mirror of https://github.com/RevCurtisP/C02.git
104 lines
3.5 KiB
Plaintext
104 lines
3.5 KiB
Plaintext
; c02 Program Initialization Code for Commodore 64
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;PETSCII Key Mappings
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DELKEY EQU $14 ;Delete/Backspace Key (Delete)
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ESCKEY EQU $03 ;Escape/Stop Key (RUN/STOP)
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RTNKEY EQU $0D ;Return/Enter Key (RETURN)
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;Zero Page Variables
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XMBANK EQU $0A ;Extended Memory Bank [Load/Verify Flag]
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XMADDR EQU $0B ;Extended Memory Address [Array Index/Flags]
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; $16 ;[Temporary String Stack Pointer]
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SRCPTR EQU $17 ;Source Pointer [Temporary String Space Pointer]
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DSTPTR EQU $19 ;Destination Pointer [Temporary String Stack]
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; $21 ;[Temporary String Stack]
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BLKPTR EQU $22 ;Block Pointer [Temporary Pointers]
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STKPTR EQU $24 ;Stack Pointer [Temporary Pointers]
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; $26-$29 ;[Floating Point Work Area]
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USRPTR EQU $35 ;[Temporary String Pointer]
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TEMP0 EQU $61 ;Temporary Variable [Floating Point Accumulator]
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TEMP1 EQU $63 ;Temporary Variable [Floating Point Accumulator]
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TEMP2 EQU $65 ;Temporary Variable [Floating Point Accumulator]
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TEMP3 EQU $67 ;Temporary Variable [Floating Point Accumulator]
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TMPPTR EQU $69 ;Temporary Pointer [Floating Point Argument]
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; $6A-$70 ;[Floating Point Argument]
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.STKEY EQU $91 ;Stop Key flag
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RDSEED EQU $A2 ;Random Seed [Software Jiffy Clock (Low Byte)]
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; $FB-$FE ;Unused Zero Page for Applications
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;System Variables
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SYSBFL EQU 88 ;System Buffer Size (88 Bytes)
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SYSBFR EQU $0200 ;System Buffer [Keyboard Buffer]
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SYSBFP EQU $0313 ;Position in System Buffer [Free Byte]
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BLKBGN EQU $0334 ;Block Start [Unused Byte]
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BLKEND EQU $0336 ;Block Start [Unused Byte]
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BLKLEN EQU $0338 ;Block Length [Unused Byte]
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RANDOM EQU $0339 ;Random Number Storage [Unused Byte]
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.STKSAV EQU $033A ;Machine Stack Storage [Unused Byte]
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; $033B ;Free Byte for User Programs
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TBFFR EQU $033C ;Cassette I/O Buffer
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STKBGN EQU $03FC ;Stack Start [Unused Byte]
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STKEND EQU $03FE ;Stack End [Unused Byte]
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;Video RAM and ROM
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VICSCN EQU $0400 ;Video Screen Memory Area (Unexpanded)
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CHRROM EQU $D000 ;Character Generator ROM
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VICCLR EQU $D800 ;Color RAM (Unexpanded)
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;ROM Routines
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FSFLFA EQU $F314 ;Find Logical File A
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;Machine Language Basic Stub
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ORG $0801 ;Start of Basic Program
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BASIC: DC $0C, $08 ;Pointer to Next Line
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DC $00, $00 ;Line Number (0)
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DC $9E ;SYS
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DC $20 ;' '
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DC $32, $30, $36 ,$32 ;"2062"
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DC $00 ;End of Line Marker
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DC $00, $00 ;End of Basic Program
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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: LDA #0 ;Clear Stop Key Flag
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STA .STKEY
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LDX .STKSAV ;Retrieve Saved Stack Pointer
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TXS ;and Restore It
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RTS
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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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;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 $E716 ;Aliased to SRCNOUT 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 $E87C ;Execute NXTLINE Routine
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;Print Zero Delimited String to Screen
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PUTSTR: TXA ;Copy LSB to Accumulator
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JMP $AB1E ;Execute STROUT
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INCLUDE "prbyte.a02" ;PRBYTE and PRHEX routine
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