Bob Barr <PICLIST@mitvma.mit.edu> wrote:

> Andy's code here will work if you need the value expressed in BCD and
> not its actual hex value.
> ....
> If you need its true hex value, you'll  need to multiply the msb
> digit's numeric value by 10 (decimal) before adding it to the lsb's
> numeric value.

    Oops, you're right.  The correct code:

    LIST R = DEC

    MOVLW   '0'
    BTFSC   CHAR1,6
    MOVLW   'A'-10
    SUBWF   CHAR1

    MOVLW   '0'
    BTFSC   CHAR2,6
    MOVLW   'A'-10
    SUBWF   CHAR2

    CLRC               ;Carry's always set here, so clear it.
    RLF     CHAR1,W    ;W = MSB * 2
    SWAPF   CHAR1      ;CHAR1 = MSB * 16
    RRF     CHAR1      ;CHAR1 = MSB * 8
    ADDWF   CHAR1,W    ;W = (MSB * 8) + (MSB * 2) = MSB * 10
    ADDWF   CHAR2,W    ;W = MSB * 10 + LSB

> In either case, you can remove the BTFSC's and the MOVLW's following
> them since the BTFSC will always skip the MOVLW. Bit 6 of your digit's
> ASCII will always be clear for decimal digits '0' through '9'.

    True, but it'll be set for hex digits 'A' through 'F'.

    If the two input bytes are hex digits in the range 0-F, you need
the
    BTFSC/MOVLWs; if they're only in the range 0-9, you don't.

    -Andy

=== Andrew Warren -- aiw@cypress.com
=== Principal Design Engineer
=== Cypress Semiconductor Corporation
===
=== Opinions expressed above do not
=== necessarily represent those of
=== Cypress Semiconductor Corporation

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