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59 lines
1.7 KiB
Plaintext
59 lines
1.7 KiB
Plaintext
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;c02 Program Initialization Code for Vic-20 - Common Code
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START: TSX ;Get Stack Pointer
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STX STKSAV ;and Save for Exit
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JMP MAIN ;Execute Program
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EXIT: LDX STKSAV ;Retrieve Saved Stack Pointer
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TXS ;and Restore It
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RTS ;Return to BASIC
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;Poll Keyboard for Character
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POLKEY EQU $FFE4 ;Aliased to Kernal GETIN Routine
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;Get Character from Keyboard
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GETKEY EQU POLKEY ;Get Key From Keybord
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;Get Character from Keyboard
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;GETKEY: JSR POLKEY ;Get Key From Keybord
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; ;The below is not working...
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; LDY $9005 ;Get Character Memory Offset
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; CPY #242 ;If Upper/Lower
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; BNE GETKEX
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; BIT $FF ; Bit 7 -> C, Bit 6 -> V
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; BVC GETKEX ; If Bit 6 Set (Alpha)
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; BCC GETKEL ; If Bit 7 Set (PETSCII Upper)
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; AND #$7F ; Clear Bit 7 (ASCII Upper)
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; BNE GETKEX ; Else
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;GETKEL: ORA #$20 ; Set Bit 5 (ASCII Lower)
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;GETKEX: ORA #$00 ;Set Flags
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; RTS
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;A = $41 %0100 0001
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;a = $C1 %1100 0001 PETSCII
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;a = $61 %0110 0001 PETSCII
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;$9005 = 240 UPR/GFX
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; 242 UPR/LWR
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;Wait for Character from Keyboard
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GETCHR: JSR GETKEY ;Poll Keyboard
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BEQ GETCHR ;If No Key, Loop
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RTS
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;Print Character to Console
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;uses direct call to SCRNOUT instead of CHROUT
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PUTCHR EQU $E742 ;Aliased to SRCOUT Routine
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;Delete Previous Character
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DELCHR: LDA #DELKEY ;Load Delete Character
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JMP PUTCHR ;Print and Return
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;Advance Character to Next line
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NEWLIN: LDX #0 ;Store 0
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STX $D3 ;in Cursor Column and
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JMP $E8C3 ;Execute NXTLINE Routine
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;Print Zero-Terminated String
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PUTSTR: TXA ;Copy LSB to Accumulator
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JMP $CB1E ;Execute STROUT Routine
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