Endace DAG 3.7G Series, Руководство пользователя

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EDM01-07: DAG 3.7G Card User Guide
Version 7: May 2006 20 ©2005
Card with
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 PC’s clock must be
accurate to UTC to within one second. This is used to initialise the DUCK.
When the external time reference source is connected to the DAG card time
synchronisation connector, the card automatically synchronises to a valid
signal.
Pulse Signal from External Source
The DAG time synchronisation connector supports an RS-422 (PPS) signal
from an external source. This is derived directly from an external reference
source, or distributed through the Endace TDS 2 (Time Distribution Server)
module which allows two DAG cards to use a single receiver. It is also
possible for more than two cards to use a single receiver by “daisy-chaining”
TDS-6 expansion modules to the TDS-2 module. Each TDS-6 , module
provides outputs for an additional 6 DAG cards.
Synchronise to an external source as follows:
dagclock –d dag0
muxin rs422
muxout none
status Synchronised Threshold 596ns Failures 0 Resyncs 0
error Freq 30ppb Phase -15ns Worst Freq 2092838ppb Worst Phase
33473626ns
crystal Actual 100000023Hz Synthesized 67108864Hz
input Total 225 Bad 0 Singles Missed 1 Longest Sequence Missed 1
start Thu Apr 28 14:55:20 2005
host Thu Apr 28 14:59:06 2005
dag Thu Apr 28 14:59:06 2005
Connecting the Time Distribution Server
You can connect the TDS 2 module to the DAG card using standard RJ-45
Ethernet cable including existing RJ-45 building cabling. The TDS may be
located up to 600m (2000ft) from the DAG card depending upon the quality
of the cable used, possible interference sources and other environmental
factors. Please refer to the TDS2/TDS6 User Guide for more in formation
Caution: Never connect a DAG card and/or the TDS 2 module to
active Ethernet equipment or telephone equipment.
Testing the Signal
For Linux and FreeBSD, when a synchronisation 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 –d dag0
dagpps
measures the input state many times over several seconds, displaying
the polarity and length of input pulse. The DAG 3.7T card also has an LED
indicator for synchronisation (PPS) signals. See Chapter 3: Configuring the
Card earlier in this User Guide for more information.