Hi,
The fSCLK spec is a maximum meaning that the fastest the clock can be is 30MHz. This is what is guaranteed, although parts will typically run up to 40MHz. It will also work with a slower clock.
Since the 1/fSCLK is the inverse of the fSCLK spec, it is specified as a minimum. The clock cycle time is guaranteed to work down to 33ns (the inverse of 30MHz) but parts typically will work at 25ns (which is the inverse of the typical 40MHz clock frequency).
Mike
