volvo sid 803a chk

[adiagnostyka]

Hi friends. I need to know how calculate checksum on sid803a . I know where is synch to cem and abs id bud i dont know how calculate chk. If someone can help me. My brain.exe stuck no this problem :)
Many thanks

[kiszka]

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[adiagnostyka]

Using apps is no problem. I have program and making synch is easy. Only problem is my curiosity :) Im just curious how to calculate chk.
I attach my dump with work ok.