Craig,
It generates the CRC file upon regeneration.
I was told one time there are 4 specific ways to make a CRC. Unfortunately I cannot remember them all but here are the ones I do know.
My favorite example to tell users what a circular reference is: Sometimes I add an empty part to an assembly and constrain it using the default part datums. Then, in the assembly, I activate the part and create part geometry using the assembly as reference in the sketch. At some point in time later as I am changing the design, I redefine the placement from the datums of the part to the surfaces of the part and abracadabra, I just made a CRC. Since the part references the assembly, it doesn't know how to build itself until it is placed and since it doesn't know how to place itself until it is built. Round and round and round. It doesn't fail, it just generates the CRC. It slows down the model.
Restructure - when you do a restructure, the resulting references sometimes create CRC
Edit references - can create them also
Steve