Rev2 User Manual Page 14 --> Global Settings --> 4. MIDI Clock Mode
I'm pretty sure you need to set it to one of the "Slave" modes
• Slave: MIDI Clock is received, but not sent.
• Slave Thru: MIDI Clock is received and passed to MIDI Out
• Slave No S/S (no start and stop): Receives MIDI Clock but does not respond to MIDI Start or Stop command.