[Diy_efi] Re: Motronic checksum

glogovacs at yahoo.co.uk glogovacs at yahoo.co.uk
Fri Jun 11 22:44:27 GMT 2004

Hello Henrik,

Yes, I was wrong, I wanted to say last 12 bits.

Which motronic are you reversing? I was looking into versions 1.3 and 2.5. 
Can you send me the bin?

A saw a message on this forum, where a guy compared stock and aftermarket 
performance motronic bins. There were only two locations different in data 
area (rev limiter and something he couldn't identify), and last two bytes. 
I've also seen a few chips that had only a couple of bytes different, and 
of course the last two bytes.. That's why I made a conclusion that checksum 
is stored in last two bytes.

As far as disassembler is concerned, I was wondering if there is an 
'intelligent' one, that can distinguish between code and data. I have a 
disassembler for 68HC11, that works flawlessly when it comes to recognition 
of code/data (that's easy because vector addresses are known from bin 
file). As for motronic, I couldn't really tell where the code 'starts'. I 
expected to find a LJMPs and beginning of the file that would point to 
code, but that was not the case. How come??

I am sure my boxes have a 8051 derivative CPU, since WinOLS software 
recognized the bins and stated the processor is 8051.

At which address the EPROM file starts, is it 0, or not?

Can you point out the code that is making the checksum calculation, so I 
can try to identify it in my EPROMs?


At 19:03 11-06-04 +0000, you wrote:
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>Today's Topics:
>    1. 1989 tpi help (laurieandmike)
>    2. Re: Motronic checksum (Henrik Johnsson)
>    3. Re: Motronic checksum (glogovacs at yahoo.co.uk)
>Message: 1
>Date: Thu, 10 Jun 2004 18:48:54 -0300
>From: "laurieandmike" <lauriecorbett at ns.sympatico.ca>
>Subject: [Diy_efi] 1989 tpi help
>To: "A list for Do-It-Yourself EFI" <diy_efi at diy-efi.org>
>Message-ID: <00c301c44f34$b9f436e0$a306260a at wolf>
>Content-Type: text/plain; charset="iso-8859-1"
>hi there i put a tpi in my 56 chevy truck
>its a 350 with a mild cam headers turbo 400 tranny
>my ? is when i start the truck up there is no trouble codes it starts 
>right up but dont want to idle untill it is warm
>and it seems it is running real rich like burn the eyes out of your head lol
>but when i unplug maf it runs ok
>what is the problem?
>can anyone help?
>-------------- next part --------------
>An HTML attachment was scrubbed...
>Message: 2
>Date: Fri, 11 Jun 2004 1:10:45 +0100
>From: "Henrik Johnsson" <henrik_j at bigfoot.com>
>Subject: Re: [Diy_efi] Motronic checksum
>To: A list for Do-It-Yourself EFI <diy_efi at diy-efi.org>
>Message-ID: <20040610231059.3952137E44 at smtp3-1-sn1.fre.skanova.net>
>Content-Type: text/plain;      charset="us-ascii"
>Hello, glogovacs
>======= At 2004-06-10, 00:07:00 you wrote: =======
> >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.
> >
>That would actually be 12 bits, wouldn't it?
> >I tried 8 bit sum, 16 bit sum... xor etc, but no success :(. I can also
> >post examples... Any help is welcome.
> >
>The checksum isn't necessarily stored in the last 2 bytes. I'm 
>disassembling an older Motronic EPROM which has the checksum in 0x7F00 and 
>0x7F01. The checksum is calculated as the sum of all bytes in the address 
>range 0x000 through 0x7EFF. Some Motronics allegedly has more than one 
>checksum though.
> >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.
> >
>It doesn't matter what disassembler you use, you will have to help it by 
>identifying which portions of the EPROM is used for code and which is used 
>for data. Also, make sure those ECUs really use an 8051-derivative.
>I believe I read in an old message on this list that the code in the EPROM 
>may be "folded", you might have to rearrange the EPROM data before 
>disassembly to get a useful result. I'm sorry I cant find that particular 
>message right now.
>Message: 3
>Date: Fri, 11 Jun 2004 01:56:57 +0200
>From: glogovacs at yahoo.co.uk
>Subject: [Diy_efi] Re: Motronic checksum
>To: diy_efi at diy-efi.org
>Message-ID: < at pop.mail.yahoo.com>
>Content-Type: text/plain; charset="us-ascii"; format=flowed
>Yes, I have an EPROM programmer... but all the software can do is calculate
>the additive checksum of the bin file. Now, a question - is it enough to
>have additive checksum corrected to stock, to have bin file 'approved' and
>running? I;ve read somewhere that Motronic makes XOR checksum as well.. is
>that true?
>ECUs I am talking about have 27256 EPROMs... since they are considerably
>larger than 2732 chips used in older Motronic boxes, can I consider I am
>having post '88 units?
>With regards,
> >Date: Wed, 9 Jun 2004 16:41:39 -0700
> >From: "FR Wilk" <kd694j0538f at hotmail.com>
> >Subject: Re: [Diy_efi] Motronic checksum
> >To: "A list for Do-It-Yourself EFI" <diy_efi at diy-efi.org>
> >Message-ID: <BAY15-DAV2kRQq5xVz500039359 at hotmail.com>
> >Content-Type: text/plain;       charset="iso-8859-1"
> >
> >Do you have a EPROM programmer? The software that comes with it will do the
> >checksum correctly.
> >
> >You have another problem. Half the code is stored in the 8051. You have to
> >download that before you can try a disassembler.
> >
> >In about 88, BOSCH started putting the whole code into the EPROMs and wiring
> >the 8051 to ignore its internal memory. This will save you from trying to
> >download an 8051's ROM.
> >
> >FR Wilk
>diy_efi mailing list
>diy_efi at diy-efi.org
>End of diy_efi Digest, Vol 9, Issue 10

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