Aaron,

Don't know if this will help but doesn't the Int on Change feature actually
may be
compiled (if your using C) into whether it is H to L or L to H?   In the Case
of
Manchester you will need to be able to have you Int Service Routine be able to
react within 1 to the Next Manchester transistion.   If you do not you INTs
will not
be logged.   Whae Speed of Manchester - this can hit in low MHz?   If so I
doubt
most PICS less the 17C42 and like could support the timing.

Eric Borcherding