[Diy_efi] Motronic checksum

glogovacs at yahoo.co.uk glogovacs at yahoo.co.uk
Wed Jun 9 23:31:33 GMT 2004

I am trying to figure out how a checksum on older Motronic eproms is 
formed. I am targeting last 2 bytes on 32kb eproms (actualy, it is last 
24bits, since the highest 4 bit nibble is always 0000). I was lucky enough 
to have access to eproms for the same car that only had a few different 
locations, and of course the checksum.

I tried 8 bit sum, 16 bit sum... xor etc, but no success :(. I can also 
post examples... Any help is welcome.

Also, can you suggest some good 8051 disassembler? I have d51, but it 
produces much garbage - considering I am dummy for i8051. I was trying to 
locate instruction that would access last two bytes of eprom, and I failed. 
Where in address space is eprom located?

I am talking about boxes 0 261 200 087 (BMW), 0 261 200 185, 0 261 200 190 
(Opel) and similar.


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