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40 lines
1.0 KiB
Plaintext
40 lines
1.0 KiB
Plaintext
;Screen Control Assembly Lanuage Routines for Apple II
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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 $FC58 ;Applesoft Routine HOME
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;Move Cursor To Home Position
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CRSRHM LDA #0 ;Set Column to 0
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TAY ;Set Row to 0
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;and Fall into SETPOS
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;Move Cursor to Specified Coordinates
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SETPOS: STA $24 ;Store Column in CH
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TYA ;Transfer Row to Accumulator
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JMP $FB5B ;Exectute Monitor Routine TABV
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;Get Cursor Position
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GETPOS: LDA $24 ;Load Column from CH
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LDY $25 ;Load Row from CV
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RTS
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;Get Screen Size
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GETSIZ: LDA $21 ;Load Width from WNDWDTH
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LDY $23 ;Load Height from WNDBTM
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RTS
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