Case STX375 Tractor.. Checksum??

[Jdaniels]

If any of the gurus could advise I would appreciate it,

2 files labeled with differrent hours. I have calculated the hours I require but there is one byte still that is confusing me and I wonder if it is a checksum?

Line 40 contains the code in question
Chip is a 24c04
Hours are i believe the first 4 bytes, it is the 5th byte that confuses me.

Thanks in advance!
Dave
myspeedometer

[Jdaniels]

Anyone had a chance yet ?

[Jdaniels]

I think I figured it out. this was the line of code i was looking at:

"DC C3 0C 00 54 DC C3 0C 00 54 DC C3 0C 00 54 96"

1st 4 bytes are definitly the hours, the 5th byte seems to be the checksum. Using an 8bit checksum of the first 4 bytes and then performing a Not operator on that value it gave me the 54. I compared the function on another dump and it gave me the right value as well. My only concern now is the possibility that the end byte here (96) may be some kind of checksum for the whole line.

Any Thoughts?

[Jdaniels]

I figgerred it all out so if anyone needs direction on this type let me know!

Thanks to all that read!

[knok]

I think I figured it out. this was the line of code i was looking at:

"DC C3 0C 00 54 DC C3 0C 00 54 DC C3 0C 00 54 96"

1st 4 bytes are definitly the hours, the 5th byte seems to be the checksum. Using an 8bit checksum of the first 4 bytes and then performing a Not operator on that value it gave me the 54. I compared the function on another dump and it gave me the right value as well. My only concern now is the possibility that the end byte here (96) may be some kind of checksum for the whole line.

Any Thoughts?
end byte was unchanged , so I believe in this case his value doesn't matter

[stevan]

Working hour must have minutes also,because dash is calculate also.So need to add one decimal more for calc.
836572 hex 0C C3 DC are hour bytes , 0C+C3+DC=1AB not FE 54 ,54 is CHK