Hi John/Scott,

Here is my version, somewhat similar to Scott's but the correction and
the end is more simpler:

(untested)
cnt16bit:
        clrf    kz
        clrf    lo
        clrf    hi

        movlw   2               ;preset 2 counts
loop    btfsc   PORTB,7
         goto   quit1           ;1

        addwf   lo,f            ;inc lo cnt
        btfsc   PORTB,7
         goto   quit2           ;2

        rlf     kz,w            ;get carry
        btfsc   PORTB,7
         goto   quit3           ;3-2

        addwf   hi,f            ;hi incremented depends on carry
        btfsc   PORTB,7
         goto   quit4           ;4-2

        skpc                    ;check if already finished
        btfsc   PORTB,7
         goto   quit5           ;5-2

        movlw   7               ;add 7 uncounted tests
        btfsc   PORTB,7
         goto   loop6           ;6-2

        btfss   PORTB,7
         goto   loop
                                ;7-2

quit7   incf    kz,f            ;add uncounted tests
quit6   incf    kz,f
quit5   incf    kz,f
quit4   incf    kz,f
quit3   addwf   hi,f            ;inc hi byte first
                                ; bec. not incr in the loop

quit1   incf    kz,w
        addwf   lo,f
        skpnc
         incf   hi,f
        return

quit2   addwf   hi,f
        return


regards,
Reggie

--
e-mail: rberdin@bigfoot.com
ICQ#:   31651436
URL:    http://www.bigfoot.com/~rberdin



John Payson wrote:
>
> |Create a delay loop that can loop for up to 2^16 times while mininmizing
> |the number of cycles per iteration.
>
> More fun variant: write a routine which, when called, will time how long
> it takes for pin RB7 to go high [assuming it isn't already].  Time should
> be kept in 16 bits, and the routine should exit if RB7 does not go high.
> within 65,536 counts.
>
> To make things a bit more interesting...
>
> [1] Consider approaches with and without RTCC
>
> [2] Try for a measurement precision of 3 cycles.
>
> [3] Try to design the loop to look for either port pin RB6 or RB7 to
>     go high, with a precision of 4 cycles.
>
> Those sound like fun little additions?  I will offer a couple little hints:
>
> [A] The code need not LOOP 65536 times; if you have, e.g., two tests within
>     a 6-cycle loop you could run the loop 32768 times and at the end check
>     which test kicked you out of it.
>
> [B] You need not exit the loop immediately upon detecting the event, prov-
>     ided the count values are correct.
>
> Have at it...