1226870's and eprom UPDATE

[Ludis Langens]

Mike Poore <Mikepoore at aol.com> wrote:
> I successfully copied my stock prom to a new eprom without a hitch. If I 
> change one parameter it won't work correctly. The ses light flickers. Someone 
> mentioned a problem with the checksum. 
>
> Is there a difference between the checksums for a TPI  Camaro and Vette?

The checksum will change with any change in the EPROM.  If the Camaro
and Vette have different data, the checksum will likely be different too.

> How can I find out how the checksum is calculated using my stock bin?

For the 6870, the first two bytes of the EPROM contain the 16 bit (big
endien) sum of all the other bytes.

> Is there a way to bypass this problem and disable checksum?

Changing location 5 from $1F to $AA, will probably disable checking of
the checksum.  This is sometimes called experimental mode.  I don't like
it because it leaves no way to know if the data has been corrupted.

-- 
Ludis Langens                               ludis (at) cruzers (dot) com
Mac, Fiero, & engine controller goodies:  http://www.cruzers.com/~ludis/