Myke Predko wrote, quoting myself:

>>  Err, no, it's the MSB actually (for most practical purposes/ timer
>> modes).  For single tones, you load the timer, enable it and count
>> clock ticks (18.6Hz) for the duration.

  That is, to determine the duration in the easiest manner.

> Are you sure about that?  When I've looked at it with a scope, it's a
> square wave.

  The timer has various modes - can output a "terminal pulse" for the
last clock cycle in mode 2, but the "standard" mode 3 rather cleverly
divides the count in two and outputs high for (N+1)/2 counts, low for
N/2 counts.  According to The Book.
--
  Cheers,
        Paul B.