Move the strings off to an external EEPROM or serial FLASH. Explain to the
customer that the PICs really aren't designed to be reprogrammed regularly
and that to prevent undetected device failure when the code memory fails,
you need to store the data in a separate device where failure detection
methods can be employed and easy replacement is possible. They should pay
the (fairly small, I guess) cost of changing the device(s). Heck, use an
Dallas Semi I button memory and just swap them around to change the set of
available strings.

---
James Newton mailto:jamesnewton@geocities.com 1-619-652-0593
http://techref.massmind.org NEW! FINALLY A REAL NAME!
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-----Original Message-----
From: pic microcontroller discussion list
[mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of andy howard
Sent: Wednesday, March 01, 2000 13:30
To: PICLIST@MITVMA.MIT.EDU
Subject: Code Protection etc.


I have a product using a 16F84 that outputs a 5 character RS232 string
using retlw tables, the exact string depending on user input via one of
several switches.

Now one of my clients needs to be able to change the string from time to
time.  I have reservations about giving them the source, since they have
a PicStart on the premises and might suddenly find no need to buy any
more of these units from me.

OTOH I have a very good relationship with these people and do a lot of
other (non-pic) consulting work for them and would like to keep it that
way, equally I'd also like to keep the code under wraps.

Is there any way I could code protect all of this and still allow them
to change the contents of the retlw tables if need be? Or if not, does
anyone have any advice on how to gently break to the client that they
can't have the code.

My two fallback positions are:

1). ...to offer to provide re-programmed PICs on an exchange basis at
cost + small handling/programming charge if they need to change it (they
won't need to change very often).

Or, if all else fails,

2). ...to give them the source, because it isn't worth falling out with
them over, and it certainly isn't worth the cost of lawyers to draw up
intellectual property contracts etc.


Which leads me to a second question. Is it possible to erase a
code-protected Flash part? And if so would it still be reliable after
re-programming?

In a few months time I will be upgrading quite a number of protected
16F877s and it goes against the grain to simply bin them all.



Cheers

Andy.











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