This is the code I use to convert the output of a DS1821 from C to F.
T_C is the temp in C and a negative would be in twos compliment.



ToF
    movlw     '+'
    movwf     Sign
    movlw    0x000
    movwf    added
    movwf    added_carry
    movwf    Temp
    movlw    0x012   ;set it too add 18 times (0x012)
    movwf    LOOP1

Negative?
     btfsc         T_C, 7
     call            Sign?
     movf          T_C, w
Adding                 ;x 18
     addwf        added
     btfsc         STATUS, C
     incf           added_carry
     bcf            STATUS, C
     decfsz       LOOP1
     goto          Adding

Divide                     ; / 10
     bsf            STATUS, C
     movlw        0x00A
     incf           Temp
     subwf        added
     btfss         STATUS, C
     goto          Dec
     goto          Divide

Dec     ;carry file / 10
     movf         added_carry, f
     btfsc         STATUS, Z
     goto         stop
     decf         added_carry
     goto         Divide
Sign?
     comf         T_C
     incf          T_C
     movlw        '-'
     movwf       Sign
     return
Pos
     movlw         0x020   ;+ 32
     addwf         Temp
     return
Twoscomp
     comf         Temp
     incf          Temp
     movlw         '+'
     movwf         Sign
     return
Neg
     movlw     0x020   ;+ 32
     subwf     Temp
     btfsc      Temp, 7
     call         Twoscomp
     return



-----Original Message-----
From: Randie Ohtsji [4555] <rohtsji@GLENVAN.GLENAYRE.COM>
To: PICLIST@MITVMA.MIT.EDU <PICLIST@MITVMA.MIT.EDU>
Date: Monday, March 09, 1998 3:28 PM
Subject: degrees C to degrees F conversion


>Hello,
>
>Does anyone have a simple way of converting from degrees Celsius
>to degrees Fahrenheit (and vice-versa) using PIC math?
>
>C -> F
>======
>C*9/5 + 32
>
>
>F -> C
>======
>(F-32)(5/9)
>
>
>Thanks in advance!
>
>-Randie
>rohtsji@glenayre.com
>