RME Fireface UCX II 40-Channel USB-B Audio/MIDI Interface - Manual (Page 46)

46 User's Guide Fireface UCX II © RME
22. Word Clock
22.1 Word Clock Input / Output
SteadyClock guarantees an excellent performance in all clock modes. Based on the highly effi-
cient jitter suppression, the Fireface refreshes and cleans up any clock signal, and provides it as
reference clock at the BNC output (see chapter 40.8).
The Fireface UCX II has one BNC socket with dual functionality
– it can serve as word clock
input OR word clock output. The current mode is set in the Settings dialog by the user.
Input Mode
The Fireface's word clock input is active when the BNC socket has has been switched to input
mode in the Settings dialog, and a valid word clock signal is present. The signal at the BNC input
can be Single, Double or Quad Speed, the Fireface UCX II automatically adapts to it. As soon as
a valid signal is detected, the WCK field is lit, and the Settings dialog shows either Lock or Sync
(see chapter 40.1).
Thanks to RME's
Signal Adaptation Circuit , the word clock input still works
correctly even with heavily mis-shaped, dc-prone, too small or overshoot-
prone signals. Thanks to automatic signal centering, 300 mV (0.3V) input
level is sufficient in principle. An additional hysteresis reduces sensitivity to
1.0 V, so that over- and undershoots and high frequency disturbances don't
cause a wrong trigger.
The Fireface UCX II word clock input can be high impedance or internally
terminated (75 Ohms). The state is comfortably selected within the Settings
dialog. To terminate the input check the option
Word Clock In Termination
under Options .
Output Mode
The same BNC socket can be used as word clock output instead of input, again configured in
the Settings dialog. The word clock output is constantly active, providing the current sample
frequency as word clock signal. As a result, in Master mode the provided word clock is defined
by the currently used software. In Slave mode the provided frequency is identical to the one pre-
sent at the currently chosen clock source. When the current clock signal fails, the Fireface UCX
II switches to Master mode and adjusts itself to the next, best matching frequency (44.1 kHz, 48
kHz etc.).
Selecting
Single Speed in the Settings dialog causes the output signal to always stay within the
range of 32 kHz to 48 kHz. So at 96 kHz and 192 kHz sample rate, the output word clock is 48
kHz.
Thanks to a low impedance, short circuit proof output, the Fireface delivers 4 Vpp to 75 Ohms.
For wrong termination with 2 x 75 Ohms (37.5 Ohms), there are still 3.3 Vpp at the output.