On Sat, Feb 23, 2002 at 03:34:58PM +0100, Joris van den Heuvel wrote:
> You cannot use external code memory on a 16F877 or any 16-series PIC for
> that matter (someone correct me if I'm wrong).

I think you have to qualify that with the adjective 'directly'. There are
any number of bytecode interpreters that can do the job. I'm 90% finished
with my NPCI project, which is a bytecode interpreter for a minature high
level language. You can see the language overview here:

http://www.finitesite.com/d3jsys/README-NPCI.html

You can run it out of an external memory, or internal memory for that matter.

One intriguing possibility is borne from the fact that PICs have reprogrammable
program memory. So in theory one could download code segments from an
external memory into the internal program memory and then execute it. However
the limitation of 1000 writes nominal doesn't make it an effective idea.

>
> You will be quite amazed at how efficient a PIC uses its program memory,
> even in C. I'm fairly experienced with PICs, I have done a project for which
> I also doubted whether 8k (in an F876) would be enough, and was planning on
> adding an external EEPROM for data. I ended up using about 1.25k for the
> program and about as much for the data.
>
> This is the project: http://home.planet.nl/~heuv0283/scan_cl/scan_cl.htm

Agreed.

BAJ

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