mirror of
https://github.com/RevCurtisP/C02.git
synced 2024-09-26 22:57:09 +00:00
100 lines
3.5 KiB
Plaintext
100 lines
3.5 KiB
Plaintext
;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
|
|
SRCLO EQU $22 ;Source Pointer LSB [Temporary Pointers]
|
|
SRCHI EQU $23 ;Source Pointer MSB [Temporary Pointers]
|
|
DSTLO EQU $25 ;Destination Pointer LSB [Temporary Pointers]
|
|
DSTHI EQU $24 ;Destination Pointer MSB [Temporary Pointers]
|
|
RDSEED EQU $A2 ;Random Seed [Software Jiffy Clock (Low Byte)]
|
|
BLKLO EQU $FD ;Block Pointer LSB [Unused Byte]
|
|
BLKHI EQU $FE ;Block Pointer MSB [Unused Byte]
|
|
STKLO EQU $FD ;Stack Pointer LSB [Unused Byte]
|
|
STKHI EQU $FE ;Stack Pointer MSB [Unused Byte]
|
|
|
|
USER0 EQU $0310 ;Free Byte for User Programs
|
|
USER1 EQU $0311 ;Free Byte for User Programs
|
|
STKSAV EQU $0312 ;Machine Stack Storage [Unused Byte]
|
|
STKSLO EQU $0313 ;Stack Start LSB [Unused Byte]
|
|
STKSHI EQU $0334 ;Stack Start MSB [Unused Byte]
|
|
STKELO EQU $0335 ;Stack End LSB [Unused Byte]
|
|
STKEHI EQU $0336 ;Stack End MSB [Unused Byte]
|
|
BLKSLO EQU $0337 ;Block Start LSB [Unused Byte]
|
|
BLKSHI EQU $0338 ;Block Start MSB [Unused Byte]
|
|
BLKELO EQU $0339 ;Block Start MSB [Unused Byte]
|
|
BLKEHI EQU $033A ;Block End MSB [Unused Byte]
|
|
BLKLEN EQU $033B ;Block Length [Unused Byte]
|
|
TBFFR EQU $033C ;Cassette I/O Buffer
|
|
TEMP0 EQU $03FC ;Temporary Variable [Unused Byte]
|
|
TEMP1 EQU $03FD ;Temporary Variable [Unused Byte]
|
|
TEMP2 EQU $03FE ;Temporary Variable [Unused Byte]
|
|
TEMP3 EQU $03FF ;Temporary Variable [Unused Byte]
|
|
|
|
;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 PLKEY
|
|
|
|
;Wait for Character from Keyboard
|
|
RDKEY: JSR GETKEY ;Poll Keyboard
|
|
BEQ RDKEY ;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
|
|
JMP PRCHR ;Print and Return
|
|
|
|
;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
|
|
|