Endace Measurement Systems Limited
http://www.endace.com
EDM01.05-04r1 DAG 3.6GE User Manual
Copyright, all rights reserved.
21
Revision 7. 22 September 2005.
5.2 Time Synchronization Configurations
Description
The DUCK is very flexible, and can be used in several ways, with or
without an external time reference source.
The use includes a single card with no reference, two cards with no
reference, and a card with reference.
In this section
This section covers the following topics of information.
•
Single Card no Reference Time Synchronization
•
Two Cards no Reference Time Synchronization
•
Card with Reference Time Synchronization
5.2.1 Single Card no Reference Time Synchronization
Description
When a single card is used with no external reference, the card can be
synchronized to the host PC’s clock.
The clock in most PC’s is not very accurate by itself, but the DUCK drifts
smoothly at the same rate as the PC clock.
If a PC is running NTP to synchronise its own clock, then the DUCK
clock is less smooth because the PC clock is adjusted in small jumps.
However, overall the DUCK clock does not drift away from UTC.
The synchronization achieved in this case is not as accurate as when using
an external reference source such as GPS.
The DUCK clock is synchronized to a PC clock by setting input
synchronization selector to overflow:
dag@endace:~$ dagclock –d dag0 none overin
muxin overin
muxout none
status Synchronized Threshold 11921ns Failures 0 Resyncs
0
error Freq 1836ppb Phase 605ns Worst Freq 143377ppb
Worst Phase 88424ns
crystal Actual 49999347Hz Synthesized 16777216Hz
input Total 87039 Bad 0 Singles Missed 0 Longest
Sequence Missed 0
start Wed Apr 27 14:27:41 2005
host Thu Apr 28 14:38:20 2005
dag Thu Apr 28 14:38:20 2005
NOTE:
dagclock
should be run only after appropriate Xilinx images have
been loaded. If the Xilinx images must be reloaded, the
dagclock
command must be rerun afterwards to restore the configuration.
