Clock driving Timers on 6678

I'm benchmarking some matrix algorithms on the 6678 demo board, and using Timer_getCount to do so. Looking at the datasheet, and other searches on the forums, I am having a tough time determining the clockbase for the timers. The datasheet says that the timers count VBUS clock cycles, but I have not found any other references to VBUS in the datasheet. Also the linked timer user guide does not seem to exist?

Thanks