*-------------------------------------------------------*
*                                                       *
* ATOB- converts a 2 char ASCII (decimal) string into a *
*       1 byte HEX number.                              *
*  Input- The address of the string in the Y register.  *
*  Output- The number, stored in the global var N.      *
*  Registers clobbered- A,B,CCR                         *
*                                                       *        
*-------------------------------------------------------*
ATOB    LDAB    0,Y             ; get the first char in the buffer
        SUBB    #$30            ; ASCII 0 = 0x30
        LDAA    #10             ; the first digit was "tens"
        MUL                     ; D = ACCB * 10
* Note: for this lab, since N cannot be greater than 13, the result in D
*       falls completely in ACCB (since ACCD = [ACCA|ACCB])
        TBA                     ; ACCA <- ACCB
        LDAB    1,Y             ; Get the second char in the buffer
        SUBB    #$30            ; ASCII 0 = 0x30
        ABA                     ; ACCA <- ( ACCA (tens) + ACCB (ones) )
        STAA    N               ; store this 
        RTS                     ;
*