mirror of
https://github.com/RevCurtisP/C02.git
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82 lines
2.4 KiB
Plaintext
82 lines
2.4 KiB
Plaintext
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;Apple 1 program initialization code for c02 programs
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;System Specific ASCII Key Mappings
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DELKEY EQU $08 ;Delete/Backspace Key (Left Arrow)
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ESCKEY EQU $1B ;Escape/Stop Key (Escape)
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RTNKEY EQU $0D ;Return/Enter Key (Return)
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;Zero Page Variables (*=System Variable)
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DSTLO EQU $06 ;Destination Pointer
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DSTHI EQU $07
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BLKLO EQU $08 ;Block Segment Pointer (block.a02)
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BLKHI EQU $09
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STKLO EQU $1D ;Stack Pointer (stack.a02)
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STKHI EQU $1E
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RANDOM EQU $1F ;Random Number
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INVFLG EQU $32 ;*Inverse Flag: $3F=Blinking, $7F=Inverse, $FF=Normal
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SRCLO EQU $71 ;Source Pointer
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SRCHI EQU $72
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RDSEED EQU $E3 ;Random Seed
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BLKSLO EQU $EB ;Block Start Address
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BLKSHI EQU $ED
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BLKELO EQU $ED ;Block End Address
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BLKEHI EQU $EE
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BLKLEN EQU $EF ;Block Segment Length
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TEMP0 EQU $FC ;Temporary Storage
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TEMP1 EQU $FD
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TEMP2 EQU $FE
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TEMP3 EQU $FF
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;I/O Locations
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KBD EQU $C000 ;Keyboard Data
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AKD EQU $C010 ;Keyboard Strobe Register
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;Monitor Routines
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PRBYTE EQU $FDDA ;Print Accumulator as Hexadecimal Number
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PRHEX EQU $FDE3 ;Print Low Nybble of Accumulator as Hex Digit
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ECHO EQU $FDF0 ;Print Character - Routine Monitor COUT1
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EXIT EQU $03D0 ;Return to Monitor - Jump Vector to DOS warm start
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ORG $0C00 ;Safe Area for Machine Language
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START: JSR NEWLIN ;Start On New Line
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JMP MAIN ;Execute Program
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;Subroutine Poll Keyboard
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PLKEY: INC RDSEED ;Cycle Random Seed
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LDA #0 ;Clear Accumulator
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BIT KBD ;Check Keyboard Strobe Bit
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BPL PLKEYR ;If Key Pressed
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LDA KBD ; Load Key Value
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STA AKD ; Clear Strobe
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PLKEYR: RTS
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;Read Keyboard
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GETKEY JSR PLKEY ;Poll Keyboard
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AND #$7F ;Strip High Bit
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RTS
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;Wait for Keypress
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RDKEY: JSR GETKEY ;Get Modified Key Code
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BEQ RDKEY ;Loop if No Key
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RTS
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;Delete Previous Character
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DELCHR: LDX #2 ;Two Characters Total
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LDA #$88 ;Load Backspace Character
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JSR $F94C ;Monitor Routine PRBLAX
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LDA #DELKEY ;Load Backspace Character
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;and Fall into PRCHR
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;Print Character to Screen
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PRCHR: ORA #$80 ;Set High Bit
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CMP #$E0 ;
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BCC PRCHRX ;If Lower Case
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AND #$1F ; Convert to Inverse
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PRCHRX: JMP ECHO ;Alias to Monitor Routine
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;Advance Character to Next line
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NEWLIN EQU $FD8E ;Monitor Routine CROUT
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