On Wed, 12 Jun 1996, Onat Ahmet wrote:

> So, is there a workaround for this problem? Such as checking
> for the interrupt flag before reading or writing to RB port?

There's the work-around described in the datasheet (this has been in
there for at least some of the 16Cxx parts for a while):

  "The interrupt on change feature is recommended for wake-up on key
   depression operation and operations where PORTB is used only for the
   interrupt on change feature.  Polling of PORTB is not recommended
   while using the interrupt on change feature."

I also recall that Microchip said, some time ago, that future revisions
would fix this feature, but I don't recall just how future that was to be.
I think it may be fixed in the A-suffix versions of the 16C7x chips, etc.