[Gmecm] Need ecu file for 1227303 ecm & checksum question

[James Ortiz]

Well i had already tried looking at different locations for the
checksum with no luck. I downloads a few bins and ecu files for other
ecm's just to get an idea of what was going on. Most of them have the
checksum at location 6, one had it at location 0.

Here is a bit of the code i've disassembled.

C8CA            ldX     #$C008
C8CD            ldD     #$3FF8
C8D0            call    LFCD0
C8D3            ldX     #$0100
C8D6            cmpY    LC006
C8DA            bne     LC8E3
C8DC            ldaA    LC008
C8DF            cmpA    #$53
C8E1            beq     LC8EF
C8E3    LC8E3   ldaA    LC008
C8E6            cmpA    #$AA
C8E8            beq     LC8EF
C8EA            bset    0, X, #%00010000
C8ED            jr      LC8F2

I'm just guessing here but it looks to me like it's loading C008 as the
start address, 3FF8 as the lenght and then calling the checksum
routine. The result is then compared to location C006.

This is another reason i think my bin may be corrupt.

James

--- Jay Vessels <jay at vessels-clan.com> wrote:

> Hi there!
> 
> I'm not sure about the program gmcks, but it sounds like it doesn't
> know 
> the checksum location for that MEMCAL.  GM placed it in different
> places 
> for different codebases, so your checksum may just be calculated in a
> 
> place that is different from what your program expects.  GM's method
> for 
> calculating the checksum didn't seem to change over the years (at
> least, 
> pre-OBD-II) so you could probably play around with the checksum
> location 
> and figure it out.
> 
> Jay Vessels
> 1982 Chevrolet S-10 Sport, 2.8V6 TBI
> 1984 Chevrolet S-10 Blazer Sport, 2.8V6 (TBI pending)



		
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