Systran SCRAMNet GT200 User manual

SCRAMNetNetwork
Skew Meter
Owner’s Manual
Document No. D-T-MU-SKEWMTR#-A-0-A2

FOREWORD
The information in this document has been carefully checked and is believed to be accurate; however, no
responsibility is assumed for inaccuracies. SYSTRAN reserves the right to make changes without notice.
SYSTRAN makes no warranty of any kind with regard to this printed material, including, but not limited
to, the implied warranties of merchantability and fitness for a particular purpose.
Copyright 1998, SYSTRAN Corporation. All Rights Reserved.
SCRAMNetis a registered trademark of SYSTRAN Corporation US Patent # 4,928,289.
STis a registered trademark of the AT&T Corporation.
Revised: August 14, 1998
SYSTRAN Corporation
4126 Linden Avenue
Dayton, OH 45432-3068 USA
[phone]

FCC
This product is intended for use in industrial, laboratory or military environments. This
product uses and emits electromagnetic radiation which may interfere with other radio
and communication devices. The user may be in violation of FCC regulations if this
device is used in other than the intended market environments.

TABLE OF CONTENTS
1.0 INTRODUCTION .....................................................................................................................1
1.1 Overview ......................................................................................................................1
1.2 Features.........................................................................................................................1
1.3 Technical Support.........................................................................................................1
1.4 Reliability .....................................................................................................................1
1.5 Related Documentation ................................................................................................2
1.6 Ordering Process...........................................................................................................3
2.0 DESCRIPTION .........................................................................................................................5
2.1 Overview ......................................................................................................................5
2.2 Connections ..................................................................................................................5
2.3 Controls ........................................................................................................................5
2.4 Indicators ......................................................................................................................6
3.0 OPERATION.............................................................................................................................7
3.1 Single-meter operation..................................................................................................7
3.2 Two-meter operation ....................................................................................................8
3.3 Notes on Operation.......................................................................................................9
4.0 ADJUSTING THE SKEW ......................................................................................................11
4.1 How to adjust the skew...............................................................................................11
4.1.1 Adjusting the Skew: ..................................................................................11
APPENDIX A……………………………………………………………………….……….…..A-
1
APPENDIX B…………………………………………………………………………….….…..B-
1
FIGURES
Figure 2-1 Skew Meter Face Plate...................................................................................................6
Figure 3-1 Connecting the cable for single-meter operation ...........................................................7
Figure 3-2 Connecting the cables for two-meter operation .............................................................9
TABLES
Table 4-1 Examples of fiber optic extender cable order numbers .................................................11
Table 4-2 Conversion from nanoseconds of skew to cable length.................................................12
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TABLE OF CONTENTS
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1.0 INTRODUCTION
1.1 Overview
This manual describes how to use the SCRAMNet+ Skew meter to measure and
minimize the skew in the paired conductors within each cable of your SCRAMNet+
network.
SCRAMNet+ (Shared Common Random Access Memory Network) is a communications
network geared toward real-time applications, and based on a replicated, shared-memory
concept.
SCRAMNet uses a pair of fiber-optic or coaxial conductors to transmit its data from one
node to another. For reliable data recovery by the receiver, the difference in accumulated
delay, or skew, of the two signal paths between active SCRAMNet nodes must be less
than 1 nanosecond. (An active node is one in which neither wire loopback nor optic
loopback is active). Cable manufacturing tolerances may cause an unacceptable amount
of skew in longer cable runs, even if the cables are equal in physical length. The
SCRAMNet+ Skew Meter can be used to measure the skew of the paired conductors and
determine what corrective action, if any, must be taken to bring it within limits.
1.2 Features
The SCRAMNet+ Skew Meter has the following features:
• Measures skew in fiber or coax paired conductors of a cable, depending on
the type of media card installed in the meter.
• Measures skews up to 120 ns (approximately 24 meters).
• Power requirement: 5VDC at 1A. A line-powered external supply is
provided.
1.3 Technical Support
Technical documentation provided with the Skew Meter discusses technology and
performance characteristics. SYSTRAN also publishes technical briefs and application
notes that cover a wide assortment of topics. The applications selected are derived from
real scenarios.
Direct any programming questions, any concerns about the functionality of this meter for
your particular application, or any questions not answered satisfactorily by this
document, to the factory by phone, or send an E-mail message to [email protected].
1.4 Reliability
SYSTRAN corporate policy is to provide the highest quality products in support of
customer needs. In addition to the physical product, SYSTRAN provides documentation,
sales and marketing support, hardware and software technical support, and timely product
delivery. The SYSTRAN commitment to quality begins with product concept, and
continues after receipt of the purchased product.
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INTRODUCTION
SYSTRAN has developed a quality system which conforms to the ISO 9001 international
standard for quality systems. ISO 9001 is the model for quality assurance in design,
development, production, installation and servicing. The ISO 9001 standard is the most
comprehensive of the conformance standards, in that it addresses all 20 clauses of the
ISO quality system requirements.
SYSTRAN’s quality system addresses the following basic quality objectives:
• Achieve, maintain and continually improve the quality of SYSTRAN products
• Improve the quality of its own operations to meet the needs of SYSTRAN
customers and stakeholders
• Provide confidence internally that quality is being fulfilled, maintained and
improved
• Provide confidence to the customer and other stakeholders that requirements for
quality will be achieved in the delivered product
SYSTRAN’s quality system was assessed by BSI QA, which is the certification division
of British Standards Institution, the largest and most respected standardization authority
in the world. SYSTRAN’s quality system was found to meet or to exceed the
international standards in all areas, and Certificate of Registration number FM 31468 was
issued to SYSTRAN on May 16, 1995.
The scope of SYSTRAN’s registration is: “Design, manufacture, and service of high
technology hardware and software computer communications products.” The registration
is maintained under BSI QA’s program of continuing assessment, under which an audit
of the quality system is performed by BSI QA every six months.
Customer feedback is an integral part of meeting SYSTRAN quality and reliability goals.
Customers are encouraged to contact the factory with any questions or suggestions
regarding unique quality requirements, or to obtain additional information about our
programs. SYSTRAN’s commitment to customers includes, but is not limited to the
following:
• Professional and quick response to customer problems using SYSTRAN’s
extensive resources.
• Incorporation of established procedures for product design, test, and production
operations, with documented milestones. Procedures are constantly reviewed and
improved, ensuring the highest possible quality.
SYSTRAN provides products and services that meet or exceed the best expectations of
our customers.
• All products receive a predictive reliability rating based upon a calculated MTBF
(Mean Time Between Failure) using the MIL-HDBK-217F. Field failures are
continuously logged and evaluated for potential failure modes and trends.
• Other environmental parameters are guaranteed by design, and are not tested.
Design reliability is ensured by methodology (top-down CAE design, VHDL, synthesis,
extensive all-cases simulation, ALPHA build and test, and BETA testing, if required) with
full concurrent engineering practices throughout.
1.5 Related Documentation
SCRAMNet Network Media User’s Guide, Systran document number D-T-MU-MEDIA.
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INTRODUCTION
1.6 Ordering Process
To learn more about SYSTRAN products or about custom-designed boards, or to place an
order, the following contacts are available:
• Phone: [phone]
• E-mail address: [email protected]
• World Wide Web address: http://www.systran.com
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INTRODUCTION
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2.0 DESCRIPTION
2.1 Overview
The Skew Meter measures the skew of a paired-conductors SCRAMNet cable by
generating two signals with a known phase relationship and driving them into one end of
the cable. At the other end of the cable the two signals are compared and the change in
the phase relationship is used to determine the propagation skew between the two
elements of the pair. The only equipment needed to measure the skew is the Skew Meter,
its power supply, and the cable to be tested.
If both ends of the cable are not close enough to each other to plug into a single Skew
Meter, two Skew Meters may be used, one to generate and transmit the signals and the
other to receive and measure them.
The Skew Meter can be supplied with a SCRAMNet+ Long-Link, Standard-Link, or
Coax-media interface. The Long-Link interface is the most likely to be used, since skew
tends to be more of a problem when long cable lengths are used.
2.2 Connections
The cable to be tested connects between the two transmit media connectors, TXA and
TXB, and the two receive media connectors, RXA and RXB. These are fiber-optic ST
connectors or copper SMA connectors, depending upon which media interface is
installed.
5 VDC power must be provided to the meter through the power jack. An external power
supply is provided so that the meter can be powered from AC wall-outlet power (100 -
240 VAC, 50/60 Hz). If this power supply cannot be used for some reason, any other
source of 5 VDC at about 1 A may be used. See Appendix A for information on providing
an alternate power source.
2.3 Controls
Power (On/Off) and Range (±12.00 ns / ±120.0 ns) toggle switches are on the front panel.
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DESCRIPTION
2.4 Indicators
Two green LEDs near the RXA and RXB inputs indicate that a signal is detected at the
associated input.
A yellow “SWAP” LED indicates that the conductor pair is cross-connected so that TXA
drives RXB and TXB drives RXA. If this light is on the connections should be swapped
at one end so that the meter correctly indicates which conductor is shorter.
The numerical display shows the amount of skew in nanoseconds. It will display a
positive number if conductor A (connecting TXA to RXA) is longer than conductor B
(connecting TXB to RXB) and a negative number if conductor B is longer.
)
NOTE: The display cannot indicate that the skew is out of range, because the
meter has no way to detect this condition. Therefore the ±120.0 ns range should
always be checked to make sure the skew is small enough before taking a reading
with the ±12.00 ns range.
Figure 2-1 Skew Meter Face Plate
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3.0 OPERATION
3.1 Single-meter operation
To measure the skew in a cable when both ends of the cable can be plugged into the same
Skew Meter, perform the following steps:
1. Apply power to the meter with the supply that came with the meter or from some
alternative source. (See Appendix A for information on providing an alternate
power source).
2. Connect one end of the cable to be tested to the TXA and TXB connectors, and
the other end to the RXA and RXB connectors.
3. Turn the Power switch on and set the Range switch to “±120.0 ns”.
4. Both green signal detect LEDs should be lit. A dark LED means that the
associated RX input isn’t receiving a signal.
5. If the yellow “SWAP” LED is lit, swap the cable connections at either TXA-
TXB or RXA-RXB. This ensures that the conductors are connected TXA to RXA
and TXB to RXB.
6. Read the amount of skew in nanoseconds from the display. If the absolute value
of the reading is less than 12 nanoseconds, set the Range switch to “±12.00 ns”
for better resolution. A positive reading indicates that conductor A (connecting
TXA to RXA) is longer than conductor B (connecting TXB to RXB). A negative
reading indicates that conductor B is longer.
TXA TXB
RXB
RXA
Figure 3-1 Connecting the cable for single-meter operation
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OPERATIONS
3.2 Two-meter operation
If the ends of the cable are physically separated and can’t be plugged into a single skew
meter, the skew of the pair can still be measured by using two skew meters, one as a
transmitter and one as a receiver.
Measure the offset between the two meters first.
1. Choose one meter to be the transmitter (“Meter 1”) and one to be the receiver
(“Meter 2”).
2. Apply power to both meters with the supplies that came with them or from some
alternative source. (See Appendix A for information on providing an alternative
power source.)
3. Connect short, equal-length conductors as shown in Figure 3-2. Turn on the
Power switches of both meters and set both Range switches to “±120.0 ns”.
4. Both of Meter 2’s green signal detect LEDs should be lit. A dark LED means that
the associated RX input isn’t receiving a signal. (The LEDs and display of Meter
1 are ignored in the two-meter setup.)
5. Record the number indicated on Meter 2’s display. This is the offset for the
±120.0 ns range.
6. Set both Range switches to “±12.00 ns”. Record the number indicated on Meter
2’s display. This is the offset for the ±12.00 ns range.
To make a skew measurement:
1. Apply power to both meters with the supplies that came with them or from some
alternative source.
2. Connect one end of the cable to be tested to the TXA and TXB connectors on
Meter 1. Turn on Meter 1’s Power switch and set its Range switch to “±120.0 ns”.
3. Connect the other end of the cable pair to the RXA and RXB connectors of Meter
2. Turn on Meter 2’s power switch and set the Range switch to “±120.0 ns”.
4. Both of Meter 2’s green signal detect LEDs should be lit. A dark LED means that
the associated RX input isn’t receiving a signal.
5. If Meter 2’s yellow “SWAP” LED is lit, swap the cable connections at either
TXA-TXB or RXA-RXB. This ensures that the conductors are connected TXA to
RXA and TXB to RXB.
6. Take the number on Meter 2’s display and subtract the offset you recorded for
the ±120.0 ns range. This is the measured skew in nanoseconds.
7. If the absolute value of the number on Meter 2’s display is less than 12
nanoseconds, set the Range switch of both meters to “±12.00 ns” for better
resolution. Subtract the offset you recorded for the ±12.00 ns range from the
number on Meter 2’s display to get the measured skew.
8. A positive reading indicates that conductor A (connecting TXA to RXA) is
longer than conductor B (connecting TXB to RXB). A negative reading indicates
that conductor B is longer.
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OPERATIONS
Meter 1 Meter 2
RXA RXB TXA TXB
RXA RXB TXA TXB
Figure 3-2 Connecting the cables for two-meter operation
)
NOTE: To avoid confusion, both RANGE switches must be in the same position!
The RANGE switch on Meter 1 controls the actual measurement range, but the
RANGE switch on Meter 2 controls the decimal point on Meter 2’s display.
3.3 Notes on Operation
• The rightmost digit of the display will drift with time and temperature and can safely
be ignored.
• Allowing the meter to warm up for five minutes or so before taking a reading will
bypass the worst of the temperature drift.
• It is normal for the meter to feel warm in operation, especially near the TX
connectors.
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OPERATIONS
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4.0 ADJUSTING THE SKEW
4.1 How to adjust the skew
Once you have measured the amount of skew in a cable, you can adjust the skew toward
zero either by cutting off a piece of the longer conductor and installing a new connector
or by connecting a short extender to the shorter conductor.
4.1.1 Adjusting the Skew:
If a short extender is needed, fiber optic extender cables are available in lengths in
multiples of 5 cm (~ 2 in). By using the Skew to length conversion Table 4-1, the
appropriate length can be ordered. The part number for the fiber optic extender cable is:
H-PR-WST1XXXX-0
The “XXXX” section of the order number represents the length of the fiber optic
extender cable ordered. See Table 4-2 for examples of order numbers for the fiber optic
extender cable.
Table 4-1 Examples of fiber optic extender cable order numbers
CABLE LENGTH ORDER NUMBER
5 cm (~ 2 in) H-PR-WST105R0-0
10 cm (~ 4 in) H-PR-WST110R0-0
1 m (~ 3.28 ft) H-PR-WST11000-0
The conversion from nanoseconds to length to be added or subtracted depends on the
signal propagation speed of your particular cable. For many cables, including Systran’s,
the propagation speed is almost exactly 20 cm/ns (7.9 in/ns). If you don’t know the
propagation speed of your cable, you can measure it by inserting a short known length
into one side of a cable pair and measuring how much the skew changes.
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ADJUSTING THE SKEW
Table 4-2 Conversion from nanoseconds of skew to cable length
Skew (ns) Length (cm) Length (in)
0.5 10 3.95
1.0 20 7.90
1.5 30 11.85
2.0 40 15.80
2.5 50 19.75
3.0 60 23.70
3.5 70 27.65
4.0 80 31.60
4.5 90 35.55
5.0 100 39.50
5.5 110 43.45
6.0 120 47.40
6.5 130 51.35
7.0 140 55.30
7.5 150 59.25
8.0 160 63.20
8.5 170 67.15
9.0 180 71.10
9.5 190 75.05
10.0 200 79.00
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A. APPENDIX SPECIFICATIONS
APPENDIX A
SPECIFICATIONS