Eric Slight <eslight@Matrox.COM> wrote:

> > > if I buy a 16F84, I am stuck with only 1K of eeprom program memory,
> > > is there a way to reroute the port for data/adress bus?
> >
> >     No.  If you want an external address/data bus, you'll need to
> >     use one of the PIC17 family.
>
> You mean I'll have to buy a bigger romable code chip ?
> or you mean there's a chip that you can hook up with the
> pic that does the job, or what? :)
>
> I used to do ram expansion when needed with  68hc11 but the pic
> doesn't work the same way and I don't know how to adress pass 3ff
> with external memory, for example

Eric:

None of the 12- and 14-bit PICs (PIC12Cxxx, PIC14xxx, PIC16C5x,
PIC16Cxx, etc.) support external program memory.

The only PICs whose I/O pins can be configured as an external
address/data bus (like the 68HC11 with which you're familiar) are
the 16-bit PICs (PIC17C4x, etc.).

If your code will not fit in your current PIC, you have two choices:

    1.  Buy a PIC with more internal program memory than what you're
        using now, or

    2.  Replace your current PIC with a PIC17Cxx device, configure
        it for either "microprocessor" or "extended microcontroller"
        mode, then add all the external memory (and address-decoding
        and latching logic) that you want.

-Andy

=== Andrew Warren - fastfwd@ix.netcom.com
=== Fast Forward Engineering - Vista, California
=== http://www.geocities.com/SiliconValley/2499 (personal)
=== http://www.netcom.com/~fastfwd (business)