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PICList Thread
'PICs Checksums'
1999\04\14@123538 by Andres Tarzia

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Does anyone knows why Microchip includes a chapter on "Checksum Computation"
in every chip's programming specification?
There is no programming command to read the checksum form the chip.
You cannot compute the checksum, send it to the chip and read the result.

So, why use it at all?

If you want an example, read document DS30262B.PDF, page #13, available from
Microchip web site. This document contains the "EPROM Memory Programming
Specification" for the PIC16F8X chips.

Thank you in advance.

Regards,
Andres Tarzia
Technology Consultant, SMART S.A.
e-mail: spam_OUTatarziaTakeThisOuTspamsmart.com.ar

1999\04\14@124955 by Nicholas Uloth

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At 01:35 PM 4/14/99 -0300, you wrote:
>Does anyone knows why Microchip includes a chapter on "Checksum Computation"
>in every chip's programming specification?
>There is no programming command to read the checksum form the chip.
>You cannot compute the checksum, send it to the chip and read the result.
>
>So, why use it at all?
>
>If you want an example, read document DS30262B.PDF, page #13, available from
>Microchip web site. This document contains the "EPROM Memory Programming
>Specification" for the PIC16F8X chips.
>
>Thank you in advance.
>
>Regards,
>Andres Tarzia
>Technology Consultant, SMART S.A.
>e-mail: .....atarziaKILLspamspam@spam@smart.com.ar

You need it if you ever write a programmer


Nic

1999\04\14@125416 by Corey Drechsler

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Andres Tarzia wrote:
> There is no programming command to read the checksum form the chip.
> You cannot compute the checksum, send it to the chip and read the result.
>
> So, why use it at all?

IIRC, the checksum is intended to be programmed into the ID locations on
the chip - which you can read back using most programmers...

Corey Drechsler

1999\04\14@221147 by Graeme Smith

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GRAEME SMITH                         email: grysmithspamKILLspamfreenet.edmonton.ab.ca
YMCA Edmonton

Address has changed with little warning!
(I moved across the hall! :) )

Email will remain constant... at least for now.


On Wed, 14 Apr 1999, Andres Tarzia wrote:

> Does anyone knows why Microchip includes a chapter on "Checksum Computation"
> in every chip's programming specification?

Every time I write a chip with picstart+ it automagically generates a
checksum. The idea is that you can put the checksum onto the chip, (or
some other paperwork related to the device, and use a simple circuit to
check it by reading the rom back out, and generating the checksum and
comparing it to the original.

Of course this is complicated by the use of Keloq type devices by the fact
that the data is encrypted, but if you take the encrypted checksum then a
device that does not generate the same checksum is no longer valid.

In MPLAB, I think there is even a "READ" command that can be used to read
the data back out of the chip....

                               GREY

1999\04\15@010901 by Tjaart van der Walt

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Andres Tarzia wrote:
>
> Does anyone knows why Microchip includes a chapter on "Checksum Computation"
> in every chip's programming specification?
> There is no programming command to read the checksum form the chip.
> You cannot compute the checksum, send it to the chip and read the result.
>
> So, why use it at all?

You are quite right - it is impossible to read it back
from 'inside'. What amuses me even more, is that the checksum
algorithm becomes useless when you use code protection.

I think an analogy would be a spare wheel painted on a car.

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1999\04\15@012400 by w. v. ooijen / f. hanneman

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> >So, why use it at all?
> You need it if you ever write a programmer
> Nic
I wrote a 16x84 programmer, but I did not use any checksumming!
Just write, readback to verify, and as last step mayby activate protection.
Wouter.

1999\04\15@093322 by Andy Kunz

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>All of them are either:
>* Commercial programmers

I fail to understand why that is a problem.  Even after reading your
reasoning.  There ARE ways to get products reliably into Argentina,
Bolivia, and Chile.  I've done it.

>* They don't work with Microsoft Windows NT 4.0

Carmacon's works with NT, and I'm pretty sure Tech-Tools upgrade does.

>so I can't trust them. That leaves commercial programmers out.

But you can get a copy of the Parallax schematic from list members who have
it (Parallax was handing them out at a show once) and get a chip for it via
the mail.  Tell the shipper to insure it for 3x its value - that will give
you 3 opportunities for them to steal and and you only pay once.

>Windows NT 4.0. If you know some do-it-yourself programmer that supports NT,
>please tellme. I searched and searched the NET and found not a single one.

Because NT takes control of the hardware so totally.

Why don't you run Linux instead - less reboots and better windowing system?
Or Win95?  It has most of the features of NT (including the unreliability)
but still lets you access the LPT hardware.

NT does, you know, allow you to control the handshaking on a serial port.

>program that could be used under NT. If it works with Windows 9x too, fine.

You need an LPT device driver.  Not a trivial task.

>Thank you very much for answering my silly questions!

My pleasure.

Andy
==================================================================
Montana Design - http://www.montanadesign.com - Electronics & Model Boats
==================================================================

1999\04\15@094512 by Holger Morgen

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Hi -

Is it not possible to CRC check coded (protected) devices?
I don't have the dockumentation here, but i seem to rember it...

/holger

{Quote hidden}

1999\04\15@100809 by Andres Tarzia

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>
>Why don't you run Linux instead - less reboots and better windowing system?
> Or Win95?  It has most of the features of NT (including the unreliability)
>but still lets you access the LPT hardware.
>
>NT does, you know, allow you to control the handshaking on a serial port.
>
>>program that could be used under NT. If it works with Windows 9x too,
fine.
>
>You need an LPT device driver.  Not a trivial task.
>
I intend to build a SERIAL programmer. No need for an LPT device driver.
Anyway, I can provide you with a "standard" NT LPT driver that you can
modify to suit your needs. It is not easy, but not much more difficult than
writing any device driver, including those for Linux.

Please, please, don't start an "I hate NT" flame here. You know, nobody is
perfect, so not everybody seems to understand the multiple advantages of
adoring Linux. Me included.

I'll take a look at the Parallax site in search of the PCB drawings, but I
think they won't have it on line. If you have it or know someone that has,
please tell me. We can get a whole lot of ICs locally, so that won't be a
problem.

Anyway, I enjoy building electronics projects a lot. So I think that I will
build my programmer despite the availability of some other device that
complies with my specifications. Didn't you ever build something so see if
you could do it? Or just for the fun of it?

Thank you very much for your help!

Regards,
Andres Tarzia
Technology Consultant, SMART S.A.
e-mail: spamBeGoneatarziaspamBeGonespamsmart.com.ar

1999\04\15@105233 by Tjaart van der Walt

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Holger Morgen wrote:
>
> Hi -
>
> Is it not possible to CRC check coded (protected) devices?
> I don't have the dockumentation here, but i seem to rember it...

You can if you use your own programmer. If you generate
a checksum with a Picstart+, (I'm not sure about the
ProMate) your checksum becomes meaningless. Check it out.

Program an old (erasable) JW part with some code and code
protection on. Change the software and reprogram. You will
see the checksum doesn't change at all.

This (and the fact that you can't reliably verify a code
protected device), prompted us to file the Promate where
it belongs (dustbin) and build our own programmer. It
verifies (high/low) before it code protects.

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1999\04\15@112952 by Andy Kunz

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>I intend to build a SERIAL programmer. No need for an LPT device driver.

You can do a serial programmer using the same techniques as was done for
the Tait-style parallel programmers.  It will work under NT - others have
already done that.  You use the handshake lines.

>Please, please, don't start an "I hate NT" flame here. You know, nobody is
>perfect, so not everybody seems to understand the multiple advantages of
>adoring Linux. Me included.

I wasn't trying to.  NT product support lags, and that's part of the
problem you are finding.  If you were using a Win95, Linux, or Mac box you
would already have your programmer done, that's what I'm saying.

>I'll take a look at the Parallax site in search of the PCB drawings, but I

It isn't there.  You should start a thread asking for them in the title.  I
know guys on the list have them, but don't recall who.

>complies with my specifications. Didn't you ever build something so see if
>you could do it? Or just for the fun of it?

Sure, all the time.

Andy

==================================================================
Montana Design - http://www.montanadesign.com - Electronics & Model Boats
==================================================================

1999\04\15@141434 by Nigel Goodwin

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In message <51691EF37C93D21195B9006008C5148C2DCD34@SMARTNTS02>, Andres
Tarzia <ATarziaEraseMEspam.....SMART.COM.AR> writes
>I tried to send this mail to you privately, but it failed. Here we go
>For the DIY programmers, *NONE* of them supports programming while running
>Windows NT 4.0. If you know some do-it-yourself programmer that supports NT,
>please tellme. I searched and searched the NET and found not a single one.

Assuming you only want to program the 16C(F)84 series, I have software
for NT using the Don McKenzie SIMMStick programmer, or any Tait style
programmer. It's available on my website, or on Don's
'http://www.dontronics.com'.
--

Nigel.

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1999\04\20@181740 by John Payson

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|What did you not like about:

|a)  Tech-Tools programmer?
|b)  Carmacon programmer?
|c)  Microchip (oh wait, never mind - bandwidth on the net <G>)
|d)  Tait-style?
|e)  Picpro

I am not familiar with the above programmers, but I can say what I
*DO* like about mine:

- Easy command-line interface: If I want to set things up to program
 the PICs for a particular project, I simply create a batch file B.BAT
 which contains, e.g.

 BURNER WOWZO.HEX D1 M2

 and then can simply type "B"[enter] when I'm in that directory and it
 will burn me a chip (assuming there's one in the burner).  None of the
 hassle of having to select a device from one menu, load a file using a
 different menu, etc.  Just type the command and ZOOM it's done (well,
 for the 16x84's it's not that fast...)

- Rapid loading/startup

- Easy hackability when needed (since I wrote it!)

- Selectable handling of unused locations:

 - Ignore (leave unprogrammed, but don't complain when blank-checking)
 - Require blank
 - Force to zero
 - Force to zero iff nonblank

- Pre-scan function which (by default) does a bad-bits test rather than
 a blank-test; this allows for code to be "added" to an OTP with care,
 but aborts without damage if the code image isn't compatible with what's
 already in the chip.

- Fuses are taken from the command-line (if specified), else from address
 2007 [400E] if present, else from address 1007 [200E] for compatibility
 with files set up for older BP software, else from my favorite default
 settings ($3FFD for 14-bit parts; $FFE for 12C508's)

- Display of calibration constant on 12C508 etc.

Do any of the other programmers support these options?

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