; Program initialization code for Oric-1

;System Specific ASCII Key Mappings
DELKEY  EQU $7F     ;Delete/Backspace Key (Delete)
ESCKEY  EQU $1B     ;Escape/Stop Key      (Escape)
RTNKEY  EQU $0D     ;Return/Enter Key     ($0D=Carriage Return)
NULKEY  EQU $00     ;No Key was Pressed   ($00=Null)

;Zero Page Locations
SRCLO   EQU $00     ;Source String Pointer (stdio.asm)
SRCHI   EQU $01
DSTLO   EQU $02     ;Destination String Pointer (string.asm)
DSTHI   EQU $03

STKSAV  EQU $04     ;Stack Pointer Storage
RDSEED  EQU $05     ;Pseudo-RANDOM Seed
RANDOM  EQU $06     ;Pseudo-RANDOM Number Storage

TEMP0   EQU $07     ;Temporary Storage
TEMP1   EQU $08
TEMP2   EQU $09
TEMP3   EQU $0A

BLKSLO  EQU $0B     ;Block Start Address
BLKSHI  EQU $0C
BLKELO  EQU $0D     ;Block End Address
BLKEHI  EQU $0E

;Oric-1 Memory Locations
CAPLCK  EQU $020C   ;Caps Lock: 127=Off, 255 = On

;Oric-1 ROM Funxtions
GTORKB EQU $E905    ;Get Character from Keyboard
VDU    EQU $F409    ;Print character in X to screen

;Oric-1 Tape images have the file extension ".tap"
;and have the following header prepended to the code
;   $16,$16,$16, $16    Tape Syncronization Pattern
;   $24                 Tape Syncronization Byte
;   $00,$00             Filler Bytes
;   $00                 Basic Program
;   $00                 No Autostart ($80 for Autostart)
;   $xx,$xx             MSB, LSB of End Address
;   $05,$01             MSB, LSB of Start Address
;   $00                 Filler Byte
;   "filename"          Up to 16 ASCII Characters
;   $00                 Strint Terminator    

;The End Address is actually one higher than the last
;byte of the Basic program and the first byte of Basic
;variable space. so the compiled program need to have
;one dummy byte added to the end.

        ORG $0501   ;Basic Program Start Address

BASIC:  .DB $0C,$05 ;Address of Next Line
        .DB $00,$00 ;Basic Line Number (0)
        .DB $BF     ;Token for Basic Call Command
        .DB $20     ;Space
        .DS "1294"  ;Address of START Label
        .DB $00     ;End of Line
        .DB $00,$00 ;End of Program Marker

START:  TXS         ;Save Stack Pointer
        STX STKSAV
        LDA #127    ;Set Caps Lock Off
        STA CAPLCK
        JMP MAIN    ;Execute Program

;Poll Character from Keyboard
PLKEY:  INC RDSEED  ;Cycle the Random Seed (if not provided by system)
        JMP GTORKB  ;Call ROM Key Reading function and return

;Read Character from Console
GETKEY;             ;Drop into RDKEY routine

;Wait for Character from Console
RDKEY:  JSR PLKEY   ;Usually calls PLKEY 
        BEQ RDKEY   ;  until a non-zero is returned
        RTS         

;Delete Previous Character
DELCHR: LDA DELKEY  ;Load Delete Character
        BNE PRCHR   ;and Print to Screem

;Advance Cursor to Next line
NEWLIN: LDA RTNKEY  ;Load Carriage Return and fall through to PRCHR

;Print Character to Screen
PRCHR:  TAX         ;Transfer Character to X Register
        JMP VDU     ;Call ROM Print Function and Return

;Exit Program and Return to Operating System or Monitor
EXIT:   LDA #255    ;Set Caps Lock On
        STA CAPLCK
        LDX STKSAV  ;Restore Stack Pointer
        TXS
        RTS         ;and Return to Basic

;Note: The following two functions replicate calls available 
;in the Apple-1 monitor and are included for test purposes
;They will likely be removed before the final release

;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


;Functions to set String Pointers
;Used by memory, stdio, stdlin, string, and stringx libraries

;Initialize Destination String Pointer
SETDST: STX DSTLO       ;Save Destination String Pointer
        STY DSTHI
        RTS

;Initialize Source String Pointer and Index
SETSRC: STX SRCLO       ;Save Source String Pointer
        STY SRCHI
        LDY #$00        ;Initialize Index Into String
        RTS