EDM01-36v10 DAG_9.2X2_Card_User_Guide - Synchronizing clock time
©2010 - 2012 Endace Technology Ltd. Confidential - Version 10 - May 2012
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Card with timing reference
Overview
To obtain the best timestamp accuracy you should connect the DAG card to an external clock reference,
such as a GPS or CDMA time receiver.
To use an external clock reference source, the host computer’s clock must be accurate to UTC to within
one second. This is used to initialize the DUCK.
When the external time reference source is connected to the DAG card time synchronization connector,
the DAG card automatically synchronizes to a valid signal.
Pulse signal from external source
The time synchronization connector supports both RS-422 (PPS) and IRIG-B (only some DAG cards)
signals from an external source. This is derived directly from an external reference source or distributed
through the Endace Time Distribution Server which allows two or more DAG cards to use a single Time
Reference Source. For details on the available Time Distribution Server see
Common Synchronization
(page 51).
Warning:
Never connect a DAG card or the Time Distribution Server to active Ethernet
equipment or telephone equipment.
Synchronize to an external source as follows:
dagclock –dX
(Where X is the device number of the DAG card you want to configure).
Output:
muxin rs422
muxout none
status Synchronised Threshold 596ns Failures 0 Resyncs 0
error Freq 30ppb Phase -15ns Worst Freq 238ppb Worst Phase 326ns
crystal Actual 100000023Hz Synthesized 67108864Hz
input Total 225 Bad 0 Singles Missed 1 Longest Sequence Missed 1
start Thu Apr 28 14:55:20 2007
host Thu Apr 28 14:59:06 2007
dag Thu Apr 28 14:59:06 2007
Testing the signal
For Linux and FreeBSD, when a synchronization source is connected the driver outputs messages to the
console log file
/var/log/messages
.
To test the signal is being received correctly and has the correct polarity use the
dagpps
tool as follows:
dagpps –dX
(Where X is the device number of the DAG card you want to configure).
dagpps
measures the input state many times over several seconds, displaying the polarity and length of
input pulse.
