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C02/include/vic3k.a02

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2018-01-28 18:30:49 +00:00
;c02 Program Initialization Code for VIC-20 with 3K Expansion
;System Specific ASCII Key Mappings
DELKEY EQU $7F ;Delete/Backspace Key (Delete)
ESCKEY EQU $03 ;Escape/Stop Key (RUN/STOP)
RTNKEY EQU $0D ;Return/Enter Key (RETURN)
;Zero Page Locations
RDSEED EQU $A2 ;Software Jiffy Clock (Low Byte)
SRCLO EQU $D1 ;Pointer to Address of Current Screen Line
SRCHI EQU $D2 ;Pointer to Address of Current Screen Line
DSTLO EQU $FB ;Free Byte for User Programs
DSTHI EQU $FC ;Free Byte for User Programs
BLKLO EQU $FD ;Free Byte for User Programs
BLKHI EQU $FE ;Free Byte for User Programs
USER0 EQU $0310 ;Free Byte for User Programs
USER1 EQU $0311 ;Free Byte for User Programs
USER2 EQU $0312 ;Free Byte for User Programs
USER3 EQU $0313 ;Free Byte for User Programs
USER4 EQU $0334 ;Free Byte for User Programs
USER5 EQU $0335 ;Free Byte for User Programs
USER6 EQU $0336 ;Free Byte for User Programs
BLKSLO EQU $0337 ;Free Byte for User Programs
BLKSHI EQU $0338 ;Free Byte for User Programs
BLKELO EQU $0339 ;Free Byte for User Programs
BLKEHI EQU $033A ;Free Byte for User Programs
STKSAV EQU $033B ;Free Byte for User Programs
TBFFR EQU $033C ;Cassette I/O Buffer
TEMP0 EQU $03FC ;Free Byte for User Programs
TEMP1 EQU $03FD ;Free Byte for User Programs
TEMP2 EQU $03FE ;Free Byte for User Programs
TEMP3 EQU $03FF ;Free Byte for User Programs
;Video RAM and ROM
VICSCN EQU $1E00 ;Video Screen Memory Area (Unexpanded)
CHRROM EQU $8000 ;Character Generator ROM
VICCLR EQU $9600 ;Color RAM (Unexpanded)
;Machine Language Basic Stub
ORG $0401 ;Start
BASIC: DC $0C, $04 ; Pointer to Next Line (1036)
DC $00, $00 ; Line Number (0)
DC $9E ; SYS
DC $20 ; ' '
DC $31, $30, $33 ,$38 ; "1038"
DC $00 ;End of Line Marker
DC $00, $00 ;End of Basic Program
START: TSX ;Get Stack Pointer
STX STKSAV ;and Save for Exit
JMP main ;Execute Program
EXIT: LDX STKSAV ;Retrieve Saved Stack Pointer
TXS ;and Restore It
RTS ;Return to BASIC
;Poll Keyboard for Character
PLKEY EQU $FFE4 ;Aliased to Kernal GETIN Routine
;Get Character from Keyboard
GETKEY: EQU RDKEY
;Wait for Character from Keyboard
RDKEY: JSR PLKEY ;Poll Keyboard
BEQ GETKEY ;If No Key, Loop
RTS
;Delete Previous Character
DELCHR: LDA #DELKEY ;Load Delete Character
JMP PRCHR :Print and Return
;Advance Character to Next line
NEWLIN: LDA #RTNKEY ;Load C/R into Accumulator
;Print Character to Console
PRCHR EQU $FFD2 ;Aliased to Kernal CHROUT Routine
;Print Byte as Two-Digit Hex Number to Console
PRBYTE: PHA ;Save Accumulater
LSR ;Shift Hi Nybble to Low Nybble
LSR
LSR
LSR
JSR prhex ; and Print it
PLA ;Restore Accumulator
; and fall into prhex
;Print Low Nybble as Hex Digit to Console
PRHEX: AND #$0F ;Strip High Nybble
CMP #$0A ;If Low Nybble >= 10
BCC PRHEXC ;
ADC #$06 ; Convert ':' to 'A'...
PRHEXC: ADC #$30 ;Convert to ASCII Character
JMP prchr ;Print Hex Digit and Return