2018-01-28 18:30:49 +00:00
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; c02 Program Initialization Code for Unexpanded VIC-20
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2018-09-17 00:30:25 +00:00
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;PETSCII Key Mappings
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DELKEY EQU $14 ;Delete/Backspace Key (Delete)
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2018-01-28 18:30:49 +00:00
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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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2018-09-17 00:30:25 +00:00
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;Zero Page Variables
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SRCLO EQU $22 ;Source Pointer LSB [Temporary Pointers]
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SRCHI EQU $23 ;Source Pointer MSB [Temporary Pointers]
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DSTLO EQU $24 ;Destination Pointer LSB [Temporary Pointers]
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DSTHI EQU $25 ;Destination Pointer MSB [Temporary Pointers]
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BLKLO EQU $26 ;Block Pointer LSB [Floating Point Work Area]
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BLKHI EQU $27 ;Block Pointer MSB [Floating Point Work Area]
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STKLO EQU $28 ;Stack Pointer LSB [Floating Point Work Area]
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STKHI EQU $29 ;Stack Pointer MSB [Floating Point Work Area]
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2019-03-23 00:28:43 +00:00
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BFRLO EQU $35 ;Buffer Pointer LSB [Temporary String Pointer]
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BFRHI EQU $36 ;Buffer Pointer MSB [Temporary String Pointer]
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2018-09-17 00:30:25 +00:00
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RDSEED EQU $A2 ;Random Seed [Software Jiffy Clock (Low Byte)]
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TEMP0 EQU $FB ;Temporary Variable [Unused Byte]
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TEMP1 EQU $FC ;Temporary Variable [Unused Byte]
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TEMP2 EQU $FD ;Temporary Variable [Unused Byte]
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TEMP3 EQU $FE ;Temporary Variable [Unused Byte]
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;System Variables
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USER3 EQU $0313 ;Free Byte for User Programs
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BLKSLO EQU $0334 ;Block Start LSB [Unused Byte]
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BLKSHI EQU $0335 ;Block Start MSB [Unused Byte]
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BLKELO EQU $0336 ;Block Start MSB [Unused Byte]
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BLKEHI EQU $0337 ;Block End MSB [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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USER11 EQU $033B ;Free Byte for User Programs
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TBFFR EQU $033C ;Cassette I/O Buffer
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STKSLO EQU $03FC ;Stack Start LSB [Unused Byte]
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STKSHI EQU $03FD ;Stack Start MSB [Unused Byte]
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STKELO EQU $03FE ;Stack End LSB [Unused Byte]
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STKEHI EQU $03FF ;Stack End MSB [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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2018-01-28 18:30:49 +00:00
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2019-03-29 23:06:12 +00:00
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;ROM Routines
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FSFLFA EQU $F314 ;Find Logical File A
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2018-01-28 18:30:49 +00:00
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;Machine Language Basic Stub
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2018-09-17 00:30:25 +00:00
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ORG $0801 ;Start of Basic Program
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BASIC: DC $0C, $10 ;Pointer to Next Line (4109)
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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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2018-01-28 18:30:49 +00:00
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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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2018-09-17 00:30:25 +00:00
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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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2018-01-28 18:30:49 +00:00
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2018-09-17 00:30:25 +00:00
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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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2018-01-28 18:30:49 +00:00
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2018-09-17 00:30:25 +00:00
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;Poll Keyboard for Character
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POLKEY EQU $FFE4 ;Aliased to Kernal GETIN Routine
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2018-01-28 18:30:49 +00:00
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2018-09-17 00:30:25 +00:00
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;Get Character from Keyboard
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GETKEY EQU POLKEY ;Get Key From Keybord
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2018-01-28 18:30:49 +00:00
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2018-09-17 00:30:25 +00:00
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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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2018-01-28 18:30:49 +00:00
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RTS
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2018-09-17 00:30:25 +00:00
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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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2018-01-28 18:30:49 +00:00
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;Delete Previous Character
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2018-09-17 00:30:25 +00:00
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DELCHR: LDA #DELKEY ;Load Delete Character
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JMP PUTCHR ;Print and Return
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2018-01-28 18:30:49 +00:00
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;Advance Character to Next line
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2018-09-17 00:30:25 +00:00
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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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2018-01-28 18:30:49 +00:00
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2018-11-07 05:11:09 +00:00
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INCLUDE "../include/prbyte.a02" ;PRBYTE and PRHEX routine
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