I've been reviewing the sonapic.asm file from Eric Smith's PIC project
page.  I've been unsuccesfull in attemping to EMAIL to
eric@goonsquad.spies.com, so I thought I'd ask a question here.

Specifically, the
following code fragment appears in error:

; delay 1 millimeter = 6 microseconds = 12 cycles at 8.0 MHz
rdloop:
        incf    range,1         ; 0 increment range
        btfsc   status,zf       ; 1
        incf    range+1,1       ; 2
        movf    range+1,w       ; 3 test for timeout - 10752 mm
        xorlw   (maxrange/256)+1        ; 4
        btfsc   status,zf       ; 5
        goto    rddone          ; 6
        btfss   portb,echo      ; 7 test for echo
        goto    rdloop          ; 8
rddone:

My calculations agree that echo transit time is approximately
6 microseconds per millimeter (3 microseconds one way).  But
I count only 10 cycles per loop--so does MPSIM (under MPLAB).

Is this a mistake, or am I missing something?

Thanks,

Dave Thomas