9.1 Synchronization 81
Connecting the External Clock
The external clock is an external device used to synchronize 2 to 6
DAT-Link
+
units. It has 6 identical connectors on its back panel that can be wired to the
DAT-Link
+ units with the provided cables. It is powered by tapping one of the
DAT-Link
+spower supply. On its front panel, a switchcho oses the clo ck frequency
it generates b etween 48kHz and 44.1kHz. This switch should b e set to the desired
frequency before issuing the commands on the computer.
Once multiple units are connected to the external clock, playback sampling-rate
synchronization can be controlled using the
-S
option to
naset
or
naplay
. For
example, to obtain the sampling rate clo ck from the external clock, you could use:
naplay -S E48000 file
where the
E
prex to the sampling rate is an abbreviation for
External
. Note that
although an external clo ck is used in the above example, the nominal sampling rate
is still sp ecied. This is necessary only when sampling-rate conversion is used to
allow the software to calculate the correct up-sampling or down-sampling ratio. The
value chosen should match the rate selected on the external clo ck.
Synchronization of start-time for playback or recording can also be achieved using
the external clock. The
READY
pin of the
Sync
connector provides an external
indication that the
DAT-Link
+ is ready to begin recording or playback. When this
signal is high the unit is ready to begin. Furthermore, if an external device forces
the
READY
signal low, then the
DAT-Link
+ will not b egin recording or playback
even if it is ready to do so. Thus, if multiple
DAT-Link
+'s are connected together
via an external clock unit, none of them will begin playback or recording until all
connected units are ready. When the last unit releases
READY
, all of the
DAT-
Link
+'s will then begin. The front panel
Pause
LED indicates the state of the
READY
pin.
Note that to playback or record from a single
DAT-Link
+ while multiple units are
connected together it is necessary to override the start-time synchronization. This
can be done by executing the command:
dlmkrdy -u unit_number
These options can be combined to, for example, playbacktwo data les simultane-
ously at the same sampling rate:
naset -u :0 -S E
naset -u :1 -S E
naplay -u :0 file0 -S E48000 &
naplay -u :1 file1 -S E48000
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