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88 lines
2.8 KiB
Plaintext
88 lines
2.8 KiB
Plaintext
;Apple 1 program initialization code for c02 programs
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SUBROUTINE _APPLE2
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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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DSTPTR EQU $06 ;Destination Pointer [Unused]
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SRCPTR EQU $08 ;Source Pointer [Unused]
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STKPTR EQU $1D ;Stack Pointer [Unused]
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RANDOM EQU $1F ;Random Number [Unused]
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.INVFLG EQU $32 ;*Inverse Flag: $3F=Blinking, $7F=Inverse, $FF=Normal
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BLKPTR EQU $3C ;Block Segment Pointer [A1]
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TEMP0 EQU $3E ;Temporary Variables [A2-A3]
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TEMP1 EQU $3F
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TEMP2 EQU $40
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TEMP3 EQU $41
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TMPPTR EQU $42 ;Temporary Pointer [A4]
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USRPTR EQU $44 ;User Pointer[A5]
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RDSEED EQU $4E ;Random Number Seed
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; $71 ;[Temporary Register]
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; $FA-$FF ;Free Zero Page for Applications
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;System Variables
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SYSBFL EQU 128 ;System Buffer Size [Max String Length]
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SYSBFR EQU $0300 ;System Buffer [Keyboard Buffer through $0380]
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SYSBFP EQU $03F6 ;System Buffer Position
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BLKLEN EQU $03F7 ;Block Segment Length
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BLKBGN EQU $03F8 ;Block Start Address
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BLKEND EQU $03FA ;Block End Address
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STKBGN EQU $03FC ;Stack Start Address
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STKEND EQU $03FE ;Stack End Address
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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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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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;Poll Keyboard for Raw Character
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POLKEY: 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 POLKER ;If Key Pressed
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LDA .KBD ; Load Key Value
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STA .AKD ; Clear Strobe
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POLKER: RTS
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;Get ASCII Character from Keyboard
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GETKEY: JSR POLKEY ;Poll Keyboard
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AND #$7F ;Strip High Bit
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RTS
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;Wait for ASCII Character from Keyboard
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GETCHR: JSR GETKEY ;Get Modified Key Code
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BEQ GETCHR ;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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PUTCHR: 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 $FDF0 ;Execute Monitor Routine COUT1
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;Advance Character to Next line
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NEWLIN EQU $FD8E ;Monitor Routine CROUT
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INCLUDE "putstr.a02" ;PUTSTR routine
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