In a message dated 98-05-21 14:12:51 EDT, you write:

<< What it comes down to is that if you didn't use the extra couple of
      instructions available on the '84, if you didn't use interrupts, and
      if you don't call subroutines more than 2 levels deep, you can
      probably port your design easily.  If you did use those extra
      instructions you can still probably modify your code easily to make it
      work.  However, if you used interrupts or need more than 2 stack
      levels, the '509 is probably not a good choice for you.  If you need
      these extra features, wait for the 12C6XX devices, which are 8 pin 14
      bit devices. >>

Thank you for taking the time to answer my question.
Do you know what those F84 extra instructions are ?

Jon