> Guys:
>
>     ; Jump to BAD if value in W is not an ASCII character
>     ; from "0" to "9", otherwise fall thru with the 0-9
>     ; value in W.  No file registers required.
>
>     ADDLW   255-"9"
>     ADDLW   ("9"-"0") + 1
>     BNC     BAD
>
> -Andy

It's a very useful test. I put this 18F routine together as part
of a module to sort commands and parameters in received
text strings. (it also needs a routine to detect and convert
lower case to upper case. And there's a pre-test for special
characters - it looks for @  ? * - that has to be worked in with
ch_skip), but as it is it will sort uppercase and ASCII numbers

It makes use of the 18F's 3 FSRs - other PICs could use FSR
and two RAM indices

sort     movlw   0x00         ;source RAM address, received text
         movwf   fsr0l
         movlw   0x20         ;destination RAM address, UC letters
         movwf   fsr1l
         movlw   0x40         ;destination RAM address, numbers
         movwf   fsr2l

         clrf    fsr0h
         clrf    fsr1h
         clrf    fsr2h

loop     movf    indf0,w      ;get char from source
         addlw   .255-"A"+1   ;test if UC letter
         addlw   ("Z"-"A")+1
         bc      number       ;not letter, try number
         movff   indf0,indf1  ;copy char to letter store
         incf    fsr0l        ;increment source index
         incf    fsr1l        ;increment letter index
         btfsc   fsr0l,5      ;test for fsr0l=32
         bra     done         ;yes
         bra     loop         ;no

number   movf    indf0,w      ;get char from source
         addlw   .255-"9"     ;test if number
         addlw   ("9"-"0")+1
         bnc     ch_skip      ;not letter or number
         movff   indf0,indf2  ;copy char to number store
         incf    fsr0l        ;increment source index
         incf    fsr2l        ;increment number index
         btfsc   fsr0l,5
         bra     done
         bra     loop

ch_skip  incf    fsr0l        ;not UC letter or number
         btfss   fsr0l,5      ;done
         bra     loop

done ............

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