Hi Alan,
In your case fCLKIN = the crystal frequency, 7.68MHz.
The "t16b" timing requirement still applies. If your processor has trouble meeting this restriction, then we recommend "re-clocking" the /SYNC pulse with an inexpensive D-Flip Flop such as the SN74LVC2G74 to sychronize the rising edges of the /SYNC and master clock.
Regards,
Chris
