Do you have 12pF caps at each of the XTAL pins to GND? Datasheet - Page 32 says they may be optional... but in reality, it depends on your specific crystal. If I read it right, based my interpretation of the datasheet, you will ONLY see the clock frequency on MCLKOUT pin... even with a crystal.
Personally, I would use TCXO and feed ttl level clock to pin MCLKIN