No sumcheck code in a '95 MEMCAL

[John Hess]

Did you checksum only the data _after_ the checksum in the PROM or check it
against the PROM checksum.  I don't know about this particular prom;  but,
bytes 0 through 8 are disregarded in the checksum on the earlier models.

-----Original Message-----
From: Ludis Langens <ludis at cruzers.com>
To: Diy_efi <diy_efi at esl.eng.ohio-state.edu>
Date: Thursday, November 05, 1998 12:05 AM
Subject: No sumcheck code in a '95 MEMCAL


>I've been disassembling a MEMCAL from 1995.  It's BCC BKLL1692, used in
>the 16196401 ECM.  It's for a W-body with the VIN X 3.4 SFI DOHC
>engine.  The 32K byte EPROM (27C256) has the standard 9 byte P4 header,
>but the sumcheck field doesn't match the computed sumcheck.  Further,
>the program code does not contain a sumchecking subroutine!
>
>Has anyone else found a MEMCAL like this?  Could this be in preperation
>for OBD II?  (This MEMCAL&ECM are just OBD I.)
>
>--
>Ludis Langens                               ludis (at) cruzers (dot) com
>Mac, Fiero, & engine controller goodies:  http://www.cruzers.com/~ludis/
>
>