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'Code Protection etc.'
2000\03\01@163153 by andy howard

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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.











.

2000\03\01@164022 by jamesnewton

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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 spam_OUTjamesnewtonTakeThisOuTspamgeocities.com 1-619-652-0593
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{Original Message removed}

2000\03\01@164645 by l.allen

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> 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,

Can you spare the i/o for an ext eeprom?
If they have a PICSTART as you say, do they have an EEPROM
programmer as well? you could tell them where to place the strings
in the ext EEPROM and burn their own... so the PIC will know
where to find them and use the ext EEPROM as the look up table.



_____________________________

Lance Allen
Technical Officer
Uni of Auckland
Psych Dept
New Zealand

http://www.psych.auckland.ac.nz

_____________________________

2000\03\01@170137 by Martin McCormick

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       One thing that came to mind right off the bat is to ask
whether or not you have any RAM to spare?  The startup routine might
put the usual 5 characters in the RAM positions unless certain
switches were set a certain way and then it would find another table
to stuff in the same slots.    If the customer needs to select the
exact characters, then you will need an input routine that captures
five user-chosen characters and stuffs them in to the five slots.  You
shouldn't have to give any code away or worry about that.  The one big
drawback I can see to this is that the end user would have to
reprogram the table each time the power to the PIC goes off.


Martin McCormick WB5AGZ  Stillwater, OK
OSU Center for Computing and Information Services Data Communications Group

andy howard writes:
>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.

2000\03\01@171159 by Tony Nixon

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andy howard wrote:
>
> 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.

Can you store the table in internal EEPROM via RS232?

Easy to change then.


--
Best regards

Tony

http://www.picnpoke.com
.....salesKILLspamspam@spam@picnpoke.com

2000\03\01@172006 by William Chops Westfield

face picon face
> 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,

Are you using all of the internal eeprom?  For something that can't spare
5 bytes?  ("Well, I can give you the ability to change the 5 character
string, but it will mean five few foo samples...")

BillW

2000\03\01@172626 by l.allen

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>
> Are you using all of the internal eeprom?  For something that can't spare
> 5 bytes?  ("Well, I can give you the ability to change the 5 character
> string, but it will mean five few foo samples...")
>
> BillW
>
Wrong person Bill.. I was replying to a query .. I suggested
external EEPROM.


_____________________________

Lance Allen
Technical Officer
Uni of Auckland
Psych Dept
New Zealand

http://www.psych.auckland.ac.nz

_____________________________

2000\03\01@180150 by Hickman, Drew

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this gets my vote.  easy, one chip solution that survives power loss and
provides the users with a way to change things on the fly.  code still
protected.

-=Dru
I.S./Network Engineer - SLSMHS
Visit my web page at http://www.geocities.com/drewhickman


> {Original Message removed}

2000\03\02@070223 by Dr. Imre Bartfai

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Hi guys,

please do not forget, the 16F84 has a BUILT-IN 64-byte EEPROM, and it is
far simpler to access than an external ones. I think to use this would the
real solution.

Regards,
Imre


On Thu, 2 Mar 2000, Lance Allen wrote:

{Quote hidden}

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