Hi, I'm having issues determining the algorithm to calculate some checksums in Volvo files. There is a separate group of checksums at the end of the file that seem to be used for the functional code segment. The only program I've seen that recalculates these checksums is the ME7 Volvo plugin from WinOLS. I am looking to add this algorithm to a standalone utility.

At 0xFFFF0, there are two 32bit values. The second is the 1's complement of the first value. I am unsure how to proceed though.

I've attached a screenshot of the disassembly from the routine used in the file for these sums. I'm having trouble following its method.
Can someone please help me determine the algorithm for this?