Endace DAG 3.7D, User Manual

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EDM01-06: DAG 3.7D Card User Guide
©2006 20 Version 1: March 2006
Two Cards No
Reference
Overview
When two DAG cards are used in a single host PC with no reference clock,
the cards must be synchronized in some way if timestamps between the two
cards are to be compared. For example, if two cards monitor different
directions of a single full-duplex link.
Synchronization between two DAG cards is achieved in two ways. One
card can be a clock master for the second, or one can synchronise to the
host and also act as a master for the second.
Synchronising Cards
If both cards are to be accurately synchronised, but not so for absolute time
of packet time-stamps being correct, then one card is configured as the
clock master for the other.
Locking Cards Together
Although the master card’s clock will drift against UTC, the cards are
locked together.
The cards are locked together by connecting the synchronisation connector
ports of both cards with a standard RJ-45 Ethernet cross-over cable.
Configure one of the cards as the master, the other defaults to being a slave.
dag@endace:~$ dagclock –d dag0 none overout
muxin none
muxout over
status Not Synchronised Threshold 596ns Failures
0 Resyncs 0
error Freq 0ppb Phase 0ns Worst Freq 0ppb Worst
Phase 0ns
crystal Actual 100000000Hz Synthesized 67108864Hz
input Total 0 Bad 0 Singles Missed 0 Longest
Sequence Missed 0
start Thu Apr 28 14:48:34 2005
host Thu Apr 28 14:48:34 2005
dag No active input - Free running
The slave card configuration is not shown, the default configuration is
sufficient.
Preventing Time-Stamps Drift
To prevent the DAG card clock time-stamps drifting against UTC, the
master can be synchronised to the host PC’s clock which in turn utilises
NTP. This then provides a master signal to the slave card.
The cards are locked together by connecting the synchronisation connector
ports of both cards with a standard RJ-45 Ethernet cross-over cable.
Configure one card to synchronize to the PC clock and output a RS-422
synchronization signal to the second card.