[rahimdiag]

Can anybody help me  for correctly what mean checksum, in detail and simply

[florinelxxl]

checksum,,with a calcany change in the content, change the amount obtained,ulation formula, algloritm, is calculated from the whole, a number is obtained,

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I think in Romanian, I do not know if it is English

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is obtained with a specific calculation formula

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is calculated across the data block, or partially.
any change in the data block, modify the amount

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important, being the amount of control, if it changes, does not recognize the processor as being fake,

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rule, if you do not correct the amount, do not write

[jakesvw]

wow that is some big words for a normal mechanic lol , dont understand it fully or how it works but my idea about it is : change some value in one blockthen u need another block to CHECK if the first one is correct , im also trying to understand how it works , but from what i have seen is example Iveco immo off in flash u change only to bytes from 0101 to 00 00 and once the ecu boot up again it have changed to something totaly not the same , but all i know is BAD CHECKSUM ecu not work LOL

[laur.c]

Can anybody help me  for correctly what mean checksum, in detail and simply

Hello,

The term is related to IT/computers, generally speaking (not necessarely with the car industry only).
Moreover, it has to deal with a method to protect the content of a file and prevent it from being used if that file has been broken/modified accidentally.
So, when you modify the content of the file because you WANT it to be different and you still want it to be "usable", then you have to "update" also the content of the checksum word, in order to protect/preserve the NEW content of the file.
Hope it's clear enough.

Regards,
Laur.

[jakesvw]

cool that part i understand but HOW to calculate it and to know what to change to get results that takes a lot of playing with hex coding

[rahimdiag]

thanks so much for respond to me
but is it this checksum is only tool to check error or to protect it from error

[laur.c]

Both check and protect, my Friend!
When you alter the initial file content, you obtain the CORRECT effect (e. g. Immo off, egr off), but as the file itself it's concerned, it is protected against ANY change, as long as the checksum word remains the old one. Therefore, it will NOT be executed.

On which value you have to change the checksum in order to match it with to the new file content... Well... That's another story!

[rahimdiag]

thanks in advance
can you put an example to clear this ?
what software it can do checksum correction ?

[laur.c]

Like someone says, info should be free. As long as your services to your customer are free as well. I'm shure you can have any checksum correction for free, as long as you can prove you have no advantage of it...

Otherwise, check again for some important forum buttons... And also check for your initial question!

Good luck,
Laur.