On Wed, 24 Dec 1997, Mike Keitz wrote:

> Keeping all this in mind, it is still possible to work around the
> limitations of the change detector and use the RB change interrupt in a
> program.  The primary consideration would be not to read or write PORTB
> except as a response to a detected change.

Or, if you have some PORTA pins available, connect them in parallel with
the PORTB pins.  After each PORTB access, read PORTA, compare.  If the
read on PORTA says the pin changed, but the interrupt routine wasn't
called, call the interrupt routine directly.  It's complex to get right,
but not impossible.

Note, you may want to put resistors in series with the PORTA pins.  That
way if there is a bug and the pins become outputs, the PIC won't get
damaged if the PORTA pin fights the PORTB pin.

--
paulh@hamjudo.com  http://www.hamjudo.com
The April 97 WebSight magazine describes me as "(presumably) normal".