Roy J. Gromlich wrote...

>I need to Read the 18Fxxx A/D and send the resulting
>16-bit number to the UART for output, thus I need to
>convert 16-bit Binary to ASCII.  I have tried several
>procedures fromn PIClist but none of them appear to
>be complete and so far none of them will make it
>through the PIC assembler (MASM).  I am getting various
>cryptic messages regarding illegal and/or missing op
>codes.  I can probably figure this out eventually, but
>I have a deadline issue and would like to know if ANYONE
>has a working & tested procedure for the 18Fxxx series
>chips with sufficient documentation that it can be used
>without a lot of hacking.

The following PIC18F code will convert an unsigned 16-bit integer
in a two-byte variable called Binreg, to unpacked 5-digit BCD in
a 5-byte variable BCDreg (both these variables are stored with
most-significant-byte/digit at the lowest address).

The unpacked BCD then can be converted to ASCII simply by adding
hexadecimal 0x30 to each digit.

Sorry for the lack of comments.  This code has been copied many
times for use on many projects over the years, and the comments
are long gone.  It's based on what I believe is commonly called
the "add-3 algorithm", I remember that much.  And it works.

        UDATA

Count   RES     1   ; loop counter
BCDreg  RES     5   ; 5-digit unpacked BCD output register
Binreg  RES     2   ; 16-bit unsigned binary input register

        CODE

        GLOBAL  UInt16toBCD5, BCDreg, Binreg

UInt16toBCD5

        movlw   16
        movwf   Count
        clrf    BCDreg+0
        clrf    BCDreg+1
        clrf    BCDreg+2
        clrf    BCDreg+3
        clrf    BCDreg+4

loop

        movlw   5
        subwf   BCDreg+0, W
        movlw   3
        btfsc   STATUS, C
        addwf   BCDreg+0, F
        movlw   5
        subwf   BCDreg+1, W
        movlw   3
        btfsc   STATUS, C
        addwf   BCDreg+1, F
        movlw   5
        subwf   BCDreg+2, W
        movlw   3
        btfsc   STATUS, C
        addwf   BCDreg+2, F
        movlw   5
        subwf   BCDreg+3, W
        movlw   3
        btfsc   STATUS, C
        addwf   BCDreg+3, F
        movlw   5
        subwf   BCDreg+4, W
        movlw   3
        btfsc   STATUS, C
        addwf   BCDreg+4, F

        bcf     STATUS, C
        rlcf    Binreg+1, F
        rlcf    Binreg+0, F

        rlcf    BCDreg+4, F
        bcf     STATUS, C
        btfsc   BCDreg+4, 4
        bsf     STATUS, C
        rlcf    BCDreg+3, F
        bcf     STATUS, C
        btfsc   BCDreg+3, 4
        bsf     STATUS, C
        rlcf    BCDreg+2, F
        bcf     STATUS, C
        btfsc   BCDreg+2, 4
        bsf     STATUS, C
        rlcf    BCDreg+1, F
        bcf     STATUS, C
        btfsc   BCDreg+1, 4
        bsf     STATUS, C
        rlcf    BCDreg+0, F

        movlw   0x0F
        andwf   BCDreg+0, F
        andwf   BCDreg+1, F
        andwf   BCDreg+2, F
        andwf   BCDreg+3, F
        andwf   BCDreg+4, F

        decfsz  Count, F
        goto    loop

        return

        END


Hope this helps a bit...

Dave D.

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