Vida CEM swapping

5ft24 · Post by **5ft24** » 08 Oct 2022, 17:51

That's it! Thank you

oscilloscope · Post by **oscilloscope** » 09 Oct 2022, 00:08

5ft24 wrote: ↑08 Oct 2022, 17:51 That's it! Thank you

No worries

oscilloscope · Post by **oscilloscope** » 09 Oct 2022, 02:18

matija0610 wrote: ↑07 Oct 2022, 21:48 Screenshot_2.png

8-bit SUM whole CONF block
I think everything is clear in the picture

I assumed that when a checksum is calculated it needed too be the entirety of the dump not just some of it. ?

Too add have you ever used the dataman software ? , that has a checksum calculator built in. It's very confusing too use I even asked the developers how it works and they didn't really give me a very clear answer.

ZRimaZ · Post by **ZRimaZ** » 09 Oct 2022, 02:24

oscilloscope wrote: ↑09 Oct 2022, 02:18

I assumed that when a checksum is calculated it needed too be the entirety of the dump not just some ...

No. Matija showed exact block which checksum has to be recalculated after config change. To be more exact, in tis particular cem, at 0xEBD00 is the lenght of config block, 0xEBD01 - checksum itself, 0xEBD02 - start of config block with lenght from 0xEBD00

oscilloscope · Post by **oscilloscope** » 09 Oct 2022, 02:54

ZRimaZ wrote: ↑09 Oct 2022, 02:24
oscilloscope wrote: ↑09 Oct 2022, 02:18

I assumed that when a checksum is calculated it needed too be the entirety of the dump not just some ...
No. Matija showed exact block which checksum has to be recalculated after config change. To be more exact, in tis particular cem, at 0xEBD00 is the lenght of config block, 0xEBD01 - checksum itself, 0xEBD02 - start of config block with lenght from 0xEBD00

so the checksum for DF (location 000EBD00) is saved within 01 its shifted to the right?

ZRimaZ · Post by **ZRimaZ** » 09 Oct 2022, 02:56

no! Read my answer one more time, looks at Matija's screenshot and analyse it one more time!

oscilloscope · Post by **oscilloscope** » 09 Oct 2022, 03:10

so 000EBD00 from DF to 000EBD80 is checksum calculated (which is high lighted in black) , is that 223 bytes calculated in the checksum?

or is DF the sum calculated for the above addresses and saved in that byte location ?

ZRimaZ · Post by **ZRimaZ** » 09 Oct 2022, 03:37

Length of xonfig block to be checksumed is 8C start of the block is next byte after DF, which is checksum

matija0610 · Post by **matija0610** » 09 Oct 2022, 04:03

ignore the whole flash, concentrate only on the configuration part.
one more time:
checksum 1 - length of config part (BC on my example)
checksum 2 - 8-bit SUM whole CONF block part (DF)
ZRimaZ drew your attention to the addresses and I think we have clarified enough.
simple, try it on an example, it will surely be clear to you

oscilloscope · Post by **oscilloscope** » 09 Oct 2022, 07:12

matija0610 wrote: ↑09 Oct 2022, 04:03 ignore the whole flash, concentrate only on the configuration part.
one more time:
checksum 1 - length of config part (BC on my example)
checksum 2 - 8-bit SUM whole CONF block part (DF)
ZRimaZ drew your attention to the addresses and I think we have clarified enough.
simple, try it on an example, it will surely be clear to you

Yes thanks for pointing out my attention was drawn to the addresses. And yet it still confused me , and no it wasn't clarified enough! ,

Now , maybe the way that Is explained it is it not clear. , I have made many tests with a checksum calculator. But I have this nagging feeling that why is the checksum at 00 ( the very first byte) isn't the checksum overriding something already there? Which could of course cause problems during the copy back over. , I could perform test after test but without a frame reference how am I ment to know what is correct or going down the wrong rabbit hole?.

Why don't you exsplain it.

Vida CEM swapping

Re: Vida CEM swapping