Symmetricom ET6000, ET6010, ET6500-OCXO, ET6500-RB1 User Manual

ET6000, ET6010, ET6500
ExacTime GPS Time Code
And Frequency Generator
Covering Configurations:
ET6000, ET6010, ET6500-TCXO
ET6000, ET6010, ET6500-OCXO
ET6000, ET6010, ET6500-RB1
Revision C
User’s Guide
8500-0105
June, 2005
ET6000, ET6010, and ET6500
EXACTIME GPS TIME CODE AND FREQUENCY GENERATOR
TABLE OF CONTENTS
SECTION
PAGE
CHAPTER ONE
GENERAL INFORMATION
1.0
1.1
1.2
1.3
1.4
INTRODUCTION ................................................................................................................ 1-1
USER'S GUIDE SUMMARY .............................................................................................. 1-1
NAVSTAR/GPS DESCRIPTION ........................................................................................ 1-2
PRODUCT DESCRIPTION ................................................................................................. 1-3
SPECIFICATIONS............................................................................................................... 1-4
1.4.1 GPS SUBSYSTEM................................................................................................ 1-4
1.4.2 TIMING OUTPUTS .............................................................................................. 1-4
1.4.3 ACCURACY ......................................................................................................... 1-7
1.4.4 TIMING INPUTS .................................................................................................. 1-7
1.4.5 J12 RS-232 I/O INTERFACE ............................................................................... 1-8
1.4.6 INTERNAL TIME BASE...................................................................................... 1-8
1.4.7 PRIMARY POWER ............................................................................................ 1-11
1.4.8 DIMENSIONS..................................................................................................... 1-13
1.4.9 WEIGHT.............................................................................................................. 1-13
1.4.10 ENVIRONMENT .............................................................................................. 1-13
1.5 ADDITIONAL SPECIFICATIONS ................................................................................... 1-14
1.5.1 ANTENNA/PREAMP ......................................................................................... 1-14
1.5.2 GPS RPU AND ANTENNA................................................................................ 1-14
1.6 FUNCTIONAL CHARACTERISTICS.............................................................................. 1-14
1.6.1 ACQUISITION.................................................................................................... 1-14
1.6.2 SIGNAL INTERRUPTION................................................................................. 1-15
1.6.3 POSITION AND VELOCITY SOLUTION........................................................ 1-15
1.6.4 DYNAMIC CAPABILITY.................................................................................. 1-16
1.6.5 RF JAMMING RESISTANCE AND BURN-OUT PROTECTION................... 1-16
1.6.6 SYSTEM STATUS AND DIAGNOSTICS ........................................................ 1-16
1.6.7 GPS SOLUTION MODES .................................................................................. 1-16
1.6.8 ELEVATION ANGLE MASK............................................................................ 1-17
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CHAPTER TWO
INSTALLATION
2.0 INTRODUCTION ................................................................................................................ 2-1
2.1 UNPACKING AND INSPECTION ..................................................................................... 2-1
2.2 RACK MOUNTING PROCEDURE .................................................................................... 2-1
2.2.1 TMRA .................................................................................................................... 2-1
2.2.2 ELEVATED AMBIENT OPERATING TEMPERATURE.................................. 2-1
2.2.3 REDUCED AIR FLOW......................................................................................... 2-2
2.2.4 MECHANICAL LOADING.................................................................................. 2-2
2.2.5 CIRCUIT OVERLOADING ................................................................................. 2-2
2.2.6 RELIABLE EARTHING....................................................................................... 2-2
2.3 ANTENNA/PREAMP INSTALLATION ............................................................................ 2-2
2.4 ANTENNA/PREAMP INTERFACE CONNECTIONS ...................................................... 2-2
2.5 PRIMARY POWER CONNECTION .................................................................................. 2-3
2.6 GPS TIMING UNIT INTERFACE CONNECTIONS ......................................................... 2-6
2.6.1 RS-232 I/O INTERFACE J12 ............................................................................... 2-6
2.6.2 PRINTER OUTPUT PORT J11 ............................................................................ 2-7
2.6.3 TIMING OUTPUTS .............................................................................................. 2-7
2.6.4 1PPS INPUT .......................................................................................................... 2-8
2.6.5 OSCILLATOR CONFIGURATION..................................................................... 2-8
CHAPTER THREE
OPERATION
3.0 INTRODUCTION ................................................................................................................ 3-1
3.1 OPERATIONAL STEPS ...................................................................................................... 3-1
3.1.1 INITIALIZATION (UNKNOWN POSITION)..................................................... 3-1
3.1.2 INITIALIZATION (KNOWN POSITION)........................................................... 3-3
3.2 OPERATIONAL CHARACTERISTICS ............................................................................. 3-4
3.3 LIQUID CRYSTAL DISPLAY............................................................................................ 3-4
3.3.1 MAIN MENU SCREEN........................................................................................ 3-4
3.3.2 POSITION MENU SCREEN ................................................................................ 3-9
3.3.3 SET-UP MENU SCREEN................................................................................... 3-10
3.3.4 RS232 I/O CONFIGURATION MENU SCREEN ............................................. 3-15
3.3.5 MULTIPLE TIME CODE OUTPUTS MENU SCREEN ................................... 3-16
3.3.6 PRESET COINCIDENCE MENU SCREEN ...................................................... 3-16
3.3.7 EXTERNAL FREQUENCY MEASUREMENT MENU SCREEN ................... 3-17
3.3.8 SINGLE EVENT LOG MENU SCREEN ........................................................... 3-18
3.3.9 50/60HZ MEASUREMENT SCREEN ............................................................... 3-19
3.3.10 AUTO DAYLIGHT SAVINGS MENU SCREEN ........................................... 3-20
3.3.11 MUX OUTPUT MENU SCREEN .................................................................... 3-21
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3.3.12 PRINTER PORT CONFIGURATION MENU SCREEN................................. 3-23
3.3.13 IEEE-488 I/O INTERFACE MENU SCREEN ................................................. 3-26
3.4 CONFIGURATION OF REAR PANEL BNC CONNECTORS J4-J9.............................. 3-26
CHAPTER FOUR
I/O PORT DATA INPUT/OUTPUT
4.0 INTRODUCTION ................................................................................................................ 4-1
4.1 SYMMETRICOM FIRMWARE VERSION........................................................................ 4-3
4.2 UTC SYNC........................................................................................................................... 4-4
4.3 GPS SYNC............................................................................................................................ 4-4
4.4 PRINT FREQUENCY OFFSET........................................................................................... 4-4
4.5 PRINT TIME, STATUS, ERROR CODE, AND SATELLITE VEHICLE NUMBERS..... 4-4
4.6 PRINT POSITION................................................................................................................ 4-6
4.7 CLEAR EVENT DATA ...................................................................................................... 4-7
4.8 PRINT EVENT DATA......................................................................................................... 4-7
4.9 REQUEST ONE EVENT LOG DATA ................................................................................ 4-8
4.10 ENABLE SINGLE EVENT LOG ...................................................................................... 4-9
4.11 DISABLE SINGLE EVENT LOG ..................................................................................... 4-9
4.12 SELECT MODE ................................................................................................................. 4-9
4.13 ENABLE TIME INTERVAL ........................................................................................... 4-10
4.14 DISABLE TIME INTERVAL.......................................................................................... 4-10
4.15 REQUEST TIME INTERVAL......................................................................................... 4-10
4.16 REQUEST ELEVATION MASK ANGLE...................................................................... 4-11
4.17 ENTER ELEVATION MASK ANGLE ........................................................................... 4-11
4.18 ENABLE DISCIPLINING ............................................................................................... 4-11
4.19 DISABLE DISCIPLINING .............................................................................................. 4-11
4.20 ENTER POSITION .......................................................................................................... 4-12
4.21 ENTER DAC VALUE...................................................................................................... 4-12
4.22 REQUEST DAC VALUE................................................................................................. 4-13
4.23 NUMBER OF POSITION AVERAGES.......................................................................... 4-13
4.24 ENTER LOCAL OFFSET ................................................................................................ 4-13
4.25 ENTER CABLE DELAY ................................................................................................. 4-14
4.26 REQUEST CABLE DELAY ............................................................................................ 4-14
4.27 RESYNCHRONIZE MINOR TIME ................................................................................ 4-14
4.28 SELECT DEFAULT VALUES ........................................................................................ 4-15
4.29 EXTERNAL FREQUENCY MEASUREMENT – SELECT INPUT FREQUENCY..... 4-15
4.30 EXTERNAL FREQUENCY MEASUREMENT – ENABLE/DISABLE ........................ 4-16
4.31 EXTERNAL FREQUENCY MEASUREMENT – REQUEST DATA ............................ 4-16
4.32 REQUEST SATELLITE SIGNAL SNR .......................................................................... 4-16
4.33 REQUEST UNIT OPERATING PARAMETERS ........................................................... 4-17
4.34 ENABLE 50/60HZ MEASUREMENT ............................................................................ 4-18
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4.35 50/60HZ SELECTION ..................................................................................................... 4-18
4.36 ENTER 50/60HZ OFFSET DATA................................................................................... 4-18
4.37 REQUEST 50/60HZ MEASUREMENT DATA............................................................... 4-19
4.38 PRINTER – SET-UP CONFIGURATION....................................................................... 4-19
4.39 PRINTER – REQUEST CONFIGURATION .................................................................. 4-20
4.40 PRINTER PORT MODE SELECTION ........................................................................... 4-20
4.41 PRINTER – SELECT OUTPUT RATE ........................................................................... 4-21
4.42 PRINTER – REQUEST OUTPUT RATE........................................................................ 4-21
4.43 ENABLE/DISABLE & DATA SELECT ......................................................................... 4-21
4.44 ENTER PRESET COINCIDENCE TIME ....................................................................... 4-23
4.45 REQUEST MUX OUTPUT ............................................................................................. 4-24
4.46 SET MUX OUTPUT ........................................................................................................ 4-25
4.47 SET MAJOR TIME – TOD (TIME OF DAY)................................................................. 4-25
4.48 SET YEAR........................................................................................................................ 4-25
4.49 AUTOMATIC DAYLIGHT SAVINGS TIME................................................................ 4-26
4.49.1 DISABLE AUTO DAYLIGHT SAVINGS TIME FUNCTION....................... 4-26
4.49.2 ENABLE AUTO DAYLIGHT SAVINGS TIME FUNCTION........................ 4-26
4.49.3 SET AUTO DAYLIGHT SAVINGS TIME DEFAULT INTERVAL ............. 4-26
4.49.4 REQUEST AUTO DAYLIGHT SAVINGS TIME INTERVAL...................... 4-27
4.49.5 SET AUTO DAYLIGHT SAVINGS TIME INTERVAL................................. 4-27
4.50 REQUEST UNIT SERIAL NUMBER ............................................................................. 4-28
CHAPTER FIVE
MAINTENANCE/TROUBLESHOOTING
5.0 MAINTENANCE ................................................................................................................. 5-1
5.1 ADJUSTMENTS .................................................................................................................. 5-1
5.1.1 INTERNAL OSCILLATOR CALIBRATION...................................................... 5-1
5.1.2 LCD ADJUSTMENT ............................................................................................ 5-3
5.1.3 AC CODE ADJUSTMENTS................................................................................. 5-3
5.1.4 10MHZ SINE WAVE............................................................................................ 5-3
5.1.5 10MHZ SQUARE WAVE..................................................................................... 5-3
5.2 TROUBLESHOOTING........................................................................................................ 5-4
5.2.1 GENERAL............................................................................................................. 5-4
5.2.2 POWER LED WILL NOT ILLUMINATE WHEN ON/OFF SWITCH IS
ACTIVATED ........................................................................................................ 5-4
5.2.3 TRACKING LED DOES NOT ILLUMINATE.................................................... 5-4
5.2.4 LOCKED LED DOES NOT ILLUMINATE ........................................................ 5-5
5.2.5 UNIT DOES NOT TRACK SATELLITES, ERROR MESSAGE/CODE –
ANTENNA UNDERCURRENT .......................................................................... 5-5
5.2.6 COLD RESET ....................................................................................................... 5-5
5.3 THEORY OF OPERATION................................................................................................. 5-6
5.3.1 GPS SYSTEM OPERATION................................................................................ 5-6
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5.3.2 MODES OF OPERATION.................................................................................... 5-6
5.3.3 EXACTIME INTERNAL CONFIGURATION .................................................... 5-8
5.3.4 MICROCOMPUTER PROGRAM THEORY OF OPERATION ......................... 5-9
APPENDIX A
ASCII CHARACTER CODE TABLE
PART ONE ................................................................................................................................. A-1
PART TWO ................................................................................................................................ A-2
PART THREE ............................................................................................................................ A-3
PART FOUR............................................................................................................................... A-4
APPENDIX B
GLOSSARY OF TERMS
A...................................................................................................................................................B-1
B...................................................................................................................................................B-2
C...................................................................................................................................................B-2
D...................................................................................................................................................B-3
E ...................................................................................................................................................B-3
F ...................................................................................................................................................B-4
G...................................................................................................................................................B-4
H...................................................................................................................................................B-5
I ....................................................................................................................................................B-5
J ....................................................................................................................................................B-6
K...................................................................................................................................................B-6
L ...................................................................................................................................................B-6
M ..................................................................................................................................................B-7
N...................................................................................................................................................B-7
O...................................................................................................................................................B-8
P ...................................................................................................................................................B-8
Q...................................................................................................................................................B-9
R...................................................................................................................................................B-9
S ...................................................................................................................................................B-9
T .................................................................................................................................................B-10
U.................................................................................................................................................B-10
V.................................................................................................................................................B-10
W................................................................................................................................................B-11
X.................................................................................................................................................B-11
Y.................................................................................................................................................B-11
Z .................................................................................................................................................B-11
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APPENDIX C
OPTION DESCRIPTIONS
GPS Opt 01/01A
GPS Opt 06A
GPS Opt 07A
GPS Opt 08CE
GPS Opt 08G
GPS Opt 08GP
GPS Opt 10B
GPS Opt 13A
GPS Opt 14
GPS Opt 15A/15P
GPS Opt 15C
GPS Opt 21A
GPS Opt 23A/23B
GPS Opt 27A,B,C,D
GPS Opt 33A
GPS Opt 33B/33C
GPS Opt 33D/33E
GPS Opt 40/40P
GPS Opt 40A/40AP
GPS Opt 40B/40BP
GPS Opt 48
Three Channel Encoder .....................................................................C-1
1 MHz Sine Wave Shaper................................................................C-16
5 MHz Sine Wave Shaper................................................................C-17
10-37VDC Dual Power Input ..........................................................C-18
38-73VDC Power Supply ................................................................C-21
38-73VDC Power Supply ................................................................C-23
Low Phase Noise Oscillator.............................................................C-28
Parallel BCD Output (Days – Milliseconds) ...................................C-31
IEEE-488 I/O Interface ....................................................................C-36
Rubidium Time Base 10MHz Oscillator (LPRO) ...........................C-42
Rubidium Time Base 10MHz Oscillator (X72)...............................C-45
10MHz Sine Wave Shaper...............................................................C-47
Lightning Arrestor (w/25 or 50 ft. Antenna Cable ..........................C-48
Signal Distribution...........................................................................C-53
1.544/2.048MHz Square Wave Output............................................C-56
T1/E1 Framed Ones – Balanced Output ..........................................C-57
T1/E1 Framed Ones – Balanced Output w/Frame Marker etc. .......C-65
GPS Option Motherboard (w/6 BNC outputs) ................................C-73
GPS Option Motherboard (w/1 BNC output) ..................................C-75
GPS Option Motherboard (w/3 BNC outputs) ................................C-77
Pulse Rate Module ...........................................................................C-79
APPENDIX D
ANTENNA REPLACEMENT KIT
D.0
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Antenna Replacement Kit ................................................................. D-1
ET6xxx ExacTime GPS TC & FG (Rev C)
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CHAPTER ONE
GENERAL INFORMATION
1.0 INTRODUCTION
This User’s Guide describes the installation and operation of the ExacTime ET6xxx Global
Positioning System (GPS) Time Code and Frequency Generator (TC&FG). Excluding options and
size, the only difference between the different configurations is the oscillator.
The following are the available configurations and their respective oscillators:
ET6000-TCXO
10MHz Voltage Controlled Temperature Compensated Crystal Oscillator.
ET6010-TCXO
ET6500-TCXO
ET6000-OCXO
ET6010-OCXO
ET6500-OCXO
10MHz Voltage Controlled Ovenized Crystal Oscillator.
ET6000-RB1
ET6010-RB1
ET6500-RB1
10MHz Rubidium Oscillator with an aging rate of 5E-11 per month.
1.1 USER'S GUIDE SUMMARY
This User’s Guide is divided into the following chapters:
A.
CHAPTER ONE - GENERAL INFORMATION
This chapter includes a general description of the GPS Timing Unit and provides
technical specifications.
B.
CHAPTER TWO - INSTALLATION
Describes initial inspection, preparation for use, interconnections to antenna/preamp,
power connections, and signal interconnections.
C.
CHAPTER THREE - OPERATION
Describes the local operation of the unit.
D.
CHAPTER FOUR - I/O PORT DATA INPUT/OUTPUT
Provides information on the protocol and data available through the RS-232C I/O
port.
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CHAPTER ONE
E.
CHAPTER FIVE - MAINTENANCE/TROUBLESHOOTING
Provides a guide to the maintenance and troubleshooting of this instrument. A
description of the available adjustments is also provided.
F.
APPENDIX A - ASCII CHARACTER CODES
Provides the cross reference of the ASCII character set to decimal, octal, and
hexadecimal numbers.
G.
APPENDIX B - ACRONYMS AND ABBREVIATIONS
Provides a list of acronyms and abbreviations used in this User’s Guide.
H.
APPENDIX C -OPTION DESCRIPTIONS
The Option Descriptions that are available with this instrument are located in this
Appendix.
I.
APPENDIX D –ANTENNA REPLACEMENT KIT
Provides superseded model information.
1.2 NAVSTAR/GPS DESCRIPTION
The Navstar/GPS satellite-based timing and navigation system consists of a constellation of high
altitude satellites orbiting the earth every twelve sidereal hours, a group of ground-based
control/monitoring stations and the user equipment which may be located on land, sea and/or air.
The GPS System was completed in the early 1990’s and provides three dimensional positioning,
velocity, and time, on a continuous world-wide basis. The constellation is comprised of twenty-one
satellites and three spares. The satellites are located in six different orbital planes inclined
approximately sixty degrees to the equator at altitudes of 10,400 miles above the earth.
The GPS Timing Unit determines time and frequency by measuring the time of arrival of the
precise timing mark and measuring the Doppler effect from one satellite. A previously entered or
determined position allows computation of the receivers time offset. An accurate timing mark
(1pps) can be set, and an input 1pps pulse can be measured with respect to UTC. The satellite
positions are known within a few meters and the satellite clocks are calibrated within a few
nanoseconds so position can be computed within an absolute accuracy of better than 120 meters
(with current selective availability).
The GPS signal transmitted from a satellite consists of two carrier frequencies. L1 at a frequency of
1575.42 MHz and L2 at a frequency of 1227.6 MHz. The L1 signal is modulated with both a
precision (P) code and a coarse acquisition (C/A) code. The precision (P) code is available to
authorized users only. The GPS Timing Unit operates on the C/A code.
Each satellite transmits a unique C/A code that reflects the satellite identity for acquisition and
tracking. The C/A PRN code is a gold code of 1023 bits repeating at a one-millisecond rate.
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ET6xxx ExacTime GPS TC & FG (Rev C)
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GENERAL INFORMATION
The L1 and L2 frequency is also modulated with a fifty-bit-per-second data stream providing
satellite ephemerides, system time, satellite clock behavior, and status information on all satellites.
The data message is contained in a data frame that is 1,500 bits long.
Ground based control/monitoring stations track the satellites and provide an upload several times
each day to provide a prediction of each satellites ephemeris and clock behavior for the next day’s
operation.
1.3 PRODUCT DESCRIPTION
The GPS Timing Unit operates on the civilian L-band (1575.42MHz) utilizing C/A (Coarse
Acquisition) code transmissions to monitor time and frequency data from the Navstar satellite
constellation. Time and frequency is determined from satellite transmissions and calculations
referenced to USNO (United States Naval Observatory) through the GPS Master Clock system.
This link provides traceability to USNO and all international time scales through the use of
publications from NIST (National Institute of Standards Technology), USNO, and BIPM (Bureau of
International Des Poids et Measurements) in Servres, France.
The unit automatically acquires and tracks satellites based on health status and elevation angle. In
the Stationary mode, time and frequency monitoring requires only one satellite, once accurate
position data has been acquired or entered, although the receiver will use as many satellites as
available. In “AUTO” mode, and the “Dynamic” mode, a minimum of four satellites are required
for the GPS Timing unit to do three dimensional (latitude, longitude, and altitude) position fixes.
The basic GPS Timing Unit configuration includes the GPS Main Module, an antenna/preamp and
a coaxial cable for interconnection. A corrected 1pps output signal and a 10MHz Sine Wave are
provided. An RS-232 I/O Port is also provided in the basic configuration which can be used to
control the unit as well to get data from the unit. The basic unit has an LCD Display and a
keyboard. It generates IRIG B Serial Time Code, and has the capability of measuring the time
interval difference between the GPS 1pps and an externally input 1pps (or it can measure an
external frequency input – Models ET6000 and ET6010 only). It contains an RS-232 printer port.
Optional features listed in Appendix C are available to meet specific requirements. Refer to the
GPS Option/Connector Configuration sheet located in this manual for the options supplied with this
instrument. The Option Descriptions are located in Appendix C.
Note: The GPS antenna and cable described in this manual have been replaced as described in
“Appendix D: Antenna Replacement Kit” on page D-1.
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CHAPTER ONE
1.4 SPECIFICATIONS
The electrical, physical, and environmental specifications for the ExacTime are listed below.
1.4.1 GPS SUBSYSTEM
A.
TIME ACCURACY
After power-up, when LOCKED and using 200 Position Averages, will be better
than ± 125 nanoseconds relative to UTC with SA on within:
4 hours using a Rubidium oscillator.
2 hours using an Oven oscillator.
1 hour using a TCXO oscillator.
B.
FREQUENCY ACCURACY
90% of the time, better than: 1E-9 for TCXO
1.5E-10 for Oven (OCXO)
1E-11 for Rubidium
C.
POSITION ACCURACY
100m 2dRMS with SA
Less than 25m SEP without SA.
D.
MAXIMUM VELOCITY
515 meters/second. (1000 knotts/hour).
E.
TRACKING CHANNELS
Eight parallel.
F.
RECEIVER FREQUENCY
L1 1.575 GHz, C/A Code.
G.
ACQUISITION TIME
Time to first fix is less than 5 minutes with timing accuracy better than two μS and
frequency accuracy better than 1E-8. Full system accuracy with oven (OCXO)
oscillator is provided within 2 hours after LOCKED.
1.4.2 TIMING OUTPUTS
Rear panel BNCs J4 through J9 can output a 10MHz sine wave, IRIG B (AC), various pulse rates,
or alarm outputs. The following is the standard output configuration for the rear panel BNC
connectors. To change the outputs from the factory set standard configuration, see the paragraph
titled “Timing Outputs” in Chapter Two and the paragraph titled “Optional Pulse Rate Outputs” in
this section of the User’s Guide. Each output is via a 50Ω driver.
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ET6xxx ExacTime GPS TC & FG (Rev C)
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GENERAL INFORMATION
A.
J4 - TRACKING
This CMOS output level is “low” when the unit is actively acquiring data from
satellites. In the Stationary Mode, the unit has to track at least one satellite for the
Tracking level to go “low”. In the Dynamic Mode, the unit has to track at least four
satellites, for the Tracking level to go “low”, and all available satellites are used for
the time solution. The Tracking level is “high” when the unit is not acquiring data
from any satellite or the satellites are not used for the time solution (as in the
Flywheel Mode).
B.
J5 - LOCKED
When this CMOS output level is “low” (LOCKED), the 1pps output is coherent to
the internal 10MHz Oscillator. The DAC voltage controls the 10MHz oscillator
from which the 1PPS is derived. When this CMOS output level is “high” (i.e., not
locked), the 1pps is constantly being corrected (jammed) to on time using the 1PPS
from the GPS Receiver Module. In this mode, the 1PPS output can jump.
C.
J6 - 1PPS
This output is a thirty to fifty μsec wide pulse at CMOS levels. The rise and fall
times are ≤ 6 nanoseconds. It is positive (rising) edge on time, within ±125
nanoseconds relative to either UTC or GPS with six or more satellite averaging with
95% confidence.
D.
J7 - 10MHz SINE WAVE
This output has a nominal amplitude of one volt RMS into a 50Ω load.
Note: The output amplitude of the 10MHz sine wave is dependent on the internal
time base. This amplitude specification is for the Voltage Controlled
Temperature Compensated Crystal oscillator.
J7 – COINCIDENCE OUTPUT (ET6500 ONLY)
The Preset Coincidence Pulse occurs 200 Nanoseconds late. Its pulse width is
approximately two (2) microseconds wide, positive edge on-time. It is capable of
driving 10 LSTTL loads.
To enable this output, on the GPS Main Assembly 100015, jumper J17 pins 7-8
(only). See Figure 2-3 in Chapter Two.
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ET6xxx ExacTime GPS TC & FG (Rev C)
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CHAPTER ONE
E.
J8 - IRIG B (AC)
This output is Amplitude Modulated IRIG B122 Serial Time Code. This output is
available only after the unit has tracked satellites and set time.
Carrier
Modulation Ratio
Amplitude
1KHz
3:1
Three volts peak-to-peak on the Mark Pulse
Note: When enabled, the unit will output a modified IRIG B per IEEE Std. 1344
that has data in the Control Function bit area. Refer to Table One at the end
of this chapter for the Control Function Bit Assignments.
F.
J9 - IRIG B (DC)
This output is Pulse Width Modulated IRIG B002 Serial Time Code at CMOS levels.
This output is available only after the unit has tracked satellites and set time
G.
J11 – PRINTER OUTPUT PORT
This DB9 connector can output data to an RS232 compatible serial printer or
terminal.
It can be configured to operate in the Standard RS232 output or the One Second
RS232 ASCII Burst Mode output. For the operation and configurations, refer to
Chapters Three and Four.
H.
OPTIONAL PULSE RATE OUTPUTS
The following is a list of optional pulse rate outputs available for selection on BNC
connectors J4-J9. They are positive (rising) edge on-time. The majority of these
rates have a 80/20 duty cycle with the exception of the 10MHz and the 5MHz which
are square waves, and the 1PPM which is 40/20.
10MHz
100KHz
100Hz
.1Hz
5MHz
10KHz/2PPH*
10Hz/1PPH*
1PPM
1MHz
1KHz
1Hz
Models ET6000 and ET6010 output 10KHz and 10Hz. Model ET6500 outputs
2PPH and 1PPH. For further clarification and/or configuration of the above outputs,
See Chapters Two and Three.
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ET6xxx ExacTime GPS TC & FG (Rev C)
Symmetricom Inc
GENERAL INFORMATION
1.4.3 ACCURACY
The accuracy of the pulse rates listed in Section 1.4.2H is the same as that in Section 1.4.1A.
1.4.4 TIMING INPUTS
A.
J10 - 1PPS INPUT (TIME INTERVAL MEASUREMENT) or
EXTERNAL FREQUENCY MEASUREMENT or
SINGLE EVENT LOG
TIME INTERVAL MEASUREMENT
Used to measure the time interval between the internally generated GPS 1PPS and an
external 1PPS input. The resolution of this measurement is 1 nanosecond with
accuracy better than 10 nanoseconds. At power-up, this feature is DISABLED. If
enabled, the measurement is displayed on the Second Menu Screen. Refer to
Chapter Three. Also see paragraphs entitled, “Enable Time Interval,” “Disable Time
Interval,” and “Request Time Interval,” in Chapter Four of this User’s Guide.
EXTERNAL FREQUENCY MEASUREMENT (MODELS ET6000 AND
ET6010 ONLY)
Frequency Range
1Hz to 10MHz (discrete, whole numbers - not fractional parts).
Input Wave Form From 1Hz to 10MHz
Rectangular or square wave (minimum pulse width fifty nanoseconds).
Amplitude Range:
Logic “0” +0.2V ±0.2VDC
Logic “1” +2.4V to +15VDC
Input Wave Form From 100KHz to 10MHz
Sinusoidal Amplitude Range: 1 - 5 volts peak-to-peak
SINGLE EVENT LOG
This option provides the capability of logging the time occurrences of up to 256
events from one input. A pulse on the event input will cause the time to be
logged/stored on either the rising (positive going) or falling (negative-going) edge of
the input pulse. The edge designated as on time is programmable via the front panel
keyboard or remotely via the RS-232 I/O. Each event will have a defining number
from zero to 255 and the channel identifier.
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ET6xxx ExacTime GPS TC & FG (Rev C)
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CHAPTER ONE
The event memory can be read and/or cleared via the RS-232 I/O. Refer to Chapter
Four of this User's Guide. If the inputs exceed 256 events (occurrences), the new
data will be lost. If two events occur less than ten milliseconds apart, it is possible
that one of the events may be lost. This will be reported as a missed event in the
status code when the data is output. This event log option can also be enabled or
disabled. Refer to Chapter Four of this User’s Guide.
The event time resolution is from hundreds of nanoseconds through hundreds-ofdays.
1.4.5 J12 RS-232 I/O INTERFACE
Full remote control of all operating functions in a complete ASCII protocol. Baud rate, parity, word
length, and stop bits are selectable. See paragraph titled, “Fourth Menu Screen – RS232 I/O
Configuration” in Chapter Three of this User’s Guide. A description of the remote control
functions is contained in Chapter Four.
1.4.6 INTERNAL TIME BASE
This unit can have one of three internal time bases depending on customer requirements. Unless
otherwise specified, the following are the specifications for the oscillators used as the internal time
base - not the specifications of the unit’s 10MHz sine wave output.
A.
VOLTAGE CONTROLLED TEMPERATURE COMPENSATED CRYSTAL
OSCILLATOR (Configuration –TCXO) with the following specifications:
OUTPUT FREQUENCY/WAVEFORM
10MHz Sine Wave.
OUTPUT AMPLITUDE OF CRYSTAL OSCILLATOR
1.0 volt peak-to-peak minimum clipped sine wave into 20KΩ load. Harmonics 20dBc maximum.
AGING RATE
1E-7 per day or ±1.0PPM maximum per year.
1-8
ET6xxx ExacTime GPS TC & FG (Rev C)
Symmetricom Inc
GENERAL INFORMATION
PHASE NOISE
The following specifications are for the 10MHz sine wave output available on rear
panel BNC connectors J4-J9:
1Hz
-72 dBc/Hz
10Hz
-93 dBc/Hz
100 Hz
-115 dBc/Hz
1KHz
-126 dBc/Hz
10KHz
-136 dBc/Hz
100 KHz
-136 dBc/Hz
TEMPERATURE RANGE AND STABILITY
±1.0PPM from -30o to +75oC.
ADJUSTMENT RANGE
±3.0PPM minimum by internal manual trimmer.
VOLTAGE CONTROL
±3.0PPM minimum from +0.5 to +4.5 VDC.
B.
LOW NOISE OVEN OSCILLATOR (Configuration –OCXO) with the
following specifications:
OUTPUT FREQUENCY/WAVEFORM
10MHz Sine Wave.
OUTPUT AMPLITUDE OF CRYSTAL OSCILLATOR
1.0 volt RMS into 50 ohms.
AGING RATE
±5 x 10-10 per day, ±5 x 10-8 per year.
TEMPERATURE STABILITY
±1 x 10-8 over a temperature range of –20ºC to +75ºC.
OPERATING TEMPERATURE
–20ºC to +75ºC.
ALTITUDE
Sea level to +50,000 feet.
ELECTRICAL TUNING
±1PPM (minimum) / ±2PPM (maximum).
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ET6xxx ExacTime GPS TC & FG (Rev C)
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CHAPTER ONE
CONTROL VOLTAGE
0 to +6 volts.
MECHANICAL FREQUENCY ADJUST
±1PPM (minimum) / ±3PPM (maximum).
The following specifications apply to the selected 10MHz sine wave output at a +13
dbm level:
HARMONICS
-45 dBc
SPURIOUS NOISE
>-70 dBc
PHASE NOISE
1Hz
10Hz
100Hz
1KHz
10KHz
100KHz
C.
-100 dBc/Hz
-120 dBc/Hz
-140 dBc/Hz
-144 dBc/Hz
-144 dBc/Hz
-144 dBc/Hz
RUBIDIUM OSCILLATOR (either X72 or LPRO) with the following
specifications:
OUTPUT FREQUENCY/WAVEFORM
10MHz Sine Wave.
OUTPUT AMPLITUDE OF OSCILLATOR
0.55VRMS ±0.05VRMS into 50 ohms.
AGING RATE
≤5 x 10-11 per month, 5 x 10-10 per year.
OPERATING TEMPERATURE
–20ºC to +70ºC measured at the base plate.
STORAGE TEMPERATURE
-55ºC to +85ºC
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ET6xxx ExacTime GPS TC & FG (Rev C)
Symmetricom Inc
GENERAL INFORMATION
ALTITUDE
-200 feet to +40,000 feet (operating).
FREQUENCY CONTROL - INTERNAL TRIM RANGE
±1.5 x 10-9
FREQUENCY CONTROL - EXTERNAL (ELECTRICAL) TRIM RANGE
±1.5 x 10-9 (0V to +5V).
The following specifications apply to the selected 10MHz sine wave output at a +13
dbm level:
HARMONICS
-42 dBc
SPURIOUS NOISE
>-80 dBc
PHASE NOISE
1Hz
10Hz
100Hz
1KHz
10KHz
100KHz
-82 dBc/Hz
-91 dBc/Hz
-131 dBc/Hz
-144 dBc/Hz
-146 dBc/Hz
-147 dBc/Hz
1.4.7 PRIMARY POWER
Models ET6000 and ET6010 utilize a Power Entry Module and the Standard Power Supply.
Input Voltage
Input Frequency Range
AC = 85 to 264 VAC (47-440 Hz) @ less than thirty watts.
DC = +120 to 373 VDC
47 to 440 Hz
Note: When using 120 VAC, install 1 Amp Line Fuses. When using 220 VAC, install ½ Amp
Line Fuses. Fuses are found in the Shipping Kit.
Model ET6500 utilizes a Power Entry and Alarm Relay Module (Assembly 55191) and the
Standard Power Supply.
This module takes a nominal input of 115 VAC or 125 VDC through a rear panel terminal strip and
provides +5 and ±12 VDC to power the GPS Time Code and Frequency Generator. It provides
timing and fault status relay closures.
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CHAPTER ONE
It also has the capability of measuring the frequency, phase angle, and elapsed time offset of an
externally applied 50 or 60Hz AC sine wave.
Input Voltage
Input Frequency Range
Fault Relay
Timing Relay
Relay Contact Ratings
50/60Hz Measurement Input
AC = 85 to 264 VAC (47-440 Hz) @ less than thirty watts.
DC = +120 to 373 VDC
47 to 440 Hz
Closure on fault.
Closure when not locked.
10 watts, 0.5 amps, 200 volts.
85-250 VAC.
Note: When using 120 VAC, install 1 Amp Line Fuses. When using 220 VAC, install ½ Amp
Line Fuses. Fuses are found in the Shipping Kit.
All input/outputs from the 55191 are from a rear panel terminal strip TB1.
All input/outputs have metal oxide varistors for transient voltage suppression.
The pin assignments for TB1 are shown below (as viewed from the rear of the unit):
TB1-1
TB1-12
Pin Assignments
TB1-1
TB1-2
TB1-3
TB1-4
TB1-5
TB1-6
TB1-7
TB1-8
TB1-9
TB1-10
TB1-11
TB1-12
1-12
AC HI Input
AC LO Input
Chassis Ground
Fault Relay - Common Contact
Fault Relay - Normally Closed Contact
Timing Relay - Common Contact
Timing Relay - Normally Closed Contact
50/60Hz Measurement Input - HI
50/60Hz Measurement Input - LO
Not Used
Not Used
Not Used
ET6xxx ExacTime GPS TC & FG (Rev C)
Symmetricom Inc
GENERAL INFORMATION
This Power Entry and Alarm Relay Module has two relay closures to indicate timing/fault of the
unit. The fault relay output on the rear panel terminal strip TB1-4 and 5 will provide contact
closure upon the following conditions:
A processor error, from the GPS Receiver Module
Loss of +5VDC.
If the DAC value goes below 300 or above 65,000.
The timing relay (output on the rear panel terminal strip TB1-6 and 7) provides a contact closure
until the unit has achieved oscillator lock. For example, until the front panel LOCKED LED
illuminates.
1.4.8 DIMENSIONS
Chassis:
Height
Width
Depth
1.75 Inches. Model ET6010 is 3.50 Inches.
17 Inches.
12 Inches Maximum.
1.4.9 WEIGHT
ExacTime Unit
Antenna/Preamp
Approximately ten pounds.
Less than 1.5 pounds.
1.4.10 ENVIRONMENT
A.
OPERATING TEMPERATURE
ExacTime Unit:
0oC to +50oC.
Antenna/Preamp:
-40oC to +85oC.
B.
STORAGE TEMPERATURE
ExacTime Unit:
-20oC to +70oC.
Antenna/Preamp:
-55oC to +100oC.
C.
HUMIDITY
ExacTime Unit
Antenna/Preamp
Symmetricom Inc
95% (non-condensing) up to 40oC.
Unlimited.
ET6xxx ExacTime GPS TC & FG (Rev C)
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CHAPTER ONE
1.5 ADDITIONAL SPECIFICATIONS
The following is additional information regarding the GPS RPU (Receiver Processing Unit) located
within the GPS Time Code and Frequency Generator, and the antenna/preamp.
1.5.1 ANTENNA/PREAMP
The antenna/preamp satisfies performance requirements at altitudes of up to +59,000 feet.
1.5.2 GPS RPU AND ANTENNA
The GPS RPU (Receiver Processor Unit) and antenna/preamp set has burn-out protection which
prevents damage from an RF signal at power densities of up to one watt at the antenna. The RF
signal must be 100MHz out of band. The C/A band of 1575.42MHz has a bandwidth of 20.48MHz.
1.6 FUNCTIONAL CHARACTERISTICS
The following is a description of the functional characteristics of the GPS RPU.
1.6.1 ACQUISITION
The GPS RPU position fix, acquisition and tracking processes feature the ability to determine its
own position (that of the antenna/preamp), not the TC&FG Module, utilizing a position averaging
technique and assuming the unit has been set to the “AUTO,” or “DYNAMIC” mode. See “Third
Menu Screen” in Chapter Three of this User’s Guide for selection and an explanation of each
MODE SELECTION using the front panel LCD and Keyboard. Mode selection may also be made
via the RS-232 Interface. See the paragraph titled “Select Mode” in Chapter Four for mode
selection using the RS-232 I/O.
The GPS RPU has an eight parallel channel design capable of tracking eight satellites
simultaneously. The module receives the L1 GPS signal (1575.42 MHz) from the antenna and
operates off the coarse/acquisition (C/A) code tracking. The code tracking is carrier aided.
Time recovery capability is inherent in the architecture.
The GPS RPU is designed specifically for precise timing applications.
Upon powering up the system, the unit begins a systematic search for satellites which are expected
to be above the horizon. In this start-up mode of operation it uses the last position data stored in the
battery backed RAM as a starting point. If it is in the A (Auto) mode, it will begin doing a running
average of position fixes. After 200 averages, the unit will have acquired its position and will
switch automatically to the S (Stationary) mode. The number of position averages is user selectable
via the RS-232 I/O. See paragraph titled “Number of Averages” in Chapter Four.
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GENERAL INFORMATION
If in the D (Dynamic) mode, the unit will use the last position data stored in battery backed RAM as
a starting point to begin its systematic search for satellites. It will continue to do three dimensional
position fixes (latitude, longitude, and altitude) upon acquiring four or more satellites until the
mode is changed. If in the “STATIONARY” mode and a known position has been entered, the unit
will use the position information stored in battery backed RAM as a starting point to begin its
systematic search for satellites.
1.6.2 SIGNAL INTERRUPTION
During GPS ExacTime operation, should the signal from the satellites be interrupted, the antenna
disconnected or blocked, the reacquisition time is dependent upon events during the interruption.
For the first minute of the interruption, the GPS RPU continues to search for the last satellite signals
to which it was locked. If the signal is regained during this minute, reacquisition will be almost
immediate if the users velocity has not changed by more than fifty meters per second.
If the velocity has changed, the Doppler frequency has shifted. The GPS RPU must finish its search
of previous satellite signals and will then expand the search to reacquire. The search time will
depend on the amount of velocity change, but it is usually within fifteen seconds.
If the signal is regained within one minute, the expanding frequency search will already have begun
cycling. In this case, reacquisition may require a few minutes depending upon where the RPU is in
the frequency search when the signal is regained.
If the signal is regained within one hour, the same search must take place, then the new ephemeris
data must be collected. In this case, reacquisition will occur within a few minutes.
The user should realize that obstructions, shading of the antenna, and satellite transmission
interruptions can degrade the signal reception and length of acquisition times.
1.6.3 POSITION AND VELOCITY SOLUTION
The position and velocity, along with the time tag of the measurement, are digitally output from the
RPU to the GPS ExacTime Processor. The position data is three dimensional and available in a
latitude, longitude, and altitude (WGS-84) coordinate frame. The GPS solutions are computed at
typically less than one second intervals.
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CHAPTER ONE
1.6.4 DYNAMIC CAPABILITY
The following specifications are operational dynamic limits for GPS Timing Unit operation.
A.
VELOCITY
The velocity of the user is limited to 515 m/sec for proper GPS Receiver operation.
B.
ACCELERATION
User acceleration cannot exceed four 4g (39.2 m/sec2).
C.
JERK
The rate of change of acceleration is not to exceed 5 m/sec3.
1.6.5 RF JAMMING RESISTANCE AND BURN-OUT PROTECTION
The GPS RPU provides resistance to all forms of jamming whose effect results in jamming to signal
power ratios of twenty-four dB or less as measured at the antenna/preamplifier interface when the
input signal is at -163 dBm. The GPS RPU/antenna set provides burn-out protection to prevent
damage at RF power densities up to one watt (CW) at the antenna, provided the signal is 100MHz
out of the GPS frequency band.
1.6.6 SYSTEM STATUS AND DIAGNOSTICS
All digital circuitry is tested to the greatest extent possible at power-up. This includes testing the
memory systems, and processor, as well as monitoring the performance of the channel processors.
Should a failure occur in any of these areas, it will be available as status on the RS-232 I/O and will
be displayed on the LCD Display as an error.
1.6.7 GPS POSITION SOLUTION MODES
The user may select either the Auto Mode or the Dynamic Mode for position solutions. (In the
Stationary Mode, the position is already predetermined.) See SELECT MODE in Chapter Three for
front panel LCD and keyboard selection. See Chapter Four for MODE SELECTION using the RS232 I/O.
The AUTO mode is actually a combination of the DYNAMIC and the STATIONARY modes.
When powered up in the AUTO mode, the unit will acquire some number of positions in the
DYNAMIC mode calculating an average latitude, longitude, and altitude when there are at least
four satellites in view. The factory set default number of averages is 200. These position averages
are loaded into battery backed memory for future use.
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ET6xxx ExacTime GPS TC & FG (Rev C)
Symmetricom Inc
GENERAL INFORMATION
The number of positions used to calculate the averages is user selectable via the RS-232 I/O
interface. Once the average position has been determined, the unit will switch to the
STATIONARY mode. The AUTO mode provides an averaged solution of the time information
from as many satellites as the receiver is tracking.
In the DYNAMIC mode, the system will select the best available satellites based on PDOP
(Position Dilution Of Precision) and provide a continuous navigational solution in three dimensions
(latitude, longitude, and altitude). The DYNAMIC mode does not automatically switch to the
STATIONARY mode.
1.6.8 ELEVATION MASK ANGLE
This mask is used to specify the elevation angle below which the use of satellites is prohibited.
Signal integrity from satellites very low on the horizon can be degraded. Obstructions will block
the signal. For land-based applications where there are local obstructions (foliage, buildings, etc.)
system performance will be smoother with an elevation mask of fifteen to twenty degrees. For
marine or aircraft applications, it is usually possible to use the satellites very close to the horizon,
although the pitch/roll should be considered. The system default is that set by the user. Refer to
Chapter Four, paragraph titled “ENTER ELEVATION MASK ANGLE” for instruction on selecting
elevation mask.
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CHAPTER ONE
Table One
Control Function Bit Assignments
Designation
Explanation
IRIG B
Control
Positive ID
Bit #
P50
1
Year, BCD 1
P51
2
Year, BCD 2
P52
3
Year, BCD 4
P53
4
Year, BCD 8
P54
5
Not Used
P55
6
Year, BCD 10
P56
7
Year, BCD 20
P57
8
Year, BCD 40
P58
9
Year, BCD 80
P59
N/A
P6
P60
10
Leap Second Pending
(LSP)
P61
11
Leap Second (LS)
P62
12
Not Used
P63
13
Not Used
P64
14
Time Offset Sign
P65
15
Time Offset - Binary 1
P66
16
Time Offset - Binary 2
P67
17
Time Offset - Binary 4
P68
P69
P70
P71
P72
P73
P74
P75
P76
P77
P78
P79
1-18
18
N/A
19
20
21
22
23
24
25
26
27
N/A
Time Offset - Binary 8
P7
Time Offset - 0.5 Hour
Time Quality
Time Quality
Time Quality
Time Quality
PARITY
Not Used
Not Used
Not Used
P8
Last two digits of year in BCD.
IBID.
IBID.
IBID.
Unassigned.
Last two digits of year in BCD.
IBID.
IBID.
IBID.
Position identifier number six.
Becomes 1 up to 59 s BEFORE leap second
insert.
0 = add leap second, 1 = delete leap second.
Time offset sign 0 = +, 1 = Offset from coded IRIG B time to UTC time.
IRIG coded time plus time offset (including
sign) equals UTC time at all times (offset will
change during daylight savings).
Position identifier number.
0 = none, 1 = additional 0.5 h time offset
4 bit code representing approx. clock time error
0000 = clock locked, maximum accuracy.
1111 = clock failed, data unreliable.
Parity on all preceding data bits.
Unassigned.
Unassigned.
Unassigned.
Position identifier number eight.
ET6xxx ExacTime GPS TC & FG (Rev C)
Symmetricom Inc
CHAPTER TWO
INSTALLATION
2.0 INTRODUCTION
This section describes the unpacking, inspection, and installation of the GPS Timing Unit.
2.1 UNPACKING AND INSPECTION
The GPS Timing Unit is packaged in one shipping container. Inspect the unit for visible damage
(scratches, dents, etc.). If the instrument is damaged, immediately notify both Symmetricom Inc
and the responsible carrier. Keep the shipping container and packing material for the carrier’s
inspection.
Note: When communicating with either Symmetricom Inc or the responsible carrier regarding
shipping damage, refer to the serial number. This number is located on the rear panel of
the GPS Timing Unit.
2.2 RACK MOUNTING PROCEDURE
The GPS Timing Unit is designed for standard nineteen inch rack mounting.
Optional chassis slides are recommended if the unit is to be installed in an equipment rack. If
slides are not used, a supporting bar or tray should be provided for the rear of the instrument.
The chassis slides attach to the sides of the GPS Timing Unit. To mount it using the optional
slide mounting kit, use the eight #6 self tapping screws provided in the kit.
*** CAUTION ***
General Cautions/Hazards to be considered when installing the GPS Timing Unit into an
equipment rack:
2.2.1 TMRA – The maximum recommended ambient temperature (Tmra) that this equipment
is specified to operate in is 50°C.
2.2.2 ELEVATED OPERATING AMBIENT TEMPERATURE – If installed in a closed or
multi-unit rack assembly, the operating ambient temperature of the rack environment
may be greater than room ambient. Therefor, consideration should be given to installing
the equipment in an environment compatible with the maximum rated ambient
temperature (Tmra).
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ET6xxx ExacTime GPS TC & FG (Rev C)
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CHAPTER TWO
2.2.3 REDUCED AIR FLOW - The equipment has no cooling fans and depends on
convection for cooling. Installation in a rack may cause an excessive heat rise if sufficient air
flow is not available. Installation should be such that the amount of air flow required for safe
operation of the equipment is not compromised.
2.2.4
MECHANICAL LOADING – Mounting of the equipment in the rack should be such
that a hazardous condition is not achieved due to uneven mechanical loading.
2.2.5 CIRCUIT OVERLOADING – Consideration should be given to the connection of the
equipment to the supply circuit and the effect that overloading of circuits might have on
over current protection and supply wiring. Appropriate consideration of equipment
nameplate ratings should be used when addressing this concern.
2.2.6 RELIABLE EARTHING – Reliable earthing of rack-mounted equipment should be
maintained. Particular attention should be given to supply connections other than direct
connections to the branch circuit (e.g., use power strips).
2.3 ANTENNA/PREAMP INSTALLATION
The antenna/preamp is enclosed in a weatherproof housing suitable for permanent installation in
an exposed location. The unit should be located with an unobstructed view of the horizon for
optimum tracking conditions. The signal will not penetrate foliage. Multi-path signals may be
generated from vertical surfaces, which are above the plane of the base of the antenna/preamp.
The antenna/preamp, which is designed for fixed ground or marine applications, requires no
special ground plane, but a large metal surface below the antenna/preamp may reduce multi-path
effects. The unit may be mounted on any level surface or on a vertical pipe having ¾ - 14 NPT
threads. See Figures 2-1, and 2-4, “Antenna/Preamp Installation,” for mounting.
*** CAUTION ***
A high powered radar beamed directly at the antenna/preamp may damage it and a signal
within a few MHz of the carrier frequency may jam the GPS RPU.
2.4 ANTENNA/PREAMP INTERFACE CONNECTIONS
A fifty foot long RG-58A/U coaxial cable is provided to connect the antenna/preamp to the GPS
Timing Unit. For cable lengths greater than seventy-five feet, an optional low loss coaxial cable
(such as Belden 9913) must be used.
Note: The GPS antenna and cable described in this manual have been replaced as described in
“Appendix D: Antenna Replacement Kit” on page D-1.
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ET6xxx ExacTime GPS TC & FG (Rev C)
Symmetricom Inc
INSTALLATION
The antenna/preamp power is provided by the GPS Timing Unit via the coaxial cable. No
additional cabling is required to power the antenna/preamp.
Cables attached to the antenna/preamp should be strain relieved and secured to some permanent
fixture.
Cables attached to the antenna/preamp which are exposed to the elements should be wrapped
with a weather-proof tape after being connected.
Cables from the antenna/preamp should be secured as required with cable clamps and should not
put a strain on the antenna/preamp connector as it may damage the unit.
2.5 PRIMARY POWER CONNECTION
The GPS Timing Unit is operated from external AC power. The AC power specifications are
listed in the specification section in Chapter One of this User’s Guide.
Models ET6000 and ET6010 utilize a power cord that plugs into a Power Entry Module.
Note: Check the AC line fuses located in the power entry module on the rear panel and assure
the correct fuse is installed for the AC Line voltage being used to power the unit. The
AC line fuses should be 1 Amp for an AC input of 120 volts or ½ amp for an AC input of
220 volts.
Model ET6500 utilizes a terminal strip Power Entry and Alarm Relay Module (Assembly
55191).
Note: Check the AC line fuses located in the power entry module inside the unit and assure the
correct fuse is installed for the AC Line voltage being used to power the unit. The AC
line fuses should be 1 Amp for an AC input of 120 volts or ½ amp for an AC input of 220
volts.
The terminal strip pin designations are shown below:
REAR VIEW OF ET6500 SHOWING 55191
POWER ENTRY AND ALARM RELAY MODULE
1
Symmetricom Inc
TB1
9
ET6xxx ExacTime GPS TC & FG (Rev C)
2-3
CHAPTER TWO
TB1 Pin 1
TB1 Pin 2
TB1 Pin 3
TB1 Pin 4
TB1 Pin 5
TB1 Pin 6
TB1 Pin 7
TB1 Pin 8
TB1 Pin 9
PIN ASSIGNMENTS
AC High Input
AC Low Input
Chassis Ground
Fault Relay – Common Contact
Fault Relay – Normally Closed Contact
Timing Relay – Common Contact
Timing Relay – Normally Closed Contact
50/60Hz Measurement Input - High
50/60Hz Measurement Input - Low
This assembly has two relay closures to indicate timing/fault of the unit. The fault relay output
on the rear panel terminal strip TB1-4 and 5 will provide contact closure upon the following
conditions:
A processor error, Channel One error, or Channel Two error from the GPS receiver.
Loss of +5VDC.
If the DAC value goes below 300 or above 65,000.
The timing relay output on the rear panel terminal strip TB1-6 and 7 provides a contact closure
until the unit has achieved unit stabilization. For example, until the front panel LOCKED LED
illuminates.
If this unit is provided with a power supply other than the standard, its specifications will be
found in the Option Description envelope located on the inside cover of this User’s Guide.
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ET6xxx ExacTime GPS TC & FG (Rev C)
Symmetricom Inc
INSTALLATION
Figure 2-1
Antenna/Preamp Installation
5000-0001 Bullet Antenna
(Mfg P/N 25045-10*)
* Dash number is the software revision. This
is subject to change without notice.
1704-9389 Type F to Type N
Connector Adapter
1. Material* PVC or CPVC Schedule 80, Gray Color.
Note: The GPS antenna and cable described in this manual have been replaced as described in
“Appendix D: Antenna Replacement Kit” on page D-1.
Symmetricom Inc
ET6xxx ExacTime GPS TC & FG (Rev C)
2-5
CHAPTER TWO
2.6 GPS TIMING UNIT INTERFACE CONNECTIONS
The GPS Timing Unit interface connections consist of cabling to the antenna/preamp assembly
from J2 on the unit’s rear panel, the RS-232 I/O port J12 (if used), and the time and frequency
inputs and outputs and/or other optional inputs or outputs.
2.6.1 RS-232 I/O INTERFACE J12
This port provides the basic read/write mode of operation.
Before connecting a peripheral device to this port, read the manual accompanying the product
and be aware of the necessary precautions. Determine the BAUD rate, parity word length, stop
bits, and interconnections with the equipment.
This I/O port is configured as a DCE, and is intended to be used by intelligent peripherals such
as a computer. The RS-232 I/O port uses a standard DB-9 I/O connector with the pin
configuration shown in Figure 2-2.
The RS-232 protocol is described in Chapter Four in the paragraph titled “Information.”
Figure 2-2
RS-232 I/O Cable Pin Assignments
GPS ExacTime
1
2
3
4
5
6
7
8
9
Computer
1
2
3
4
5
6
7
8
9
RX
TX
DTR
GND
DSR
RTS
CTS
The RS-232 I/O interface uses a standard PC compatible one-to-one cable using nine Pin D type
connectors. Handshaking is not used. Pin 6 (DSR) and pin 8 (CTS) on J12 are internally set
high.
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ET6xxx ExacTime GPS TC & FG (Rev C)
Symmetricom Inc
INSTALLATION
2.6.2 PRINTER OUTPUT PORT J11
This connector can output data to an RS232 compatible serial printer or terminal. It can be
configured to output data in the Standard configuration or the One Second ASCII Burst Mode
Output. Refer to Chapter Three (Tenth Menu Screen) for more specific details on configuration
and operation.
Connector configuration:
1
2
3
4
5
6
7
8
9
NOT USED
INPUT LINE TO ET6XXX - NOT USED
TX (Data Out)
NOT USED
GROUND
NOT USED
NO CONNECTION
OUTPUT LINE FROM ET6XXX - NOT USED
NOT USED
2.6.3 TIMING OUTPUTS
Various timing output signals can be provided on the rear panel BNC connectors J4 through J9.
The selection of these outputs is made using jumper pins/blocks on the GPS Main Assembly
100015, as shown in Figure 2-3, and the front panel keyboard, or via the RS-232 I/O.
To check or reconfigure these outputs via the front panel keyboard, see the paragraph titled
“Configuration of Rear Panel BNC Connectors J4-J9” in Chapter Three of this User’s Guide.
To check or reconfigure these outputs via the RS-232 I/O, see the paragraphs titled “Request
MUX Outputs,” and “Set MUX Output” in Chapter Four of this User’s Guide.
The standard configuration is as follows:
J4 Tracking (TTL)*
J5 Locked (TTL)**
J6 1pps
J7 10MHz Sine Wave
J8 IRIG B (AC)
J9 IRIG B (DC)
J10 1pps Input
Symmetricom Inc
Jumper J14 7 and 8, and J24 1 and 2.
Jumper J15 7 and 8, and J25 1 and 2.
Jumper J16 1 and 2.
Jumper J17 5 and 6.
Jumper J18 3 and4, and J28 1 and 2.
Jumper J19 1 and 2, and J29 1 and 2.
(Time Interval Measurement).
ET6xxx ExacTime GPS TC & FG (Rev C)
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CHAPTER TWO
* Tracking output is low when unit is tracking, high when unit is not tracking.
** Locked output is low when unit is locked, high when unit is not locked.
For additional pulse rate selections available on BNC connectors J4-J9, see Chapter One of this
User’s Guide.
Configurations other than the standard above will be found in the GPS Option/Connector
Configuration Sheet located in this User’s Guide.
2.6.4 1PPS INPUT
A 1pps pulse can be input on a rear panel BNC connector labeled J10. This input can be utilized
when making time interval measurements between the internal corrected GPS 1pps and an
external 1pps input pulse. This is a multipurpose input that may also be optionally utilized to
record an event or accept a frequency for external measurement purposes.
2.6.5 OSCILLATOR CONFIGURATION
The jumper blocks at J27 enable the processor (and the program) to determine which oscillator is
installed on the board. This provides for the selection of the specific gain and correction voltage
(i.e. the discipline voltage) for each oscillator. The jumpers are factory set for the oscillator in
your specific configuration, and shouldn’t need to be changed unless the oscillator type is
changed.
J27 OSCILLATOR CONFIGURATION
TCXO
OCXO
LPRO
RB
1
2
1
2
1
2
1
2
3
4
3
4
3
4
3
4
For the TCXO, no jumpers are installed.
For the OCXO, jumper pins 1-2.
For the Rubidium LPRO, jumper pins 3-4.
For the Rubidium X-72, jumper pins 1-2, and 3-4.
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ET6xxx ExacTime GPS TC & FG (Rev C)
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Symmetricom Inc
J9
6
8
5
7
10 MHz Sine Unused -
7
5
8
6
4
2
4
2
Unused -
10 MHz Sine -
AC Code Out -
MUX Ch: 4 -
7
5
3
1
J17
J7
8
6
4
2
Unused -
10 MHz Sine -
AC Code Out -
MUX Ch: 3 -
7
5
3
1
J16
J6
8
6
4
2
Notes:
1. Mux Channel 1 can be output on both J4 and J9.
2. Mux Channel 2 can be output on both J5 and J8.
3. Shaded areas are the standard (default) configuration.
Inset
ET6xxx ExacTime GPS TC & FG (Rev C)
J15
5
7
3
1
4
3
Relay-
2
1
J25
Buffered Out -
4
2
Relay-
3
1
J24
The diagram below illustrates the jumper positions
for "Relay Outputs."
Buffered Out -
4
2
8
6
4
2
Relay-
3
1
Locked-
J24 & J25 above are jumpered for "Buffered
Outputs."
J5
J25
10 MHz Sine -
AC Code Out -
MUX Ch: 2 -
Buffered Out -
Example: Inserting jumper blocks into J14-5&6, and J24-1&2 will output a 10 MHz sine wave on rear panel BNC connector J4.
Unused -
10 MHz Sine -
3
4
3
AC Code Out -
AC Code Out -
J18
1
MUX Ch: 2 -
3
2
Event 3 In -
1
J19
4
Buffered Out -
1
3
Event 2 In
-
2
J28
J8
MUX Ch: 1 -
1
J29
Buffered Out -
Time Interval Input
Ext. Freq. Measurement Input
Event 1 Input
J10
Rear
4
7
5
3
1
J14
8
6
4
2
Relay-
3
2
J24
1
Main GPS Board
Assembly 100015
Tracking -
10 MHz Sine -
AC Code Out -
MUX Ch: 1 -
Buffered Out -
See Inset
Below
J4
INSTALLATION
Figure 2-3
GPS Main Assembly 100015
2-9
CHAPTER TWO
Figure 2-4
Antenna/Preamp Installation
5000-0001
Bullet Antenna
(Mfg P/N 25045-10)
1704-9389 Type F
to Type N Connector
Adapter
Antenna Mast 711700:
Secure to an existing vent pipe using hose
clamps or secure to a flat surface using
pipe straps and screws.
Antenna Cable with
Type N Connector
Note: The GPS antenna and cable described in this manual have been replaced as described in
“Appendix D: Antenna Replacement Kit” on page D-1.
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ET6xxx ExacTime GPS TC & FG (Rev C)
Symmetricom Inc
CHAPTER THREE
OPERATION
3.0
INTRODUCTION
This chapter describes the operation of the basic GPS ExacTime. Operating instructions for the
optional features are contained Appendix C of this User’s Guide.
Note: The GPS antenna and cable described in this manual have been replaced as described in
“Appendix D: Antenna Replacement Kit” on page D-1.
3.1
OPERATIONAL STEPS
The following are the initial installation steps necessary for the operation of your unit:
•
Connect the appropriate input/output cables and components including as a minimum the
power cable, the antenna, and antenna cable.
•
Apply power to the unit. Initially the front panel TRACKING and LOCKED LED’s will
flash and the POWER LED will illuminate. This signifies that the microprocessor and
associated circuitry have been initialized correctly and are operating.
•
At this point, the Operational Mode needs to be selected. See the section entitled “SET-UP
MENU SCREEN – SET MODE” (this chapter). The criteria for selecting the various modes
can be summarized as follows:
AUTO – Use if your position (i.e. the position of the antenna) is unknown, and
stationary. This is the default mode. See section titled “Initialization (Unknown
Position).”
DYNAMIC - This mode would be selected if the unit is mounted in a moving vehicle.
By definition, your position is unknown. See section titled “Initialization (Unknown
Position).”
STATIONARY - Use if your position is known, stationary, and accurately surveyed.
See the section titled “Initialization (Known Position).”
FLYWHEEL – To use your unit as a time code generator only. Position is not
determined and the internal oscillator is not disciplined.
3.1.1 INITIALIZATION (UNKNOWN POSITION)
•
Set the SET MODE to “AUTO” if it is not already in the “AUTO” mode. The unit will then
start to track satellites (refer to the Main Menu Screen – this chapter). When satellites are
acquired and ready for time solution, the TRACKING LED will illuminate signifying that
the unit is tracking satellites.
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•
The message “GPS Time Not Acquired” will be displayed until the unit receives the Leap
Second information. At that point, the unit will set time and the message “ZZZZ Stabilizing
XX” will be displayed.
ZZZZ = The internal 10MHz oscillator installed in the unit. Either TCXO, OCXO,
LPRO, or X72. (LPRO and X72 are both versions of a Rubidium oscillator.)
XX = A number (10 to 1) indicating the progression through a series of oscillator
stabilization steps.
•
After the oscillator stabilization step is finished, the unit will begin doing position averaging
in order to derive the position. The number of averages is set to the default number of 200
but is user selectable via the RS-232 I/O Interface. See paragraph titled “Number of Position
Averages” in Chapter Four of this User’s Guide. A position fix takes approximately seven
seconds, so the position averaging itself could take about 20 minutes.
•
Once the unit has accomplished its position averaging, the unit will switch to the
STATIONARY mode. At this time, the 1pps will be coherent with the internal disciplined
10MHz oscillator.
•
Unit stabilizing will begin. The unit starts to discipline the internal oscillator. Once the
unit’s discipline process has stabilized, the LOCKED LED will illuminate indicating that the
unit is completely functional.
For a TCXO oscillator, this process will take about 30 minutes.
For a OCXO oscillator, this process will take about 90 minutes.
For a Rubidium oscillator, this process will take about 3.5 hours.
•
If the LOCKED front panel LED does not illuminate within the specified time above, check
the DAC value displayed on the POSITION MENU SCREEN, and/or the status displayed on
the MAIN MENU SCREEN, or via the RS-232 I/O interface (see Chapter Four, paragraphs
titled “Request DAC Value,” and “Print Time, Status, Error Code, and Satellite Vehicle
Numbers” respectively). If DAC value number has approached either one of its extremes
(00000 or 65535), the internal oscillator needs to be nulled/calibrated. Refer to the “Internal
Oscillator Calibration” procedure in Chapter Five of this User’s Guide.
•
If the unit stops tracking satellites at any point after initial power-up, the TRACKING LED
will be turned off. At that time, an internal elapsed time counter will be started and the short
term oscillator stability will be stored in memory. Based upon the type of internal 10MHz
oscillator installed in the unit, the LOCKED LED will remain illuminated until the internal
elapsed time counter has timed out.
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ET6xxx ExacTime GPS TC & FG (Rev C)
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OPERATION
For a TCXO oscillator, it will take about 30 minutes.
For a OCXO oscillator, it will take about 60 minutes.
For a Rubidium oscillator, it will take about 4 hours.
3.1.2
•
INITIALIZATION (KNOWN POSITION)
Set the SET MODE to “STATIONARY” mode. See paragraph titled “Select Mode” under
the SET-UP MENU SCREEN in this chapter for mode selection.
Enter the known position (latitude, longitude, and altitude) of the GPS antenna. (The GPS
antenna described in this manual has been replaced as described in “Appendix D: Antenna
Replacement Kit” on page D-1.)
•
) See paragraph titled “Set Position” in this chapter.
•
The unit will start to track satellites (refer to the Main Menu Screen – this chapter). When
satellites are acquired and ready for time solution, the TRACKING LED will illuminate
signifying that the unit is tracking satellites.
•
The message “GPS Time Not Acquired” will be displayed until the unit receives the Leap
Second information. At that point, the unit will set time and the message “ZZZZ Stabilizing
XX” will be displayed.
ZZZZ = The internal 10MHz oscillator installed in the unit. Either TCXO, OCXO,
LPRO, or X72. (LPRO and X72 are both versions of a Rubidium oscillator.)
XX = A number (10 to 1) indicating the progression through a series of oscillator
stabilization steps.
•
After the oscillator stabilization step is finished, unit stabilizing will begin. The unit starts to
discipline the internal oscillator. Once the unit’s discipline process has stabilized, the
LOCKED LED will illuminate indicating that the unit is completely functional.
For a TCXO oscillator, this process will take about 30 minutes.
For a OCXO oscillator, this process will take about 90 minutes.
For a Rubidium oscillator, this process will take about 3.5 hours.
•
If the LOCKED front panel LED does not illuminate within the specified time above, check
the DAC value displayed on the POSITION MENU SCREEN, and/or the status displayed on
the MAIN MENU SCREEN, or via the RS-232 I/O interface (see Chapter Four, paragraphs
titled “Request DAC Value,” and “Print Time, Status, Error Code, and Satellite Vehicle
Numbers” respectively). If DAC value number has approached either one of its extremes
(00000 or 65535), the internal oscillator needs to be nulled/calibrated. Refer to the “Internal
Oscillator Calibration” procedure in Chapter Five of this User’s Guide.
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CHAPTER THREE
•
If the unit stops tracking satellites at any point after initial power-up, the TRACKING LED
will be turned off. At that time, an internal elapsed time counter will be started and the short
term oscillator stability will be stored in memory. Based upon the type of internal 10MHz
oscillator installed in the unit, the LOCKED LED will remain illuminated until the internal
elapsed time counter has timed out.
For a TCXO oscillator, it will take about 30 minutes.
For a OCXO oscillator, it will take about 60 minutes.
For a Rubidium oscillator, it will take about 4 hours.
3.2
OPERATIONAL CHARACTERISTICS
The standard internal time base is a voltage controlled temperature compensated 10MHz crystal
oscillator. When the disciplining feature is ENABLED, its frequency is controlled/corrected to
the internal GPS 1pps using a DAC (Digital to Analog Converter). Disciplining of the oscillator
occurs only when it is ENABLED and used as the unit’s time base, and when the GPS ExacTime
is actively tracking a satellite. During periods when there are no satellites in view or when the
unit isn’t tracking, the last DAC value is retained, and the unit continues to operate normally.
The outputs are then as accurate as the drift/aging rate of the oscillator. See Chapter Four,
paragraphs titled “Enable Disciplining,” and “Disable Disciplining” in this User’s Guide for
enabling and disabling disciplining.
Disciplining is ENABLED by default when the unit is powered.
3.3
LIQUID CRYSTAL DISPLAY
The front panel LCD Display contains two rows of forty characters per row. It displays at least
ten separate MENU screens that are changed by pushing the front panel MENU keyboard
switch.
3.3.1 MAIN MENU SCREEN
When power is first applied to the TC&FG, the LCD displays an Initial Menu Screen that
contains the unit’s ID followed by four digits that correspond to the serial number of the unit.
After approximately 5 seconds, the display then switches to the Main Menu Screen.
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ET6xxx ExacTime GPS TC & FG (Rev C)
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OPERATION
Note: If you have just installed revised/upgraded firmware or performed a “Cold Reset” (see
Chapter Five), an additional extra screen will be displayed in front of your Main Menu
Screen. This screen will only appear the first time power is applied to your unit after a
Cold Reset or the new firmware has been installed. After that, the normal Main Menu
Screen will appear. This additional Initial Calibration screen is shown below:
Column:
1
5
10
15
20
25
30
35
40
|
|
|
|
|
|
|
|
|
Row 1
000.00:00:12 < DOING TIME INT. CALIB. >
Row 2
142 195 073
123 157 056 198
This
internal, automatic
Time Interval Calibration is necessary to get accurate nanosecond time interval resolution for the
measurement of the GPS and external 1PPS. In the example above, 142 and 123 are the current
values, 195 and 157 are the high values, 073 and 056 are the low values, and 198 is the number
of seconds remaining until the calibration is finished. This number starts at 250 and decrements
to zero at a one second rate.
If the MENU key is pressed prior to completing the calibration process, the calibration will be
interrupted and the process aborted. However, an additional menu screen (this Time Interval
Calibration MENU) will be enabled. The user can access this screen if he cycles through the
various menus by pushing the MENU key. This Calibration Menu screen will enable the
nanosecond time interval calibration to be completed at a later date.
It is important to note that if this automatic time interval calibration is interrupted prior to
its completion, it will be necessary to restart and complete it (using the TIME INTERVAL
CALIBRATION MENU screen) or inaccurate time interval measurements will result.
The following is the normal MAIN MENU that is displayed. It contains the following
information:
Symmetricom Firmware Version.
Synchronization.
Time (Seconds through Days).
Status and Error Messages.
Frequency Offset.
Satellite PRN Identification.
Mode.
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A sample of the MAIN MENU SCREEN is shown below:
Column:
1
5
10
15
20
25
30
35
40
|
|
|
|
|
|
|
|
|
123.25:59:59 U < DOING GPS CORRECTION >
Row 1
Row 2
FRQ:+5437E-12 PRN:03 12 15 21 MODE:D6
At power up, the type of oscillator installed in the unit and the software version appear on the
first row of the LCD display. The oscillator can be a TCXO, OCXO, LPRO, or X72 (LPRO and
X72 are Rubidium oscillators). The software version appears as DTxxxxxx, where DTxxxxxx is
the Operational Software Version.
The time-of-year is displayed in Row One, starting with Column One and consists of day-ofyear, hour, minute, and second. This can be UTC, or GPS time, or display the local time offset
depending on which mode has been selected via the RS-232 I/O port, or via the front panel LCD
and keyboard. For remote selection, see the paragraph titled “UTC Sync” to select UTC time
synchronization, and the paragraph titled “GPS Sync” to select GPS synchronization in Chapter
Four of this User’s Guide. For local selection, refer to the paragraph titled “Set Time,” under
SET-UP MENU SCREEN in this section, to select UTC or GPS synchronization using the front
panel LCD and keyboard. See paragraph titled “Enter Local Time Offset” in Chapter Four of
this User’s Guide to enter the desired local time offset via the RS-232 I/O port. The local time
offset may also be entered into the unit using the front panel keyboard and LCD. See paragraph
titled “Local Time Offset” under the SET-UP MENU SCREEN in this chapter.
The letter “U” or “G” which is displayed in Row One, Column Fourteen, denotes whether UTC
(U) or GPS (G) synchronization has been selected. An extra letter “L” is displayed next to the
letter “U” or “G” if the local time offset is not equal to zero. An “L” indicates that the time is
offset by a Local Time Offset.
When the GPS TC&FG is synchronized to UTC time, the time-of-year is displayed and the GPS
corrected 1pps output is on-time with UTC within ±125 nanoseconds with SA (Selective
Availability).
When the GPS TC&FG is synchronized to GPS time, there is a time difference between UTC
and GPS time. As of 9 September, 2000, the difference was thirteen seconds because of the leap
second difference. Leap seconds are added to or subtracted from UTC time, but not GPS time.
Status and error messages are displayed in Row One, starting at Column Fifteen. The status and
error messages alternate every ten seconds. At initial power-up, this area will display the
Symmetricom firmware version for a few seconds.
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ET6xxx ExacTime GPS TC & FG (Rev C)
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OPERATION
The possible status messages displayed are:
Doing GPS Corrections.
GPS Time Not Acquired.
PDOP is Too High.
No Usable Satellites.
Position Survey XXXXX
ZZZZ Stabilizing XX.
Unit Stabilizing XXX
Flywheel Mode.
The “STATUS CODES” are via the RS-232 I/O when requested, and output by the printer port if
the option is implemented. The characters S00 through S15 are printed for the status.
The status message, “DOING GPS CORRECTIONS” is an indication that the GPS Unit is
performing the tasks appropriate to the selected mode of operation. The operational modes
include AUTO, DYNAMIC, STATIONARY, and FLYWHEEL selections. The various modes
will be detailed in subsequent sections of this User’s Guide and are listed here only to aid in
understanding of the “STATUS MESSAGES.”
The status message “PDOP IS TOO HIGH” indicates that the Position Dilution Of Precision
(PDOP) exceeds a limit.
The status message, “NO USABLE SATELLITES” is similar to the “DOING GPS
CORRECTIONS” status message, except that the GPS Time has been previously acquired and
has been maintained to at least the oscillator reference precision since the last usable satellite
was visible. Refer to the paragraph titled “Set Mode (Mode Selection)” in this chapter.
The status message “ZZZZ Stabilizing XX,” where the two digit number (ten to 00) following
“ZZZZ Stabilizing” represents how far away the oscillator is from stabilization. At power on it
will be ten and then down count to 00. The length of time the unit has been OFF and the
ambient temperature will affect how long the oscillator takes to stabilize. Refer to paragraph
titled “Operational Steps” in this chapter. The “ZZZZ” indicates the type of oscillator installed
in the unit. It can be a TCXO (Temperature Controlled Crystal Oscillator), an OCXO (Oven
Controlled Crystal Oscillator), an LPRO (Low Profile Rubidium Oscillator), or an X72
(Rubidium Oscillator).
The status message “Position Survey XXXXX” where the five digit number after the message
“Position Survey” represents the number of averages remaining before the LOCKED LED will
illuminate. The number starts at the maximum number programmed (default is 200) and counts
down to 0000. This message is applicable only in the AUTO MODE of operation. Refer to the
paragraph titled “Number of Position Averages” for selection of number of averages.
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CHAPTER THREE
The status message “Unit Stabilizing XXX” is displayed during the Unit Stabilization process.
The XXX is a three digit number that represents (in minutes) how far the unit is from being
LOCKED.
The status message “Flywheel Mode” is displayed if the Flywheel Mode has been selected.
Refer to the paragraph titled “Set Mode (Mode Selection)” in this chapter.
The possible Error Messages displayed are:
Character
E00
E02
E04
E08
Definition
System Check OK.
Processor Failure.
Ant. Undercurrent
Ant. Overcurrent
The character error codes are for the RS-232 I/O port and optional printer port outputs.
The “Error Codes” are provided for the same reason as the “Status Codes” in the previous
paragraph.
The error message “System Check OK” is displayed when there are no problems with the system
and “all is well.”
The error message “Processor Failure” indicates a signal processor error has been detected.
After this error is detected, it will remain until the receiver is reset.
The error message “Ant. Undercurrent” indicates that the GPS RPU is not providing sufficient
current to the antenna. The probable cause of this message is a discontinuity in the antenna cable
or a failure of the antenna/preamp itself. Check the antenna/preamp cable connections since they
are the most likely cause of the discontinuity.
The error message “Ant. Overcurrent” indicates that the GPS RPU is providing too much current
to the antenna. The probable cause of this message is a short in the antenna cable or a failure of
the antenna/preamp itself. Check the antenna/preamp cable connections since they are the most
likely cause of the short.
The frequency offset is displayed in Row Two starting with Column One. This offset is the
calculated difference between the units local time base and the GPS System frequency. It
consists of either a plus (+) or minus (-) followed by a four digit number expressed in parts to 109
or 10-12 (the E-exponent).
Note: The GPS antenna and cable described in this manual have been replaced as described in
“Appendix D: Antenna Replacement Kit” on page D-1.
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OPERATION
The satellite PRN identifications are displayed in Row Two starting with Column Fifteen. These
are the SV numbers that the unit is currently tracking. They can consist of up to four two digit
numbers.
The mode is displayed in Row Two starting at Column Thirty-One. A character, which indicates
the mode is followed by a number, which indicates the number of satellites, which are in view of
the antenna. “A” represents AUTO mode, “D” represents DYNAMIC mode, “S” represents
STATIONARY mode, and “F” represents FLYWHEEL mode.
3.3.2 POSITION MENU SCREEN
Depressing the MENU keyboard switch once will display this screen. This screen contains the
following information:
Latitude, Longitude, and Altitude.
PDOP Value.
GPS Week Number.
Year.
DAC Value.
Time Interval.
Note: Depressing the MENU keyboard switch and continuously holding it down for more than
two seconds will display the previous menu screen.
A sample of the Position Menu Screen is shown below:
Column:
1
5
10
15
20
25
30
35
40
|
|
|
|
|
|
|
|
|
Row 1
33º48.8241N 117º53.3970W +0026M PDOP:09
Row 2
WK:0698 YR:98
DAC:32767 INT:340276.512µS
Latitude, expressed
in Degrees, Minutes, N (North), or S (South) is displayed in Row 1 starting at Column 1. It is
followed by Longitude expressed in degrees, minutes, W (West), or E (East). Next is the
altitude, starting with a plus (+) or minus (-) followed by four digits expressed in meters.
If the unit is in the DYNAMIC mode and actively tracking more than four satellites, the PDOP
value is shown in Row One starting at Column thirty-three. It is a two digit value which reflects
the geometry of the satellites currently being tracked.
The four digit GPS week number is displayed at the start of Row Two.
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CHAPTER THREE
The two digit year (YR) is shown in Row Two starting at Column Nine. Starting at Column
Sixteen of Row Two is the DAC, a 5 digit (00000 to 65535) number which is a digital
representation of the analog voltage (0 to +5volts) that controls/disciplines the internal 10MHz
oscillator.
The last data displayed in this screen is the Time Interval (INT) which is an example of the time
interval measurement between the 1PPS output and an externally supplied 1PPS input.
Time Interval Measurement is operational in the AUTO, DYNAMIC, and STATIONARY
modes when “LOCKED” with the following qualification: If after achieving “LOCKED” the
unit loses satellites and the “TRACKING” and “LOCKED” LEDs go out, this function will still
be operational until satellites are reacquired. At that point, it won’t be operational again until
“LOCKED” has been achieved. This function is always available in “FLYWHEEL” mode.
3.3.3 SET-UP MENU SCREEN
Subsequent pushing of the MENU keyboard switch will display the Set-up Menu Screen which
is shown below and contains the following choices:
Column:
1
5
10
15
20
25
30
35
40
|
|
|
|
|
|
|
|
|
Row 1
1>SET MODE 3>SET POSITION 5>OFFSET 00.0H
2>SET TIME 4>SIGNAL LEVEL 6>SET DAC
Row 2
If the
#0 keyboard switch
is pressed, the operational software version and the current Leap Second will appear in the lower
right-hand corner (in place of “SET DAC”).
A.
1> SET MODE (MODE SELECTION)
To set the mode, press the #1 keyboard switch. The display will change to that as shown
below:
0>AUTO 1>STATIONARY 4>DYNAMIC 5>FLYWHEEL
OPERATING MODE: AUTO
Choice “0>AUTO”
Depressing the “0” keyboard switch selects the “AUTO” mode. Pressing the MENU
keyboard switch will return the display to the SET-UP MENU SCREEN. The “AUTO”
mode uses four satellites. If more than four satellites are in view and useable, a set of
four based on optimal satellite (minimum PDOP) geometry is automatically selected for
use.
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ET6xxx ExacTime GPS TC & FG (Rev C)
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OPERATION
In this mode, after an initial warm-up delay, and an oscillator stability check/delay, the
unit will be in the Dynamic mode and will begin doing position averaging. The position
average is actually a running average of each subsequent position value. The number of
averages is user selectable but the default number is 200. A position fix takes
approximately three seconds, so the position averaging itself could take about ten
minutes.
Once the unit has completed its position averaging, it will switch to the Unit Stabilizing
mode. At this time, the 1pps will be coherent with the internal disciplined 10MHz
oscillator, and the oscillator discipline process begins. At the end of Unit Stabilizing, the
front panel LOCKED LED will illuminate.
For additional information on the “AUTO” mode, see Chapter Five.
Choice “1>STATIONARY” (Timing Mode)
Depressing the “1” keyboard switch selects the “STATIONARY” Mode. Pressing the
MENU keyboard switch returns the display to the SET-UP MENU SCREEN.
The “STATIONARY” (Timing) mode is the most frequently used mode of operation for
timing applications. This mode of operation assumes that the current position (longitude,
latitude, and altitude) is accurate. It uses an averaged solution of the time information
from as many satellites as the receiver is tracking, up to eight.
For additional information on the “STATIONARY” mode, Chapter Five.
Choice “4>DYNAMIC” (Survey Mode)
Depressing the “4” keyboard switch selects the “DYNAMIC” mode and the “Operating
Mode” changes to “Survey Mode” Pressing the MENU keyboard switch returns the
display to the SET-UP MENU SCREEN.
This choice forces the GPS Receiver to remain in the position survey mode at all times.
When three satellites are in view, the unit will perform two-dimensional “position fixes”
(latitude, and longitude). When four satellites are in view, the unit will perform threedimensional “position fixes” (latitude, longitude, and altitude).
For additional information on the “DYNAMIC” mode, see Chapter Five.
Choice “5>FW” (Flywheel Mode)
Depressing the “5” keyboard switch selects the “FLYWHEEL” mode and the “Operating
Mode” changes to “FLYWHEEL.” Pressing the MENU keyboard switch returns the
display to the SET-UP MENU SCREEN.
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This choice forces the TC&FG into the Flywheel (time code generator) mode. In this
mode the unit does not get synchronization from the GPS RPU (Receiver Processor
Unit). The internal oscillator is not disciplined. The antenna may or may not be
connected. No error messages are displayed or generated via the RS-232 I/O. To set
generated time, refer to “SET TIME (TIME SELECTION).
B.
2> SET TIME (SET TIME SELECTION)
Pressing the #2 keyboard switch selects the “SET TIME.” The display will switch to that
shown on the following page.
Setting the time is only applicable if the unit is not actively tracking one or more
satellites.
ENTER TIME XXX XX:XX:XX
If it is desired to set “TIME” and use the GPS system as a time code generator for any
number of reasons such as a faulty antenna, the desired “TIME” may be entered using the
numeric keys of the keyboard. Three digits must be entered for the day-of-year, two
digits for the hour, two digits for the minute and two digits for the seconds. Leading
“zeroes” are required if necessary.
The GPS receiver will use this “TIME” input as its time until the time is acquired from a
GPS satellite. The 1pps output of the GPS receiver will not be on time with UTC or
GPS, whichever has been selected, until the GPS receiver has acquired time from the
satellites.
If the optional “Preset Year” feature is installed, a “Preset Year” message will be
displayed when you have finished entering the time of year, or by pressing the MENU
keyboard switch. The following message will appear which will enable year preset:
ENTER YEAR XX
ENTER TIME XXX XX:XX:XX
Note: If the user enters a two-digit number between 91 and 99, the year is assumed to be
1991 to 1999. If the user enters a two-digit number between 00 and 90, the year is
assumed to be 2000 to 2090.
Pressing the menu key of the keyboard while the “SET TIME” display is selected leads
to a sub menu display as follows:
1>SYNC XXX
XXX is UTC or GPS
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OPERATION
When this display is shown pressing the “1” key of the keyboard causes “SYNC” to
toggle between UTC and GPS.
C.
3> SET POSITION (ENTER POSITION SELECTED)
Pressing the “3” keyboard switch selects “3>SET POSITION” which allows the user to
enter an accurate position comprised of latitude and longitude in degrees, and minutes to
the nearest thousandth of a minute, the Hemisphere (North, South, East, or West) and the
altitude in meters referred to WGS-84. This causes the display to change to that shown
on the following page:
ENTER LATITUDE: XX XX:XXX
Using the numeric keys of the keyboard enter the latitude in degrees and minutes to the
thousandth of a minute and the display will change to that shown below:
ENTER 1 = NORTH, 2 = SOUTH
Using the numeric keys of the keyboard enter either a “1” for the Northern Hemisphere,
or a “2” for the Southern Hemisphere and the display will change to that shown below:
ENTER LONGITUDE: XXX.XX.XXX
Using the numeric keys of the keyboard, enter the longitude in degrees and minutes to the
thousandth of a minute, and the display will change to that shown below:
ENTER 1 = EAST, 2 = WEST
Using the numeric keys of the keyboard enter either a “1” for the Eastern Hemisphere or
a “2” for the Western Hemisphere and the display will change to that shown below:
ENTER ALTITUDE: XXXX METERS
Using the numeric keys of the keyboard, enter a four digit WGS-84 altitude in meters and
the display will change to that shown below:
ENTER 1 = POS, 2 = NEG
Using the numeric keys of the keyboard, enter either a “1” for a positive altitude, or a “2”
for a negative altitude, for above or below the GPS Reference Sphere (WGS-84).
Note: If a mistake has been made while entering this data, press the MENU keyboard
switch to exit, then return to this selection and reenter the data.
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D.
4> SNR (SIGNAL NOISE DENSITY RATIO)
To request the signal SNR of the satellites currently being “tracked” by the receiver,
press the “4” keyboard switch. The information may take up to ten seconds to be
displayed. Each satellite number and its corresponding signal SNR will be displayed.
The signal SNR is measured at antenna input. Typically it is a number between 30 to 55.
(The larger the number, the better.)
Pressing the MENU key of the keyboard will return the display to the “MAIN MENU
SCREEN.”
E.
5> OFFSET (LOCAL TIME OFFSET SELECTION)
Choice “5>” is the local time offset. This allows the user to input a desired time offset
(in ½ hour increments) whereas the LCD, Optional LED display, and/or time output
would be offset from the selected UTC or GPS time by the number of hours input. All
offset entries are positive (0.00 to 23.5) and are calculated as west of the Greenwich
Meridian.
The current offset will be displayed. Pressing the “5” keyboard switch will allow entry
of the new offset.
Example:
California is eight hours later than GMT. The local time offset entry would be 08.0.
Japan is nine hours earlier than GMT. The local time offset entry would be 15.0.
The calculation for negative local time offsets (for example, nine hours earlier) is as
follows:
(Offset) +24 = entry
(-9) +24 = 15
F.
6> SET DAC
Choice “6>” allows the user to enter a DAC (Digital to Analog Converter) value from
00000 to 65535. This value is a digital representation of the analog voltage (0 to +5
volts) that is used to control the internal oscillator. This feature is especially useful when
attempting to null the oscillator (see Chapter Five).
When keyboard switch 6 is pressed, it allows the user to enter a five digit DAC value, the
midrange being 32767.
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OPERATION
3.3.4 RS-232 I/O CONFIGURATION MENU SCREEN
Subsequent pushing of the MENU keyboard switch will display the RS-232 Configuration Menu
Screen which is shown below and contains the following choices:
Column:
1
5
10
15
20
25
30
35
40
|
|
|
|
|
|
|
|
|
Row 1
RS232 IO:<1> 9600<2> ODD<3>8 BITS/1 STOP
Row 2
5>CABLE DLY:0050’<6>1344: ON <7>TI: OFF
This
screen allows front
panel keyboard selection of the RS-232 I/O parameters and the antenna cable delay.
Use the “1” keyboard switch to select the BAUD RATE. Keep pressing the “1” keyboard switch
until the desired baud rate appears. The choices are as follows:
50, 300, 600, 1200, 2400, 4800, 9600, 19200
Use the “2” keyboard switch to select the PARITY. Keep pressing the “2” keyboard switch until
the desired parity appears. The choices are as follows:
NONE, ODD, and EVEN
Use the “3” keyboard switch to select the desired number of data bits (word length). Keep
pressing the “3” keyboard switch to cycle through the choices which are 7 DATA BITS, and 1
STOP BIT, or 8 DATA BITS and 1 STOP BIT.
The antenna cable length can be entered by pressing the “5” keyboard switch and entering four
digits in feet which corresponds to the length of the antenna cable. This will make the 1pps
output on time by compensating for the propagation delay of the cable.
The “6” keyboard switch allows the user to generate either a modified IRIG B per IEEE Std.
1344 (ON) or the standard IRIG B (OFF) with zeros in the control function area. It is an
alternate action switch. For the format of IEEE Std. 1344, see Chapter One.
The “7” keyboard switch allows the user to enable or disable time interval measurement, and to
select the rising or falling edge of the input pulse as the start (trigger) of this measurement.
Sequentially pushing the switch produces the following:
Off
On 1 (selecting the rising edge as the on-time point)
Off
On 0 (selecting the falling edge as the on-time point)
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3.3.5 MULTIPLE TIME CODE OUTPUTS MENU SCREEN (MODELS ET6000 and
ET6010 only)
If the MENU keyboard switch is pushed again, the LCD will display the Multiple Time Code
Outputs Menu Screen which is shown on below. Although this screen is displayed, it is only
applicable if the TC&FG is configured and furnished with the Multiple Time Code Outputs
option, GPS Opt 01 (Assembly 55116).
Column:
Row 1
1
5
10
|
|
|
CODE SELECT:
Row 2
1> CODE-1
15
|
20
|
2> CODE-2
25
|
30
|
35
|
40
|
3> CODE-3
If this option is provided, its Option Description will be located in Appendix C of this manual.
3.3.6 PRESET COINCIDENCE MENU SCREEN (MODEL ET6500 ONLY)
Subsequent pushing of the MENU keyboard switch will display the Preset Coincidence Menu
Screen which will look similar to the following:
Column:
1
5
10
15
20
25
30
35
40
|
|
|
|
|
|
|
|
|
Row 1
COINCIDENCE:
D
H M S mS
uS
nS
Row 2
TIME
:
XXX
XX:XX:XX.XXX
XXX
X00
This
feature provides the
ability to preset a coincidence time into the GPS TC & FG from hundreds of days through tenths
of microseconds. When the coincidence time equals the GPS time, a 2 microsecond positive
going pulse is output. This coincidence output is on rear panel BNC J7 (Refer to Chapter One)
NOTE: Preset coincidence time should not be entered until the unit is actively tracking
satellites and the LOCK LED is illuminated.
Also, the preset coincidence time has to be at least 2 seconds greater than the GPS time.
Enter the preset coincidence time using the numbered keypads 0-9 starting with hundreds of
days. If an error is made while entering the time, finish entering the time, cycle back through the
menus and then reenter the time.
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OPERATION
3.3.7 EXTERNAL FREQUENCY MEASUREMENT MENU SCREEN (MODELS
ET6000 and ET6010 only)
Subsequent pushing of the MENU keyboard switch will display the External Frequency
Measurement Menu Screen which is shown below and contains the following choices:
Column:
Row 1
1
5
10
15
20
25
30
35
|
|
|
|
|
|
|
|
EXT FRQ:+0000E-14 / +0000E+00 SEC *
Row 2
1>ENTER FRQ
A.
40
|
<2>ENABLE<3>DISABLE
OPERATION
This feature provides the capability of using the GPS TC/FG to measure the stability/drift
of an external signal.
Note: Because J10 is a multipurpose input connector, when the External Frequency
measurement option is enabled, the Single Event Log and the 1PPS Input option
(Time Interval Measurement) are disabled.
External Frequency Measurement is operational in the AUTO, DYNAMIC, and
STATIONARY modes when “LOCKED” with the following qualification: If after
achieving “LOCKED” the unit loses satellites and the “TRACKING” and “LOCKED”
LEDs go out, this function will still be operational until satellites are reacquired. At that
point, it won’t be operational again until “LOCKED” has been achieved. This function is
always available in “FLYWHEEL” mode.
The external frequency measurement can be set-up/configured from either the front panel
keyboard and LCD display or remotely via the RS-232 I/O port.
Pushing keyboard switch “1” followed by a number (00000001 to 10000000) will input
the frequency that the user is going to measure.
Pushing keyboard switch “2” will ENABLE the external frequency measurement option.
Pushing keyboard switch three will disable it.
Once the correct input frequency has been entered and the option turned on (enabled) if
the unit is not locked, “NOTLK” will appear in place of the asterisk (*). If the external
frequency measurement option is enabled and the unit is tracking a satellite, an asterisk
will appear. If the option is disabled, nothing will appear in this area.
If the unit is locked, the measurement count (once per second) will start to increment.
The number is auto scaled, so it will count from 0000E+00 to 9999E+00. The next count
will go to 0100E+02, etc.
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The actual external frequency measurement number itself is also auto scaled. It will
display measurements in parts to E-09, E-12, or E-14. If the input offset/measurement is
greater than 1x10-5 or if the input signal contains noise, “TOO HIGH” will be displayed.
The external frequency input is divided down to 1pps, and then compared against the
unit’s internal 1PPS. It is important to enter the correct frequency number or it will cause
a large error in the final result.
The measurement number is a relative frequency error between the unit and the external
frequency source. If the unit’s frequency is lower than the frequency of the external
source, a negative number is displayed. If the unit’s frequency is higher than the
frequency of the external source, a positive number is displayed.
3.3.8 SINGLE EVENT LOG MENU SCREEN
Subsequent pushing of the MENU keyboard switch will display the Single Event Log Menu
Screen which is shown below and contains these choices:
Column:
1
5
10
15
20
25
30
35
40
|
|
|
|
|
|
|
|
|
Row 1
EVENT LOG<1>STOP<2>CLR<3>EDGE000<4>START
Row 2
S00
E000 ?
<5>← <6>→
Single Event Log is operational in the AUTO, DYNAMIC, and STATIONARY modes when
“LOCKED” with the following qualification: If after achieving “LOCKED” the unit loses
satellites and the “TRACKING” and “LOCKED” LEDs go out, this function will still be
operational until satellites are reacquired. At that point, it won’t be operational again until
“LOCKED” has been achieved. This function is always available in “FLYWHEEL” mode.
The event log can also be programmed, read, and/or cleared, using the front panel keyboard.
Pushing keyboard switch “1” stops the event log.
Pushing keyboard switch “2” clears the event log.
Pushing keyboard switch “3” selects which edge of the event input pulse to trigger on. (0 =
falling edge, 1 = rising edge). The first digit is for Channel Three and the second digit is for
Channel Two (neither of which are active in this option). The third digit is for Channel One.
Keep pushing keyboard switch “3” until the correct number (either one or zero) appears in the
third digit. The one or zero appearing in the first and second digits is ignored in this option,
therefore the contents of these digits will not be important to the unit.
Pushing keyboard switch “4” starts the events log.
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OPERATION
Pushing keyboard switch “5” will send you to the previous event.
Pushing keyboard switch “6” will send you to the next event.
The second line of the LCD displays the status, event number, and the time of the event.
EXAMPLE
Note: The number enclosed in the arrows indicates the keyboard number.
(<1> = keyboard switch number one.)
EVENT LOG<1>STOP<2>CLR<3>EDGE100<4>START
S00*E010 1 165,21:16:04,3267548<5> <6>
100 = Rising edge on channel three, falling edge on channels two and one.
S00 = Event status NORMAL
* = Event Log ENABLED. A blank means the event log has been DISABLED.
E010 = Event Number Ten
1 = Channel Number One
165 = Day-of-Year
21 = Hours
16 = Minutes
04 = Seconds
3267548 = Subseconds (tenths of seconds through hundreds-of-nanoseconds).
3.3.9 50/60HZ MEASUREMENT MENU SCREEN (MODEL ET6500 ONLY)
The 50/60Hz measurement features can be programmed using the front panel keypad switches.
Cycle through the various menus on the LCD display, using the MENU switch, until the
50/60Hz Measurement screen appears. It will look similar to the following:
Column:
1
5
10
15
20
25
30
35
40
|
|
|
|
|
|
|
|
|
Row 1
FRQ:60.0001HZ PHASE:123.4° ERR:-00.4315S
Row 2
1>OFFSET:+00.0005 <4>OFF <5>ON <6>60HZ/OFF
50/60Hz Measurement is operational in the AUTO, DYNAMIC, and STATIONARY modes
when “LOCKED” with the following qualification: If after achieving “LOCKED” the unit loses
satellites and the “TRACKING” and “LOCKED” LEDs go out, this function will still be
operational until satellites are reacquired. At that point, it won’t be operational again until
“LOCKED” has been achieved. This function is always available in “FLYWHEEL” mode.
Operation of the 50/60Hz measurement feature is as follows:
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CHAPTER THREE
With the unit operating, connect the AC source to be measured to TB1-8 and TB1-9 (50/60Hz
Measurement Input). Make sure that when plugging in the cable to the AC power source that it
is correctly polarized. For example, the pin labeled AC HI (50/60Hz Measurement Input - HI) is
plugged into the AC HOT receptacle. If this connection is reversed, the phase angle
measurement will be off by 180o.
The frequency measurement is made by counting the number of 50/60Hz sine waves occurring
between successive corrected 1pps pulses from the GPS receiver.
The phase angle measurement is made by calculating where the 1pps pulse occurs in relationship
to the 50/60Hz sine wave.
The error calculation is the accumulated time error based on whether the sine wave is fast or
slow. A time error offset can be entered when the 50/60Hz measurement is OFF, which is used
as a starting point for the error calculation.
Pushing keypad switch number one will program the offset. Note that an offset cannot be
entered until the measurement is stopped. OFF will appear in the lower right hand corner of the
LCD display. If the unit is not locked, ERR will appear. If the measurement is started, ON will
appear. Keypad switch number two will select “+” (plus) and switch number three will select “” (minus). The number of seconds offset can then be entered using the keypad switches up to
99.999 seconds.
Pushing the number four key will stop the measurement, and OFF will appear on the LCD
display in the lower right-hand corner.
Pushing the number five key will start the measurement, and ON will appear in the lower righthand corner of the LCD display. If the unit is not locked, ERR will appear in the lower right
hand corner of the LCD display.
Pushing the number six key of the keypad selects either 50Hz or 60Hz. 50Hz or 60Hz selection
can only be done when the unit is not doing measurements. OFF is displayed in the lower right
hand corner of the LCD display.
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OPERATION
3.3.10 AUTO DAYLIGHT SAVINGS MENU SCREEN
Subsequent pushing of the MENU keyboard switch will display the Auto Daylight Savings
Menu Screen which is shown below and contains this choice:
Column:
1
5
10
15
20
25
30
35
40
|
|
|
|
|
|
|
|
|
Row 1
AUTO DAYLIGHT SAVING <1> OFF
Row 2
Pushing the “1” keyboard switch will alternately enable or disable the Auto Daylight Savings
Time feature. It can also be programmed to automatically turn on/off for up to ten years using
the RS-232 I/O port. Refer to Chapter Four of this manual.
3.3.11 MUX OUTPUT MENU SCREEN
Subsequent pushing of the MENU keyboard switch will display the Mux Output Menu Screen
which is shown below and contains these choices:
Column:
1
5
10
15
20
25
30
35
40
|
|
|
|
|
|
|
|
|
Row 1
MUX OUT <1>CH: 1 <2>OUTPUT:DC CODE
Row 2
<3,5>KEYLOCK:
OFF
The rear panel BNC connectors (J4 through J9) can be configured to output various timing
signals using the internal jumper pins and the front panel keyboard.
If the MUX input to any output buffer is jumper selected, one of sixteen inputs to that
multiplexer can be selected via the front panel keyboard.
This menu screen allows selection of the outputs on the rear panel BNC connectors J4 through
J9.
Pushing the “1” front panel keyboard switch cycles through the output channels (1-4).
Channel One controls MUX outputs on J4 and J9.
Channel Two controls MUX outputs on J5 and J8.
Channel Three controls MUX outputs on J6.
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CHAPTER THREE
Channel Four controls MUX outputs on J7.
Pushing the “2” front panel keyboard switch cycles through the outputs available for the
respective channel selected.
The choices are as follows (see the paragraph entitled “Optional Pulse Rate Outputs” in Chapter
One):
10MHz
5MHz
1MHz
100KHz
10KHz/2PPH*
1KHz
100Hz
10Hz/1PPH*
1Hz
.1Hz
1PPM
TRACKING
LOCKED
+5 VOLTS
1PPS
DC CODE
1PPS is a 30-50uS wide pulse, positive edge on-time.
Tracking output is a TTL low when not tracking and a TTL high when tracking.
Locked output is a TTL low when not locked and a TTL high when locked.
* Models ET6000 and ET6010 output 10KHz and 10Hz. Model ET6500 outputs 2PPS and
1PPH.
Note: The MUX outputs can also be read and selected via the RS-232 I/O port. See paragraphs
titled “Request MUX Output” and “Set MUX Output” in Chapter Four of this User’s
Guide.
The standard configuration is as follows:
J4 - TRACKING (TTL)
J5 - LOCKED (TTL)
J6 - 1PPS
J7 - 10MHz SINE WAVE
J8 - IRIG B (AC)
J9 - IRIG B (DC)
J10 - 1PPS INPUT (Time Interval Measurement)
Configurations other than the above standard will be found in the GPS Option/Connector
Configuration Sheet included in this User’s Guide.
The internal jumper pins are shown in Figure 2-3 in Chapter Two.
Jumpers J14 and J24 are associated with BNC J4. Jumpers J15 and J25 are associated with BNC
J5, etc. The basic circuitry is explained in the following example:
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OPERATION
•
Jumpering J24 pins 1 and 2 connects the output of a buffer to J4.
•
J14 selects the input to that buffer. J14 pins 2, 4, 6, and 8 are connected in common to the
buffer input.
•
J14 pins 1, 3, 5, and 7 select various inputs to that buffer as shown in Figure 2-3 in Chapter
Two.
•
The MUX input (jumpering pins J14 1 and 2) selects a 16:1 software controlled multiplexer,
the output of which is selectable using the front panel keyboard switches (or via the RS-232
I/O).
•
The output buffer can also be used to provide a relay closure on J4. The relay closure will
either be an open or closure to ground. To enable this configuration, jumper J24 pins 1 and
3, and J24 pins 2 and 4.
• BNC’s J6 and J7 don’t have the optional relay configuration.
•
If the MUX input to any output buffer is jumper selected, one of the sixteen inputs to that
multiplexer can be selected by the front panel keyboard.
Pushing the “3” followed by “5” front panel keyboard allows the user to enable or disable
operation of the front panel keyboard. The default condition for Keyboard Lock is OFF. This
means that the keyboard functions normally. If the user wishes to activate Keyboard Lock, push
the “3” followed by “5” keyboard switch.
When Keyboard Lock is ON, only the MENU key will function. Nothing can be entered or
changed from the front panel. If the user wishes to turn OFF Keyboard Lock, cycle through the
various menus until the Mux Output Menu Screen appears. Push the “3” followed by “5”
keyboard switch and XXXX will appear on the screen. Enter 9975 and Keyboard Lock will turn
to OFF.
3.3.12 PRINTER PORT CONFIGURATION MENU SCREEN
Subsequent pushing of the MENU keyboard switch will display the Printer Port Configuration
Menu Screen, which is shown below and contains these choices:
Column:
Row 1
1
5
10
15
20
25
30
35
40
|
|
|
|
|
|
|
|
|
PRINTER :<1> 9600<2>NONE<3>8BIT<4>1 STP
Row 2
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CHAPTER THREE
This screen allows front panel keyboard selection of the Printer Output port parameters.
Use the “1” keyboard switch to select the BAUD RATE. Keep pressing the “1” keyboard switch
until the desired baud rate appears. The choices are as follows:
50, 300, 600, 1200, 2400, 4800, 9600, 19200
Use the “2” keyboard switch to select the PARITY. Keep pressing the “2” keyboard switch until
the desired parity appears. The choices are as follows:
NONE, ODD, and EVEN
Use the “3” keyboard switch to select the desired number of data bits (word length). The choices
are 7 or 8 data bits.
Use keyboard switch “4” to select the number of stop bits (1 or 2).
Use keyboard switch “5” to select the printer output format, either “Standard” or “One Second
Burst”.
Standard RS232 Printer Output
This printer port provides the ability to output time, mode, status, frequency, position, and other
optional data to an RS-232 compatible serial printer or terminal.
For the J11 connector pin assignments, refer to Chapter One.
The following are examples of output data:
94 027.17:04:38 M0 S00 E00 25 00 00 00 -0019-E12 33 48.8270N 117 53.3864W +0028 T1
705337.516
94 027.17:04:43 M0 S00 E00 25 00 00 00 -0019-E12 33 48.8270N 117 53.3864W +0028 T1
705337.516
94 027.17:04:48 M0 S00 E00 25 00 00 00 -0019-E12 33 48.8270N 117 53.3864W +0028 T1
705337.516
94 = year
027.17:04:38 = time (days, hours, minutes, seconds)
M0 - mode (start-up mode)
* S00 = status code (doing GPS corrections)
* E00 = error code (system check OK)
25 00 00 00 = tracking satellite vehicle 25
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OPERATION
-0019E-12- frequency offset measured in parts to 10-12
33 48.8270N = latitude 33 degrees 48.8270 minutes, north
117 53.3864W - longitude 117 degrees 53.3864 minutes, west
+0028 = altitude in meters
T1 705337.516 = time interval in microseconds
* For a listing of status codes and error codes, see Chapter Four of this User’s Guide.
External frequency measurement can be substituted for time interval if available and previously
enabled.One Second Burst (RS232 ASCII Time Burst Mode Output)
This interface is configured as Data Terminal Equipment (DTE), synchronous 1PPS “Burst”
mode, using 9600 Baud. No control/handshake lines are utilized. The time word output is
shown below in Table 1. Each byte consists of one start bit, eight data bits, one parity bit (odd)
and one stop bit. However, this configuration can be changed using the front panel keyboard
switches or remotely using the RS-232 I/O.
The data transmission is serial asynchronous by character, and the ASCII character code is used.
The time information is interpreted as being UTC time.
(SOH) DDD:HH:MM:SSQ (CR) (LF)
See Table 1 for the definition of each field contained in this time information string.
Field
(SOH)
DDD
HH
MM
SS
Q
(CR)
(LF)
Table 1
Protocol 1
Time Information
Definition
Start of Header (ASCII control character).
Day of Year.
Hours (24-hour clock).
Minutes.
Seconds.
Quality indicator (see description below).
Carriage Return (ASCII control character).
Line Feed (ASCII control character).
The on-time point is at the beginning of the Carriage Return character.
Quality Indicator:
This indicator is an estimation of the accuracy of the unit’s 1PPS compared to the GPS
system 1PPS.
Symmetricom Inc
ET6xxx ExacTime GPS TC & FG (Rev C)
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CHAPTER THREE
ASCII
Character
(space)
.
*
#
?
HEX
Equivalent
20
2E
2A
23
3F
Definition
< 1 microsecond
< 10 microseconds
< 100 microseconds
< 1 millisecond
> 1 millisecond (unknown)
3.3.13 IEEE-488 I/O INTERFACE MENU SCREEN (MODELS ET6000 AND ET6010
ONLY)
If the keyboard switch is pushed again, the LCD will display the IEEE-488 I/O Interface Menu
Screen, which is shown below. Although this screen is displayed, it is only applicable if the
TC&FG is configured and furnished with the IEEE-488 I/O Interface option, GPS Opt 14
(Assembly 55115).
Column:
Row 1
1
5
10
15
20
|
|
|
|
|
<1> IEEE488 ADDR.17
25
|
30
|
35
|
40
|
Row 2
If this option is provided, its Option Description will be located in Appendix C of this manual.
3.4 CONFIGURATION OF REAR PANEL BNC CONNECTORS J4-J9
The rear panel BNC connectors (J4 through J9) can be configured to output various timing
signals using the internal jumper pins and the front panel keyboard.
Per Figure 2-3 in Chapter Two, the following table details the various outputs available at J4:
JUMPER BLOCK J24
pins 1 and 2 shorted
pins 1 and 2 shorted
pins 1 and 2 shorted
pins 1 and 2 shorted
pins 1 and 3 shorted
3-26
JUMPER BLOCK J14
pins 1 and 2 shorted
pins 3 and 4 shorted
pins 5 and 6 shorted
pins 7 and 8 shorted
pins 2 and 4 shorted
OUTPUT AT J4
1 of 16 selectable Channel 1 Mux outputs
IRIG B AC code out
10MHz sine wave output
Tracking TTL output
Tracking (relay closure to ground)
ET6xxx ExacTime GPS TC & FG (Rev C)
Symmetricom Inc
OPERATION
Per Figure 2-3 in Chapter Two, the following table details the various outputs available at J5:
JUMPER BLOCK J25
pins 1 and 2 shorted
pins 1 and 2 shorted
pins 1 and 2 shorted
pins 1 and 2 shorted
pins 1 and 3 shorted
JUMPER BLOCK J15
pins 1 and 2 shorted
pins 3 and 4 shorted
pins 5 and 6 shorted
pins 7 and 8 shorted
pins 2 and 4 shorted
OUTPUT AT J5
1 of 16 selectable Channel 2 Mux outputs
IRIG B AC code out
10MHz sine wave output
Locked TTL output
Locked (relay closure to ground)
Per Figure 2-3 in Chapter Two, the following table details the various outputs available at J6:
JUMPER BLOCK J16
pins 1 and 2 shorted
pins 3 and 4 shorted
pins 5 and 6 shorted
pins 7 and 8 shorted
OUTPUT AT J6
1 of 16 selectable Channel 3 Mux outputs
IRIG B AC code out
10MHz sine wave output
unused
Per Figure 2-3 in Chapter Two, the following table details the various outputs available at J7:
JUMPER BLOCK J17
pins 1 and 2 shorted
pins 3 and 4 shorted
pins 5 and 6 shorted
pins 7 and 8 shorted
OUTPUT AT J7
1 of 16 selectable Channel 4 Mux outputs
IRIG B AC code out
10MHz sine wave output
unused
Per Figure 2-3 in Chapter Two, the following table details the various outputs available at J8:
JUMPER BLOCK J28
pins 1 and 2 shorted
pins 1 and 2 shorted
pins 1 and 2 shorted
pins 1 and 2 shorted
pins 3 and 4 shorted
JUMPER BLOCK J18
pins 1 and 2 shorted
pins 3 and 4 shorted
pins 5 and 6 shorted
pins 7 and 8 shorted
N/A
OUTPUT AT J8
1 of 16 selectable Channel 2 Mux outputs
IRIG B AC code out
10MHz sine wave output
unused
Event 3 input
Per Figure 2-3 in Chapter Two, the following table details the various outputs available at J9:
JUMPER BLOCK J29
pins 1 and 2 shorted
pins 1 and 2 shorted
pins 1 and 2 shorted
pins 1 and 2 shorted
pins 3 and 4 shorted
Symmetricom Inc
JUMPER BLOCK J19
pins 1 and 2 shorted
pins 3 and 4 shorted
pins 5 and 6 shorted
pins 7 and 8 shorted
N/A
OUTPUT AT J9
1 of 16 selectable Channel 1 Mux outputs
IRIG B AC code out
10MHz sine wave output
unused
Event 2 input
ET6xxx ExacTime GPS TC & FG (Rev C)
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This Page Intentionally Left Blank
3-28
ET6xxx ExacTime GPS TC & FG (Rev C)
Symmetricom Inc
CHAPTER FOUR
I/O PORT DATA INPUT/OUTPUT
4.0
INTRODUCTION
The GPS timing unit has been equipped with an RS-232 interface using a nine pin connector
designated as RS-232 I/O J12. It can be used to communicate to and from the GPS ExacTime
unit. All communication is in the ASCII format. The standard character protocol is one start bit,
eight data bits, an odd parity bit, and one stop bit. However, the baud rate, number of data bits,
parity, and number of stop bits are selectable using the front panel keyboard switches. See
Chapter Three, “Additional Menu Screens.”
The interface cable pin assignments and designations are shown in Chapter Two.
All communication to the GPS ExacTime Unit consists of two or three categories of characters.
The first category is a single character, which is always an ASCII $ (Hex 24). This is the
attention/log-on character. The second category is an ID ASCII character, which is a command
to the GPS ExacTime Unit. The third category (which may or may not be applicable) is a series
of ASCII data bits to input data into the GPS ExacTime Unit. Leading zeros must be used where
necessary. For example, if the number is fifty-two, and if the data to be entered is a four digit
number, then it must be entered as 0052.
Note: If a mistake is made while inputting new characters (prior to the last character), issuing
the “$” character, this will cause a reset, and the new (correct) characters can be input.
When entering data via the RS-232 I/O port, if there is a pause longer than three seconds
between input values, communication with the GPS timing unit will terminate.
Table 4-1 shows the command options available. The ASCII character is shown following its
HEX equivalent. Following the table, each command is described with the necessary steps for
execution.
Table 4-1 is located on the following page.
Symmetricom Inc
ET6xxx ExacTime GPS TC & FG (Rev C)
4-1
CHAPTER FOUR
ASCII ID
Character
`
c
d
e
f
=
i
j
k
p
l
m
r
s
t
u
x
y
z
{
}
~
N
Q
|
T
U
W
X
Y
Z
[
HEX
Character
60
63
64
65
66
3D
69
6A
6B
70
6C
6D
72
73
74
75
78
79
7A
7B
7D
7E
4E
51
7C
54
55
57
58
59
5A
5B
Table 4-1
RS-232 ASCII I/O Command Table
Description
Symmetricom Firmware Version.
UTC Sync.
GPS Sync.
Print Frequency Offset.
Print Time, Status, Error Code, and SV Number.
Print Year (4 digits), Time, Status, Error Code and SV Number.
Print Position.
Clear Event Data.
Print Event Data.
Request One Event Log Data.
Enable Event Log.
Disable Event Log.
Select Mode.
Enable Time Interval.
Disable Time Interval.
Request Time Interval.
Request Elevation Mask Angle.
Enter Elevation Mask Angle.
Enable Discipline.
Disable Discipline.
Enter Position.
Enter DAC Value.
Request DAC Value.
Enter Number of Position Averages.
Enter Local Time Offset.
Enter Cable Delay.
Request Cable Delay.
Re-synchronize Minor Time.
Select Default Values.
*External Frequency Measurement – Select Input Frequency
*External Frequency Measurement – Enable/Disable
*External Frequency Measurement – Request Data
* Models ET6000 and ET6010 only.
The remainder of Table 4-1 is continued on the following page.
4-2
ET6xxx ExacTime GPS TC & FG (Rev C)
Symmetricom Inc
I/O PORT DATA INPUT/OUTPUT
ASCII ID
Character
]
^
B
L
D
A
C
H
I
>
g
h
n
o
JR
JS
K
<
OD
OE
OF
OR
OS
E
@
Table 4-1
RS-232 ASCII I/O Command Table, Continued…
HEX
Description
Character
5D
Request Satellite SNR.
5E
Request Unit Operating Parameters.
42
Enable/Disable 50/60Hz Measurement (Model 6500 only).
4C
50/60Hz Selection (Model 6500 only).
44
Enter 50/60Hz Offset Data (Model 6500 only)
41
Request 50/60Hz Measurement Data (Model 6500 only).
43
**Enter IEEE-488 Address. (Models 6000 and 6010 only)
48
Printer – Set-Up Configuration.
49
Printer – Request Configuration.
3E
Printer port Mode selection.
67
Printer – Select Output Rate.
68
Printer – Request Output Rate.
6E
Printer – Enable/Disable & Data Select.
6F
Enter Preset Coincidence Time (Model 6500 only).
4A, 52
Request MUX output.
4A, 53
Set MUX output.
4B
Set Major Time.
3C
Set Year.
4F, 44
Disable Auto Daylight Savings Time Function.
4F, 45
Enable Auto Daylight Savings Time Function.
4F, 46
Set Auto Daylight Savings Time Default Interval.
4F, 52
Request Auto Daylight Savings Time Interval.
4F, 53
Set Auto Daylight Savings Time Interval.
45
** Set-Up Three Channel Encoder (Models 6000 and 6010 only).
40
Request Unit Serial Number
** Optional. Refer to the Option Description in Appendix C.
4.1
SYMMETRICOM FIRMWARE VERSION
This command outputs the Symmetricom firmware version installed in the unit.
•
The user inputs $`(HEX 24/HEX 60).
•
The unit will respond with eight characters followed by CR/LF.
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ET6xxx ExacTime GPS TC & FG (Rev C)
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CHAPTER FOUR
4.2
UTC SYNC
This command will synchronize the unit to the Universal Time Coordinated time standard.
•
The user inputs $c (HEX 24/HEX 63).
•
The unit will respond with OK, followed by CR/LF.
4.3
GPS SYNC
This command will synchronize the unit to the Global Positioning System time standard.
•
The user inputs $d (HEX 24/HEX 64).
•
The unit will respond with OK, followed by CR/LF.
4.4
PRINT FREQUENCY OFFSET
This command will output the calculated difference between the units’ local time base and the
GPS system frequency.
•
The user inputs $e (HEX 24/HEX 65).
•
The unit will respond with a plus or minus sign, four digits, and an exponent having the
weight of parts in 10-9 or 10-12.
Example:
+0579E-09
4.5
PRINT TIME, STATUS, ERROR CODE, AND SATELLITE VEHICLE
NUMBERS
This command allows the user to print the year, day-of-year, hour, minute, second, millisecond,
status code, error code, and the vehicle numbers of the satellites being tracked. The Status
Codes are shown in Table 4-2 and the Error Codes are shown in Table 4-3.
Table 4-2
Status Codes
Characters
S00
S01
S02
S05
Table 4-2 continued on next page.
4-4
Definition
Doing GPS Correction.
GPS time not acquired.
Waiting for almanac.
Unit stabilizing.
ET6xxx ExacTime GPS TC & FG (Rev C)
Symmetricom Inc
I/O PORT DATA INPUT/OUTPUT
Characters
S08
S14
S15
S16
Definition
No useable satellites.
Oscillator stabilizing.
Position Survey
Flywheel Mode
Note: If a Status Code is produced other than those listed above, the error is undefined.
Table 4-3
Error Codes
Characters
E00
E02
E04
E08
•
If the user inputs $f (HEX 24/HEX 66).
•
The unit will respond with the following:
Definition
System check OK.
Processor error.
Ant. Undercurrent
Ant. Overcurrent
3 digits of day of year.
2 digits of hour.
2 digits of minute.
2 digits of second.
3 digits of milliseconds (space).
3 character status code (space).
3 character error code (space).
Up to 4 satellite vehicle numbers CR/LF.
Each satellite vehicle is identified by its PRN I.D.
Example:
056.12:13:45.768 S00 E00 03 13 20 26
It is the 56th day of the year (February 25th).
The time is 12 hours, 13 minutes, 45 seconds and 768 milliseconds.
The unit is doing GPS corrections.
The system check is OK.
The unit is tracking satellites 3, 13, 20, and 26.
•
If the user inputs $ = (HEX 24/HEX 3D).
Symmetricom Inc
ET6xxx ExacTime GPS TC & FG (Rev C)
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CHAPTER FOUR
The unit will respond with the following:
4 digits of year.
3 digits of day of year.
2 digits of hour.
2 digits of minute.
2 digits of second.
3 digits of milliseconds (space).
3 character status code (space).
3 character error code (space).
Up to 4 satellite vehicle numbers CR/LF.
Each satellite vehicle is identified by its PRN I.D.
Example:
1999 056.12:13:45.768 S00 E00 03 13 20 26
Year = 1999
It is the 56th day of the year (February 25th).
The time is 12 hours, 13 minutes, 45 seconds and 768 milliseconds.
The unit is doing GPS corrections.
The system check is OK.
The unit is tracking satellites 3, 13, 20, and 26.
4.6
PRINT POSITION
This command allows the user to read the accurate position known to the GPS ExacTime unit.
The latitude will be expressed in units of degrees and minutes labeled North or South, relative to
the equatorial plane which is defined as zero latitude. The longitude will be expressed in units of
degrees and minutes labeled East or West relative to the Greenwich Meridian. The altitude will
be expressed in meters either above (+) or below (-) the GPS Reference Sphere (WGS-84).
Altitude can be negative, and a sea level altitude may be above or below the GPS Reference
Sphere.
•
The user inputs $i (HEX 24/HEX 69).
•
The unit will respond with the following:
2 digits of degrees latitude (space).
2 digits of minutes latitude.
4 digits of ten thousandths of minutes latitude.
N or S (space).
3 digits of degrees longitude (space).
2 digits of minutes longitude.
4-6
ET6xxx ExacTime GPS TC & FG (Rev C)
Symmetricom Inc
I/O PORT DATA INPUT/OUTPUT
4 digits of ten thousandths of minutes longitude.
E or W (space).
+ or -.
4 digits of altitude in meters CR/LF.
Example:
4.7
33 48.8241N 117 53.3970W +0026
CLEAR EVENT DATA
This command clears any previously stored events from memory, if the event option has been
installed in the unit.
•
The user inputs $j (HEX 24/HEX 6A).
•
The unit will respond with OK, followed by CR/LF.
4.8
PRINT EVENT DATA
The GPS Timing Unit has the optional capability of storing up to 256 events from up to three
inputs (channels). When the command is sent to print the event data, the first response is three
characters representing event status. The user responds with a % character. This is followed by
the unit outputting the event number, the channel number, and the time the event occurred.
When this first event has been output, the user must respond with a % character within three
seconds signifying the event information has been taken. The unit will then output the second
event.
This process of outputting the data followed by the user’s response (%) continues until all events
have been output. If the user does not take the data and respond with a % within three seconds,
communication with the GPS timing unit will terminate. If no data is available, the unit will
respond with a question mark. If more than 256 events occur, subsequent events will be lost or
overwritten. If two events occur very close together, it is possible that one of the events could be
missed. If that happens, the fact that an event has been missed will be reported in the event
status. Table 4-4 shows the possible event status codes.
Code
S00
S02
Symmetricom Inc
Table 4-4
Event Status Codes
Definition
Normal.
Missed event Channel One.
ET6xxx ExacTime GPS TC & FG (Rev C)
4-7
CHAPTER FOUR
In the following example are the steps for printing (outputting) the single event log:
•
The user inputs $k (HEX 24/HEX 6B).
•
The unit responds with S00 CR/LF.
•
The user responds with %.
•
•
•
The unit will then output the first event. E000 1 056.12:13:45.1437952 CR/LF.
•
The unit will output the second event. E001 1 056.12:13:46.5327642 CR/LF.
•
When this data has been taken, the user responds with %.
•
The unit will then output E002 ? CR/LF.
When this data has been taken, the user responds with %.
The question mark signifies that there is no data available. Event E001 was the last event.
In the above example, S00 indicates no missing events. The first event (E000) occurred on
Channel One at the specified time. The second event (E001) occurred on Channel One at the
specified time.
4.9
REQUEST ONE EVENT LOG DATA
This command allows the user to request data from any one of the 256 events.
•
•
The user inputs $p (HEX 24/HEX 70) followed by “aaa” where aaa is the three digit event
number.
The unit will respond with:
Sbb (space) Eaaa (space) xx (space) ddd.hh:mm:ss.ccccccc CR/LF
Where:
4-8
bb =
aaa =
xx =
ddd =
hh =
mm =
ss =
cc =
event status
requested event number
event channel number
days
hours
minutes
seconds
subseconds
ET6xxx ExacTime GPS TC & FG (Rev C)
Symmetricom Inc
I/O PORT DATA INPUT/OUTPUT
Example:
•
•
User inputs $p125
Unit responds with S00 E125 01 056.12:13:45.1234567 CR/LF
The above example is event status 00, event number 125, event channel number 01, 56 days, 13
hours, 13 minutes, 45 seconds, and 123.4567 milliseconds.
4.10
ENABLE SINGLE EVENT LOG
This command enables the event log option. It consists of the log-on command followed by
three digits. Entering “111” signifies that the positive/rising edge of the input pulse is the ontime edge of the event. Entering “000” signifies that the negative/falling edge of the input pulse
is the on-time edge of the event.
When sent, this command automatically disables the 1pps time interval function.
•
The user inputs $1 (HEX 24/HEX 6C) and 3 digits.
•
The unit will respond with OK, followed by CR/LF.
Example: 000
The above example will enable the single event log. The on-time edge of the input pulses will
be the negative/falling edge.
4.11
DISABLE SINGLE EVENT LOG
This command disables the event data log.
•
User inputs $m (HEX 24/HEX 6D).
•
The unit responds with OK CR/LF.
4.12
SELECT MODE
This command allows the user to select the mode of operation. This one digit command
indicates the following modes:
0
1
4
5
=
=
=
=
AUTO Mode.
Stationary Mode (Timing Mode).
Dynamic.
Flywheel Mode.
Symmetricom Inc
ET6xxx ExacTime GPS TC & FG (Rev C)
4-9
CHAPTER FOUR
The user inputs $r (HEX 24/HEX 72) 0.
•
The unit responds with OK CR/LF.
The example above selects the AUTO mode of operation.
4.13
ENABLE TIME INTERVAL
This command enables the time interval measurement using the external 1pps input. The
command must also indicate which edge of the 1pps input is going to be used.
0 = Negative/falling edge.
1 = Positive/rising edge.
This command automatically disables the event log feature.
•
The user inputs $s (HEX 24/HEX 73) 1.
•
The unit responds with OK CR/LF.
The example above enables the time interval measurement feature and selects the positive edge
of the 1pps input as the on-time edge.
4.14
DISABLE TIME INTERVAL
This command disables the time interval measurement.
•
The user inputs $t (HEX 24/HEX 74).
•
The unit responds with OK CR/LF.
4.15
REQUEST TIME INTERVAL
This command allows the user to request the time interval measurement between the internal
GPS corrected 1pps pulse and an external 1pps input pulse. The response consists of three digits
of milliseconds, three digits of microseconds, and a decimal point followed by three digits of
nanoseconds.
•
The user inputs $u (HEX 24/HEX 75).
•
The unit responds with 134276.512 CR/LF.
4-10
ET6xxx ExacTime GPS TC & FG (Rev C)
Symmetricom Inc
I/O PORT DATA INPUT/OUTPUT
The example above indicates that the difference between the internal GPS corrected 1pps pulse
and the external 1pps pulse is 134276.512 microseconds.
Every time a measurement needs to be taken, a request has to be issued.
4.16
REQUEST ELEVATION MASK ANGLE
This command allows the user to view the currently selected mask angle.
The mask angle is the minimum angle (in degrees) for tracking satellites. The minimum angle is
0º.
•
The user inputs $x (HEX24/HEX78).
•
The unit responds with 05 CR/LF.
The example above indicates an elevation mask angle of five degrees, which is the default.
4.17
ENTER ELEVATION MASK ANGLE
This command allows the user to input/change the mask angle.
•
The user inputs $y (HEX 24/HEX 79) 05.
•
The unit responds with OK CR/LF.
The above example indicates that the user inputs an elevation angle mask of five degrees.
4.18
ENABLE DISCIPLINING
This command allows the user to enable the discipline feature. The internal time base is
periodically disciplined/corrected to the GPS time base.
•
The user inputs $z (HEX 24/HEX 7A).
•
The unit responds with OK CR/LF.
4.19
DISABLE DISCIPLINING
This command allows the user to disable the discipline feature.
•
The user inputs $ { (HEX 24/HEX 7B).
Symmetricom Inc
ET6xxx ExacTime GPS TC & FG (Rev C)
4-11
CHAPTER FOUR
•
The unit responds with OK CR/LF.
4.20
ENTER POSITION
This command allows the user to manually enter the position of the antenna/preamp.
The command consists of :
Two digits of degrees latitude.
Two digits of minutes latitude.
Three digits of sub-minutes latitude.
N (North) or S (South).
Three digits of degrees longitude.
Two digits of minutes longitude.
Three digits of sub-minutes longitude.
E (East) or W (West).
+ (plus) or - (minus).
Four digits of altitude in meters.
•
•
The user inputs $ } (HEX 24/HEX 7D) 3348824N11753397W+0026
•
The unit responds with OK CR/LF.
The above example is entering Symmetricom’s position of:
Latitude 33o 48.824 N.
Longitude 117o 53.397 W.
Altitude + 0026 meters.
4.21
ENTER DAC VALUE
This command allows the user to manually enter a DAC (Digital to Analog Converter) value that
is used to adjust the internal time base. This would typically be done prior to the front panel
LOCKED LED turning on, if disciplining was turned off, or to null/calibrate the internal
oscillator.
The DAC value consists of five digits from 00000 to 65535. If a number is entered that is
greater than 65535, it will automatically be converted to 65535.
•
The user inputs $ ~ (HEX 24/HEX 7E) 32767.
•
The unit responds with OK CR/LF.
4-12
ET6xxx ExacTime GPS TC & FG (Rev C)
Symmetricom Inc
I/O PORT DATA INPUT/OUTPUT
The above example sets the DAC value at approximately the middle of its range.
4.22
REQUEST DAC VALUE
This command allows the user to request the current DAC value.
•
The user inputs $ N (HEX 24/HEX 4E).
•
The unit responds with a five digit value followed by CR/LF.
4.23
ENTER NUMBER OF POSITION AVERAGES
This command allows the user to select the number of position averages that will be used to
calculate position in the start-up mode of operation. The command is comprised of five digits
representing a number from 00010 to 99999. Ten (0010) is the smallest number of position
averages that can be entered. The default is 200.
•
The user inputs $Q (HEX 24/HEX 51) followed by four digits.
•
The unit responds with OK CR/LF.
Note: The timing accuracy of this unit is directly related to the position accuracy. The more
accurate the position, the more accurate the time. It is recommended that for timing
accuracy of ≤ 300 nanoseconds, 2,000 to 5,000 position averages be performed to insure
an accurate position or input an accurate, surveyed position into the unit.
4.24
ENTER LOCAL OFFSET
This command allows the user to input a desired time offset (in ½ hour increments) whereas the
LCD or optional LED display and/or time outputs would be offset from the selected UTC or
GPS time by the number of hours input. All offsets entered (00.0 to 23.5) are positive and
calculated as west of the Greenwich Meridian (or input an accurate, surveyed position into the
unit).
•
The user inputs $| (HEX 24/HEX 7C) 07.0.
•
The unit responds with OK CR/LF.
The above example (07.0) inputs a local time offset to correspond to daylight savings time in the
Pacific Time Zone.
Symmetricom Inc
ET6xxx ExacTime GPS TC & FG (Rev C)
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CHAPTER FOUR
4.25
ENTER CABLE DELAY
This command allows the user to enter a cable delay that compensates for the propagation delay
between the antenna/preamp and the RPU caused by the cable. The delay is approximately 1.5
nanoseconds per foot of antenna cable. The user simply enters the total length of antenna cable
as a four digit number expressed in feet.
•
The user inputs $T (HEX 24/HEX 54) 0100.
•
The unit responds with OK CR/LF.
In the above example, the user has input cable delay to compensate for one-hundred feet of
antenna cable.
4.26
REQUEST CABLE DELAY
This command allows the user to interrogate the GPS ExacTime unit and find out what cable
delay the unit is currently using.
•
The user inputs $U (HEX 24/HEX 55).
•
The unit responds with a four digit number that equates to the length of antenna cable (in
feet) that is stored in memory, followed by CR/LF.
Note: This command would only be applicable if the user has changed antenna cable length and
is unsure what delay has been programmed into the GPS ExacTime unit.
4.27
RESYNCHRONIZE MINOR TIME
This command allows the user to manually re-synchronize the minor time (subseconds) to the
GPS on-time 1pps pulse. This command must be issued if the antenna cable length is changed
and subsequently a new cable delay is entered.
•
The user inputs $W (HEX 24/HEX 57).
•
The unit responds with OK CR/LF.
4-14
ET6xxx ExacTime GPS TC & FG (Rev C)
Symmetricom Inc
I/O PORT DATA INPUT/OUTPUT
4.28
SELECT DEFAULT VALUES
This command allows the user to input/reset a series of default parameters into the GPS
ExacTime Unit, which are:
Elevation Angle
Mode
Position Average Number
Time Interval
Event Log
Exact Frequency Measurement
Local Offset
Cable Delay
Position
MUX Outputs
•
The user inputs $X (HEX 24/HEX 58).
•
The unit responds with OK CR/LF.
4.29
5o
Start-up (AUTO).
200
Disabled, falling edge.
Disabled, falling edge (all three events).
Disabled.
00.0
50
Symmetricom’s
CH1 IRIG B DC
CH2 10MHz
CH3 1pps
CH4 10HMz
EXTERNAL FREQUENCY MEASUREMENT – SELECT INPUT FREQUENCY
This command allows the user to specify the input frequency.
•
User inputs $Y (HEX 24/HEX 59) followed by eight digits and CR/LF. The eight (8) digits
correspond to the input frequency. Leading zeros are required to be entered.
•
The unit responds with OK CR/LF.
Example: $Y01000000 CR/LF
The above example illustrates selecting an input frequency of 1MHz.
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CHAPTER FOUR
4.30
EXTERNAL FREQUENCY MEASUREMENT – ENABLE/DISABLE
This command allows the user to enable the external frequency measurement option.
•
The user inputs $Z (HEX 24/HEX 5A) followed by a 1.
•
The unit responds with OK CR/LF.
This command allows the user to disable the external frequency measurement option.
•
The user inputs $Z (HEX 24/HEX 5A) followed by a 0.
•
The unit responds with OK CR/LF.
4.31
EXTERNAL FREQUENCY MEASUREMENT – REQUEST DATA
This command allows the user to request the external frequency measurement data. The
measurement and subsequent calculation is done at least once every five seconds and is averaged
over the time period beginning when the external frequency measurement option was enabled.
•
The user inputs $[ (HEX 24/HEX 5B).
•
The unit responds with a + or -, four digits representing the magnitude of drift/stability, E-,
two digits (exponent - power of ten), space, four digits representing the time period in
seconds, E+, two digits (exponent - power of ten).
4.32
REQUEST SATELLITE SIGNAL SNR
This command allows the user to obtain the signal SNR (Signal Noise Density Ratio) of each
satellite in view. The larger the number, the greater the signal strength. Typical values are
between 30 and 55.
•
The user inputs $] (HEX 24/HEX 5D).
•
The unit responds with #, two digits of the satellite PRN number, and three digits of signal
SNR. This format will be printed for each satellite in view.
If the signal SNR is 0.00, the satellite has not been acquired.
The last satellite’s information will be followed by CR/LF.
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I/O PORT DATA INPUT/OUTPUT
Example:
#12 +053 # 24 + 046 CR/LF
The above example illustrates the unit responding with a signal SNR of +53 for satellite vehicle
twelve and +46 for satellite vehicle twenty-four. The actual message will contain more satellites
than this example.
4.33
REQUEST UNIT OPERATING PARAMETERS
This command allows the user to request a number of operating parameters that aren’t available
with other specific commands.
•
The user inputs $^ (HEX 24/HEX 5E).
•
The unit will respond with the following example:
U M0 D1 L00 LS13 PA0200 PR0 OS0 GPIB17 LK1
U
G
M0
D1
L00
LS13
PA02000
PR0
OS0
GPIB17
LK1
Table 4-6
Operating Parameters
UTC sync.
GPS sync.
Mode 0 (Auto mode). 1 = Stationary, 2 = Dynamic, and
5 = Flywheel.
Discipline. 1 = on, 0 = off.
Local time offset.
Number (13) of Leap Seconds.
Number of Position Averages.
Printer option. 0 = off, 1 = on.
External Oscillator. 0 = internal. 1 = external.
The address (17) of the IEEE-488 interface. This number
will be meaningful only if the option is installed.
1 = Unit Locked
0 = Unit Unlocked
The last response is CR/LF.
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4.34
ENABLE/DISABLE 50/60Hz MEASUREMENT (MODEL ET6500 ONLY)
This command allows the user to enable or disable the 50/60Hz measurement feature.
•
The user inputs $B (HEX 24, HEX 42) followed by either a zero or a one. Zero turns the
option OFF, and one turns the option ON.
•
The unit responds with OK CR/LF.
Example:
$B1
The above example illustrates enabling the 50/60Hz measurement option.
If the unit is not locked, and it isn’t available, the message “NOT LOCK” will be sent.
4.35
50/60Hz SELECTION (MODEL ET6500 ONLY)
This command allows the user to select either the 50Hz or 60Hz measurement features.
•
The user inputs $L (HEX 24, HEX 4C) followed by either a zero or a one. (Zero for 50Hz
measurement, one for 60Hz measurement.) If the unit is not doing measurements, the RS232 will respond with OK (CR) (LF), otherwise the unit will respond with ? (CR) (LF).
4.36
ENTER 50/60Hz OFFSET DATA (MODEL ET6500 ONLY)
This command allows the user to enter a starting point for the time error calculation.
•
The user inputs $D (HEX 24, HEX 44) followed by one digit (sign), two digits of seconds, a
decimal point, followed by three digits of milliseconds. The sign digit’s definition is 1 = +
(plus) and
0 = - (minus).
•
The unit responds OK CR/LF.
Example:
$D 023.406
The above example illustrates entering a time error offset of –20.346 seconds.
Note: The time error offset can only be entered if the 50/60Hz measurement
option is OFF.
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I/O PORT DATA INPUT/OUTPUT
If a time offset is entered while the 50/60Hz option is enabled, the message “OPT ON” will be
sent, and the time offset data is ignored.
The offset is stored in battery backed RAM, so it will be retained if the unit is turned OFF and
then back ON again.
4.37
REQUEST 50/60Hz MEASUREMENT DATA (MODEL ET6500 ONLY)
This command allows the user to obtain the 50/60Hz measurement data.
•
The user enters $A (HEX 24, HEX 41).
•
The unit responds with XX.XXXX, space, Hz (representing frequency measurement), space,
±XX.XXXX, space, SEC (representing accumulated time error), space, XXX.X space, DEG
(representing phase angle measurement), space +XX.XXX, space, OFFSET (representing
time offset), CR/LF.
Example:
60.1324 Hz + 01.357 SEC 180.2 DEG + 01.206 OFFSET CR/LF
The above response states that the frequency measurement is 60.1324Hz, and the accumulated
time error is +1.3574 seconds.
The 60Hz measurement data is also available on the 50/60Hz measurement screen of the front
panel LCD display. The format is as follows:
FRQ: 60.1324HZ PHASE: 180.2o ERROR: +01.3574S
1>OFFSET:+01.206S<4>OFF<5>ON<6>60HZ/ ON
If the 50/60Hz option is not enabled, ON will be replaced by OFF. When the unit is first turned
on, it will come up in the OFF (default) mode. If the 50/60Hz option is turned on prior to the
unit achieving LOCK, ON will be replaced by ERR and measurement data will not be available.
When measuring the 60Hz with a time period of 16.66 milliseconds, if a measurement occurs
outside a one millisecond window of that time period (such as a noise spike), the measurement is
ignored, and an error is counted. If 1,000 successive errors are read, the message ERR appears,
and the 60Hz measurement option is turned OFF.
4.38
PRINTER – SET-UP CONFIGURATION
This command allows the user to set-up the printer configuration. It is applicable to both the
Standard RS232 Printer Output and the One Second Burst RS232 ASCII Time Output.
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CHAPTER FOUR
•
The user enters $H (HEX 24/HEX 48) followed by abcd where:
a = baud rate (0-7)
0 = 50
1 = 300
2 = 600
3 = 1200
4 = 2400
5 = 4800
6 = 9600
7 = 19200
b = number of data bits
0=7
1=8
c = parity
0 = none
1 = odd
2 = even
d = number of stop bits
0=1
1=2
4.39
PRINTER – REQUEST CONFIGURATION
This command allows the user to request the current printer set-up. It is applicable to both the
Standard RS232 Printer Output and the One Second Burst RS232 ASCII Time Output.
•
The user enters $I (HEX 24/HEX 49).
•
The unit responds with: 09600 8/7 N/O/E 1/2<CR><LF>.
(Baud Rate) (8 or 7 data bits) (none, odd, or even parity) (1 or 2 stop bits)
(carriage return) (line feed).
4.40
PRINTER PORT MODE SELECTION
This command allows the user to specify the printer mode or output format . The selection is
either “Standard” or “One Second Burst”. For a detailed description of these two formats, refer
to Chapter Three – Operation.
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I/O PORT DATA INPUT/OUTPUT
•
The user inputs $> (HEX 24/HEX 3E) followed by either a 0 or a 1.
The “0” is for the standard format.
The “1” is for the one second burst format.
•
The unit responds with OK CR/LF.
4.41
PRINTER – SELECT OUTPUT RATE
This command allows the user to specify the interval rate at which the data is output. It can be
any time from three (3) seconds to 9999 seconds. (Leading zeros are required). It is applicable
only to the Standard RS232 Printer Output.
•
User inputs $g (HEX 24/HEX 67) followed by four (4) digits corresponding to the number of
seconds.
Example: $g0005
•
The unit responds with OK CR/LF (carriage return/line feed).
Example: $g0005
The above example illustrates selecting an output interval rate of five seconds.
4.42
PRINTER – REQUEST OUTPUT RATE
This command allows the user to determine what is the current output rate. It is applicable only
to the Standard RS232 Printer Output.
•
User inputs $h(HEX 24/HEX 68).
•
The unit responds with four (4) digits followed by CR/LF. These four digits correspond to
the output interval rate in seconds.
4.43
PRINTER – ENABLE/DISABLE & DATA SELECT
This command is applicable only to the Standard RS232 Printer Output.
•
User inputs $n (HEX 24/HEX 6E) followed by three (3) digits.
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•
The first digit enables or disables the printer port.
0 = printer port disabled
1 = printer port enabled
•
The second digit enables or disables position information output.
0 = position information disabled
1 = position information enabled
•
The third digit enables or disables the output of option data (if available).
0 = option data disabled
1 = option data enabled (if the option itself is available and has been
previously turned on)
Example: $n101
The unit responds with OK CR/LF.
The above example illustrates the user turning on the printer port, not outputting any position
information, but outputting option data (such as external frequency measurement). Refer to the
following examples of output data:
94 027.17:04:38 M0 S00 E00 25 00 00 00 -0019-E12 33 48.8270N 117 53.3864W +0028 T1
705337.512
94 027.17:04:43 M0 S00 E00 25 00 00 00 -0019-E12 33 48.8270N 117 53.3864W +0028 T1
705337.512
94 027.17:04:48 M0 S00 E00 25 00 00 00 -0019-E12 33 48.8270N 117 53.3864W +0028 T1
705337.512
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I/O PORT DATA INPUT/OUTPUT
94 = year
027.17:04:38 = time (days, hours, minutes, seconds)
M0 - mode (start-up mode)
* S00 = status code (doing GPS corrections)
* E00 = error code (system check OK)
25 00 00 00 = tracking satellite vehicle 25
-0019E-12- frequency offset measured in parts to 10-12
33 48.8270N = latitude 33 degrees 48.8270 minutes, north
117 53.3864W - longitude 117 degrees 53.3864 minutes, west
+0028 = altitude in meters
T1 705337.512 = time interval in microseconds
* For a listing of status codes and error codes, refer to Chapter Three.
External frequency measurement or another option can be substituted for time interval if
available and previously enabled.
4.44
ENTER PRESET COINCIDENCE TIME (MODEL ET6500 ONLY)
This feature provides the ability to preset a coincidence time into the GPS Time Code and
Frequency Generator from hundreds-of-days through tenths of microseconds. When the
coincidence time equals the GPS time, a two microsecond positive going pulse is output. For the
specific output connector, refer to Chapter One.
•
The user inputs $o (Hex 24/Hex 6F). (The $ is the attention/log-on character. The “o” is the
ID ASCII character).
•
Then enter sixteen ASCII digits to preset the coincidence time (starting with hundreds of
days):
Example:
0562347269785673
This example shows entering the preset coincidence time of:
056 days, 23 hours, 47 minutes, 26 seconds, 978 milliseconds, 567 microseconds, and
300 nanoseconds (or 3 tenths of a microsecond).
The preset coincidence pulse occurs 200 nanoseconds late. It’s pulse width is approximately two
microseconds wide, positive edge on-time. It is capable of driving ten LSTTL loads.
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CHAPTER FOUR
4.45
REQUEST MUX OUTPUT
This command allows the user to find out which output is selected on the four multiplexed
channels. The command consists of the log-in character ($-HEX 24), the primary character (JHEX 4A), and the secondary character (R-HEX 52).
•
The user inputs $JR (HEX 24/HEX 4A/HEX 52).
•
The unit responds with :
1 aa 2 aa 3 aa 4 aa CR/LF.
The digits 1-4 correspond to the MUX channels. “aa” (two digits) corresponds to Table 4-7.
Table 4-7
Request MUX Output
00
10MHz
01
5MHz
02
1MHz
03
100KHz
04
10KHz/2PPH*
05
1KHz
06
100Hz
07
10Hz/1PPH**
08
1Hz
09
.1Hz
10
1PPM
11
TRACKING
12
LOCKED
13
+5 Volts
14
1pps
15
DC Code
* 10KHz is output in Models ET6000 and ET6010. 2PPH is output in Model ET6500.
** 10Hz is output in Models ET6000 and ET6010. 1PPH is output in Model ET6500.
See Chapter One of this User’s Guide for specifications.
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I/O PORT DATA INPUT/OUTPUT
4.46
SET MUX OUTPUT
This command allows the user to select the signal output on the four multiplexed channels. The
command consists of the log-on character ($-HEX 24), the primary character (J-HEX 4A) and
the secondary character (S-HEX 53).
•
The user enters $JS (HEX 24/HEX 4A/HEX 53) followed by:
aabbccdd
Where:
aa corresponds to 2 digits = Channel 1.
bb corresponds to 2 digits = Channel 2.
cc corresponds to 2 digits = Channel 3.
dd corresponds to 2 digits = Channel 4.
Note: The digits (00-15) are the same as in Table 4-7.
4.47
SET MAJOR TIME – TOD (TIME OF DAY)
This command allows the user to input and change the TOD. This command is only useful when
the unit is in the “Flywheel” mode (See Chapter Three) It consists of the attention/log-on
character, the command character, and nine characters representing days (day-of-year), hours,
minutes, and seconds.
•
The user enter $K (HEX 24/HEX 4B) followed by:
DDDHHMMSS
•
The unit responds with OK CR/LF.
4.48
SET YEAR
This command allows the user to enter two (2) digits of year into the GPS time. It consists of the
attention/log-on character, the command character, and 2 characters representing year.
•
The user enters $< (HEX 24/HEX 3C) followed by two digits.
•
The unit responds with OK CR/LF.
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CHAPTER FOUR
4.49
AUTOMATIC DAYLIGHT SAVINGS TIME
This feature provides the capability of offsetting the time by one hour to compensate for daylight
savings time. It can be turned on and off using the front panel keyboard. It can also be
programmed to automatically turn on /off for up to ten years using the RS-232 I/O port. Each
time this feature is accessed from the I/O port, two commands need to be issued which consist
of:
A Primary Command
• The user inputs $O (HEX 24/HEX 4F).
A Secondary Command
One of five secondary commands can be issued (in conjunction with the primary command) to
perform the following functions:
4.49.1 DISABLE AUTO DAYLIGHT SAVINGS TIME FUNCTION
This command disables the daylight savings time feature.
•
The user inputs D (HEX 44).
•
The unit responds with OK followed by CR/LF (carriage return/line feed).
Example: $OD
4.49.2 ENABLE AUTO DAYLIGHT SAVINGS TIME FUNCTION
This command enables the daylight savings time feature.
•
The user inputs E (HEX 45).
•
The unit responds with OK followed by CR/LF.
Example: $OE
4.49.3 SET AUTO DAYLIGHT SAVINGS TIME DEFAULT INTERVAL
This command allows the following daylight savings time intervals to be loaded into memory.
If you want the unit to automatically increment/decrement, the following command must be
proceeded by the ENABLE command.
•
The user inputs F (HEX 46).
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I/O PORT DATA INPUT/OUTPUT
•
The unit responds with OK followed by CR/LF.
Example: $OF
4.49.4 REQUEST AUTO DAYLIGHT SAVINGS TIME INTERVAL
This command returns a start and stop time for a specific interval.
•
The user inputs R (HEX 52) followed by an interval number of 0-9 (HEX 30 - HEX 39).
•
The unit responds with:
#c Yaa Dbbb Hmm Dbbb Hmm CR/LF
where:
c = interval number (0-9)
aa = year
bbb = Julian day
mm = hour
•
The first group Dbbb Hmm indicates the start time of daylight savings.
•
The second group Dbbb Hmm indicates the stop time of daylight savings.
Example: $OR3
4.49.5 SET AUTO DAYLIGHT SAVINGS TIME INTERVAL
This command allows the user to program a daylight savings time interval.
•
The user inputs S (HEX 53) followed by:
caabbbmmbbbmm
where c, aa, bbb, and mm have the same weight/value as explained in the
REQUEST command.
Example: $OS4050920130102
General Specifications
If the stop time is greater than the start time, then the interval is assumed to be in the same year.
If the stop time is less than the start time, then the stop time is assumed to be in the next year.
Performing a “Cold Reset” will disable the Daylight Savings time feature and load in the ten
default time intervals.
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CHAPTER FOUR
Each time interval must be at least two hours in duration.
Any changes must be made at least one hour prior to the next time interval.
The time intervals do not have to be programmed in sequence.
All set-ups are stored in battery backed RAM so they are retained if the unit is turned off and
back on again.
Table 4-8
Automatic Daylight Savings Time – Default Values
(Default)
Interval
0
1
2
3
4
5
6
7
8
9
4.50
First Sunday of April
Julian
Year
Day
Hour
01
091
01
02
097
01
03
096
01
04
095
01
05
093
01
06
092
01
07
091
01
08
097
01
09
095
01
10
094
01
Last Sunday of October
Julian
Year
Day
Hour
01
301
02
02
300
02
03
299
02
04
305
02
05
303
02
06
302
02
07
301
02
08
300
02
09
298
02
10
304
02
REQUEST UNIT SERIAL NUMBER
This command allows the user to request the unit’s serial number (the same serial number that is
on the rear panel).
•
The user inputs $@ (HEX 24/HEX 40).
•
The unit will respond with four characters followed by CR/LF.
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CHAPTER FIVE
MAINTENANCE/TROUBLESHOOTING
5.0
MAINTENANCE
This unit utilizes solid-state components. There are no moving parts (except switches etc.) or
parts with limited life.
5.1
ADJUSTMENTS
Periodically the internal time base may have to be nulled/calibrated due to aging and drift of the
oscillator.
5.1.1 INTERNAL OSCILLATOR CALIBRATION
It is recommended that the oscillator be nulled when the DAC value starts to approach 5,000 or
60,000.
The GPS TC&FG will have one of three oscillators installed in it:
•
A voltage controlled temperature compensated crystal oscillator (TCXO) located on the GPS
Main Assembly 100015 in location Y3.
•
A low noise oven oscillator located on the GPS Main Assembly 100015 in location Y1.
•
An X72 or LPRO rubidium oscillator attached to the bottom plate of the chassis assembly.
This oscillator has no mechanical adjustment.
There are two methods to null/calibrate the internal oscillator. Use whichever method is suitable
to your means and capabilities.
A.
First Method
The oscillator can be nulled against a known frequency standard with an
oscilloscope or other suitable means by using the following steps:
1. Turn on the unit and wait approximately one hour for the oscillator to warm up
and stabilize.
2. Sync one trace of an oscilloscope on the known frequency standard. Using the
other trace, monitor the 10MHz output of the unit. Remove the top cover of the
unit.
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CHAPTER FIVE
3. The input of the DAC must be held static prior to the nulling oscillator. This
can be accomplished one of three ways:
•
Disconnect the antenna from the rear of the unit.
•
Select the FLYWHEEL mode.
•
Disable disciplining. Refer to Chapter Four, “Disable Disciplining” in the
User’s Guide.
4. Set the DAC value to it’s midpoint 32767. Refer to Chapter Four ,“Enter DAC
Value” in the User’s Guide.
5. The oscillator is adjusted using a plastic adjustment tool. Depending on which
oscillator is installed, the adjustment screw (inside the oscillator) is in one of two
locations:
•
The voltage controlled temperature compensated crystal oscillator located on
the GPS Main Assembly 100015 in location Y3 has its adjustment access hole
on the top of the oscillator.
•
The low noise oven oscillator located on the GPS Main Assembly 100015 in
location Y1 has its access hole on the side of the oscillator. There is an access
screw used to seal the oscillator that has to be removed first. Remember, after
the adjustment is complete, replace the access screw.
6. Adjust the oscillator until the 10MHz output is stable with respect to the
frequency standard.
7. Enable disciplining. Refer to Chapter Four, “Enable Disciplining” in the
User’s Guide. Replace the top cover.
8. After approximately one hour, check the DAC value number again. If it has
changed by more than ±5000 from 32767, repeat steps two through six.
B.
Second Method
If a known frequency standard is not available, the oscillator may be nulled as
follows:
1. Set the unit to operate in the STATIONARY mode. Wait until the unit is
LOCKED.
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MAINTENANCE/TROUBLESHOOTING
2. Read the DAC value either from the RS-232 I/O port, or from the LCD
display.
3. Remove the top cover. Locate the oscillator and its adjustment access hole.
4. SLOWLY (no more than 45o each time) adjust the oscillator and watch the
DAC value change. If the DAC value is 65535, turn the oscillator adjustment
counterclockwise, which will decrease the frequency and the DAC value. If the
DAC value is 00000, turn the oscillator adjustment clockwise, which will increase
the frequency and the DAC value.
5. Wait approximately one minute between each adjustment to allow the
oscillator to stabilize.
6. Keep adjusting the oscillator in the appropriate direction until the DAC value
is approximately at its midpoint (32767). Replace the top cover.
7. If after approximately one hour, the DAC value has changed by more than
±5,000 from 32767, repeat steps one through six.
5.1.2 LCD ADJUSTMENT
The contrast of the LCD display may be adjusted using potentiometer R99.
5.1.3 AC CODE ADJUSTMENTS
The modulation ratio of the AC code output can be adjusted from a typical range of 2:1 to 6:1. It
has been factory adjusted for a ratio of 3:1. The modulation ratio adjustment is potentiometer
R107.
The code output amplitude (level) is adjusted using potentiometer R108. It can be adjusted to
approximately eight volts peak-to-peak, terminated into 50Ω.
5.1.4 10MHz SINE WAVE
The amplitude (level) of the 10MHz sine wave output can be adjusted using potentiometer R30.
The nominal amplitude is approximately 1 volt RMS terminated into 50Ω.
5.1.5 10MHZ SQUARE WAVE
The duty cycle (symmetry) of the 10MHz square wave output can be adjusted to approximate
50/50% using potentiometer R60. When making this adjustment, monitor the 10MHz square
wave at the rear panel BNC output.
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CHAPTER FIVE
5.2
TROUBLESHOOTING
5.2.1 GENERAL
If at any time the unit fails to operate or operates intermittently, it is a good idea to remove the
top cover and look for any visible problems or damage. Make sure all cables are securely
connected. Insure all integrated circuits are mounted into their sockets where applicable. Look
for damaged components.
Because the design of the unit utilizes LSI (Large Scale Integrated) circuits, and is
microprocessor based, much of the operation is controlled by firmware/software. There are few
user serviceable components. If severe problems are encountered, consult the factory.
Note: When servicing the power supply, disconnect the AC power from the unit.
5.2.2 POWER LED WILL NOT ILLUMINATE WHEN ON/OFF SWITCH IS
ACTIVATED
DC voltage is not present on J21 input connector pins on Assembly 100015.
Table 5-1
J21 Input Connector Pins
J21 pin 1
Ground.
J21 pin 2
-12 volts.
J21 pin 3
+12 volts.
J21 pin 4
+5 volts.
•
Check the fuses in the power entry module.
•
Check power wiring connections.
5.2.3 TRACKING LED DOES NOT ILLUMINATE
•
Antenna/preamp is defective.
•
Cable or connections between the antenna/preamp and the unit are open or intermittent.
•
OnCore GPS Module (55182) is defective.
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MAINTENANCE/TROUBLESHOOTING
5.2.4 LOCKED LED DOES NOT ILLUMINATE
•
Internal oscillator may have to be nulled/calibrated.
•
Elevation Mask value may be set too high.
5.2.5 UNIT DOES NOT TRACK STATELLITES, ERROR MESSAGE/CODE – ANT.
UNDERCURRENT
•
Antenna/preamp failure.
•
Antenna cable open or shorted (center conductor to shield).
5.2.6 COLD RESET
A “COLD RESET” needs to be performed upon the following conditions:
•
The unit fails to operate or operates intermittently and it is not a power, tracking, or locked
problem.
Cold Reset Procedure
• Turn off or disconnect AC power.
•
While holding down the MENU key of the keyboard, reapply power and observe the LCD
display to read:
COLD RESET DONE, UNIT SET TO DEFAULT
PLEASE RELEASE COLD RESET SWITCH
•
Release the MENU key of the keyboard.
•
The default values have now been loaded into the unit.
•
Each of the above default values needs to be examined and changed/reentered as necessary.
(See Section 4.31). If the unit is left in the default “AUTO” mode, it will find its own
position.
Note: If new software has been installed in the unit, a cold reset will automatically be
performed the first time power is applied. The following message will appear on the
LCD for approximately four seconds:
COLD RESET DONE, UNIT SET TO DEFAULT
Symmetricom Inc
ET6xxx ExacTime GPS TC & FG (Rev C)
5-5
CHAPTER FIVE
5.3
THEORY OF OPERATION
5.3.1
GPS SYSTEM OPERATION
Before going into the Theory of Operation of the ExacTime GPS Time and Frequency Generator we
must first understand the operation of the GPS system and what the Satellites are providing. The
GPS system is a ranging system, in which satellites inform the ground user equipment where they
are located and give the time information. The function of the user equipment is to determine its
position (X, Y, and Z) as well as the time (T). This is accomplished through the use of simultaneous
equations. Since there are four unknowns it requires at least four satellites to solve the equations. At
power-on the user equipment has no idea where it is located or what time it is. Once it has acquired
(TRACKED) four satellites, it can begin the process of solving the equations. Once a position has
been determined, it can be loaded into memory and used to solve for the time only. Another aspect
of the GPS system that is in need of some explanation is a deterrent function known as Selective
Availability (SA). This is a purposeful degradation of the GPS system’s performance so that an
enemy of the United States can not use the system accurately against us in time of a war. Although
SA is not currently activated, it can be at any time. The degradation that takes place is from twentyfive meters to one-hundred meters Spherical Error of Probability (SEP) for position information and
one-hundred nanoseconds to 300 nanoseconds 95% of the time for Time information.
5.3.2
MODES OF OPERATION
Now that we understand that a GPS is a ranging system and the user equipment must calculate its
position as well as time, we will now take a look at the different MODES of operation of the
equipment and understand how it affects the operation of the equipment. There are several modes of
operation for the ExacTime (Auto, Stationary, Dynamic, and Flywheel). We will start off with the
Flywheel mode and work our way back to the normal Auto mode.
A.
FLYWHEEL MODE
Flywheel mode is a new, optional mode in which the unit is powered-on and does not
operate from GPS information. The operator can set the time and the unit will function as a
stand-alone clock and frequency source. No correction to the time or frequency are done by
the unit, it simply continues from the last information in terms of the DAC value, position
data, output selection, etc.
5-6
ET6xxx ExacTime GPS TC & FG (Rev C)
Symmetricom Inc
MAINTENANCE/TROUBLESHOOTING
B.
DYNAMIC MODE
The Dynamic mode of operation is a mode in that it is solving for all four variables (X, Y, Z,
and T) at the same time. This mode is used either by the system to determine its location or
used in a three-dimensional moving platform (i.e. aircraft). The GPS receiver used in the
ExacTime is a OnCore Module. This receiver has eight channels in which to decode satellite
information (what is referred to as tracking a satellite). Four of the channels will be
collecting data from four satellites while the remaining four channels will be collecting data
from as many as four more satellites in a multiplex scheme. In this way the receivers
processor can be solving for the four unknowns from as many as four sets of equations at the
same time. This is referred to as an “over-determined solution.” Some of the effects of SA
can be smoothed out using this process. However, in this mode the time information is
moving as well as a function of newly calculated positions each second. This is not the most
stable timing mode to operate in, but for moving platforms it is the best mode of operation.
C.
STATIONARY MODE
It is better to refer the Stationary mode as a one-dimensional mode. The receiver will use the
stored position in memory and solve for the time information from as many as eight satellite
at the same time. The receiver will then provide an average solution of the time information
to the ExacTime, thus providing a more stable time in which to operate under the effects of
SA. This is the best timing mode of operation as long as the equipment is in a static
environment and a good position has been entered into memory.
D.
AUTO MODE
The Auto mode is a preprogrammed mode in the ExacTime and is the default mode that the
unit is shipped to the customer in. At power-on the unit does not know where it is nor what
time it is, thus it must determine all of this. At power-on the Auto mode commands the
receiver into the Dynamic mode of operation so that it can determine the location as well as
time. The ExacTime will first set an approximate time and position as soon as it tracks four
satellites. It will then begin stabilizing the internal oscillator in order to get it close to the
correct frequency. After completion of the oscillator stabilization the unit will begin
collecting position information. It will average the default selection of 200 positions, the
unit can be set to collect as many as 99,999 positions. After the 200 positions have been
collected it will command the receiver into a Stationary mode, load the average position into
the receiver, set time and begin normal Stationary mode of operation. We will discuss this
normal mode of operation in more detail later.
Symmetricom Inc
ET6xxx ExacTime GPS TC & FG (Rev C)
5-7
CHAPTER FIVE
5.3.3
EXACTIME INTERNAL CONFIGURATION
The ExacTime unit is comprised of several sub-assemblies, power supplies, main clock assembly,
GPS receiver, front panel LCD display, front panel keypad, optional rubidium oscillator, option
motherboard, plug-in option assemblies. For the purpose of this discussion a configuration including
a rubidium oscillator, 1MHz and 5MHz sine wave output options will be used in the understanding
of the ExacTime’s operation (please see Figure 5-1).
A
POWER SUPPLY (P/N 8010-LPT4-2)
The basic power supply in this configuration is 8010-LPT4-2. This supply is used to power
the ExacTime and all of the electronic assemblies (i.e. main assembly, front panel
assemblies, GPS receiver, and option motherboard). It provides the system with a regulated
+5 volts, +12 Volts and -12 Volts. All of the electronics use these voltages to operate within
the ExacTime.. Without some or all of the voltages the unit will not operate correctly.
When checking for any problem within the ExacTime it would be good to verify all of the
power supply voltages to be assured they are correct. This can be done at the connector
located at the supply or at the end of the power cable.
B.
GPS MAIN BOARD (P/N 100015)
This main assembly is the center of the unit. It includes a microcomputer, memory, I/O
interface, buffers, and all of the additional circuits to support the ExacTime’s functions. The
computer provides information to the front panel LCD for display of information to the
operators as to the status, error, and many other operational information and selections. It
interfaces to the front panel keypad and scans for operator key depressions and displays the
selected information. All inputs and outputs at the rear panel with the exceptions of the ones
provided by the option motherboard come from the main assembly. All outputs are buffered
so as to prevent any damage to the unit should any output be shorted for any reason. Located
on the main assembly is the Oncore Receiver Module as a plug-in assembly. It is held in
place by four small screws and connects via an OSX connector and a multi-pin DIP
connector. We will discuss the operation of the Main Assembly later in this section in more
detail.
C.
FRONT PANEL KEYPAD & LCD ASSEMBLY (P/N 55158)
The front panel keypad is a board that has small buttons and rubber fingers that go through
the front panel to provide the operator with a colored push button and tactile feedback of a
button push. The push buttons are scanned by the main assembly computer for operator
entry of information or commands. This board provides the mounting for the LCD display
as well. The LCD provides all of the operator information, menu selections, and operator
feedback of entries. The interface is through two multi-pin ribbon cables to the Main
Assembly.
5-8
ET6xxx ExacTime GPS TC & FG (Rev C)
Symmetricom Inc
MAINTENANCE/TROUBLESHOOTING
D.
OPTION MOTHERBOARD (P/N 35007)
The option motherboard is used in order to expand the capabilities of the ExacTime. It
provides a computer buss command interface to option assemblies, if required, as well as
basic 1pps, 10MHz, 5MHz, 1MHz, IRIG B and other signals that may be required for option
expansion. The option slots (1-4) provide this information to optional plug-in assemblies
(see the ExacTime Configuration Guide for a list of the option assemblies available). For
this example the only option assemblies plugged in are the 1MHz and 5MHz sine wave
shapers. The sine wave shapers simply take the 1MHz or 5MHz TTL square wave signals
provided on the buss interface and provide a sine wave output to the rear panel BNC
connectors on the option motherboard. The option motherboard provides buffers before the
signals go the BNC connector so as to prevent and damage should the output be shorted for
any reason. Additional options could be added to this configuration as there are two
additional slots available for customer expansion. Should any of the option outputs fail it is
a simple matter to determine if the buffer has failed or the module assembly has failed by
swapping the modules. The sine wave shapers are interchangeable and can be plugged in to
any slot or from another unit. Power is provided to the assembly through a parallel cable
from the power supply.
E.
X72 RUBIDIUM OSCILLATOR (OPTIONAL)
The internal oscillator can be an X72 Rubidium Oscillator. Its interface to the GPS Main
board (100015) is through a cable assembly attached to connector J23. The 10MHz
frequency output and the control voltage to adjust the frequency of the oscillator are via this
cable assembly. The control voltage is provided by a digital-to-analog converter on the main
assembly. It is used to discipline (control) the frequency output to the GPS reference.
5.3.4 MICROCOMPUTER PROGRAM THEORY OF OPERATION
The microprocessor clock provides a system where by the time as well as the frequencies generated
are “disciplined” i.e. phase locked to the GPS reference information. Looking at Figure 5-1 there are
two things that form the interface between the receiver and the clock. The first is an RS-422 I/O that
provides all of the operating commands, status, and GPS data to the clock. The second is an on-time
1pps reference pulse. Once the receiver has positioned the 1pps reference, and after it begins
tracking satellites, the difference (BIAS) between the 1pps reference and the real “on-time” 1pps is
measured. During the “Oscillator Stabilize” phase, the clock will take this BIAS information and
control the internal oscillator’s frequency to correct for any frequency offset. When the unit turns on
the LOCK LED, the current BIAS information is measured again and the difference (after much
filtering) is used to control the frequency of the internal oscillator.
Symmetricom Inc
ET6xxx ExacTime GPS TC & FG (Rev C)
5-9
CHAPTER FIVE
1PPS ref
1PPS
Phase
Comp.
DAC
OSC
Divider
Phase Lock Loop Clock
For a very simple way to look at this process we can use the above diagram of a phase lock loop to
describe the function that is taking place. As you can see the 1pps that is derived from the oscillator
can be controlled by the DAC so that the phase relationship is that of the measured BIAS
information along with the 1pps reference. In this way all of the frequencies as well as the time
information provided by the clock is “disciplined” to the GPS reference information. Both the
integration (filtering) of the information in the computer as well as the oscillator stability form a very
stable system especially when the oscillator is a rubidium oscillator.
5-10
ET6xxx ExacTime GPS TC & FG (Rev C)
Symmetricom Inc
MAINTENANCE/TROUBLESHOOTING
Symptom
No Lights and No
Display
No Information on
LCD
1
2
3
Blown Fuse
No DC Power to (100015)
Main Board
1
Ribbon Cable Not
Connected
Contrast Not Adjusted
Bad LCD
LCD Drivers Bad
2
3
4
Time Does Not
Count
Will Not Acquire
SV’s
1
4
5
6
Bad Oncore (GPS Receiver
Module)
No GPS Signal from
Antenna
No Power to Antenna (S/B
+ 5 Vdc on J2)
DAC Level at Extremes
(S/B 20000 - 40000)
No 10 MHz
Bad Oncore
Bad 100015 Main Board
1
10MHz not stable
2
Bad Main Board
1
Amplitude too Low
2
3
Bad Sine wave Shaper
Board
Bad Motherboard
4
Bad 100015 Main Board
1
2
3
Will Not Lock
No Output from 1
or 5MHz Option
Symmetricom Inc
Possible Cause
No Input Power
Solution
Check AC power cord…is it correctly and
firmly installed?
Check if AC line fuses are open.
Check J21 for proper cable connection.
Check J21 for correct voltages:
Pin 1 - +12 Volts
Pin 2 - +5 Volts
Pin 3 - +5 Volts
Pin 4 - Ground
Pin 5 – Ground
Pin 6 - -12 Volts
Check Cable for proper seating.
Check pot.R99 for proper adjustment.
Change LCD with a known good one.
Change 100015 main board with a known
good one. (Contact Symmetricom for repair).
Swap Oncore with a known good one.
(Contact Symmetricom for repair).
Check all antenna cable connections.
Swap antenna with a known good one.
Check continuity of cable 812502-14.
Swap Oncore with a known good one.
Do a cold reset - See “Cold Reset” in this
chapter of the User's Guide.
Check 10MHz output from Oscillator.
Swap Oncore with a known good one.
Swap 100015 with a known good one.
(Contact Symmetricom for repair).
Check stability of 10MHz from oscillator
against a known standard.
Swap 100015 with a known good one.
(Contact Symmetricom for repair).
Check amplitude adjustment pot on sine wave
shaper board.
Swap shaper with a known good one.
(Contact Symmetricom for repair).
Swap option motherboard with a known good
one. (Contact Symmetricom for repair).
Swap 100015 with a known good one.
(Contact Symmetricom for repair).
ET6xxx ExacTime GPS TC & FG (Rev C)
5-11
CHAPTER FIVE
Symptom
Cannot
Communicate Via
RS-232
No / Wrong
Output J4-J9
Push Buttons
Don’t Work
1
Possible Cause
RS-232 Cable Not
Connected
Solution
Check RS-232 cable connection at J12 on rear
panel.
2
Wrong Parameters
3
I/O Glitch
4
Bad 100015 Main Board
1
Wrong or Missing Jumper
Check RS-232 I/O parameters for
compatibility with system.
Try cold reset - See “Cold Reset” in this
chapter of the User's Guide.
Swap 100015 with a known good one.
(Contact Symmetricom for repair).
Check Jumper Configuration on 100015.
2
Bad 100015 Main Board
1
Interface Cable Not
Connected
Bad Switch
2
5-12
Swap 100015 with known good. (Contact
Symmetricom for repair).
Check cable 812515-3 for proper seating.
Swap front panel assembly with a known good
one. (Contact Symmetricom for repair).
ET6xxx ExacTime GPS TC & FG (Rev C)
Symmetricom Inc
MAINTENANCE/TROUBLESHOOTING
Figure 5-1
ET6000 Block Diagram
LCD Front Panel
Display
Front Panel
Keypad
100015 Main
Assembly
J26
J22
PRINTER
PORT
1PPS
INPUT
GPS
Receiver
IRIG B
(DC)
1PPS (ref)
RS-422 I/O
IRIG B
(AC)
J33
Buffer and I/O
Interface
Microprocessor
Clock
10MHz
1PPS
LOCKED
TRACKING
RS-232 I/O
Power Supply
+5VDC
+/-12VDC
POWER
DAC
J21
J2
J3
J20
10MHz
10MHz
Oscillator
1MHz
Sine
1MHz Sine
POWER
Option
Motherboard
POWER
5MHz
Sine
5MHz Sine
AC
Power
Input
Symmetricom Inc
ET6xxx ExacTime GPS TC & FG (Rev C)
5-13
CHAPTER FIVE
This Page Intentionally Left Blank
5-14
ET6xxx ExacTime GPS TC & FG (Rev C)
Symmetricom Inc
APPENDIX A
ASCII CHARACTER CODE TABLE
DEC
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
ASCII Character Code Table
Part One
OCT
HEX
000
00
001
01
002
02
003
03
004
04
005
05
006
06
007
07
010
08
011
09
012
0A
013
0B
014
0C
015
0D
016
0E
017
0F
020
10
021
11
022
12
023
13
024
14
025
15
026
16
027
17
030
18
031
19
032
1A
033
1B
034
1C
035
1D
036
1E
037
1F
CHAR
NUL (^ )
SOH (^A)
STX (^B)
ETX (^C)
EOT (^D)
ENQ (^E)
ACK (^F)
BEL (^G)
BS (^H)
HT (^I)
LF (^J)
VT (^K)
FF (^L)
CR (^M)
SO (^N)
SI (^O)
DLE (^P)
DC1 (^Q)
DC2 (^R)
DC3 (^S)
DC4 (^T)
NAK (^U)
SYN (^V)
ETB (^W)
CAN (^X)
EM (^Y)
SUB (^Z)
ESC (^[ )
FS (^ \ )
GS (^ ] )
RS (^^)
US (^_ )
Note: First ^ denotes the Control Key.
Symmetricom Inc
ET6xxx ExacTime GPS TC & FG (Rev C)
A-1
APPENDIX A
DEC
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
A-2
ASCII Character Code Table
Part Two
OCT
HEX
040
20
041
21
042
22
043
23
044
24
045
25
046
26
047
27
050
28
051
29
052
2A
053
2B
054
2C
055
2D
056
2E
057
2F
060
30
061
31
062
32
063
33
064
34
065
35
066
36
067
37
070
38
071
39
072
3A
073
3B
074
3C
075
3D
076
3E
077
3F
ET6xxx ExacTime GPS TC & FG (Rev C)
CHAR
SP
!
”
#
$
%
&
’
(
)
*
+
,
.
/
0
1
2
3
4
5
6
7
8
9
:
;
<
=
>
?
Symmetricom Inc
ASCII CHARACTER CODE TABLE
DEC
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
Symmetricom Inc
ASCII Character Code Table
Part Three
OCT
HEX
100
40
101
41
102
42
103
43
104
44
105
45
106
46
107
47
110
48
111
49
112
4A
113
4B
114
4C
115
4D
116
4E
117
4F
120
50
121
51
122
52
123
53
124
54
125
55
126
56
127
57
130
58
131
59
132
5A
133
5B
134
5C
135
5D
136
5E
137
5F
ET6xxx ExacTime GPS TC & FG (Rev C)
CHAR
@
A
B
C
D
E
F
G
H
I
J
K
L
M
N
O
P
Q
R
S
T
U
V
W
X
Y
Z
[
\
]
^
_
A-3
APPENDIX A
DEC
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
A-4
ASCII Character Code Table
Part Four
OCT
HEX
140
60
141
61
142
62
143
63
144
64
145
65
146
66
147
67
150
68
151
69
152
6A
153
6B
154
6C
155
6D
156
6E
157
6F
160
70
161
71
162
72
163
73
164
74
165
75
166
76
167
77
170
77
171
79
172
7A
173
7B
174
7C
175
7D
176
7E
177
7F
ET6xxx ExacTime GPS TC & FG (Rev C)
CHAR
`
a
b
c
d
e
f
g
h
i
j
k
l
m
n
o
p
q
r
s
t
u
v
w
x
y
z
{
|
}
~
DEL
Symmetricom Inc
APPENDIX B
GLOSSARY OF TERMS
2-D, 3-D
Refers to two-dimensional and three-dimensional positions. A 2-D position
provides latitude and longitude only. In a 2-D position fix, the altitude is assumed
to be fixed. Only three satellites are required to do a 2-D position. A 3-D
position fix provides the altitude in addition to the latitude and longitude and
requires four satellites.
-AACPOS
Accurate Position.
Almanac
A reduced precision subset of the ephemeris parameters. The almanac data is
used by the GPS satellite receiver to compute the elevation and azimuth angle of
the satellite. Each satellite broadcasts the almanacs for all satellites.
ALT
Altitude.
Anywhere Fix
The ability of a receiver to start position calculations without being given an approximate
location and appropriate time.
APPOS
Approximate Position.
ASCII
American Standard Code for Information Interchange.
Azimuth
The angle for true North of the horizontal projection of the line of sight vector measured
clockwise.
AZM
Azimuth.
Symmetricom Inc
ET6xxx ExacTime GPS TC&FG (Rev C)
B-1
APPENDIX B
-BBandwidth
The range of frequencies in a signal.
BIPM
Bureau International des Poids et Measurements, located in Sevres, France.
BPS
Bits per second (data transmission rate from the satellites).
-CCarrier
A signal that can be varied from a known reference by modulation.
Carrier Frequency
The frequency of the un-modulated fundamental output of a radio transmitter.
C/A
Coarse/Acquisition code. This is the civilian code made available by the DoD. It is also
known as SPS (Standard Positioning Service).
Channel
Refers to the GPS receiver hardware that is required to lock to a satellite, make the range
measurements, and collect data from the satellite.
Clock Bias
The difference between the clock’s indicated time and true universal time.
Control Segment
A world-wide network of GPS monitoring and control stations that ensure the accuracy
of
satellite positions and their clocks.
B-2
ET6xxx ExacTime GPS TC & FG (Rev C)
Symmetricom Inc
ACRONYMS AND ABBREVIATIONS
-DData Message
A 1500 bit message included in the GPS signal which reports the satellite’s location,
clock corrections, and health. Rough information on the other satellites in the
constellation is also included.
DCE
Data Communications Equipment (See RS-232-C).
DoD
Department of Defense.
DOP
Dilution of Precision.
Doppler Shift
The apparent change in the frequency of a signal caused by the relative motion of the
transmitter and receiver.
DoT
Department of Transportation.
DTE
Data Terminal Equipment (See RS-232-C).
-EECEF
Earth Centered - Earth Fixed.
EIA
Electronic Industries Association.
Elevation Angle
The angle between the line of sight vector and the horizontal plane.
Symmetricom Inc
ET6xxx ExacTime GPS TC & FG (Rev C)
B-3
APPENDIX B
Elevation Mask
Refers to the angle below which a satellite is considered unusable. It is used to prevent
the receiver from searching for satellites which are obscured by buildings or mountains.
Ephemeris
A set of parameters that describe the satellite orbit very accurately. It is used by the
receiver to compute the position of the satellite. This information is broadcast by the
satellites.
-FFRQ
Frequency.
-GGDOP
GDOP refers to the Geometric Dilution of Precision. It describes how much of an
uncertainty in range affects the uncertainty in position. The GDOP depends on where the
satellites are relative to the user.
A large GDOP means that a small error in range will translate into a large error in
position. GDOP has two components:
PDOP (Position Dilution of Precision).
TDOP (Time Dilution of Precision).
Geoid
Refers to the actual physical shape of the earth which is hard to describe mathematically
due to the irregularities of the local surface and the land-sea variations.
GMT
Greenwich Mean Time.
GMT Offset/Local Time Offset
An example of the difference between local time and GMT time is:
EST (Eastern Standard Time) minus GMT time is five hours.
B-4
ET6xxx ExacTime GPS TC & FG (Rev C)
Symmetricom Inc
ACRONYMS AND ABBREVIATIONS
GPIB
General Purpose Interface Bus (IEEE-488 Interface).
GPS
Global Positioning System. Consists of twenty-four NAVSTAR satellites in six
different orbits, the ground control and monitor stations, and the user community.
-HHandover Word
The word in the GPS message that contains synchronization information for the transfer
of tracking from the C/A to P code.
HDOP, VDOP
HDOP and VDOP are the horizontal and vertical components of the PDOP. They
describe how an uncertainty in range effects the horizontal position (latitude and
longitude) and the vertical position (altitude). For 2-D position fixes HDOP is all that
counts.
-IICD
Interface Control Document.
ID
Identification.
I/F
Interface.
I/O
Input/Output.
ION
Ionosphere/Ionospheric.
Symmetricom Inc
ET6xxx ExacTime GPS TC & FG (Rev C)
B-5
APPENDIX B
Ionosphere
The band of charged particles eighty to 120 miles above the earth’s surface.
Ionospheric Refraction
The change in the propagation speed of a signal as it passes through the ionosphere.
-JNo glossary terms have been defined for “J.”
- KNo glossary terms have been defined for “K.”
-LL1
The primary L-Band signal radiated by each NAVSTAR satellite at 1575.42 MHz. The
L1 beacon is modulated with the C/A and P codes with the NAV message. L2 is
centered
at 1227.60.
LAT
Latitude.
LON
Longitude.
LSB
Least Significant Bit.
B-6
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ACRONYMS AND ABBREVIATIONS
-MMSB
Most Significant Bit.
Monitor Station
One of five world-wide stations maintained by DoD and used in the GPS control
segment to monitor and control the satellite clock and orbital parameters. Corrections are
calculated and uploaded to each satellite once each day.
Multipath Errors
Errors caused by the interference of a signal that has reached the GPS receiver by two or
more different paths. Usually caused by one path being bounced or reflected.
-NNAV
Navigation.
NAV DATA
The 1500 bit navigation message broadcast by each satellite at fifty BPS (Bits Per
Second) on both the L1 and L2 beacons. This message contains system time, clock
correction parameters, ionospheric delay model parameters, the satellite Ephermeris and
health status. This information is used to process GPS signals to obtain the users position
and velocity.
NAVSTAR
The name given to GPS satellites.
NIST
National Institute of Standards Technology.
ns/nsec
Nanosecond.
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ET6xxx ExacTime GPS TC & FG (Rev C)
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APPENDIX B
-ONo glossary terms have been defined for “O.”
-PP Code
The protected or military code used on both L1 and L2 GPS beacons. This code is
available only to authorized users.
PDOP
PDOP refers to the Position Dilution of Precision. PDOP is composed of HDOP and
VDOP. It has typically good values between two and seven. See HDOP and VDOP.
PPS
Precision Positioning Service. The most accurate dynamic positioning possible with
GPS, based on dual frequency P code.
PRN
Pseudo Random Number
p/s
Picoseconds per second.
Pseudo Random Code
A signal with random noise-like proportions. It is a very complicated but repeated
pattern of ones and zeros.
Pseudo-Range
A measure of the range from the GPS receiver (antenna) to the satellite. Pseudo-range is
obtained by multiplying the speed of light by the apparent transit time of the signal from
the satellite. Pseudo-range differs from actual range because the satellite and user clocks
are offset from GPS system time by propagation delays and other errors.
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ACRONYMS AND ABBREVIATIONS
-QNo glossary terms have been defined for “Q.”
-RRise/Set Time
Refers to the period during which a satellite is visible. For example, when it has an
elevation angle that is above the elevation mask. A satellite is said to rise when the
elevation angle exceeds the elevation mask, and set when the elevation drops below the
mask.
RS-232-C
An EIA specification.
-SS/A
Selective Availability. Selective availability is essentially a method for artificially
creating a significant clock error in the satellites. When implemented, it is the largest
source of error in the GPS system.
SCH
Schedule.
SEP
Spherical Error Probable.
SPS
Standard Positioning Service. The normal civilian positioning accuracy obtained by
using the single frequency C/A code.
SS
Space Segment.
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ET6xxx ExacTime GPS TC & FG (Rev C)
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APPENDIX B
SV
Space Vehicle (GPS satellite).
-TTDOP
TDOP refers to the Time Dilution of Precision. It depends on the uncertainty in the clock
bias.
TI
Time Interval.
-Uμs
Microsecond.
USNO
United States Naval Observatory.
UTC
Universal Time Coordinated. The time standard maintained by the U.S. Naval
Observatory. GPS Time is directly related to UTC time.
-VNo glossary terms have been defined for “V.”
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ACRONYMS AND ABBREVIATIONS
-WWK
Week Number.
WGS-72
Word Geodetic System (1972). A mathematical reference ellipsoid used by GPS, having
a semi-major axis of 6378.137 kilometers and a flattening of 1/298.26.
WGS-84
Word Geodetic System (1984). A mathematical reference ellipsoid used by GPS, having
a semi-major axis of 6378.137 kilometers and a flattening of 1/298.257223563.
-XNo glossary terms have been defined for “X.”
-YNo glossary terms have been defined for “Y.”
-ZNo glossary terms have been defined for “Z.”
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ET6xxx ExacTime GPS TC & FG (Rev C)
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APPENDIX B
This Page Intentionally Left Blank.
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APPENDIX C
OPTION DESCRIPTIONS
GPS OPTION 01/01A
1.0
THREE CHANNEL ENCODER
ASSEMBLY 55116
INTRODUCTION
This Option description provides a functional explanation of the Three Channel Encoder which
can be installed inside the ExacTime unit.
Option 01 describes the modulated serial time code output code selection, specifications and
adjustments. Option 01A describes the optional DC serial code output specifications.
1.1
FUNCTIONAL EXPLANATION
The ExacTime GPS Time Code and Frequency Generator has the capability of generating three
modulated time code outputs on rear panel BNC connectors J3a, J3b, J3c, J3d, J3e or J3f. For the
specific connections used, refer to the GPS Option/Connector Configuration sheet in the front of
the ExacTime User’s Guide. Each of these connectors can output any of the following codes:
IRIG A132
IRIG H112
IRIG B122
IRIG H122
IRIG G142
XR3
IRIG E112
2137
IRIG E122
NASA 36
These modulated codes are generated using the Three Channel Encoder, Assembly 55116. Code
type selection is remotely selected via the RS-232 I/O Port, rear panel connector J12 or via the
front panel keypad. SW4 located on Assembly 55116 (plugged into the option area of the
Synchronized Time Code/Frequency Module) must have the jumper block shorting the pins.
For the optional DC Code Output, Option 01A, connectors see the GPS Option/Connector
Configuration sheet in the ExacTime User’s Guide.
1.2
OUTPUT SPECIFICATIONS
Note: Changing the Code Output selection may change the output amplitude. See Table 01-2
for amplitude and modulation ratio controls.
1.2.1 OUTPUT AMPLITUDE (MODULATED)
Nominal 3 volts peak-to-peak into a 50Ω load (adjustable)
1.2.2 MODULATION RATIO
Nominal 3:1, adjustable from 2:1 to 6:1
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ET6xxx ExacTime GPS TC & FG (Rev C)
C-1
APPENDIX C
1.2.3 DC CODE (OPTION 01A)
0 to +5 volts into a 50Ω load.
1.2.4 CONTROL VIA THE RS-232 I/O PORT
The following command allows the user to select the type of modulated output codes generated
by the Three Channel Encoder (Assembly 55116). Each rear panel BNC connector (J3a, J3b,
J3c, J3d, J3e, or J3f) may be individually programmed. If Option 01A (DC Code Output) is
installed, see the GPS Option/Connector Configuration sheet in the User’s Guide.
To Program one channel of the Encoder:
•
•
•
The user inputs $E (HEX 24) (HEX 45).
The user inputs a digit (1 to 3) to select the specific channel.
The user inputs a two-digit number to select the code type based on the following table:
Code Output Selection
00 = IRIG A
01 = IRIG B
02 = IRIG G
03 = IRIG E 100 Hz
04 = IRIG E 1 kHz
05 = IRIG H 100 Hz
06 = IRIG H 1 kHz
07 = XR3
08 = 2137
09 = NASA 36
•
The system responds with OK CR/LF.
Example: $E102
The above example will program Channel 1 of the Three Channel Encoder to output IRIG G on
the rear panel BNC connector J3a or J3d. Refer to the GPS Option/Connector Configuration
Sheet in the User’s Guide.
If a cold reset was performed and the Three Channel Encoder was not programmed afterwards,
all three Channels will output IRIG B.
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OPTION DESCRIPTIONS
1.2.5 CONTROL VIA THE FRONT PANEL KEYPAD
This screen provides choices on selecting the code output of the Three Channel Encoder. This
screen contains the following choices:
CODE SELECT
1<CODE-1
2>CODE-2
3>CODE-3
Code-1 corresponds to code output on BNC J3a or J3d.
Code-2 corresponds to code output on BNC J3b or J3e.
Code-3 corresponds to code output on BNC J3c or J3f.
The above three channels (the number 1, 2, or 3), and the screen will display the code output
choices for that channel. Select the number 0-9 which corresponds to the desired output code.
Then the display will return to the fourth menu screen to program the other two outputs from the
Three Channel Encoder.
To return to the first menu screen, press the “MENU” keyboard switch.
If local control of this module is desires (using the DIP switches), the jumper pins located at
SW4 must not havae the jumper block shorting the pins. Then code output selection is made
using DIP switches SW1, SW2, and SW3, located on Assembly 55116. Refer to Table 01-1 on
the following page.
Code
IRIG A132
IRIG B122
IRIG G142
IRIG E112
IRIG E122
IRIG E112
IRIG H122
XR3
2137
NASA 36
Binary
Weight
Symmetricom Inc
Table 01-1
Modulated Time Code Output Selection
Switch
Switch
Switch
Switch
Section 4
Section 3
Section 2
Section 1
Closed
Closed
Closed
Closed
Open
Closed
Closed
Closed
Closed
Open
Closed
Closed
Open
Open
Closed
Closed
Closed
Closed
Open
Closed
Open
Closed
Open
Closed
Closed
Open
Open
Closed
Closed
Closed
Closed
Open
Closed
Closed
Closed
Open
Open
Closed
Closed
Open
1
2
4
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ET6 ExacTime GPS TC & FG (Rev C)
C-3
APPENDIX C
Note: Each of the three DIP switches works identically.
SW1 controls code output on rear panel BNC J3a or J3d.
SW2 controls code output on rear panel BNC J3b or J3e.
SW3 controls code output on rear panel BNC J3c or J3f.
The modulation ratio and amplitude can be individually adjusted for each of the three channels
as follows:
Table 01-2
Amplitude and Modulation Radio Controls
Channel 1
Channel 2
Channel 3
(BNC J3)
(BNC J5)
(BNC J6)
Modulation
R10
R12
R14
Ratio
Amplitude
R11
R13
R15
Detailed definitions and specifications for each of the time codes that are generated by the Three
Channel Encoder are provided on the following pages.
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OPTION DESCRIPTIONS
1.3
OUTPUT FORMATS
1.3.1 IRIG FORMAT A
Time Frame = 0.1 Second
0
10
30
20
40
50
Time = 091 Days : 14 Hours : 08 Minutes : 32.8 Seconds
Reference Marker = 0.8 mS
Seconds
P0
PR 1
2
4
8
BCD Time of Year
Hours
Minutes
10
20 40
P1 1
2
4
8
10
20
40
P2 1
2
4
8
0.1 Sec
Days
10 20
1
P3
2
4
10 20
8
40
80
P4 100 200
1
4
2
8
P5
Binary One = 0.5 mS
Binary Zero = 0.2 mS
Reference = 0.8 mS
Time Frame = 0.1 Second
50
60
80
70
90
Time of Day
(Straight Binary Seconds)
Control Functions
P5
P6
0
P8 20
P7
21
22
23
24
25
26
27
28
P9 29
210 211 212 213
214 215
216
1.0 mS (Element Rate = 1000 PPS)
•
•
•
Time Frame: 0.1 second. Code Digit Weighting Options: BCD, SB, or both.
Binary Coded Decimal Time-of-Year CODE WORD - 34 binary digits.
Seconds, minutes, hours, days, and 0.1 seconds. Recycles yearly.
Straight Binary Time-of-Day CODE WORD - 17 binary digits.
Seconds only. Recycles each 24 hours (86399).
Code Word Structure: BCD
Word begins at INDEX COUNT 1. Binary coded elements occur between POSITION
IDENTIFIER ELEMENTS (seven for seconds, seven for minutes, six for hours, ten for days, and
four for 0.1 seconds) until the CODE WORD is complete. A POSITION IDENTIFIER occurs
between decimal digits in each group to provide separation for visual resolution.
Code Word Structure: SB
Word begins at INDEX COUNT 80. Seventeen binary-coded elements occur, with a POSITION
IDENTIFIER between the 9th and 10th binary-coded elements.
Least Significant Digit
Occurs first, except for fractional seconds information, which occurs following the day-of-year
information.
Element Rates Available
• 1000 per second (basic element rate).
• 100 per second (POSITION IDENTIFIER rate).
• 10 per second (frame rate).
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P0
PR
APPENDIX C
Element Identification
• “On-Time” reference point for each element is its leading edge.
• INDEX MARKER duration: 0.2 milliseconds. (Binary Zero or uncoded Element.)
• CODE DIGIT duration: 0.5 milliseconds. (Binary One.)
• POSITION IDENTIFIER: 0.8 milliseconds.
• REFERENCE MARKER: Two consecutive POSITION IDENTIFIERS. (The “on-time”
point, to which the CODE WORD refers, is the leading edge of the second POSITION
IDENTIFIER.)
Resolution
One millisecond (unmodulated): 0.1 millisecond (modulated).
Carrier Frequency
10kHz when modulated.
1.3.2 IRIG FORMAT B
Time Frame = 1 Second
0
10
30
20
50
40
Time = 091 Days : 14 Hours : 08 Minutes : 32 Seconds
Reference Marker = 8 mS
Seconds
P0
PR 1
2
4
8
BCD Time of Year
Hours
Minutes
10
20 40
P1 1
2
4
8
10
20
40
P2 1
2
4
8
10 20
Days
P3
1
2
4
10 20
8
40
80
P4 100 200
P5
Binary One = 5 mS
Binary Zero = 2 mS
Reference = 8 mS
0
Time Frame = 1 Second
50
60
70
90
80
Time of Day
Straight Binary Seconds
Control Functions
P5
P6
P7
P8 20
21
22
23
24
25
26
27
28
P9 29
210 211
212 213 214
10 mS (Element Rate = 100 PPS)
•
•
•
Time Frame: 1 second. Code Digit Weighting Options: BCD, SB, or both.
Binary Coded Decimal Time-of-Year CODE WORD - 30 binary digits. Seconds,
minutes, hours, and days. Recycles yearly.
Straight Binary Time-of-Day CODE WORD - 17 binary digits. Seconds only. Recycles
each 24 hours (86399).
Code Word Structure: BCD
Word begins at INDEX COUNT 1. Binary coded elements occur between POSITION
IDENTIFIER ELEMENTS (seven for seconds, seven for minutes, six for hours, ten for days)
until the CODE WORD is complete. A POSITION IDENTIFIER occurs between decimal digits
in each group to provide separation for visual resolution.
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215 216
P0
PR
OPTION DESCRIPTIONS
Code Word Structure: SB
Word begins at INDEX COUNT 80. Seventeen binary-coded elements occur, with a POSITION
IDENTIFIER between the 9th and 10th binary-coded elements.
Least Significant Digit
Occurs first.
Element Rates Available
• 100 per second (basic element rate).
• 10 per second (POSITION IDENTIFIER rate).
• One per second (frame rate).
Element Identification
• “On-Time” reference point for each element is its leading edge.
• INDEX MARKER duration: 2 milliseconds. (Binary Zero or uncoded Element.)
• CODE DIGIT duration: 5 milliseconds. (Binary One.)
• POSITION IDENTIFIER duration: 8 milliseconds.
• REFERENCE MARKER: One per second. Two consecutive POSITION IDENTIFIERS.
(The “on-time” point, to which the CODE WORD refers, is the leading edge of the second
POSITION IDENTIFIER.)
Resolution
10 milliseconds (unmodulated): One millisecond (modulated).
Carrier Frequency
1kHz when modulated.
1.3.3
IRIG FORMAT G
Time Frame = 0.01 Second
0
10
30
20
40
50
Time = 091 Days : 14 Hours : 08 Minutes : 32.86 Seconds
Reference Marker = 80 µS
Seconds
P0 PR 1
2
4
8
BCD Time of Year
Hours
Minutes
10
20 40
P1 1
2
4
8
10
20
40
P2 1
2
4
8
10 20
Days
P3
1
2
4
8
10 20
40
0.1 Sec
80
P4 100 200
1
2
4
8
P5
Binary One = 50 µS
Binary Zero = 20 µS
Reference = 80 µS
Time Frame = 0.01 Second
50
60
0.01 Sec
P5 1
2
4
80
70
90
0
Control Functions
8
P6
P7
P8
P9
P0
100µS (Element Rate = 10 KPPS)
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PR
APPENDIX C
•
•
Time Frame: 0.01 seconds. Code Digit Weighting Options: BCD Time-of-Year.
Code Word - 38 binary digits. Seconds, minutes, hours, and days, 0.1 seconds, and 0.01
seconds. Recycles yearly.
Code Word Structure: BCD
Word begins at INDEX COUNT 1. Binary coded elements occur between POSITION
IDENTIFIER ELEMENTS (seven for seconds, seven for minutes, six for hours, ten for days,
four for 0.01 seconds) until the CODE WORD is complete. A POSITION IDENTIFIER occurs
between decimal digits in each group to provide separation for visual resolution.
Least Significant Digit
Occurs first, except for fractional seconds information, which occurs following the Day-of-Year
information.
Element Rates Available
• 10000 per second (basic element rate).
• 1000 per second (POSITION IDENTIFIER rate).
• 100 per second (frame rate).
Element Identification
• “On-Time” reference point for each element is its leading edge.
• INDEX MARKER duration: 0.02 milliseconds. (Binary Zero or uncoded Element.)
• CODE DIGIT duration: 0.05 milliseconds. (Binary One.)
• POSITION IDENTIFIER duration: 0.08 milliseconds.
• REFERENCE MARKER: One per second. Two consecutive POSITION IDENTIFIERS.
(The “on-time” point, to which the CODE WORD refers, is the leading edge of the second
POSITION IDENTIFIER.)
Resolution
0.10 milliseconds (unmodulated): 0.01 millisecond (modulated).
Carrier Frequency
100kHz when modulated.
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OPTION DESCRIPTIONS
1.3.4 IRIG FORMAT E
Time Frame = 10 Seconds
10
0
20
30
40
50
Time = 091 Days : 14 Hours : 08 Minutes : 30 Seconds
Reference Marker = 80 mS
BCD Time of Year
Seconds
P0
PR 1
2
4
8
Minutes
10
20 40
P1 1
2
4
8
Hours
10
20
40
P2 1
2
4
8
Days
10 20
P3
1
2
4
8
10 20
40
80
P4 100 200
P5
Binary One = 50 mS
Binary Zero = 20 mS
Reference = 80 mS
Time Frame = 10 Seconds
60
50
80
70
90
Time of Day
(Straight Binary Seconds)
Control Functions
P5
P6
0
P8 20
P7
21
22
23
24
25
26
27
28
P9 29
210 211 212 213
214 215
216
10 mS (Element Rate = 10 PPS)
•
•
Time Frame: 10 seconds. Code Digit Weighting Options: BCD.
Binary Coded Decimal Time-of-Year CODE WORD - 26 binary digits.
Seconds, minutes, hours, and days. Recycles yearly.
Code Word Structure: BCD
Word begins at INDEX COUNT 6. Binary coded elements occur between POSITION
IDENTIFIER ELEMENTS (three for seconds, seven for minutes, six for hours, ten for days)
until the CODE WORD is complete. A POSITION IDENTIFIER occurs between decimal digits
in each group to provide separation for visual resolution.
Least Significant Digit
Occurs first.
Element Rates Available
• 10 per second (basic element rate).
• One per second (POSITION IDENTIFIER rate).
• 0.1 per second (frame rate).
Element Identification
• “On-Time” reference point for each element is its leading edge.
• INDEX MARKER duration: 20 milliseconds. (Binary Zero or uncoded Element.)
• CODE DIGIT duration: 50 milliseconds. (Binary One.)
• POSITION IDENTIFIER duration: 80 milliseconds. (Refers to the leading edge of the
succeeding elements.)
• REFERENCE MARKER: One per 10 seconds. Two consecutive POSITION
IDENTIFIERS. (The “on-time” point, to which the CODE WORD refers, is the leading edge
of the second POSITION IDENTIFIER.)
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P0
PR
APPENDIX C
Resolution
100 milliseconds (unmodulated): One millisecond (modulated).
Carrier Frequency
1kHz or 100Hz when modulated.
1.3.5
IRIG FORMAT H
Time Frame = 1 Minute
10
0
20
30
40
0
50
Time = 191 Days : 14 Hours : 38 Minutes
BCD Time of Year
Minutes
Reference Marker = 0.8 Seconds
P0 PR
P1 1
2
4
8
10 20 40
P2 1
2
4
8
Control Functions
Days
Hours
10 20
P3 1
2
4
8
10 20 40 80
P4 100 200
P5
Binary One = 0.5 Sec
Binary Zero = 0.2 Sec
Reference = 0.8 sec
•
•
Time Frame: One minute. Code Digit Weighting Options: BCD.
Binary Coded Decimal Time-of-Year CODE WORD - 23 binary digits. Minutes, hours,
and days. Recycles yearly.
Code Word Structure: BCD
Word begins at INDEX COUNT 10. Binary coded elements occur between POSITION
IDENTIFIER ELEMENTS (seven for minutes, six for hours, ten for days) until the CODE
WORD is complete. A POSITION IDENTIFIER occurs between decimal digits in each group to
provide separation for visual resolution.
Least Significant Digit
Occurs first.
Element Rates Available
• One per second (basic element rate).
• One per ten seconds (POSITION IDENTIFIER rate).
• One per minute (frame rate).
Element Identification
• “On-Time” reference point for each element is its leading edge.
• INDEX MARKER duration: 0.2 seconds. (Binary Zero or uncoded Element.)
• CODE DIGIT duration: 0.5 seconds. (Binary One.)
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P0 PR
OPTION DESCRIPTIONS
•
•
POSITION IDENTIFIER duration: 0.8 seconds.
REFERENCE MARKER: One per minute. Two consecutive POSITION IDENTIFIERS.
(The “on-time” point, to which the CODE WORD refers, is the leading edge of the second
POSITION IDENTIFIER.)
Resolution
One second (unmodulated). 0.01 millisecond (modulated 100Hz). 0.001 seconds (modulated
100Hz).
Carrier Frequency
1 kHz or 100Hz where modulated.
1.3.6 XR3 FORMAT
Time Frame = 1 Second
0
40
80
160
120
200
240
280
320
400
360
440
480
520
560
600
640
680
720
760
800
800 mS
840
880
920
200 mS
Time = 14 Hours : 08 Minutes : 32 Seconds
Units of
Hours
Tens of
Hours
20
10
8
4
Tens of
Minutes
2
1
40
20
Tens of
Seconds
Units of
Minutes
10
8
4
2
1
40
20
Units of
Seconds
10
8
4
2
1
Binary One = 24 mS
Binary Zero = 12 mS
Reference = 36 mS
•
•
Time Frame: One second. Code Digit Weighting Options: BCD.
Binary Coded Decimal Time-of-Year CODE WORD - 20 binary digits. Hours, minutes,
and seconds. Recycles every 24 hours.
Code Word Structure: BCD
Word begins at INDEX COUNT 1. Binary coded elements occur between POSITION
IDENTIFIER ELEMENTS (six for hours, seven for minutes, seven for seconds) until the CODE
WORD is complete.
Least Significant Digit
Occurs first.
Element Rates Available
• 25 per second (basic element rate). Four consecutive pulses missing at the end of the frame.
• One per second (frame rate).
Element Identification
• “On-Time” reference point for each element is its trailing edge.
• Binary zero duration: 12 milliseconds.
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C-11
960
0
APPENDIX C
•
•
CODE DIGIT duration: 24 milliseconds. (Binary One.)
REFERENCE MARKER: One per second. Duration is 36 milliseconds. (The “on-time”
point, to which the CODE WORD refers, is the leading edge of the second POSITION
IDENTIFIER.)
Resolution
One second (frame rate, unmodulated). 40 millisecond during code word only. Four
milliseconds (modulated).
Carrier Frequency
250Hz.
1.3.7 2137 FORMAT
Time Frame = 1 Second
0
40
80
160
120
200
240
280
320
400
360
440
480
520
560
600
640
680
720
760
800
800 mS
840
880
920
200 mS
Time = 14 Hours : 08 Minutes : 32 Seconds
Units of
Hours
Tens of
Hours
20
10
8
4
Tens of
Minutes
2
1
40
20
Tens of
Seconds
Units of
Minutes
10
8
4
2
1
40
20
Units of
Seconds
10
8
4
2
1
Binary One = 24 mS
Binary Zero = 12 mS
Reference = 36 mS
•
•
Time Frame: One second. Code Digit Weighting Options: BCD.
Binary Coded Decimal Time-of-Year CODE WORD - 20 binary digits. Hours, minutes,
and seconds. Recycles every 24 hours.
Code Word Structure: BCD
Word begins at INDEX COUNT 1. Binary coded elements occur between POSITION
IDENTIFIER ELEMENTS (six for hours, seven for minutes, seven for seconds) until the CODE
WORD is complete.
Least Significant Digit
Occurs first.
Element Rates Available
• 25 per second (basic element rate). Four consecutive pulses missing at the end of the frame.
• One per second (frame rate).
Element Identification
• “On-Time” reference point for each element is its trailing edge.
• Binary zero duration: 12 milliseconds.
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960
0
OPTION DESCRIPTIONS
•
•
CODE DIGIT duration: 24 milliseconds. (Binary One.)
REFERENCE MARKER: One per second. Duration is 36 milliseconds. (The “on-time”
point, to which the CODE WORD refers, is the leading edge of the second POSITION
IDENTIFIER.)
Resolution
One second (frame rate, unmodulated). 40 millisecond during code word only. Four
milliseconds (modulated).
Carrier Frequency
1 kHz.
1.3.8 NASA 36-BIT TIME CODE
Time Frame = 1 Second
0
10
20
Tens of
Seconds
Units of
Seconds
1
2
4
30
8
10
40
Tens of
Minutes
Units of
Minutes
1
20 40
2
4
50
8
10
20
Units of
Hours
40
1
2
4
8
Binary One = 6 mS
Binary Zero = 2 mS
Reference = 6 mS
Time Frame = 1 Second
50
60
70
80
90
0
Time = 191 Days : 14 Hours : 08 Minutes : 32 Seconds
Units of
Days
Tens of
Hours
10 20
40
1
2
4
Tens of
Days
10 20
8
40
Hundreds of
Days
80
Reference
Marker
100 200
10 mS (Element Rate = 100 PPS)
•
•
Control
Functions
100 mS
Time Frame: One second. Code Digit Weighting Options: BCD.
Binary Coded Decimal Time-of-Year CODE WORD - 30 binary digits. Seconds, minutes,
hours, and days. Recycles yearly.
Code Word Structure: BCD
Word begins at INDEX COUNT 1. Binary coded elements occur between POSITION
IDENTIFIER ELEMENTS in four digit groups until the CODE WORD is complete. A CODE
DIGIT occurs between decimal digits in each group to provide separation for visual resolution.
Least Significant Digit
Occurs first.
Element Rates Available
• 100 per second (basic element rate).
• One per second (frame rate).
Symmetricom Inc
ET6 ExacTime GPS TC & FG (Rev C)
C-13
APPENDIX C
Element Identification
• “On-Time” reference point for each element is its leading edge.
• INDEX MARKER duration: Two milliseconds. (Binary Zero or uncoded Element.)
• CODE DIGIT duration: Six milliseconds. (Binary One.)
• POSITION IDENTIFIER duration: Six milliseconds.
• REFERENCE MARKER: Five consecutive POSITION IDENTIFIERS, followed by an
INDEX MARKER. (The “on-time” point, to which the CODE WORD refers, is the leading
edge of the INDEX MARKER following the four POSITION IDENTIFIERS.)
Resolution
10 milliseconds (unmodulated). One millisecond (modulated).
Carrier Frequency
1kHz when modulated.
C-14
ET6xxx ExacTime GPS TC & FG (Rev C)
Symmetricom Inc
OPTION DESCRIPTIONS
ASSEMBLY 55116
Symmetricom Inc
ET6 ExacTime GPS TC & FG (Rev C)
C-15
APPENDIX C
GPS OPTION 06A
1.0
1 MHZ SINE WAVE SHAPER
ASSEMBLY 20457-15
INTRODUCTION
This option description provides Phase Noise and Harmonic specifications, an explanation of the
Sine Wave Shaper logic used to develop the Sine Wave output and adjustment of the output
amplitude.
This Shaper/Assembly can be plugged into the J7/J9, J8/J10, J18/J22, or J19/J23 option areas of
the GPS Motherboard Assembly. The 1 MHz Sine Wave output will be present on rear panel
BNCs J3B, J3C, J3E, or J3F respectively.
1.1
PHASE NOISE AND HARMONIC SPECIFICATIONS
The following specifications apply at 13dbm output level using an oven oscillator. These
specifications are worst case.
Harmonics
Spurious Noise
Phase Noise
1Hz
10Hz
100Hz
1KHz
10KHz
100KHz
1.2
-35 dBc
-35 dBc
-82 dBc/Hz
-110 dBc/Hz
-112 dBc/Hz
-114 dBc/Hz
-120 dBc/Hz
-120 dBc/Hz
FUNCTIONAL EXPLANATION
A 1 MHz square wave derived from the 10MHz internal oscillator is input to J1 pin 7 of the Sine
Wave Shaper Assembly. The signal is filtered and shaped to generate the 1 MHz Sine Wave
output at P1 pin 2 of the same assembly.
This signal is then routed to a rear panel BNC. Refer to the GPS Option/Connector
Configuration sheet at the beginning of the ExacTime User’s Guide for the output connector
designation. Refer to the Top Assembly Drawing for connector location. This signal is
adjustable from zero to six volts peak-to-peak and has been factory adjusted to three volts peakto-peak into a 50Ω load.
1.3
OUTPUT AMPLITUDE ADJUSTMENT
The output amplitude of this signal can be adjusted to the desired amplitude using LEVEL
potentiometer R13, on the Sine Wave Shaper assembly.
C-16
ET6xxx ExacTime GPS TC & FG (Rev C)
Symmetricom Inc
OPTION DESCRIPTIONS
GPS OPTION 07A
1.0
5 MHZ SINE WAVE SHAPER
ASSEMBLY 20457-25
INTRODUCTION
This option description provides Phase Noise and Harmonic specifications, an explanation of the
Sine Wave Shaper logic used to develop the Sine Wave output and adjustment of the output
amplitude.
This Shaper/Assembly can be plugged into the J7/J9, J8/J10, J18/J22, or J19/J23 option areas of
the GPS Motherboard Assembly. The 5 MHz Sine Wave output will be present on rear panel
BNCs J3B, J3C, J3E, or J3F respectively.
1.1
SPECIFICATIONS
The following specifications apply at 13dbm output level using an oven oscillator. These
specifications are worst case.
Harmonics
Spurious Noise
Phase Noise
1Hz
10Hz
100Hz
1KHz
10KHz
100KHz
1.2
-35 dBc
-35 dBc
-76 dBc/Hz
-103 dBc/Hz
-112 dBc/Hz
-114 dBc/Hz
-116 dBc/Hz
-119 dBc/Hz
FUNCTIONAL EXPLANATION
A 5 MHz square wave derived from the 10MHz internal oscillator is input to J1 pin 7 of the Sine
Wave Shaper Assembly. The signal is filtered and shaped to generate the 5 MHz Sine Wave
output at P1 pin 2 of the same assembly.
This signal is then routed to a rear panel BNC. Refer to the GPS Option/Connector
Configuration sheet at the beginning of the ExacTime User’s Guide for the output connector
designation. Refer to the Top Assembly Drawing for connector location. This signal is
adjustable from zero to six volts peak-to-peak and has been factory adjusted to three volts peakto-peak into a 50Ω load.
1.3
OUTPUT AMPLITUDE ADJUSTMENT
The output amplitude of this signal can be adjusted to the desired amplitude using LEVEL
potentiometer R13, on the Sine Wave Shaper assembly.
Symmetricom Inc
ET6 ExacTime GPS TC & FG (Rev C)
C-17
APPENDIX C
GPS OPTION 08CE
1.0
10-37VDC DUAL POWER INPUT
ASSEMBLY 100002
INTRODUCTION
This option provides the ability to use one of two DC sources to power the GPS TC&FG.
1.1
FUNCTIONAL EXPLANATION
Two separate DC inputs labeled J1A and J2A and a On/Off switch are located on the rear of the
unit. These inputs are routed through the switch, separate fuses and bridge rectifiers, and
connected together to the input of a single DC/DC converter. This DC/DC converter supplies +5
and +/-12VDC to power the unit.
Because the two DC inputs are routed through bridge rectifiers, the individual input pins are not
polarity sensitive. Because the outputs of the two bridge rectifiers are connected together to
form the input to the DC/DC converter, which ever input is the higher DC voltage will power the
unit. If the higher DC input is lost (or not present), the other DC input will power the unit.
1.2
SPECIFICATIONS
Input Voltage/Current:
+10VDC to +37VDC.
Approximately 1.5 amps @ +10VDC.
Approximately .5 amps @ +37VDC.
Note: The input current is dependent on the number of options installed in the GPS
TC&FG.
Internal Fuses:
C-18
F1 protects DC input from connector J1A.
F2 protects DC input from connector J1B.
Fuses are 4 amp, slow blow, 5x20 millimeters (located on Assembly
100002).
ET6xxx ExacTime GPS TC & FG (Rev C)
Symmetricom Inc
OPTION DESCRIPTIONS
Input Connector Pin Assignments:
Input 1
J1A pin 1
J1A pin 2
J1A pin 3
DC Input 1
Chassis Ground
DC Input 1 Return (Signal Ground)
Input 2
J1B pin 1
J1B pin 2
J1B pin 3
DC Input 2
Chassis Ground
DC Input 2 Return (Signal Ground)
o
o
o
Symmetricom Inc
Pin 1
ET6 ExacTime GPS TC & FG (Rev C)
C-19
APPENDIX C
ASSEMBLY 100002
C-20
ET6xxx ExacTime GPS TC & FG (Rev C)
Symmetricom Inc
OPTION DESCRIPTIONS
GPS OPTION 08G
1.0
38-73VDC POWER SUPPLY
ASSEMBLY 55194
INTRODUCTION
This option takes two nominal inputs of 48V through a rear panel terminal strip and provides +5
and ±12 VDC to power the GPS Time Code and Frequency Generator.
All inputs to Assembly 55194 are from rear panel terminal strip TB1.
All inputs have metal oxide varistors for transient voltage suppression.
The pin assignments for TB1 are shown below (as viewed from the rear of the unit):
Figure One
+
TB1-1
TB1-2
TB1-3
TB1-4
TB1-5
TB1-6
1.1
–
C
C
–
+
Pin Assignments
+ 48V (INPUT A)
Return (INPUT A)
Chassis Ground
Chassis Ground
Return (INPUT B)
+48V (INPUT B)
SPECIFICATIONS
DC Input Voltage Range:
DC = 38-73 VDC
DC Input Current (Max.) @ 38V:
.6 amps
DC Input Current (Max.) @ 73V:
.3 amps
Note: The input current is dependent on the number of options installed in the
GPS TC&FG.
Internal Voltages Generated:
Max Current available for above voltages:
Max Watts:
Internal Fuses:
Symmetricom Inc
+5V, +12V, -12V
5A, 1A,
1A
25watts
F1 protects DC input from Input A.
F2 protects DC input from Input B.
Fuses are 1 amp, fast blow, 5x20 millimeters (located on Assembly
55193).
ET6 ExacTime GPS TC & FG (Rev C)
C-21
APPENDIX C
1.2
OPERATION
This option has two DC inputs A and B. These dual inputs provide for a backup supply. If one
supply goes down, the other takes over. The dual inputs are diode 'ORed' together using bridge
rectifiers. Because of this, the DC input with the higher voltage will be used to power the unit.
Even though the inputs are labeled + and - , it really doesn't matter how they are connected. The
labeling is to eliminate confusion. Both inputs have 1 amp (normal blow) fuses for protection.
1.3
TEMPERATURE
The operating temperature of the unit should not exceed +40°C. This limitation is due to the fact
that there is no forced air flow over the DC-DC converter.
C-22
ET6xxx ExacTime GPS TC & FG (Rev C)
Symmetricom Inc
OPTION DESCRIPTIONS
GPS OPTION 08GP
1.0
38-73VDC POWER SUPPLY
ASSEMBLY 55187
INTRODUCTION
This option takes a nominal input of 48V through a rear panel terminal strip and provides +5 and
±12 VDC to power the GPS Time Code and Frequency Generator. It also provides timing and
fault status relay closures.
Optionally it can provide the capability of measuring the frequency, phase angle, and elapsed
time offset of an externally applied fifty or sixty AC sine wave.
All input/outputs from Assembly 55187 are from a rear panel terminal strip TB1.
All input/outputs have metal oxide varistors for transient voltage suppression.
The pin assignments for TB1 are shown below (as viewed from the rear of the unit):
Figure One
TB1-1
TB1-12
Pin Assignments
TB1-1
TB1-2
TB1-3
TB1-4
TB1-5
TB1-6
TB1-7
TB1-8
TB1-9
TB1-10
TB1-11
TB1-12
Symmetricom Inc
DC In 1
DC In 1 Return
Chassis Ground
Fault Relay - Common Contact
Fault Relay - Normally Closed Contact
Timing Relay - Common Contact
Timing Relay - Normally Closed Contact
50/60Hz Measurement Input - HI
50/60Hz Measurement Input - LO
DC In 2 (optional)
DC In 2 Return (optional)
Chassis Ground (optional)
ET6xxx ExacTime GPS TC & FG (Rev C)
C-23
APPENDIX C
1.1
SPECIFICATIONS
DC Input Voltage Range:
DC = 38-73 VDC
DC Input Current (Max.) @ 38V:
.6 amps
DC Input Current (Max.) @ 73V:
.3 amps
Note: The input current is dependent on the number of options installed in the GPS
TC&FG.
Fault Relay:
Timing Relay:
Relay Contact Ratings:
50/60Hz Measurement Input:
1.2
Closure on fault.
Closure when not locked.
10 watts, 0.5 amps, 200 volts.
85-250 VAC.
OPERATION
This option has two relay closures to indicate timing/fault of the unit. The fault relay output on
the rear panel terminal strip TB1-4 and 5 will provide contact closure upon the following
conditions:
A processor error, Channel One error, or Channel Two error from the GPS receiver
(SVee Six Module).
Loss of +5VDC.
If the DAC value goes below 300 or above 65,000.
The timing relay (output on the rear panel terminal strip TB1-6 and 7) provides a contact closure
until the unit has achieved oscillator lock. For example, until the front panel LOCKED LED
illuminates.
Operation of the optional 50/60Hz measurement feature is as follows:
With the unit operating, connect the AC measurement source to TB1-8 and TB1-9 (50/60Hz
Measurement Input). Make sure that when plugging in the cable to the AC power source that it
is correctly polarized. For example, the pin labeled AC HI (50/60Hz Measurement Input - HI) is
plugged into the AC HOT receptacle. If this connection is reversed, the phase angle
measurement will be off by 180o.
The frequency measurement is made by counting the number of 50/60Hz sine waves occurring
between successive corrected 1pps pulses from the GPS receiver.
The phase angle measurement is made by calculating where the 1pps pulse occurs in relationship
to the 50/60Hz sine wave.
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ET6xxx ExacTime GPS TC & FG (Rev C)
Symmetricom Inc
OPTION DESCRIPTIONS
The error calculation is the accumulated time error based on whether the sine wave is fast or
slow. A time error offset can be entered when the 50/60Hz measurement is OFF, which is used
as a starting point for the error calculation.
The 50/60Hz measurement features can be programmed using the front panel keypad switches.
Cycle through the various menus on the LCD display, using the MENU switch, until the
50/60Hz measurement screen appears. It will look similar to the following:
FRQ:60.0001Hz PHASE:123.4o ERR:-0.431 S
1>OFFSET:+0.0000S<4>OFF<5>ON<6>60Hz/ OFF
Pushing keypad switch number one will program the offset. Note that an offset cannot be
entered until the measurement is stopped. OFF will appear in the lower right hand corner of the
LCD display. If the unit is not locked, ERR will appear. If the measurement is started, ON will
appear. Keypad switch number two will select “+” (plus) and switch number three will select “-”
(minus). The number of seconds offset can then be entered using the keypad switches up to
9.9999 seconds.
Pushing the number four key will stop the measurement, and OFF will appear on the LCD
display in the lower right-hand corner.
Pushing the number five key will start the measurement, and ON will appear after the <5>. If
the unit is not locked, ERR will appear in the lower right hand corner of the LCD display.
Pushing the number six key of the keypad selects either 50Hz or 60Hz. 50Hz or 60Hz selection
can only be done when the unit is not doing measurements. OFF is displayed in the lower right
hand corner of the LCD display.
The following features are input/selected via the RS-232 I/O port:
1.3
50/60Hz SELECTION
This command allows the user to select either the 50Hz or 60Hz measurement features.
•
1.4
The user inputs $L (HEX 24, HEX 4C) followed by either a zero or a one. (Zero for 50Hz
measurement, one for 60Hz measurement.) If the unit is not doing measurements, the RS232 will respond with OK (CR) (LF), otherwise the unit will respond with ? (CR) (LF).
ENABLE/DISABLE 50/60Hz MEASUREMENT
This command allows the user to enable or disable the 50/60Hz measurement feature.
•
The user inputs $B (HEX 24, HEX 42) followed by either a zero or a one. Zero turns the
option OFF, and one turns the option ON.
Symmetricom Inc
ET6xxx ExacTime GPS TC & FG (Rev C)
C-25
APPENDIX C
•
The unit responds with OK CR/LF.
Example:
$B1
The above example illustrates enabling the 50/60Hz measurement option.
If the option is turned ON (enabled) and it isn’t available, the message “OPT?” will be sent.
1.5
ENTER 50/60Hz OFFSET DATA
This command allows the user to enter a starting point for the time error calculation.
•
The user inputs $D (HEX 24, HEX 44) followed by one digit (sign), decimal point, followed
by four digits. The sign digit’s definition is 1 = + (plus) and 0 = - (minus).
•
The unit responds OK CR/LF.
Example:
$D 02.3406
The above example illustrates entering a time error offset of -2.0346 seconds.
Note: The time error offset can only be entered if the 50/60Hz measurement option is OFF.
If a time offset is entered while the 50/60Hz option is enabled, the message OPT ON will be
sent, and the time offset data is ignored.
The offset is stored in battery backed RAM, so it will be retained if the unit is turned OFF and
then back ON again.
1.6
REQUEST 50/60Hz MEASUREMENT DATA
This command allows the user to obtain the 50/60Hz measurement data.
•
The user enters $A (HEX 24, HEX 41).
•
The unit responds with XX.XXXX, space, Hz (representing frequency measurement), space,
±X.XXX, space, SEC (representing accumulated time error), space, XXX.X space, DEG
(representing phase angle measurement), space +X.XXXX, space, OFFSET (representing
time offset), CR/LF.
Example:
60.1324Hz + 1.357SEC 180.2DEG + 1.206 OFFSET CR/LF
The above response states that the frequency measurement is 60.1324Hz, and the accumulated
time error is +1.206 seconds.
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ET6xxx ExacTime GPS TC & FG (Rev C)
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OPTION DESCRIPTIONS
The 60Hz measurement data is also available on the 50/60Hz measurement screen of the front
panel LCD display. The format is as follows:
FRQ: 60.1324HZ PHASE: 180.2o ERROR: +1.357
1>OFFSET:+1.206S<4>OFF<5>ON<6>60HZ/ ON
If the 50/60Hz option is not enabled, ON will be replaced by OFF. When the unit is first turned
on, it will come up in the OFF (default) mode. If the 50/60Hz option is turned on prior to the
unit achieving LOCK, ON will be replaced by ERR and measurement data will not be available.
When measuring the 60Hz with a time period of 16.66 milliseconds, if a measurement occurs
outside a one millisecond window of that time period (such as a noise spike), the measurement is
ignored, and an error is counted. If 1,000 successive errors are read, the message ERR appears,
and the 60Hz measurement option is turned OFF.
Symmetricom Inc
ET6xxx ExacTime GPS TC & FG (Rev C)
C-27
APPENDIX C
GPS OPTION 10B
1.0
LOW PHASE NOISE OSCILLATOR
PIEZO
INTRODUCTION
This option provides an internal disciplined 10MHz Oven Oscillator as the unit’s time base. This
10MHz time base is frequency corrected using a DAC (Digital to Analog Converter) and locked
to the GPS corrected 1PPS.
1.1
SPECIFICATIONS
Output Frequency/ Waveform:
Output Amplitude:
Aging Rate:
Temperature Stability:
Operating Temperature:
Altitude:
Electrical Tuning:
Control Voltage:
Mechanical Frequency Adjust:
10MHz sine wave
1.0 VRMS into 50Ω
+5 x 10-10 per day
+1.5 x 10-8 per year
+3 x 10-8 over a
temperature range of -20oC to +75oC
-20oC to +75oC
Sea level to 50,000 feet
+1PPM (minimum)
+2PPM (maximum)
0 to 6 Volts
+1PPM (minimum)
+3PPM (maximum)
The following specifications apply to the Selected 10 MHz Output at a 13dbm output level.:
Harmonics:
-35 dBc
Spurious Noise:
>-35 dBc
Phase Noise:
1Hz
-85 dBc/Hz
10Hz
-113 dBc/Hz
100Hz
-134 dBc/Hz
1KHz
-144 dBc/Hz
10KHz
-148 dBc/Hz
It is recommended that the oscillator be nulled when the DAC value starts to approach either
extreme of 5,000 or 60,000. There is a hole on the left side panel of the unit for the oscillator
adjustment. The screw must be removed to provide access to this adjustment.
There are two methods to null/calibrate the internal oscillator.
1.2
CALIBRATION - FIRST METHOD
The oscillator can be nulled against a known frequency standard with an oscilloscope or other
suitable means by using the following steps:
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ET6xxx ExacTime GPS TC & FG (Rev C)
Symmetricom Inc
OPTION DESCRIPTIONS
1. Turn on the unit and wait approximately one hour for the oscillator to warm up and stabilize.
2. Sync one trace of an oscilloscope on the known frequency standard. Using the other trace,
monitor the 10MHz output of the unit.
3. The input of the DAC must be held static prior to nulling the oscillator. This can be
accomplished one of three ways:
•
Disconnect the antenna input from the rear of the unit.
•
Select the single satellite mode (1SV), and select a satellite that is not in view (or pick
SV33 which doesn’t exist).
•
Disable disciplining, refer to Chapter Four, “Disable Disciplining” in the User’s
Guide.
4. Set the DAC value to it’s midpoint 32767. Refer to Chapter Four, “Enter DAC Value” in the
User’s Guide.
5. Adjust the oscillator until the 10MHz output is stable with respect to the frequency standard.
6. Reinstall the screw. Enable disciplining. Refer to Chapter Four, “Enable Disciplining” in
the User’s Guide.
7. After approximately one hour, check the DAC value number again. If it has changed by
more than ±5000 from 32767, repeat steps two through six.
1.3
CALIBRATION - SECOND METHOD
If a known frequency standard is not available, the oscillator may be nulled as follows:
1. Set the unit to operate in the single satellite (1SV) mode. Make sure the unit is tracking a
satellite.
2. Read the DAC value either from the RS-232 I/O port, or from the LCD display.
3. The oscillator is located on the GPS Main Assembly 35002 in location Y1. Remove the
oscillator adjustment access screw to provide access to the oscillator adjustment.
4. SLOWLY (no more than 45o each time) adjust the oscillator and watch the DAC value
change. If the DAC value is 65535, turn the oscillator adjustment counterclockwise which
will decrease the frequency and the DAC value. If the DAC value is 00000, turn the
oscillator adjustment clockwise which will increase the frequency and the DAC value.
Symmetricom Inc
ET6xxx ExacTime GPS TC & FG (Rev C)
C-29
APPENDIX C
5. Wait approximately one minute between each adjustment to allow the oscillator to stabilize.
6. Keep adjusting the oscillator in the appropriate direction until the DAC value is
approximately at its midpoint (32767).
7. Install the screw in the oscillator adjustment access hole.
8. If after approximately one hour, the DAC value has changed by more than ±5,000 from
32767, repeat steps one through six.
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ET6xxx ExacTime GPS TC & FG (Rev C)
Symmetricom Inc
OPTION DESCRIPTIONS
GPS OPTION 13A
1.0
PARALLEL BCD OUTPUT DAYS –MILLISECONDS
ASSEMBLY 55128
INTRODUCTION
This option provides a precision time output consisting of BCD day of year, hours, minutes,
seconds, and milliseconds.
Optionally, three selectable rate outputs can also be provided on separate BNC connectors.
1.1
SPECIFICATIONS
Parallel BCD time, in conjunction with cable assembly 812362-27 output on a 50 pin 3M ribbon
type connector.
1.1.1 OUTPUT CHARACTERISTICS
All outputs are positive true logic, except where noted. HCMOS compatible. Each output
capable of sinking and sourcing four milliamperes.
1.1.2 MATING CONNECTOR
The suggested mating connector is 3M, manufacturer’s Part Number 3425-6000 or 3425-6050 or
equivalent.
1.1.3 PIN ASSIGNMENTS
See Table One.
Two sample time pulses are provided in the connector J3B. One sample time pulse is at the least
significant bit (LSB) rate:
Connector J3B Pin 38 is 1pps (STP 1P).
Connector J3B Pin 48 is 1kpps (STP 1K).
Symmetricom Inc
ET6xxx ExacTime GPS TC & FG (Rev C)
C-31
APPENDIX C
SAMPLE TIME PULSES:
ON TIME POINT
1 MILLISECOND
CONNECTOR PIN 48 (ST1K)
40 MICROSCEOND PULSE WIDTH OF ST1P
CONNECTOR PIN 38 (ST1P)
CONNECTOR PIN 1 (mS1)
CONNECTOR PIN 48 (ST1K)
CONNECTOR PIN 38 (ST1P)
ST1P STARTS 500 NANOSECONDS AFTER ST1K
Both pulses have a 20/80 duty cycle. When the pulse is low, the data is changing and is not
valid. When the pulse is true, the data is stable/valid and can be sampled.
For the rear panel connector designation and location, refer to the GPS Option/Connector
Configuration sheet at the beginning of the ExacTime User’s Guide accompanying this Option
Description.
1.2
OPERATION
This operation applies only to the three optional pulse rate outputs.
For the purposes of this Option Description, Channel One equates to Output One, Channel Two
equates to Output Two, and Channel Three equates to Output Three.
The three selectable pulse rate outputs can be programmed to provide the following rates:
1 10 2400.
The three selectable pulse rates can be programmed from the front panel using the keypad.
Cycle through the various menu screens using the MENU switch until the PULSE RATES
screen appears.
•
Sequentially pushing keyboard Switch One will cycle through the three channels.
C-32
ET6xxx ExacTime GPS TC & FG (Rev C)
Symmetricom Inc
OPTION DESCRIPTIONS
•
Sequentially pushing keyboard Switch Two will cycle through the various pulse rates,
starting with 1pps.
•
When all the parameters are selected for a channel (output), the #4 keyboard switch must be
pushed for them to be entered.
The selectable pulse rates can also be controlled/programmed via the RS232 I/O. To set up the
pulse rates, the user must perform the following steps:
The user enters $f (HEX 24/HEX 46) followed by six digits.
The first digit (after log-on and I.D. characters) is the channel (output) select.
0 = Channel One
1 = Channel Two
3 = Channel Three
The next two digits are a code to select the pulse rate.
01 = 1pps
02 = 10pps
03 = 2400pps
The last three digits are required for a complete command, but any digit can be entered because
they aren’t used.
Example: $F103XXX
The above example indicates the user selecting Channel Two to have a
pulse rate of 2400pps.
The unit responds with OK CR/LF
To request a pulse rate via the RS-232 I/O, the user performs the following steps:
The user enters $G (HEX 24/HEX 47).
Channel (output) number
Space
Four digits of pulse rate followed by pps
space
(the above is repeated for each channel followed by CR/LF).
Symmetricom Inc
ET6xxx ExacTime GPS TC & FG (Rev C)
C-33
APPENDIX C
Example: 1 1 2 2400 3 10 CR/LF
The above example illustrates Channel One with a pulse rate of 1 pps, Channel Two with a pulse
rate of 2400 pps, and Channel Three with a pulse rate of 10pps, carriage return/line feed.
Table One
J3B
Rear Panel Connector Pin Assignments
Pin
Signal
Pin
Signal
mS1
D20
1
26
M40
S2
2
27
mS2
D40
3
28
H1
S4
4
29
mS4
D80
5
30
H2
S8
6
31
mS8
D100
7
32
H4
S10
8
33
mS10
D200
9
34
H8
S20
10
35
mS20
GND
11
36
H10
S40
12
37
mS40
ST1P
13
38
H20
M1
14
39
mS80
GND
15
40
D1
M2
16
41
mS100
N/U
17
42
D2
M4
18
43
mS200
UNLOCKED
19
*44
D4
M8
20
45
mS400
GND
21
46
D8
M10
22
47
mS800
ST1K
23
48
D10
M20
24
49
S1
GND
25
50
* True when unit is unlocked. Low when unit is locked.
C-34
ET6xxx ExacTime GPS TC & FG (Rev C)
Symmetricom Inc
OPTION DESCRIPTIONS
ASSEMBLY 55128
Symmetricom Inc
ET6xxx ExacTime GPS TC & FG (Rev C)
C-35
APPENDIX C
GPS OPTION 14
1.0
IEEE-488 I/O INTERFACE
ASSEMBLY 55089 OR 55115
INTRODUCTION
This assembly is designed in accordance with the IEEE-488/1978 specification and is used to
provide the electrical interface between the GPS Time Code and Frequency Generator (TC &
FG) and the IEEE-488 bus.
When programmed as a listener, this assembly provides the capability to remotely control the TC
& FG. When programmed as a talker, this assembly provides the capability to output time,
status, location, etc. Five of the eight bus control lines (DAV, NRFD, NDAC, ATN and IFC) are
used in this option. EOI, SRQ and REN have no assigned function. The controller cannot
perform a serial poll of this assembly.
It is not recommended that the IEEE-488 and the RS-232 I/O be operated simultaneously.
1.1
INSTALLATION
This assembly is plugged into and works in conjunction with the motherboard option (GPS
Option 40) of the time code and frequency generator. Interconnection to the IEEE-488 bus is
provided through rear panel connector J13.Refer to the GPS Option Connection/Configuration
sheet in the User’s Guide.
1.2
OPERATION
The first step in using the IEEE-488 I/O port is to program/select the Device Address. The
current IEEE-488 address may be found by pressing the front panel MENU keypad switch until
the IEEE-488 screen (as shown below) is displayed on the LCD display.
<1> IEEE488 ADDR.17
If desired, the address may be changed by pressing the 1 key of the keypad, which causes the two
digits following ADDR. to change to “xx” prompting the user to enter a two digit address. A
leading zero is required if address is less than 10.
If a cold reset was performed at power up, the default address will be 17. The address can be
changed by closing (pushing down) rear panel DIP switch SW2, position 3. Watch the display,
and the address will increment at one second intervals.
When the desired address is reached, open (push up) DIP switch SW2, position 3. The Device
Address can also be selected via the RS-232 I/O port. The user inputs $CXX. (The XX
corresponds to a two digit device address number). The unit will respond with OK CR/LF
(carriage return/line feed).
C-36
ET6xxx ExacTime GPS TC & FG (Rev C)
Symmetricom Inc
OPTION DESCRIPTIONS
All communication to or from the IEEE-488 port is in the ASCII format. At power up, the
interface is in the wait/idle state. To talk to our interface, send the following
commands/mnemonics in the order listed below:
UNL (unlisten)
MTA (my talk address containing the address of the controller)
LAG (listen address group containing the address of our interface)
The attention/log-on character (see Section 4.1 of the main Manual)
The command/ID character
The specific data (if applicable).
Note: With the exception of UNL, MTA, and lAG, the protocol is identical to
that of the RS-232 I/O. When communicating to the 488 interface, if more than 30
seconds elapses between commands, the I/O will time out and the communication will
have to be repeated.
If after talking to our interface, it is necessary to receive some data, send the following
commands/mnemonics:
UNL (unlisten)
MLA (my listen address containing the address of the controller)
TAG (talker address group containing the address of our interface).
Our interface will always respond with specific data followed by CR/LF.
1.3
MAINTENANCE
No routine maintenance is required.
Symmetricom Inc
ET6xxx ExacTime GPS TC & FG (Rev C)
C-37
APPENDIX C
Table One
IEEE-488 Bus Interface Connector Pin Assignment
J13 Pin
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
C-38
Signal
D101
D102
D103
D104
EOI
DAV
NRFD
NDAC
IFC
SRQ
ATN
GND
D105
D106
D107
D108
REN
GND
GND
GND
GND
GND
GND
GND
ET6xxx ExacTime GPS TC & FG (Rev C)
Symmetricom Inc
OPTION DESCRIPTIONS
ASCII
Char
`
c
d
e
f
HEX
Char
60
63
64
65
66
i
j
k
l
m
o
p
q
r
s
t
u
x
y
z
{
}
∼
DEL
P
Q
R
|
S
69
6A
6B
6C
6D
6F
70
71
72
73
74
75
78
79
7A
7B
7D
7E
7F
50
51
52
7C
53
T
U
V
W
X
54
55
56
57
58
Symmetricom Inc
Table Two
Applicable Command/Character ID
Description
Symmetricom Firmware Version
UTC Sync
GPS Sync
Print Frequency Offset
Print Time, Status, Error Code and Satellite Vehicle
Numbers
Print Position
Clear Event Data (See Note 1)
Print Event Data (See Note 1)
Enable Event Log (See Note 1)
Disable Event Log (See Note 1)
Preset Coincidence (See Note 2)
Request Single Event (See Note 1)
Request Ephemeris Data
Select Mode
Enable Time Interval
Disable Time Interval
Request Time Interval
Request Mask Levels
Enter Mask Levels
Enable Discipline
Disable Discipline
Enter Position
Enter DAC Value
Request DAC Value
Select Output Code
Enter Number of Position Averages
Enter Local Time Offset (1 Hour)
Enter Local Time Offset (1/2 Hour)
Select Satellite Vehicle Number (for Single Satellite
Mode)
Enter Cable Delay
Request Cable Delay
Enter PDOP Limit
Resynchronize Minor Time
Select Default Values
ET6xxx ExacTime GPS TC & FG (Rev C)
Format/
Response
User’s Guide
User’s Guide
User’s Guide
User’s Guide
User’s Guide
User’s Guide
Opt. Des. 04, 05
Opt. Des. 04, 05
Opt. Des. 04, 05
Opt. Des. 04. 05
Opt. Des. 09
Opt. Des. 04, 05
User’s Guide
User’s Guide
User’s Guide
User’s Guide
User’s Guide
User’s Guide
User’s Guide
User’s Guide
User’s Guide
User’s Guide
User’s Guide
User’s Guide
User’s Guide
User’s Guide
User’s Guide
User’s Guide
User’s Guide
User’s Guide
User’s Guide
User’s Guide
User’s Guide
User’s Guide
C-39
APPENDIX C
ASCII
Char
Z
HEX
Char
5A
[
5B
]
^
A
5D
5E
41
B
C
42
43
Table Two Continued
Applicable Command/Character ID
Description
Enable/Disable External Frequency Measurement
(See Note 4)
Request External Frequency Measurement Data (See
Note 4)
Request Satellite Signal Strength
Request Unit Operating Parameters
Request External 50/60 Hz Measurement Data (See
Note 3)
Set-up External 50/60 Hz Measurement (See Note 3)
Enter IEEE-488 Address
Format/
Response
Opt. Des. 02
Opt. Des. 02
User’s Guide
User’s Guide
Opt. Des. 08AE
Opt. Des. 08AE
This Opt. Des.
Note 1: Single or Triple Event Log Option, Option 04 or 05 must be installed.
See GPS Option Description 04 or 05.
Note 2: Preset Coincidence, Option 09 must be installed. See GPS Option
Description 09.
Note 3: 115VAC/125VDC Power Supply with 50/60Hz Measurement Option,
Option 08AE must be installed. See GPS Option Description 08AE.
Note 4: External Frequency Measurement Option, Option 02 must be installed.
See GPS Option Description 02.
C-40
ET6xxx ExacTime GPS TC & FG (Rev C)
Symmetricom Inc
OPTION DESCRIPTIONS
ASSEMBLY 55115
Symmetricom Inc
ET6xxx ExacTime GPS TC & FG (Rev C)
C-41
APPENDIX C
GPS OPTION 15A / GPS OPTION 15P
10 MHZ OSCILLATOR
1.0
RUBIDIUM TIME BASE
MODEL LPRO
INTRODUCTION
These options provide an internal, disciplined 10MHz Rubidium Oscillator as the unit’s time
base. This 10MHz time base is frequency corrected using a DAC (Digital to Analog Converter)
and locked to the GPS corrected 1PPS.
GPS Option 15P is identical to 15A except that 15P includes the 812515-19, Cable Assembly,
which goes between J2 of the 55189 Power Entry and Alarm Relays Assembly and J1A of the 24
Volt Power Supply, providing an AC input to this supply. Cable Assembly 812503-12, which is
used to interface between J20 of the 35002 GPS Main Assembly and J1 of the 55189 Power
Entry and Alarm Relays Assembly is also provided.
The signal connections provided between J20 of the GPS Main Assembly and J2 of the 55189
Power Entry and Alarm Relays Assembly are as follows:
1.1
J2
PIN
1
2
3
4
5
6
7
8
9
10
7
8
9
10
SIGNAL
LOCK\
TRK\
OUT5
OUT6
PD0
EXTFRE
Q
PD7
VDD (+5)
PD6
GND
SPECIFICATIONS
Output Frequency/ Waveform:
Output Amplitude:
Aging Rate:
Operating Temperature:
Storage Temperature:
Altitude:
Trim Range:
C-42
J20
PIN
1
2
3
4
5
6
10MHz sine wave
1.0 VRMS into 50Ω
≤ 5 x 10-11 per month
5 x 10-10 per year
-20oC Base Plate to +70oC Base Plate
-55oC to +85oC
-200 feet to +20,000 feet
> +1 x 10-9
ET6xxx ExacTime GPS TC & FG (Rev C)
Symmetricom Inc
OPTION DESCRIPTIONS
External Frequency Control:
(Electrical):
< -1 x 10-9 at 0V
> +1 x 10-9 at +5V
The following specifications apply to the Selected 10 MHz Output at a 13dbm output level:
Harmonics:
Spurious Noise:
Phase Noise:
1Hz
10Hz
100Hz
1KHz
10KHz
-37 dBc
>-70 dBc
-76 dBc/Hz
-91 dBc/Hz
-131 dBc/Hz
-144 dBc/Hz
-146 dBc/Hz
It is recommended that the oscillator be nulled when the DAC value starts to approach either
extreme of 5,000 or 60,000. There is a hole on top of the oscillator for the oscillator adjustment
control.
There are two methods to null/calibrate the internal oscillator.
FIRST METHOD
The oscillator can be nulled against a known frequency standard with an oscilloscope or other
suitable means by using the following steps:
1.
Turn on the unit and wait approximately one hour for the oscillator to warm up and
stabilize.
2.
Sync one trace of an oscilloscope on the known frequency standard. Using the other
trace, monitor the 10MHz output of the unit.
3.
The input of the DAC must be held static prior to the nulling oscillator. This can be
accomplished one of three ways:
4.
•
Disconnect the antenna from the rear of the unit.
•
Select the single satellite mode (1SV), and select a satellite that is not in view (or Pick
SV33 which doesn’t exist).
•
Disable disciplining. Refer to Chapter Four, “Disable Disciplining” in the User’s
Guide.
Set the DAC value to it’s midpoint 32767. Refer to Chapter Four ,“Enter DAC Value” in
the User’s Guide.
Symmetricom Inc
ET6xxx ExacTime GPS TC & FG (Rev C)
C-43
APPENDIX C
5.
Adjust the oscillator until the 10MHz output is stable with respect to the frequency
standard.
6.
Enable disciplining. Refer to Chapter Four, “Enable Disciplining” in the User’s Guide.
7.
After approximately one hour, check the DAC value number again. If it has changed by
more than ±5000 from 32767, repeat steps two through six.
SECOND METHOD
If a known frequency standard is not available, the oscillator may be null as follows:
1.
Set the unit to operate in the single satellite (1SV) mode. Make sure the unit is tracking a
satellite.
2.
Read the DAC value either from the RS-232 I/O port, or from the LCD display.
3.
The oscillator is located in front of the GPS Main Board on the Chassis Assembly.
4.
SLOWLY (no more than 45o each time) adjust the oscillator and watch the DAC value
change. If the DAC value is 65535, turn the oscillator adjustment counterclockwise,
which will decrease the frequency and the DAC value. If the DAC value is 00000, turn
the oscillator adjustment clockwise, which will increase the frequency and the DAC
value.
5.
Wait approximately one minute between each adjustment to allow the oscillator to
stabilize.
6.
Keep adjusting the oscillator in the appropriate direction until the DAC value is
approximately at its midpoint (32767).
7.
If after approximately one hour, the DAC value has changed by more than ±5,000 from
32767, repeat steps one through six.
C-44
ET6xxx ExacTime GPS TC & FG (Rev C)
Symmetricom Inc
OPTION DESCRIPTIONS
GPS OPTION 15C
10 MHZ OSCILLATOR
1.O
RUBIDIUM TIME BASE
MODEL X72
INTRODUCTION
This option provides an internal, disciplined 10MHz Rubidium Oscillator as the unit’s time base.
This 10MHz time base is frequency corrected using a serial interface between the X72 and the
GPS Main board (100015), and locked to the GPS corrected 1PPS.
The signal connections provided between the X72 connector and connector J23 on the GPS Main
board are as follows:
J23
PIN
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
Symmetricom Inc
SIGNAL
VDD (Power Input)
VDD
VDD
VDD
VDD
VDD
VDD
SERVICE
DOUT
DIN
FREQ CTRL
VSS (Power and Signal Return)
VSS
VSS
VSS
VSS
VSS
VSS
1PPS IN
1PPS OUT
LOCK (if low, Rb oscillator locked)
FXQ (VCXO freq. output)
FACMOS RTN
FACMOS OUT
FSINE RTN
FSINE OUT
ET6xxx ExacTime GPS TC & FG (Rev C)
C-45
APPENDIX C
1.1
SPECIFICATIONS
Output Frequency/ Waveform:
10MHz sine wave
Output Amplitude:
7.8 dBm into 50Ω
Aging Rate:
APPLICATION
AGING
TEMP. COEFFICIENT
PROFILE
AP1
≤ 1 x 10-10 (-40oC to +85oC)
≤ 5 x 10-11 per month
AP2
≤ 2 x 10-10 (0oC to +70oC)
≤ 3 x 10-11 per day or
≤ 2 x 10-10 per month
AP3
(-40oC to +85oC)
≤ 5 x 10-8 over 20 years
Operating Temperature:
Storage Temperature:
Supply Voltage:
Warm-up Time:
-40oC Base Plate to +85oC Base Plate
-55oC to +100oC
+5VDC ±10%
5 minutes to lock (accuracy @ lock ≤ 5 x 10-8)
7.5 minutes (accuracy ≤ 1 x 10-9)
The following specifications apply to the Selected 10 MHz Output (from the ET6000 etc.) at a
13dbm output level:
Harmonics:
Spurious Noise:
Phase Noise:
1Hz
10Hz
100Hz
1KHz
10KHz
-37 dBc
>-70 dBc
-76 dBc/Hz
-91 dBc/Hz
-131 dBc/Hz
-144 dBc/Hz
-146 dBc/Hz
No mechanical calibration adjustment is required (or available).
C-46
ET6xxx ExacTime GPS TC & FG (Rev C)
Symmetricom Inc
OPTION DESCRIPTIONS
GPS OPTION 21A
1.0
10 MHZ SINE WAVE SHAPER
ASSEMBLY 20457-45
INTRODUCTION
This Option Description provides specifications, an explanation of the Sine Wave Shaper logic
used to develop the Sine Wave output and adjustment of the output amplitude.
This Shaper Assembly can be plugged into the J7/J9, J8/J10, J18/J22, or J19/J23 area of the
35007 Motherboard Assembly. The 10MHz Sine Wave output will be present on the rear panel
BNC, J3A, J3B, J3D, or J3E respectively.
1.1
SPECIFICATIONS
The following specifications apply at 13dbm output level using an oven oscillator. These
specifications are worst case.
Harmonics:
Spurious Noise:
Phase Noise:
1Hz
10Hz
100Hz
1KHz
10KHz
100KHz
1.2
-35 dBc
-35 dBc
-72 dBc/Hz
-94 dBc/Hz
-112 dBc/Hz
-115 dBc/Hz
-117 dBc/Hz
-121 dBc/Hz
FUNCTIONAL EXPLANATION
A 10MHz square wave derived from the 10MHz internal oscillator is input to J1 pin 9 of the Sine
Wave Shaper Assembly. The signal is filtered and shaped to generate the 10MHz Sine Wave
output at P1 pin 2 of the same assembly.
This signal is then routed to a rear panel BNC. Refer to the GPS Option/Connector
Configuration sheet in the User’s Guide for the output connector designation. Refer to the Top
Assembly Drawing for connector location. This signal is adjustable from zero to six volts peakto-peak and has been factory adjusted to three volts peak-to-peak into a 50Ω load.
1.3
OUTPUT AMPLITUDE ADJUSTMENT
The output amplitude of this signal can be adjusted to the desired amplitude using LEVEL
potentiometer R13, on the Sine Wave Shaper assembly.
Symmetricom Inc
ET6xxx ExacTime GPS TC & FG (Rev C)
C-47
APPENDIX C
GPS OPTION 23A/23B
1.0
LIGHTNING ARRESTOR
W/25 OR 50 FOOT ANTENNA CABLE
INTRODUCTION
This option provides protection of the GPS unit from external over-voltage transients which can
be created through lightning, static discharges, switch processes, direct contact with power lines,
or through earth currents.
The lightning and nuclear EMP arrestors limit the amplitude and duration of the disturbing
interference voltages. Therefore these arrestors improve the over-voltage resistance of in-line
equipment, systems and components.
Note: The antenna cable described in this manual has been replaced as described in “Appendix
D: Antenna Replacement Kit” on page D-1.
The 23A option comes with a twenty-five foot length of 9913 Antenna Cable and the 23B
option comes with a fifty foot length of 9913 Antenna Cable. Both cables have Type N positive
connectors on each end.
This Option may require that the GPS unit to which it is connected have a Bias T Assembly
installed externally. This assembly would furnish a separate +5 volts to power the antenna. See
the Bias T installation procedure furnished with the Bias T.
1.1
1.2
C-48
SPECIFICATIONS FOR THE 9913 LOW LOSS COAXIAL ANTENNA CABLE
Cable Diameter
0.45 Inches
Center Conductor
10 (Solid) .108 Stranded Copper .90 Ω per 1000 ft.
Shield
90% Tinned Copper Braid.
Attenuation
Nominal 5.6 dB per 100 ft at 1.5GHz.
Cable Jacket
Black PVC
SPECIFICATIONS FOR THE LIGHTNING ARRESTOR
Frequency Range
1565 to 1586 MHz
Return Loss
> 20dB from 1565 to 1586 MHz
Insertion Loss
< 0.5 dB from 1565 to 1585 MHz
Impedance
50 Ω
Connector
Type N
ET6xxx ExacTime GPS TC & FG (Rev C)
Symmetricom Inc
OPTION DESCRIPTIONS
1.3
Environment:
-40oC to +85oC
Sealing:
Waterproof IP66 Standard (Mil, etc.)
Bypass Voltage:
6 Volt Max. with Gas Insert.
Bypass Current:
1 Amp
DC Resistance :
<1Ω
Length:
4.53 Inches
Width:
1.36 Inches.
Depth:
2.6 Inches Not Including Type N Connectors.
LIGHTNING ARRESTOR INSTALLATION
The following installation procedure balances the voltage potential thus preventing inductive
interference to parallel signal lines within the protected area.
•
Mount the Lightning Arrestor on a metal mounting plate or bar (customer furnished) with a
thickness not to exceed 0.33 inches. See Figure One.
•
The Lightning Arrestor should be mounted so that the mounting plate and the Lightning
Arrestor are outside of the enclosure where the GPS unit is housed.
•
The Lightning Arrestor should be placed on the unprotected side.
•
The connection between the mounting plate and the ground terminal should be accomplished
with a low resistance path such as a copper strap (customer furnished).
•
The contact surface of the mounting plate must be conductive (free of any paint, anodization
or oxides). Tighten the mounting nut to reduce the contact resistance between the arrestor
body and the mounting plate.
•
Connect an AWG 5 or larger wire between the ground terminal on the mounting plate to a
good earth ground. Remove the gas capsule arrestor access cover and insert the gas arrestor
capsule into the lightning arrestor body and tighten the capsule holder to a minimum torque
of 4.43 foot pounds.
•
When connecting the cable from the antenna to the Lightning Arrestor, install a drip loop
before it enters the arrestor. This keeps any large amounts of moisture from coming down
the cable and collecting at the connector, causing a loss and/or failure.
Symmetricom Inc
ET6xxx ExacTime GPS TC & FG (Rev C)
C-49
APPENDIX C
•
Both inside and outside, secure the cable as close as possible to the arrestor. This relieves
strain on the N connectors and the arrestor.
* * * WARNING * * *
Please adhere to the following recommendations to prevent accidents during the installation of
the Lightning Arrestor:
Disconnect or switch off in-line equipment when installing or inspecting the Lightning
Arrestor. Also, do not install or inspect the Lightning Arrestor during an electrical storm.
When connecting the Lightning Arrestor or when changing the gas capsule arrestor, make sure
that the connecting equipment and components are disconnected or switched off.
C-50
ET6xxx ExacTime GPS TC & FG (Rev C)
Symmetricom Inc
OPTION DESCRIPTIONS
Figure One
Lightning Arrestor Mounting
To Antenna
Access to
Non-radioactive
Gas Capsule Arrestor
73 Z-0-0-448
Ground
Terminal
1/4"
Outside
Lightning Arrestor
3403.17.0016
Copper Ground Strap
(Customer Furnished)
Ground
Terminal 1/4"
Inside
Symmetricom Inc
Mounting Plate
(Customer Furnished)
To
GPS
ET6xxx ExacTime GPS TC & FG (Rev C)
C-51
APPENDIX C
Figure Two
Lightning Arrestor Mounting
Dimensions
4.5276
(115)
4.1339
(105)
Mounting
Hole
0.1732
(4.4)
ANTENNA
1.122
(28.5)
2.5129
(64)
2.1654
(55)
EQUIPMENT
Clearance Hole
Mounting Hole
On Mounting
0.1732
Plate
(4.4)
NOTE
0.625
Number in ( ) is Millimeters
(16)
C-52
ET6xxx ExacTime GPS TC & FG (Rev C)
0.3346
(8.5)
Max.
Symmetricom Inc
OPTION DESCRIPTIONS
GPS OPTION 27A/B/C/D
1.0
SIGNAL DISTRIBUTION
ASSEMBLY 55143
INTRODUCTION
This option, in conjunction with various plug-in modules provides up to twelve independently
buffered signal outputs. The types of signals and signal characteristics are dependent on the
buffer modules and the input to the module. This input is jumper selectable and located
underneath each module.
1.1
CONFIGURATION
The module sockets are labeled U1 through U12. On the left side of the card edge are twelve
output connectors, J1-J12. J1 corresponds to socket U1, etc. The 14 pin jumper arrangement
inside each socket selects the input to the plug-in module. Various modules are available to
provide analog and digital buffered outputs. Rear panel output connector designations and signal
characteristics are described in the GPS Option/Connector Configuration sheet located at the
front of the ExacTime User’s Guide. The type of module plugged into each socket depends on
the jumper selected input. Analog buffers can output both digital and analog signals. For digital
signals requiring specific pulse widths and on-time edges, digital buffers are required.
The typical module input selection for U1 is as follows:
U1A-1 to U1A-28
U1A-2 to U1A-27
U1A-3 to U1A-26
U1A-4 to U1A-25
U1A-5 to U1A-24
U1A-6 to U1A-23
U1A-7 to U1A-22
U1A-8 to U1A-21
U1A-9 to U1A-20
U1A-10 to U1A-19
U1A-11 to U1A-18
U1A-12 to U1A-17
U1A-13 to U1A-16
U1A-14 to U1A-15
1MHz Square Wave
Out 1
5MHz Square Wave
Out 2
10MHz Square Wave
1pps
AC Modulated Code
DC Level Shift Code
Locked
PD7
PD6
Spare 1
Spare 2
Spare 3
All other modules input selection is similar. Out1, Out 2, Spare 1, Spare 2, and Spare 3 can be
optionally jumpered to other signals dependent on customer requirements. PD6 and PD7 are
software controlled optional signals.
Symmetricom Inc
ET6xxx ExacTime GPS TC & FG (Rev C)
C-53
APPENDIX C
1.2
GPS Option 27A - Output Connections - Assembly 55143
Pin 1 and Pin 2 of connectors J1 through J12 are the signal and the ground return pins,
respectively, for Options 27B and 27D.
Pin 1 and Pin 2 of connectors J1 through J12 are the “signal hi” and the “signal lo” pins
respectively for Option 27C.
Pin 1 of connector J1 through J12 is the uppermost pin and Pin 2 is the pin nearest to the PC
board.
1.3
GPS Option 27B - Analog Buffer - 50Ω Driver - Assembly 35001
This analog buffer plug in module is a gain of one amplifier capable of driving 50Ω. The output
amplitude is dependent on the input amplitude. Its frequency response is from DC to 10MHz.
1.4
GPS Option 27C - RS-422 Differential Buffer - Assembly 35028
This RS-422 buffer plug in module is a differential line driver with output levels of 0 to +5 volts.
It is a line driver for digital data transmission over balanced lines. It is designed to provide
unipolar differential drive to twisted-pair or parallel-wire transmission lines.
1.5
GPS Option 27D - Pulse Buffer - Assembly 35000
This pulse buffer plug in module outputs a 0 to +10 volt positive going signal. Dash numbers
determine the input on-time edge selection and pulse width.
Example:
C-54
35000-110
Triggers on input negative/falling edge. 20µs pulse
width.
35000-210
Triggers on input positive/rising edge. 20µs pulse
width.
ET6xxx ExacTime GPS TC & FG (Rev C)
Symmetricom Inc
OPTION DESCRIPTIONS
ASSEMBLY 55143
Symmetricom Inc
ET6xxx ExacTime GPS TC & FG (Rev C)
C-55
APPENDIX C
GPS OPTION 33A
1.0
1.544/2.048 MHZ SQUARE WAVE OUTPUT
ASSEMBLY 55138
INTRODUCTION
The 1.544/2.048MHz Output Assembly 55138 provides a 1.544MHz T1 square wave clock or a
2.048MHz E1 square wave clock (switch selectable).
1.1
CONFIGURATION
It is a single width assembly that is mounted on the GPS Motherboard (GPS Option 40). The
Motherboard provides support for this assembly, an interface to the GPS Main Assembly, and
interface to the rear panel output BNC’s.
The Motherboard has four (4) single width option areas. Where the 1.544/2.048 Output
Assembly is installed determines the rear panel output BNC.
The following is the correlation between the option area and the output:
Option Area
J7/J9
J8/J10
J18/J22
J19/J23
Rear Panel
BNC
J3B
J3C
J3E
J3F
The buffered output can provide TTL levels into 50Ω.
1.2
OPTIONAL FEATURES
The following features are switch selectable:
S1 open/up
S1 closed/down
Selects T1 1.544MHz output
Selects E1 2.048MHz output
S2 open/up
Allows the square wave to be synchronized to 1PPS. This is a factory test
position only.
Prohibits the square wave from being synchronized.
S2 closed/down
S3 closed/down
S3 open/up
C-56
The square wave is output only while the unit is in the LOCK mode
The square wave will be output regardless of whether the unit is locked or
not.
ET6xxx ExacTime GPS TC & FG (Rev C)
Symmetricom Inc
OPTION DESCRIPTIONS
GPS OPTION 33B
T1 FRAMED ONES – BALANCED OUTPUT
ASSEMBLY 55155
E1 FRAMED ONES – BALANCED OUTPUT
ASSEMBLY 55155-1
GPS OPTION 33C
1.0
INTRODUCTION
This optional assembly (Option 33B - T1 or Option 33C - E1) uses a DS1 (or a CEPT)
Telecommunications Synthesizer and can serve as a stand alone Stratum 1 Master Clock when
installed in an instrument that has a Rubidium Oscillator as its time base. Or it can be a
component of a master clock system. This assembly can be installed in locations J7/J9 J8/J10 or
J18/J22 J19/J23 of the GPS Option 40 Motherboard Assembly. For the location of the 55155 (or
55155-1) Assembly and the rear panel output connector designations, characteristics, and
locations, refer to the GPS Option/Connector Configuration Sheet located inside the cover of the
ExacTime User’s Guide.
For a more in-depth description of T1 and/or E1 and the options provided on this assembly, refer
to the following:
•
CCITT Standards G.704, G.706, and G.732.
•
Also ATT pub 43801, ATT C.B. #142, and ATT C.B. #144.
1.1
•
GENERAL DESCRIPTION – GENERATION OF T1 (1.544MHz)
Assembly 55155 generates the T1 (1.544MHz) framed all ones, DS1 signal. It provides the
following output to the rear panel of this instrument. The connector pin assignments are:
Pin
1
2
3
Signal
Balanced 1.544MHz framed all ones, DS1 Hi.
Balanced 1.544MHz framed all ones, DS1 Lo.
Output Transformer Center Tap.
Adding a jumper from E3 to E4 on the 55155 assembly allows the transformer center tap to be
grounded.
The output is frequency locked to an internal 10MHz reference.
The DS1 signal is switch selectable to provide various features. (See Table One below).
•
Down is the closed (0) position.
•
Up is the open (1) position.
•
Switch 1-1 selects between T1 and E1 functions.
Symmetricom Inc
ET6xxx ExacTime GPS TC & FG (Rev C)
C-57
APPENDIX C
Switc
h
1-1
1-2
1-3
2-1
2-2
2-3
2-4
TABLE ONE
Closed (0)
Selects E1
*Inhibits 1pps Sync
*Allows framed output during
alarms.
N/A
*ABCD Data = Zero
*Transmit Link Data Zeros
*Internally Generate S Bit
Open (1)
*Selects T1
Enables 1pps Sync
Inhibits framed output during
alarms.
N/A
ABCD Data = One
Transmit Link Data Ones
Insert transmit link data into S
bit.
Mode 193E
Transmit Yellow Alarm
E1 Output
2-5
*Mode 193S
2-6
*Disabled
3-1
*T1 Output
3-2
See Table Two below.
3-3
See Table Two below.
3-4
See Table Two below.
3-5
*Inhibit Bit 7 Stuffing.
Enable Bit 7 Stuffing.
3-6
Inhibit B8ZS
Enable B8ZS
* The normal, as shipped position of each switch.
TABLE TWO
LINE LENGTH SELECTION
SW3- SW3- SW3- Option Selected
Application
4
3
2
0
0
0
Test Mode
Do Not Use
0
0
1
-7.5 dB BuildT1 CSU
out
0
1
0
-15 dB Build-out T1 CSU
*0
*1
*1
0 dB Build-out
T1 CSU, DSX-1 Cross
0-133 feet
Connect
1
0
0
133 - 266 Feet
DSX - 1 Cross Connect
1
0
1
266 - 399 Feet
DSX - 1 Cross Connect
1
1
0
399 - 533 Feet
DSX - Cross Connect
1
1
1
533 - 655 Feet
DSX - Cross Connect
* The normal, as shipped position of each switch.
Table Three is a list of specifications applicable to GPS Option 33B (T1 Assembly 55155)
C-58
ET6xxx ExacTime GPS TC & FG (Rev C)
Symmetricom Inc
OPTION DESCRIPTIONS
TABLE THREE
SPECIFICATIONS, 55155
Outputs
DS1
Signal Type
Frequency
Format
DS1, Balanced
1.544 MHz
Framed All 1’s (D4 or
ESF)
<0.05 U.I.
See Note
Jitter
Connector
Note: See the GPS Option/Connector Configuration Sheet in the ExacTime User’s Guide.
Figure One
D4 and Extended Superframe Formats
Frame Format
Frame
M+1
Frame
M
Bit No.
1
2
3
4
190
191
1
192
2
3
4
F = Frame Bit
0
Frame No.
Frame No.
1
2
3
2
0
3
4
5
6
7
8
9
0
0
Multi-Frame
+M
1 0 0 0 1
10 11 12
1
2
3
4
Extended Superframe Format
0
Frame Bits
1
0
D4 Format
Multi-frame
M
1 1 0 1 1 1
4
Multi-frame
M
1
0
5
6
7
8
9
0
1
Multi-frame
M+1
0
1
10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
1
2
3
4
5
0
6
7
8
FDL bits are all zeros. Appropriate CRC check sums are generated.
Symmetricom Inc
ET6xxx ExacTime GPS TC & FG (Rev C)
C-59
APPENDIX C
1.2
•
GENERAL DESCRIPTION – GENERATION OF E1 (2.048MHz)
Assembly 55155-1 generates the E1 (2.048MHz) CEPT signal and associated outputs. It
provides the following output to the rear panel of this instrument. The connector pin
assignments are as follows:
Pin
1
2
3
Signal
Balanced 2.048MHz framed all ones, CEPT Hi.
Balanced 2.048MHz framed all ones, CEPT Lo.
Output Transformer Center Tap.
Adding a jumper from E3 to E4 on the 55155 assembly allows the transformer center tap to be
grounded.
The output is frequency locked to an internal 10MHz reference.
The CEPT signal is switch selectable to provide various features. (See Table Four).
•
Down is the closed (0) position.
•
Up is the open (1) position.
•
Switch 1-1 selects between T1 and E1 functions.
C-60
ET6xxx ExacTime GPS TC & FG (Rev C)
Symmetricom Inc
OPTION DESCRIPTIONS
Switc
h
1-1
1-2
1-3
Closed (0)
TABLE FOUR
Open (1)
Selects T1
Enables 1pps Sync
Inhibits framed output during
alarms.
2-1
*Transmit Extra Data Ones
2-2
*CAS Signaling One
2-3
Transmit
National/International
One
2-4
*Disable Remote Alarm
Enable Remote Alarm
2-5
*Disable Distant MultiEnable Distant Multi-Frame
Frame Alarm
Alarm
2-6
*AMI Coding
HDB3 Coding
3-1
T1 Output
*E1 Output
3-2
*
3-3
*
3-4
*
3-5
*Disable CRC4 Multi-frame Enable CRC4 Multi-frame
3-6
Enable CAS Multi-frame
*Disable CAS Multi-frame
* The normal, as shipped position of each switch.
Symmetricom Inc
*Selects E1
*Inhibits 1pps Sync
*Allows framed output
during alarms.
Transmit Extra Data Zeros
CAS Signaling Zero
Transmit
National/International Zero
ET6xxx ExacTime GPS TC & FG (Rev C)
C-61
APPENDIX C
Figure Two
Time Slot, Frame, and CEPT Formats
Time Slot Format (8 Bits/Time Slot)
Time Slot
M
Bit Number
1
2
3
4
5
Time Slot
M+1
6
7
8
1
2
3
4
Frame Format (Thirty-Two Time Slots/Frame)
Frame
M
Time Slot Number
0
1
2
Frame
M+1
3
29 30 31
0
1
2
3
4
CEPT Format (Sixteen Frames/Multi-Frame)
Multi-Frame
M
0
1
2
3
4
5
6
7
8
9
Multi-Frame
M+1
10 11 12 13 14 15
0
1
2
3
Frame Number
Table Five is a list of specifications applicable to GPS Option 33C (E1 Assembly 55155-1).
C-62
ET6xxx ExacTime GPS TC & FG (Rev C)
Symmetricom Inc
OPTION DESCRIPTIONS
TABLE FIVE
SPECIFICATIONS, 55155-1
Outputs
CEPT
Signal Type
Frequency
Format
Jitter
Connector
CEPT, Balanced
2.048 MHz
Framed All 1’s
<0.05 U.I.
See Note
Note: See the GPS Option/Connector Sheet in the ExacTime User’s Guide.
Symmetricom Inc
ET6xxx ExacTime GPS TC & FG (Rev C)
C-63
APPENDIX C
ASSEMBLY 55155
C-64
ET6xxx ExacTime GPS TC & FG (Rev C)
Symmetricom Inc
OPTION DESCRIPTIONS
GPS OPTION 33D
GPS OPTION 33E
1.0
T1 FRAMED ONES - BALANCED OUTPUT
ASSEMBLY 55155-2
E1 FRAMED ONES - BALANCED OUTPUT
ASSEMBLY 55155-12
INTRODUCTION
This optional assembly (Option 33D - T1 or Option 33E - E1) uses a DS1 (or a CEPT)
Telecommunications Synthesizer and can serve as a stand alone Stratum 1 Master Clock when
installed in an instrument that has a Rubidium Oscillator as its time base. Or it can be a
component of a master clock system. This assembly can be installed in locations J7/J9 J8/J10 or
J18/J22 J19/J23 of the GPS Option 40 Motherboard Assembly. For the location of the 55155-2
(or 55155-12) Assembly and the rear panel output connector designations, characteristics, and
locations, refer to the GPS Option/Connector Configuration Sheet located inside the cover of the
ExacTime User’s Guide.
For a more in-depth description of T1 and/or E1 and the options provided on this assembly, refer
to the following:
•
CCITT Standards G.704, G.706, and G.732.
•
Also ATT pub 43801, ATT C.B. #142, and ATT C.B. #144.
1.1
•
GENERAL DESCRIPTION – GENERATION OF T1 (1.544MHz)
Assembly 55155-2 generates the T1 (1.544MHz) framed all ones, DS1 signal and associated
outputs. It provides the following input/outputs on a rear panel (20) pin connector. The
connector pin assignments are as follows:
Pin
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
Symmetricom Inc
Signal
Balanced 1.544MHz framed all ones, DS1 Hi.
Aux. Alarm Relay Common Contact.
Balanced 1.544 MHz framed all ones, DS1 Hi.
Aux. Alarm Relay Normally Closed Contact.
Output Transformer Center Tap.
Aux. Alarm Relay Normally Open Contact.
Alarm Relay Normally Open Contact.
Alarm Relay Common Contact.
Alarm Relay Normally Closed Contact.
Not Used.
SYNC Input.
Sync Input Return.
8kHz TTL Output.
GND.
1.544MHz TTL Clock Output
ET6xxx ExacTime GPS TC & FG (Rev C)
C-65
APPENDIX C
16
17
18
19
20
GND.
Not Used.
Not Used.
Not Used.
Not Used.
SYNC input allows the DS1 and Frame Alignment outputs to be synchronized to an external
reference of 8kHz or sub-multiple of 8kHz.
Alarm relay closure is a summary alarm closure.
Adding a jumper from E3 to E4 on the 55155-2 assembly allows the transformer center tap to be
grounded.
All of these optional outputs are frequency locked to an internal 10MHz reference.
The DS1 signal is switch selectable to provide various features. (See Table One below).
•
Down is the closed (0) position.
•
Up is the open (1) position.
•
Switch 1-1 selects between T1 and E1 functions.
TABLE ONE
Switch
Closed (0)
Open (1)
1-1
Selects E1
*Selects T1
1-2
*Inhibits 1pps Sync
Enables 1pps Sync
1-3
*Allows framed output during Inhibits framed output during
alarms.
alarms.
2-1
N/A
N/A
2-2
*ABCD Data = Zero
ABCD Data = One
2-3
*Transmit Link Data Zeros
Transmit Link Data Ones
2-4
*Internally Generate S Bit
Insert transmit link data into S bit.
2-5
*Mode 193S
Mode 193E
2-6
*Disabled
Transmit Yellow Alarm
3-1
*T1 Output
E1 Output
3-2
See Table Two below.
3-3
See Table Two below.
3-4
See Table Two below.
3-5
*Inhibit Bit 7 Stuffing.
Enable Bit 7 Stuffing.
3-6
Inhibit B8ZS
Enable B8ZS
* The normal, as shipped position of each switch.
C-66
ET6xxx ExacTime GPS TC & FG (Rev C)
Symmetricom Inc
OPTION DESCRIPTIONS
TABLE TWO
LINE LENGTH SELECTION
SW3-4 SW3-3
SW3-2
Option Selected
Application
0
0
0
Test Mode
Do Not Use
0
0
1
-7.5 dB Build-out
T1 CSU
0
1
0
-15 dB Build-out
T1 CSU
*0
*1
*1
0 dB Build-out
T1 CSU, DSX-1 Cross
0-133 feet
Connect
1
0
0
133 - 266 Feet
DSX - 1 Cross Connect
1
0
1
266 - 399 Feet
DSX - 1 Cross Connect
1
1
0
399 - 533 Feet
DSX - Cross Connect
1
1
1
533 - 655 Feet
DSX - Cross Connect
* The normal, as shipped position of each switch.
Table Three is a list of specifications applicable to GPS Option 33D (T1 Assembly 55155-2)
TABLE THREE
SPECIFICATIONS, 55155-2
Outputs
DS1
Signal Type
Frequency
Format
Jitter
Connector
Frame Marker Signal Type
Frequency
Connector
Signal Type
TTL Clock
Frequency
Connector
Frame Synchronization
Inputs
Frequency
Connector
Summary Alarm
Monitor
Contact Rating
(maximum)
Connector
Symmetricom Inc
DS1, Balanced
1.544 MHz
Framed All 1’s (D4 or ESF)
<0.05 U.I.
See Note
TTL
8 kHz
See Note
TTL
1.544 MHz
See Note
TTL compatible, active low
8 kHz or sub-multiple of 8 kHz
See Note
Contact Closure
2 A at 30 V dc
See Note
ET6xxx ExacTime GPS TC & FG (Rev C)
C-67
APPENDIX C
Note: See the GPS Option/Connector Configuration Sheet in the ExacTime User’s
Guide.
Figure One
D4 and Extended Superframe Formats
Frame Format
Frame
M+1
Frame
M
Bit No.
1
2
3
4
190
191
1
192
2
3
4
F = Frame Bit
0
Frame No.
Frame No.
1
2
3
2
0
3
4
5
6
7
8
9
0
0
Multi-Frame
+M
1 0 0 0 1
10 11 12
1
2
3
4
Extended Superframe Format
0
Frame Bits
1
0
D4 Format
Multi-frame
M
1 1 0 1 1 1
4
Multi-frame
M
1
0
5
6
7
8
9
0
1
Multi-frame
M+1
0
1
10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
1
2
3
4
5
0
6
7
8
FDL bits are all zeros. Appropriate CRC check sums are generated.
C-68
ET6xxx ExacTime GPS TC & FG (Rev C)
Symmetricom Inc
OPTION DESCRIPTIONS
1.2
•
GENERAL DESCRIPTION – GENERATION OF E1 (2.048 MHz)
Assembly 55155-12 generates the E1 (2.048 MHz) CEPT signal and associated outputs. It
provides the following input/outputs on a rear panel (20) pin connector. The connector pin
assignments are as follows:
Pin
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
Signal
Balanced 2.048MHz framed all ones, CEPT Hi.
Aux. Alarm Relay Common Contact.
Balanced 2.048MHz framed all ones, CEPT Hi.
Aux. Alarm Relay Normally Closed Contact.
Output Transformer Center Tap.
Aux. Alarm Relay Normally Open Contact.
Alarm Relay Normally Open Contact.
Alarm Relay Common Contact.
Alarm Relay Normally Closed Contact.
Not Used.
SYNC Input.
SYNC Input Return (GND).
8kHz TTL Output.
GND.
2.048Mhz TTL Clock Output.
GND.
Not Used.
Not Used.
Not Used.
Not Used.
SYNC input allows the CEPT and frame alignment outputs to be synchronized to an external
reference of 8kHz or sub-multiple of 8kHz.
Alarm relay closure is a summary alarm closure.
Adding a jumper from E3 to E4 on the 55155-12 assembly allows the transformer center tap to
be grounded.
All three of these optional outputs are frequency locked to an internal 10MHz reference.
The CEPT signal is switch selectable to provide various features. (See Table Four).
•
Down is the closed (0) position.
•
Up is the open (1) position.
Symmetricom Inc
ET6xxx ExacTime GPS TC & FG (Rev C)
C-69
APPENDIX C
•
Switch 1-1 selects between T1 and E1 functions.
Switc
h
1-1
1-2
1-3
2-1
2-2
2-3
2-4
2-5
2-6
3-1
3-2
3-3
3-4
3-5
3-6
*
C-70
TABLE FOUR
Closed (0)
Open (1)
*Selects E1
*Inhibits 1pps Sync
*Allows framed output during
alarms.
Transmit Extra Data Zeros
CAS Signaling Zero
Transmit National/International
Zero
*Disable Remote Alarm
*Disable Distant Multi-Frame
Alarm
*AMI Coding
T1 Output
Selects T1
Enables 1pps Sync
Inhibits framed output during
alarms.
*Transmit Extra Data Ones
*CAS Signaling One
Transmit
National/International One
Enable Remote Alarm
Enable Distant Multi-Frame
Alarm
HDB3 Coding
*E1 Output
*
*
*
*Disable CRC4 Multi-frame
Enable CRC4 Multi-frame
Enable CAS Multi-frame
*Disable CAS Multi-frame
The normal, as shipped position of each switch.
ET6xxx ExacTime GPS TC & FG (Rev C)
Symmetricom Inc
OPTION DESCRIPTIONS
TABLE FIVE
SPECIFICATIONS, 55155-12
Outputs
CEPT
Frame
Marker
TTL Clock
Inputs
Monitor
Signal Type
Frequency
Format
Jitter
Connector
Signal Type
CEPT, Balanced
2.048 MHz
Framed All 1’s
<0.05 U.I.
See Note
TTL
Frequency
Connector
Signal Type
Frequency
Connector
Frame
Synchronization
Frequency
8 kHz
See Note
TTL
1.544 MHz
See Note
TTL compatible, active
low
8 kHz or sub-multiple of
8 kHz
See Note
Contact Closure
2 A at 30 V dc
Connector
Summary Alarm
Contact Rating
(maximum)
Connector
See Note
Note: See the GPS Option/Connector Configuration Sheet in the ExacTime User’s
Guide.
Symmetricom Inc
ET6xxx ExacTime GPS TC & FG (Rev C)
C-71
APPENDIX C
Figure Two
Time Slot, Frame, and CEPT Formats
Time Slot Format (8 Bits/Time Slot)
Time Slot
M
Bit Number
1
2
3
4
5
Time Slot
M+1
6
7
8
1
2
3
4
Frame Format (Thirty-Two Time Slots/Frame)
Frame
M
Time Slot Number
0
1
2
Frame
M+1
3
29 30 31
0
1
2
3
4
CEPT Format (Sixteen Frames/Multi-Frame)
Multi-Frame
M
0
1
2
3
4
5
6
7
8
9
Multi-Frame
M+1
10 11 12 13 14 15
0
1
2
3
Frame Number
Note: For a top assembly view of this module, see the previous section
.
C-72
ET6xxx ExacTime GPS TC & FG (Rev C)
Symmetricom Inc
OPTION DESCRIPTIONS
GPS OPTION 40
GPS OPTION MOTHERBOARD
ASSEMBLY 35007
W/6 BNC OUTPUTS
GPS OPTION 40P
1.0
INTRODUCTION
GPS Option 40 (Motherboard Assembly 35007) provides the expansion capability to add
optional assemblies to the GPS Timing Unit. It provides a platform to support these assemblies
and an interface between these assemblies and the GPS Main Assembly 35002.
The Motherboard Assembly can support two double width options or four single width options.
Also, depending upon the options themselves and if space permits, some options can be stacked
on top of other options.
The motherboard is also provided with a variety of rear panel butch plates and output connectors
depending upon the options supplied.
GPS Option 40P is identical to 40 except that 40P includes the 812363-9 cable used to connect
J2 of the 35007 Motherboard Assembly to J1 of the 55189 Power Entry and Alarm Relays
Assembly. It provides the signal paths to and from the 55189 Assembly to the GPS Main
Assembly 35002.
1.1
OPERATIONAL FEATURES
The basic Motherboard has four plug-in option areas J7/J9, J8/J10, J18/J22, and J19/J23. Each
of these option areas provides one or two single-ended BNC outputs. However, depending upon
the option installed, some of these outputs may or may not be used.
Rear Panel Output Connector designations and signal characteristics are described in the GPS
Option/Connector Configuration sheet located at the front of the ExacTime User’s Guide.
The following is the correlation between the option area and the output:
J7/J9 area
J8/J10
J18/J22
J19/J23
Rear panel BNC J3B, optional J3A.
Rear panel BNC J3C.
Rear panel BNC J3E, optional J3D.
Rear panel BNC J3F.
Each of the above outputs is provided via a 250 milliampere high speed buffer/driver. The gain
of the buffer is 1:1 so the output amplitude is dependent on the input and the load.
Symmetricom Inc
ET6xxx ExacTime GPS TC & FG (Rev C)
C-73
APPENDIX C
For GPS Option 40P, the signal connections provided at J2 of the 35007 Motherboard Assembly
are as follows:
J2 PIN
1
2
3
4
5
6
7
8
9
10
C-74
SIGNAL
LOCK\
TRK\
OUT5
OUT6
PD0
EXTFREQ
PD7
VDD (+5)
PD6
GND
ET6xxx ExacTime GPS TC & FG (Rev C)
Symmetricom Inc
OPTION DESCRIPTIONS
GPS OPTION 40A
GPS OPTION MOTHERBOARD
ASSEMBLY 35007-1
W/1 BNC OUTPUT
GPS OPTION 40AP
1.0
INTRODUCTION
GPS Option 40A (GPS Motherboard Assembly 35007-1) provides the expansion capability to
add optional assemblies to the GPS Timing Unit. It provides a platform to support these
assemblies and an interface between these assemblies and the GPS Main Assembly 35002.
The motherboard assembly can support two double width options or four single width options.
Also, depending upon the options themselves, and if space permits, some options can be stacked
on top of other options.
The motherboard is also provided with a variety of rear panel butch plates and output connectors
depending upon the option supplied.
GPS Option 40AP is identical to 40A except that 40AP includes the 812363-9 cable used to
connect J2 of the 35007 Motherboard Assembly to J1 of the 55189 Power Entry and Alarm
Relays Assembly. It provides the signal paths to and from the 55189 Assembly to the GPS Main
Assembly 35002.
1.1
OPERATIONAL FEATURES
The basic motherboard has four plug-in option areas, J7/J9, J8/J10, J18/J22, and J19/J23. Each
of these option areas provides one or two single-ended BNC outputs. However, depending upon
the option installed, some of these outputs may or may not be used.
In this particular configuration, the output connector(s) for the optional assembly plugged into
the J8/J10 and J7/J9 areas of the motherboard require excessive rear panel space. This requires
removing motherboard BNCs J3A through J3E. The only remaining option area with access to a
rear panel BNC is J19/J23.
The following is the correlation between the option area and the output.
J19/J23
Rear Panel BNC J3F.
The above output is provided via a 250 milliamphere high speed buffer/driver. The gain of the
buffer is 1:1 so the output amplitude is dependant upon the input and the load.
Symmetricom Inc
ET6xxx ExacTime GPS TC & FG (Rev C)
C-75
APPENDIX C
For GPS Option 40AP, the signal connections provided at J2 of the 35007 Motherboard
Assembly are as follows:
J2 PIN
1
2
3
4
5
6
7
8
9
10
C-76
SIGNAL
LOCK\
TRK\
OUT5
OUT6
PD0
EXTFREQ
PD7
VDD (+5)
PD6
GND
ET6xxx ExacTime GPS TC & FG (Rev C)
Symmetricom Inc
OPTION DESCRIPTIONS
GPS OPTION 40B
GPS OPTION MOTHERBOARD
ASSEMBLY 35007-2
W/3 BNC OUTPUTS
GPS OPTION 40BP
1.0
INTRODUCTION
GPS Option 40B (Motherboard Assembly 35007-2) provides the expansion capability to add
optional assemblies to the GPS Timing Unit. It provides a platform to support these assemblies
and an interface between these assemblies and the GPS Main Assembly 35002.
The Motherboard Assembly can support two double width options or four single width options.
Also, depending upon the options themselves and if space permits, some options can be stacked
on top of other options.
The motherboard is also provided with a variety of rear panel butch plates and output connectors
depending upon the option supplied.
GPS Option 40AP is identical to 40A except that 40AP includes the 812363-9 cable used to
connect J2 of the 35007 Motherboard Assembly to J1 of the 55189 Power Entry and Alarm
Relays Assembly. It provides the signal paths to and from the 55189 Assembly to the GPS Main
Assembly 35002.
1.1
OPERATIONAL FEATURES
The basic motherboard has four plug-in option areas, J7/J9, J8/J10, J18/J22, and J19/J23. Each
of these option areas provides one or two single-ended BNC outputs. However, depending upon
the option installed, some of these outputs may or may not be used.
In this particular configuration, the output connector(s) for the optional assembly plugged into
the J8/J10 and J7/J9 areas of the motherboard require excessive rear panel space. This requires
removing motherboard BNCs J3A, J3B and J3C. The only remaining option areas with direct
access to a rear panel BNC are J19/J23 and J18/J22.
Rear Panel Output Connector designations and signal characteristics are described in the GPS
Option/Connector Configuration sheet located at the front of the ExacTime User’s Guide.
Symmetricom Inc
ET6xxx ExacTime GPS TC & FG (Rev C)
C-77
APPENDIX C
The following is the correlation between the option area and the output:
AREA
J18/J22
J19/J23
REAR PANEL
BNC
J13E
J3F
OPTIONAL
BNC
J13D
Each of the outputs is provided via a 250 milliamphere high speed buffer/driver. The gain of the
buffer is 1:1 so the output amplitude is dependent on the input and the load.
For GPS Option 40BP, the signal connections provided at J2 of the 35007 Motherboard
Assembly are as follows:
J2 PIN
1
2
3
4
5
6
7
8
9
10
C-78
SIGNAL
LOCK\
TRK\
OUT5
OUT6
PD0
EXTFREQ
PD7
VDD (+5)
PD6
GND
ET6xxx ExacTime GPS TC & FG (Rev C)
Symmetricom Inc
OPTION DESCRIPTIONS
GPS OPTION 48
1.0
PULSE RATE MODULE
ASSEMBLY 100001 and 100001-1
INTRODUCTION
This option provides the capability of generating 3 (three) separate pulse rate outputs. Each of
the outputs can be one of sixteen individually selected pulse rates.
This assembly is installed on the GPS Motherboard Assembly 35007 (typically GPS Option 40).
Pulse Rate Module Assembly 100001 provides the three pulse rate outputs on SMB connectors
that are usually connected via coax cables to rear panel BNC connectors in a 2U (3 ½ inch high)
ExacTime chassis. Assembly 100001-1 is also installed on the GPS Motherboard Assembly.
However, its pulse rate outputs are routed to the Motherboard Buffers/Drivers and appear on
three of the six rear panel BNC connectors J3A through J3F.
For the assembly type and pulse rate output connector designations, refer to the GPS
Option/Connector Configuration sheet in the ExacTime User’s Guide.
1.1
FUNCTIONAL EXPLANATION
The three separate pulse rates are generated by PGA (Programmable Gate Array) U1 which is
programmed/configured by PROM (Programmable Read-Only Memory) U2 at initial power on.
These pulse rates are buffered by Buffer/Driver U3 and output on SMB connectors J2, J3, and
J4, or input directly to the Motherboard and output on its BNC connectors. Table 1 below shows
the relationship of the 3 pulse rate outputs and their respective output connectors.
TABLE 1
PULSE
RATE
OUTPUT
Output 1
Output 2
Output 3
ASSEMBLY 100001 OUTPUT
CONNECTOR
DESIGNATION
SMB J4 (See Note 1)
SMB J3 (See Note 1)
SMB J2 (See Note 1)
ASSEMBLY 100001-1 OUTPUT
CONNECTOR DESIGNATION
Motherboard BNC J3A or J3D (See Note 2)
Motherboard BNC J3B or J3E (See Note 2)
Motherboard BNC J3C or J3F (See Note 2)
Note 1: These outputs are cabled internally in the ExacTime and appear on rear panel
BNC connectors. Refer to the GPS Option/Connector Configuration sheet in the
ExacTime User’s Guide for connector designations and locations.
Note 2:The specific Motherboard BNC designation is dependant on which Motherboard
option area the Pulse Rate Module is installed. Refer to the GPS
Option/Connector Configuration sheet in the ExacTime User’s Guide for
connector designations and locations.
Symmetricom Inc
ET6xxx ExacTime GPS TC & FG (Rev C)
C-79
APPENDIX C
The specific pulse rate of each of the three outputs is individually selected by a 5 position DIP
switch.
Switch SW1 controls the pulse rate of Output 1.
Switch SW2 controls the pulse rate of Output 2.
Switch SW3 controls the pulse rate of Output 3.
Switch SW4 is not used in this configuration, however if installed, its switches need to be
“Open”.
The pulse rate selection for each of the outputs is the same and is shown in Table 2 on the next
page.
Switch position “Closed” means pushed down.
Switch position “Open” means pushed up.
TABLE 2
Pulse Rate Selection
(Typical of switches SW1, SW2 & SW3)
Switch Position
1
Closed
Open
Closed
Open
Closed
Open
Closed
Open
Closed
Open
Closed
Open
Closed
Open
Closed
Open
1.2
3
Closed
Closed
Closed
Closed
Open
Open
Open
Open
Closed
Closed
Closed
Closed
Open
Open
Open
Open
4
Closed
Closed
Closed
Closed
Closed
Closed
Closed
Closed
Open
Open
Open
Open
Open
Open
Open
Open
5
Open
Open
Open
Open
Open
Open
Open
Open
Open
Open
Open
Open
Open
Open
Open
Open
1PPS
5PPS
10PPS
20PPS
30PPS
40PPS
50PPS
60PPS
80PPS
90PPS
100PPS
120PPS
180PPS
200PPS
240PPS
500PPS
OUTPUT SPECIFICATIONS
Form Factor:
On-Time Edge:
Characteristics:
C-80
2
Closed
Closed
Open
Open
Closed
Closed
Open
Open
Closed
Closed
Open
Open
Closed
Closed
Open
Open
Output Pulse
Rate
Square Wave (50/50% duty cycle).
Rising edge.
TTL levels into 50 ohms.
ET6xxx ExacTime GPS TC & FG (Rev C)
Symmetricom Inc
OPTION DESCRIPTIONS
ASSEMBLY 100001
Symmetricom Inc
ET6xxx ExacTime GPS TC & FG (Rev C)
C-81
APPENDIX C
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C-82
ET6xxx ExacTime GPS TC & FG (Rev C)
Symmetricom Inc
APPENDIX D
ANTENNA REPLACEMENT KIT
D.0 ANTENNA REPLACEMENT KIT
Please note that the GPS antenna equipment described in this manual has been superseded by the
following Standard Antenna Kit, consisting of:
•
•
•
One wide-range 5-12 VDC L1 antenna
One 50 ft. length of Belden 9104 coaxial cable with BNC(m) and TNC(m) connectors
Adaptors are included for GPS receivers that have a non-BNC antenna connector
The Antenna Kit can be ordered with optional cable lengths and accessories. Please note the
following when setting up longer cable runs:
•
•
•
Using Belden 9104, the maximum cable length without amplification is 150 feet
Using Belden 9104, the maximum cable length using the optional in-line amplifier is 300 feet
For cable runs longer than 300 feet, an optional GPS Down/Up Converter kit is available
Other GPS Antenna Options:
•
•
A Lightning Arrestor kit
A 1:2 splitter (distributes the signal from a single antenna to two GPS receivers)
Symmetricom Inc
ET6xxx ExacTime GPS TC & FG (Rev C)
A-1
APPENDIX D
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A-2
ET6xxx ExacTime GPS TC & FG (Rev C)
Symmetricom Inc
SYMMETRICOM TIMING & TEST
MEASUREMENT
3750 Westwind Blvd.
Santa Rosa, California 95403 USA
Tel: 707-528-1230
Fax: 707-527-6640
[email protected]
www.symmetricom.com
For more information about the complete range of Quality
Timing Products from the Symmetricom group of companies
call 1-800-544-0233 in the US and Canada.
Or visit our site on the world wide web at
http://www.Symmetricom.com for continuously updated
product specifications, news and information.

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