[Diy_efi] Lucas Hotwire checksums

[Alexis PAVLOV]

Hi Mike,

The checksum is usually either a 8 bit sum of all bytes, or
a 8 bit sum of odd/even bytes (giving 2 bytes), or the
same scheme but using the XOR instead of ADD.
The checksum bytes are usually located at the very end of
the EPROM (this is a natural solution in order to never
change their location).

Alexei


Mike V wrote:
> 
> At 06:07 PM 7/26/2004 +1000, you wrote:
> >Hello to all as I have just joined this list. I am a computer programmer
> >and ex-mechanic who is currently adapting the Rover Lucas Hotwire ECU
> >(14CUX with what appears to be a ZC93116CP Motorola processor) for use in
> >an old series 3 Land Rover. I have built an EPROM emulator and have
> >written simple software to allow me to edit the fuel maps successfully.My
> >problem is that when I 'burn' a chip (m27c256b) and install it I am
> >getting 'ROM memory error' when the car is run. The vehicle runs OK but
> >occasionally plays up after the error is thrown. I am sure this is a
> >checksum error and know that it is likely that the algorithm to calculate
> >it is proprietary. Does anyone have any information regarding this.
> 
> If you don't find the answer you're looking for, maybe pick a place
> in the fuel table that you'll never reach, and make "ballancing" entries
> there, so that your sum total doesn't change.  You know, that corner
>   of the table that represents closed throttle and 6,000 RPM.  <grin>
> MIke V
> 
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