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https://github.com/RevCurtisP/C02.git
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110 lines
3.3 KiB
Plaintext
110 lines
3.3 KiB
Plaintext
;Apple 1 program initialization code for c02 programs
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;System Specific ASCII Key Mappings
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DELKEY EQU $5F ;Delete/Backspace Key (Left Arrow/Underscore)
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ESCKEY EQU $1B ;Escape/Stop Key (Escape)
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RTNKEY EQU $0D ;Return/Enter Key (Carriage Return)
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;Locations used by Monitor
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XAML EQU $24 ;Examine Index
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XAMH EQU $25 ;
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STL EQU $26 ;Store Index
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STH EQU $27 ;
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HEXL EQU $28 ;Hex Data
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HEXH EQU $29 ;
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YSAVE EQU $2A ;Y Register Storage
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MODE EQU $2B ;Mode: Store, Examine, Block Examine
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BUFFER EQU $200 ;Input Buffer
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;Standard Library Variables
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SRCLO EQU $30 ;Source String Pointer (stdio.a02)
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SRCHI EQU $31
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DSTLO EQU $32 ;Destination String Pointer (string.a02)
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DSTHI EQU $33
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BLKLO EQU $34 ;Block Segment Pointer (block.a02)
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BLKHI EQU $35
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PTRLO EQU $35 ;System Pointer (pointer.a02)
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PTRHI EQU $36
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RDSEED EQU $3E ;Pseudo-RANDOM Seed
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RANDOM EQU $3F ;Pseudo-RANDOM Number Storage
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TEMP0 EQU $40 ;Temporary Storage
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TEMP1 EQU $41
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TEMP2 EQU $42
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TEMP3 EQU $43
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BLKSLO EQU $4A ;Block Start Address
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BLKSHI EQU $4B
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BLKELO EQU $4C ;Block End Address
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BLKEHI EQU $4D
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BLKLEN EQU $4E ;Block Segment Length
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;PIA 6820 Registers
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KBD EQU $D010 ;Keyboard Data
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KBDCR EQU $D011 ;Keyboard Control Register
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DSP EQU $D012 ;Display Data
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DSPCR EQU $D013 ;Display Control Register
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EXIT EQU $FF00 ;Monitor Entry Point
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ECHO EQU $FFEF ;Subroutine - Print Character in Accumulator
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PRBYTE EQU $FFDC ;Subroutine - Print Accumulator as Hexadadecimal number
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PRHEX EQU $FFE5 ;Subroutine - Print Low Nybble of Accumulator as Hex Digit
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ORG $0300 ;Start one page above Monitor input buffer
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START: LDX #$FF ;Reset stack - the monitor doesn't do this
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TXS ; (probably because of lack of space)
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LDA #$0D ;Move cursor to next line before
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JSR ECHO ; executing program
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JMP MAIN ;Execute Program
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;Subroutine Poll Keyboard
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PLKEY: INC RDSEED ;Cycle Keypress Counter
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BIT KBDCR ;Check the Keyboard Control Register
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BMI RDKEYA ;If Key Pressed, Read Key
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LDA #0 ;Otherwise Return ASCII NUL
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RTS
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RDKEY: INC RDSEED ;Cycle Keypress Counter
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RDKEYC: BIT KBDCR ;Check the Keyboard Control Register
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BPL RDKEYC ; and loop if key not pressed
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RDKEYA: LDA KBD ; Read key into Accumulator
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RTS
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GETKEY: JSR RDKEY ;Subroutine - Read ASCII from Keyboard
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GETKEA: AND #$7F ;Strip High Bit
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BIT GETKEM ;If Character is in
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BEQ GETKEX ; Alpha Block ($40-$74)
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AND #$5F ; Strip Bit 5
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GETKEX: RTS
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GETKEM: DC $40 ;Character Block Bit Mask
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PRCHR EQU ECHO ;Alias to Monitor Routine
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;Delete Previous Character
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DELCHR: LDA #DELKEY ;Load Underscore Character
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JMP PRCHR ; and Print it
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;Advance Character to Next line
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NEWLIN: LDA #$0D ;Load C/R into Accumulator
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JMP PRCHR ; and Print it
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;Initialize Destination String Pointer and Index
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SETDST: STX DSTLO ;Save Destination String Pointer
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STY DSTHI
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RTS
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;Initialize Source String Pointer and Index
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SETSRC: STX SRCLO ;Save Source String Pointer
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STY SRCHI
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LDY #$00 ;Initialize Index Into String
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RTS
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;Retrieve Source String Pointer
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GETSRC: LDX SRCLO
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LDY SRCHI
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RTS
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