uses of synchronized clocks in test and measurement systems
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CHESS
March 3, 2009
Uses of Synchronized Clocks in Test and Measurement Systems
Jeff Burch, Adam Cataldo, John Eidson, Andrew Fernandez, Conrad Proft, Dieter Vook
Measurement Research Laboratory, Agilent Technologies, Inc.
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Slide 2 March 3, 2009
Agenda
1. Overview of clock synchronization and driving applications
2. Test & measurement (LXI Class B instrumentation & DAQ)
3. Experimental results
4. Conclusions
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Slide 3 March 3, 2009
Purpose of IEEE 1588
NETWORK
IEEE 1588 is a protocol designed to synchronize real-time clocks in the nodes of a distributed system that communicate using a network
• It does not say how to use these clocks (this is specified by the respective application areas)
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Slide 4 March 3, 2009
Coupling IEEE 1588 to your application
IEEE 1588 Clock
Latchtrigger-in
timestampgenerating timestamps
IEEE 1588 Clock
Comparator trigger-out
event time generating events
Latch
IEEE 1588 Clock Synthesizer waveform
generating waveforms
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Slide 5 March 3, 2009
Synchronization Basics – Delay Request-Response Mechanism
Mastertime
Slavetime
t1
t4
t3
t2
Timestamps knownby slave
t-ms
t-sm
Sync
Follow_Up
Delay_Req
Delay_Resp
t1, t2, t3, t4
t1, t2, t3
t2t1, t2
Grandmaster- M S- BC - M S- OC
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Slide 6 March 3, 2009
Under the assumption that the link is symmetric
Offset = (Slave time) – (Master time) = [(t2 – t1) – (t4 – t3)]/2 = [(t-ms) – (t-sm)]/2
(propagation time) = [(t2 – t1) + (t4 – t3)]/2 = [(t-ms) + (t-sm)]/2
Can rewrite the offset as
Offset = t2 – t1 – (propagation time) = (t-ms) – (propagation time)
If the link is not symmetric
• The propagation time computed as above is the mean of the master-to-slave and slave-to- master propagation times
• The offset is in error by the difference between the actual master-to-slave and mean propagation times
Synchronization Basics – Delay Request-Response Mechanism - 2
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Slide 7 March 3, 2009
Synchronization Basics – Peer Delay Mechanism
Mastertime
Slavetime
t1
t4
t3
t2
Timestamps knownby slave
t-ms
t-sm
Sync
Follow_Up
Pdelay_Req
Pdelay_Resp
t3, t4, t5, t6
t3
t2t1, t2
Grandmaster- M S- BC - M S- OC
t5
t6Pdelay_Resp_Follow_Upt6
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Slide 8 March 3, 2009
IEEE 1588
MASTER SLAVE
T1
T2
T4
T3
Sync
Delay_Req
PHY
MAC
OS
Application Code
IEEE 1588 Code
IEEE 1588 Packet Detection
IEEE 1588 Clock
IEEE 1588 Control
Application IEEE 1588 Timing Support (e.g. time stamping, time triggers…)
MII
LAN
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Slide 9 March 3, 2009
The residence time is accumulated in a field of the Sync (one-step clock) or Follow_Up (two-step clock) messages
End-to-End Transparent Clocks
Residence time bridgeIngress Egress
- +Ingress timestamp Egress timestamp
++
Message at ingress Message at egress
Preamble
PTP messagepayload
NetworkprotocolheadersCorrection field
Preamble
PTP messagepayload
NetworkprotocolheadersCorrection field
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Slide 10 March 3, 2009
How well can you synchronize?
SyncE Enabled
Measured Quantity
Mean Standard Deviation
Peak-to-peak
No 10 MHz clock output
-2.148 ns 5.237 ns 48.3 ns
Yes 10 MHz clock output
319 ps 80.6 ps 900 ps
Yes 1 pulse per second output
1.005 ns 2.8 ps 2.02 ns
From: “DP83640 Synchronous Ethernet Mode: Achieving Sub-nanosecond Accuracy in PTP Applications, National Semiconductor Application Note 1730, David Miller,
September 2007
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Slide 11 March 3, 2009
Infrastructure:
• Boundary and transparent clocks (IEEE 1588 bridges): Hirschmann, Westermo, Cisco, others
• GPS master clocks: Symmetricom, Meinberg, Westermo,…
Silicon: • Microprocessors with embedded 1588: Intel, Hyperstone, Freescale,
AMCC,…
• PHY/MAC level: National Semiconductor, others in proto or 1st silicon (some also implement synchronous Ethernet)
Protocol & misc:
• 1588 stacks, IP blocks, consulting: IXXAT, U. Zurich, MoreThanIP, others
• Wireshark
Products (partial listing)
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Slide 12 March 3, 2009
WebsitesGeneral IEEE 1588 site: contains product pointers, conference records, general guidance, standards related
http://ieee1588.nist.gov/
ISPCS (International IEEE Symposium on Precision Clock Synchronization) site: Conference on IEEE 1588 and related subjects
http://www.ispcs.org/
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Slide 13 March 3, 2009
RoboTeam in Action: Process Relative Motion
Courtesy of Kuka Robotics Corp.
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Slide 14 March 3, 2009
e.g. high speed printing Courtesy of Bosch-Rexroth.
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Slide 15 March 3, 2009
IEEE 1588 enabled flight test instrumentation in the forward fuselage of a test aircraft. (Data acquisition)
Courtesy of Teletronics
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Slide 16 March 3, 2009
GE uses 1588 in the Mark™ Vie control system for large generators, turbines, wind farms, and other DCS applications. (>50K I/O Packs with 1588 shipped to date)
http://gepower.com/prod_serv/products/oc/en/control_solution/ppc_markviedcs_cs.htm
Power System Applications (Courtesy of General Electric)
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Slide 17 March 3, 2009
IEEE Power System Relaying Committee (PSRC) recently approved formation
of Working Group H7 "IEEE 1588 Profile for Protection Applications"
Power System Applications
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Slide 18 March 3, 2009
Cellular backhaul is the major telecom application to date. Metro-Ethernet in field trial. Femtocells beginning.
Companies involved (partial list):
• Nokia-Siemens, Brilliant, Semtech, Zarlink, …
Telecommunications Applications
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Slide 19 March 3, 2009
Consumer electronics: IEEE 802.1as
http://www.ieee802.org/1/pages/802.1as.html
The “AVB” effort should be carefully investigated by both PTIDES and PRET.
Audio/video systems applications
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Slide 20 March 3, 2009
LXI Class-C Instrument
LXI Class A&B Instrument Overview
TSTTRXTX
PHYMeas FW Meas HW DUT
LXI Class B Instrument
LAN TCP HTTP
SCPI
App Code
IEEE1588
UDP
P2P
LXI Class B• IEEE1588 Clock Sync• Peer-to-Peer Messages• Event Logs• Downloaded Application Code
LXI Class A Instrument
Trigger Bus
8 LVDS
LXI Class A• Trigger Bus
Event Log
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Slide 21 March 3, 2009
LXI Class A&B benefits
Class B:
• Increased visibility of system configuration, timing and performance
• Increased visibility for fault diagnosis and trouble shooting
• Ability to precisely time measurement execution and state evolution system-wide
• Increased ability to optimize system performance, e.g. throughput, timing precision
• Increased ability to do cross domain measurement correlations based on precisely time stamped data
Class A:
• Increased traditional triggering flexibility: 8-wide, daisy chain
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Slide 22 March 3, 2009
DEMO TIME!
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Slide 23 March 3, 2009
LXI Class B experimental test system
Test system block diagram
Experiments:
1. Frequency response
2. Fault shutdown
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Slide 24 March 3, 2009
LXI Class B experimental test system
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Slide 25 March 3, 2009
PC Paced Instrument Sequencing-frequency response
*TRG; *OPC?
DONE
HW Trigger
HW Trigger*TRG; *OPC?
DONE
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Slide 26 March 3, 2009
Instrument Sequencing by PC (Baseline)
Irregular signal timing due to timing jitter in PC
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Slide 27 March 3, 2009
Peer-to-Peer Instrument Sequencing
MEASURE
STEP
COMPLETE
STEP
MEASURE
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Slide 28 March 3, 2009
Instrument Sequencing by P2P Messages
More regular signal timing
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Slide 29 March 3, 2009
LXI Class B: Time-Triggered Instrument Sequencing
COMPLETE
TTTT
TT
TT
TT
TT
TT
TT
Time overlap
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Slide 30 March 3, 2009
Instrument Sequencing by Time-Triggers
Shorter interval due to overlap
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Slide 31 March 3, 2009
Sequencing to measure frequency response
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Slide 32 March 3, 2009
Power Supply Shutdown
TS
FAULTPOLL
FAULT
SHUTDOWN
SHUTDOWNTT = TS + Δ2TT = TS + Δ1
SHUTDOWN
TSFAULT
SHUTDOWNSHUTDOWN
PC Polled
P2P Timed
P2P Immediate
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Slide 33 March 3, 2009
PC polled
TT-Fault FET
PS-Volt
FG-out
DMM-off
1. Short PS load
2. PS shuts off
3. Turn off FG
4. Turn off DMM
Asynchronous Fault
Protect
Shutdown
Shutdown
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Slide 34 March 3, 2009
Time-Triggered Emergency Shutdown
Asynchronous Fault
Protect
Shutdown
Shutdown
Δ1
Δ2
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Slide 35 March 3, 2009
Power Shutdown performance
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Slide 36 March 3, 2009
Power Shutdown Event Log-based Analysis
PS
Common Time Scale
FGEN
DMM
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Slide 37 March 3, 2009
Conclusions: Benefits of Class A & B:
• Increased visibility of system configuration, timing and performance
• Increased visibility for fault diagnosis and trouble shooting
• Ability to precisely time measurement execution and state evolution system-wide
• Increased ability to optimize system performance, e.g. throughput, timing precision
• Increased ability to do cross domain measurement correlations based on precisely time stamped data
• Increased traditional triggering flexibility: 8-wide, daisy chain
Performance measurements illustrate these benefits.
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