Print Form Feed
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JMP PUTCHR ;and Return
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;Move Cursor Home
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CRSRHM EQU $E395 ;Aliad to HOME Routine
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;Move Cursor to Specified Coordinates
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SETPOS: STA $E9 ;Set CURCOL
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STY $E8 ;Set CURROW
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JMP $E39D ;Set Pointers and Return
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;Get Cursor Position
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GETPOS: LDA $E9 ;Load Column Position
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LDY $E8 ;Load Row Position
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RTS ;Return Cursor Column in A, Row in Y
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;Get Screen Size
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GETSIZ: LDA #32 ;Return 32 Columns
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TAY ;and 32 Rows
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RTS
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