gnupic: Help/Hint needed
Subject:
Re: Help/Hint needed
From:
James H. grosbach ####@####.####
Date:
18 Jan 2001 16:47:41 -0000
Message-Id: <01011809560301.06927@humbaba.microchip.com>
On Thursday 18 January 2001 08:22, you wrote:
> I wonder if someone out there knows the answers (or some hints) to the
> following questions about the PIC16F and PIC18C families.
>
> 1) Can I have an external ROM or Flash (say 512K or more)holding some
> instructions and then read them from PIC in real-time. (the problem is that
> PIC program memory may not be enough to hold the entire program.)
Not currently. The 18C family is designed with this in mind, but no 16 or 18
parts are currently available with an external address bus.
> 2) Would it be possible to do the above with two or more PICS each holding
> part of the program?
You might have to implement some sort of RPC mechanism for interprocessor
communication, but it is possible, yes. Whether this is a feasible thing in
practical terms would be very application specific. For example, if there's
little to no data that interrupt handlers for different events need to share,
one PIC could respond to one set and another PIC to another set. If data
needs to be shared, it gets quite a bit harder.
> 3) Can I have an external (S)RAM (say 128K or more) holding part of the
> processing data (say an image that must be processed, but takes more
> space than PIC's data memory) and send it to PIC during the real-time
> operation?
You could probably do something like hook the address lines up to a couple of
ports and the data lines to another port (or multiplex the address ports) and
implement the reads in an access function. That's basically what the 17C does
in hardware for external memory. That's a lot of pins to tie up, though.
You'd probably be better served with a serial memory of some sort for this.
> 4) Where can I find a good proto board for PIC17C7X?
One of the PICDEM boards supports the 17C family. I think it's PICDEM3, but
I'm not positive on that.
A caveat: this is in no way an official responce from Microchip or anything
like that. I just subscribe to the gnupic list like everybody else and happen
to work at the chip.
-jim
--
James Grosbach
Principal Compiler Engineer
Microchip Technology
