;c02 Program Initialization Code for Vic-20 - Common Code

;PETSCII Key Mappings
DELKEY  EQU $14   ;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 $24   ;Destination Pointer LSB [Temporary Pointers]
DSTHI   EQU $25   ;Destination Pointer MSB [Temporary Pointers]
BLKLO   EQU $26   ;Block Pointer LSB [Floating Point Work Area]
BLKHI   EQU $27   ;Block Pointer MSB [Floating Point Work Area]
STKLO   EQU $28   ;Stack Pointer LSB [Floating Point Work Area]
STKHI   EQU $29   ;Stack Pointer MSB [Floating Point Work Area]
BFRLO   EQU $35   ;Buffer Pointer LSB [Temporary String Pointer]
BFRHI   EQU $36   ;Buffer Pointer MSB [Temporary String Pointer]
RDSEED  EQU $A2   ;Random Seed [Software Jiffy Clock (Low Byte)
TEMP0   EQU $FB   ;Temporary Variable [Unused Byte]
TEMP1   EQU $FC   ;Temporary Variable [Unused Byte]
TEMP2   EQU $FD   ;Temporary Variable [Unused Byte]
TEMP3   EQU $FE   ;Temporary Variable [Unused Byte]

;System Variables
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

BLKSLO  EQU $0334 ;Block Start LSB [Unused Byte]
BLKSHI  EQU $0335 ;Block Start MSB [Unused Byte]
BLKELO  EQU $0336 ;Block Start MSB [Unused Byte]
BLKEHI  EQU $0337 ;Block End MSB [Unused Byte]
BLKLEN  EQU $0338 ;Block Length [Unused Byte]

RANDOM  EQU $0339 ;Random Number Storage [Unused Byte]
STKSAV  EQU $033A ;Machine Stack Storage [Unused Byte]
USER11  EQU $033B ;Free Byte for User Programs
TBFFR   EQU $033C ;Cassette I/O Buffer

STKSLO  EQU $03FC ;Stack Start LSB [Unused Byte]
STKSHI  EQU $03FD ;Stack Start MSB [Unused Byte]
STKELO  EQU $03FE ;Stack End LSB   [Unused Byte]
STKEHI  EQU $03FF ;Stack End MSB   [Unused Byte]

;ROM Routines
FSFLFA  EQU $F3D4 ;Find Logical File A

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
POLKEY  EQU $FFE4   ;Aliased to Kernal GETIN Routine

;Get Character from Keyboard
GETKEY  EQU POLKEY  ;Get Key From Keybord

;Get Character from Keyboard
;GETKEY: JSR POLKEY  ;Get Key From Keybord
;        ;The below is not working...
;        LDY $9005   ;Get Character Memory Offset
;        CPY #242    ;If Upper/Lower
;        BNE GETKEX
;        BIT $FF     ;  Bit 7 -> C, Bit 6 -> V
;        BVC GETKEX  ;  If Bit 6 Set (Alpha)
;        BCC GETKEL  ;    If Bit 7 Set (PETSCII Upper)
;        AND #$7F    ;      Clear Bit 7 (ASCII Upper)
;        BNE GETKEX  ;    Else
;GETKEL: ORA #$20    ;      Set Bit 5 (ASCII Lower)
;GETKEX: ORA #$00    ;Set Flags
;        RTS

;A = $41 %0100 0001
;a = $C1 %1100 0001 PETSCII
;a = $61 %0110 0001 PETSCII
;$9005 = 240 UPR/GFX
;        242 UPR/LWR

;Wait for Character from Keyboard
GETCHR: JSR GETKEY  ;Poll Keyboard
        BEQ GETCHR  ;If No Key, Loop
        RTS

;Print Character to Console
;uses direct call to SCRNOUT instead of CHROUT 
PUTCHR  EQU $E742   ;Aliased to SRCOUT Routine

;Delete Previous Character
DELCHR: LDA #DELKEY ;Load Delete Character
        JMP PUTCHR  ;Print and Return

;Advance Character to Next line
NEWLIN: LDX #0      ;Store 0
        STX $D3     ;in Cursor Column and
        JMP $E8C3   ;Execute NXTLINE Routine