User's Guide
WCM MKII © RME
6
9. Setup and Operation
9.1 General
As soon as a valid word clock signal is present the green 'Lock' LED beside the input jack lights
up. To switch from the
DIGI
's internal clock to the
WCM
's clock, activate the mode 'Word
Clock' in the field 'Clock Mode' in the Settings dialog. Under 'Output Status' the third line indi-
cates the state of the output circuit (master or slave). It will change to 'Word Clock'. This dis-
play realizes the same functionality as the green 'Lock' LED besides the BNC input jack. There-
fore you'll see directly on your screen when a valid word clock signal is received and used by
the
WCM
.
The word clock output is always active. It sends the current sample frequency of the
DIGI96
series card as word clock signal. As long as the
DIGI
works in 'Master' mode (field 'Clock
Mode'), the sent word clock has very low jitter (< 1 ns). In 'AutoSync' mode the amount of jitter
depends on the quality of the signal received at the digital input.
The word clock signal received by the
WCM
can be distributed to other devices by using the
WCM
's word clock output. With this the usual T-adapter can be avoided, and the
WCM
operates as
Signal Refresher
. This application is especially useful as the
WCM
's outstanding
input (1 Vpp instead of usual 3 Vpp sensitivity, DC filter, Signal Adaptation Circuit) guarantees
a stable function even with very critical word clock signals.
9.2 Test Mode
Pushing the switch 'Test Mode' forces the
WCM
to generate its own quarz crystal controlled
word clock, and to send it to all connected DIGIs. With this the internal generator provides two
functions:
•
Test Mode: The internal word clock signal replaces the external one at the BNC jack
The
WCM
includes a built in word clock generator for test purposes. It generates a square
wave signal at 44.1 kHz or 48 kHz (S3 = ON), which is fed internally to the BNC input jack
when the switch
Test Mode
is activated. The BNC jack is then out of function, an external sig-
nal at this jack will be disconnected automatically.
The test generator enables a complete test of the
WCM
and its correct function in combina-
tion with the
DIGI96
series card, because the test signal runs through the same circuits and
path as an externally fed signal.
So when connecting a BNC cable and activating the external word clock signal do not cause
the green LED to light up, and the field Output Status does not show 'Word Clock', then a sim-
ple push on the test switch is enough to verify the function of the whole system, and to be sure
the fault is on the external equipment's side.
•
Masterclock: The master clock allows to synchronize all connected
DIGI
s, and all de-
voices hooked up to the
DIGI
s.
The
DIGI
will send the input's word clock signal straight to its output when in 'Word Clock'
mode. Therefore in test mode the
WCM
can be used as central word clock generator, gener-
ating the so called 'house clock'. Additional when using more than one card this mode offers a
very convenient way of synchronizing all cards. Just make sure the clock mode 'Word Clock' is
selected in all DIGI96 series Settings dialogs.
