From: garyl@moe.corollary.COM (Gary Lorman)
Subject: Re: electronic odometers (was: Used BMW Question ..... ???)
Organization: Corollary, Inc.
Lines: 42

In article <9833@dirac.physics.purdue.edu> lovall@bohr.physics.purdue.edu (Daniel L. Lovall) writes:
>In article <CONRADIE.40.734872761@firga.sun.ac.za> CONRADIE@firga.sun.ac.za (Gerrit Conradie) writes:
>
>.....
>
>>However, if I were to design a BMW's electronics, I will use a counter to 
>>count the number of times the car passed 1 million miles (or whatever), and 
>>store it in the car computer's memory. This could be read when doing a 
>>diagnostics test. Ditto for the date of the odometer. As easy as this is, I 
>>don't know why manafucturers don't do it (don't they?) to prevent illegal 
>>odometer tampering.
>>
>>But as a previous writer said, it will in any case take aeons to reset an 
>>odometer, mechanic or electronic by simulating a driving car. It will be 
>>easier to reprogram it. How, I don't know.
>
>It shouldn't be THAT hard if you know much about digital electronics.  If the
>counter is made with standard TTL chips, all you should need to do is find
>the chip(s) used for counting, figure out what mileage you want to put in,
>and preset it but wiring the preset pins directly to low/high (you'd also have
>to know what the conventions are for low and high).  It might be a little more
>involved than this, but it shouldn't be beyond someone with a BSEE or BS EET.
>All the display does is convert what the counter chips say into digits using
>a "translation table" stored in ROM.
>
>selah,
>
>Dan
>
But, those chips are probably inside a custom chip, (to make it smaller and
use less power) and the preset/data pins are not going to be available.
It would probably not be TTL but might be CMOS 
(wider operating voltage range), not that the tecnology would make 
much difference.
Plus the custom chip would probably be potted (encapsulated with epoxy).
Good luck.

-- 
--garyl-------------------------------------------------------------------------
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