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Brandywine GPS8 Plus User Manual

Gps time and frequency system
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Enlarged version
User Guide
GPS Time and Frequency System
Model GPS8 Plus
P/N 071000003
Revision 2.0
October 2004
Brandywine Communications
2230 South Fairview Street
Santa Ana, CA 92704
(714) 755 1050
(714) 755 0175
http://www.brandywinecomm.com
MANUAL P/N 900000007 REV 2.0

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  • Page 1 User Guide GPS Time and Frequency System Model GPS8 Plus P/N 071000003 Revision 2.0 October 2004 Brandywine Communications 2230 South Fairview Street Santa Ana, CA 92704 (714) 755 1050 (714) 755 0175 http://www.brandywinecomm.com MANUAL P/N 900000007 REV 2.0...
  • Page 2 Revision History REVISION DATE COMMENTS 09-16-04 Preliminary release of GPS8 Plus user guide. 10-11-04 Revision of entire user guide. MANUAL P/N 900000007 REV 2.0...
  • Page 3 Safety Warnings WARNING: This unit contains lethal AC voltages. Disconnect the unit from the AC supply before removing the cover. WARNING: The lightning flash with an arrowhead inside of an equilateral triangle is intended to alert the user to the presence of un-insulated “dangerous voltage”...

  • Page 4: Table Of Contents

    Operation........................14 Serial Communications ....................17 TxD1/RxD1 (Rear Panel J13) Baud Rate and Character Format........ 18 TxD1/RxD1 (Rear Panel J13) User Commands and GPS8 Plus Responses ..... 19 Message Formats......................22 3.6.1 Time and Date with Status, Position Averager Status, and Output Status ..22 3.6.2...
  • Page 5 Frequency Control......................63 4.9.1 Test Configuration of Frequency Controller ............64 4.10 Position Mode Configuration ..................64 4.10.1 Position Mode Selection ..................65 4.11 Local Time Configuration ..................... 65 4.11.1 Local Time Offset Adjustment ................65 4.12 Time Code Configuration ..................... 66 4.12.1 Time Code Selection ...................

  • Page 6: Introduction

    Defense and is traceable to the USA Naval Observatory. The standard GPS8 Plus uses the C/A code. The GPS8 Plus provides a wide range of output options to form a complete time and frequency management system. In addition, satellite data and navigational information is outputted in the form of longitude, latitude, and altitude for applications where precise positions must be known.

  • Page 7: Specification

    Specification SPECIFICATION DESCRIPTION OPTION Satellite Signal GPS L1 1.57542 GHz Satellite Code C/A 1.023 MHz Receiver Type Parallel eight channels (8 satellites tracked continuously and simultaneously) Receiver Sensitivity -133 dBm Input Impedance 50 ohm Standard Antenna Active omni-directional 30 dB gain Cold Start Requirement Automatic (no time or position input needed) Typically 8 minutes to time synchronization...
  • Page 8 SPECIFICATION DESCRIPTION OPTION Static Operation Standard 2.3 meters N/S 1.9 meters E/W 5.0 meters Vertical Deviation Position Average (measured in northern hemisphere over sixteen 24 hours averaged positions) Mobile Operation 460 meters per second Maximum Operational Velocity Disciplined Oscillator 3 x 10 Control Resolution (Rb_2) SPECIFICATION DESCRIPTION...
  • Page 9 INPUTS AND OUTPUTS DESCRIPTION OPTION Telecom Frequency E1 2.048 MHz Options Below T1 1.544 MHz Alarm Free contacts from status monitor 5-PIN din changeover relay and center contact can 180 DEG be linked to + 5 V or 0 V internally Port 1 TxD1/RxD1 RS232 (OR RS422 user 9 way D...
  • Page 10 INPUTS AND OUTPUTS DESCRIPTION OPTION Telco (two) J6 & J5 Outputs are link selectable (internally) 75R BNC with the following options: Telecom (2.048 MHz or 1.544 MHz as selected above) 1 MHz (internal jumper selection) 5 MHz (internal jumper selection) 10 MHz (internal jumper selection) Output level 0 to 5 V from 75R Output level square wave 2.37 Vpp into...

  • Page 11: Controls, Indicators, And Connectors

    Controls, Indicators, and Connectors Figure 1 and Figure 2 show the GPS8 Plus front panel, rear panel, indicators, connectors, and controls. The following two tables below describe these indicators, connectors, and controls. INDICATOR DESCRIPTION Power Green LED indicates that the primary power is available.
  • Page 12 Frequency 1 Status 2 -Green LED showing frequency 1 output 2 is active Frequency 1 -BNC socket (isolated) 50R Frequency 1 Status 1 -Green LED showing frequency 1 output 1 is active Table 2 GPS8 Plus Rear Panel MANUAL P/N 900000007 REV 2.0...

  • Page 13: Installation

    • 1 user guide Installation and Testing The standard GPS8 Plus is housed in a 19” 1U rack mounting case, which can be installed in a rack using the front panel mounting slots. The active high gain antenna is a sealed omni-directional device, which must be mounted with the cable exit at the bottom.

  • Page 14: Operating Instructions

    24 hours after the unit is switched on. As described in section 2.3 when the GPS8 Plus is switched on it will carry out a self-test routine before entering the operational program, which sets the correct initial conditions for the receiver system.
  • Page 15 The illustration shows the raw time data before processing is carried out by the GPS8 Plus is improved by a factor of 3 when the GPS8 Plus has averaged its position. The vertical scale on the graphs is the 1 PPS deviations in nanoseconds.
  • Page 16 F U R 4 . L O G - 2 5 0 - 5 0 0 E l a p s e d t i m e i n H o u r s Illustration 1 GPS8 Plus Averaging Position Result MANUAL P/N 900000007 REV 2.0...

  • Page 17: Serial Communications

    Serial Communications The GPS8 Plus has two asynchronous serial ports that communicate with the user. They are suitable for connection to other units such as printers, computers, and terminals. They can be configured as RS232 or RS422 ports by turning around a simple header inside the unit.

  • Page 18: Txd1/Rxd1 (Rear Panel J13) Baud Rate And Character Format

    SW1 (a red 8-way switch pack) located on the main PCB controls TxD1/RxD1 baud rate and character format at J13. Prior to the alteration of the switch, disconnect the power connection to the GPS8 Plus and practice all normal safety precautions when opening the unit to access the 8-way DIL switch SW1.

  • Page 19: Txd1/Rxd1 (Rear Panel J13) User Commands And Gps8 Plus Responses

    If there is no time delay between the characters sent to the GPS8 Plus, the maximum baud rate for the user commands is 4800. The requested record will be directed to the GPS8 Plus serial port TxD1 output. All characters transmitted by the GPS8 Plus are consistent with ASCII character or control codes.
  • Page 20 If the checksum is attached by the user, it will be checked by the GPS8 Plus and the message will be rejected if an error is detected. Errors in the format of the message will also cause a rejection.
  • Page 21 The GPS8 Plus continuously polls the GPS receiver for satellite status and associated information. If the user request requires information from the GPS engine, the GPS8 Plus immediately forwards the information it has already acquired in its internal buffer. The associated response is returned immediately.

  • Page 22: Message Formats

    $PRCCG, A, 007, 19:53:19, 07/06/00, 9, 3, 1, 0000, 00*09 FIELD CONTENTS OF FIELD Fixed text “A” Version number of GPS8 Plus firmware 000 to 999 Hours minutes seconds Day of month, month, and year The status is the ASCII representation of a hexadecimal character between 0 and F.

  • Page 23: Sounder Control

    3.6.2 Sounder Control Requested by b< >0 <CR><LF> The GPS8 Plus sounder can be turned on and off by this command. The sound output can be triggered by the GPS receiver 1 PPS (provided that the satellites are being received and the position has been found) or it can be initiated by the 1 PPS derived from the GPS8 Plus precision time base.
  • Page 24 Remember that if the checksum is omitted in the user command to the GPS8 Plus, the ‘*’ must be omitted from the end of the message so that the GPS8 Plus recognizes that no checksum is available. Two forms exist as seen below: •...
  • Page 25 3.6.3.1 Examples of 1 Pulse Commands and Responses Note that the examples of the 1 pulse commands and responses are when the UTC or local time is specified. 1. $PRCCG, C, L202500, +100*79<CR><LF> The pulse output commences at 20 hours 25 minutes 00 seconds local time and is active at +5 V for 100 ms.

  • Page 26: Dilution Of Precision Values And Satellites Used

    3. $PRCCG, C, P2, -1*54<CR><LF> The pulse output has a period of 2 ms and is active high for 1 ms. This is a square wave at 500 Hz. The negative edges will remain synchronized with the seconds’ edges because the period of 2 ms is a sub-multiple of 1 second and a negative pulse is specified.

  • Page 27: Time Code And Serial Data Output Formats

    GPS8 Plus that describes its time code outputs and serial data formats. The same message format transmitted to the GPS8 Plus can be used to set the time code and serial data formats. The pulsed output is reported only. Use the ‘c’...
  • Page 28 3.6.5.1 Example Messages MESSAGE DESCRIPTION $PRCCG, E, 1, 1, 1, 1*2C<CR><LF> -TC1 at J8 modulated time code output is IRIG B (1 KHz carrier). -TC2 at J10 pulse output is IRIG B (0 and 5 V from 50R). -TxD1 at J12 is type 2 serial data request only (this output is not currently changed by the command).
  • Page 29 To change TC2 to a timed pulse output, the ‘c’ command must be used because the specification of the pulse time or pulse period and pulse duration is required. This example message $PRCCG, C, P2, +1*52<CR><LF> makes TC2 output a 1 ms positive pulse with a 2 ms period (500 Hz and +ve edge on time).

  • Page 30: Frequency And Phase Controller Data

    +XX.X Reserved for temperature in +0.0 is 4 chars degrees Celsius (not used in GPS8 Plus controller, which +69.9 is 5 chars outputs +69.4) Fixed 2 ASCII hex chars Status of phase and frequency controller (00 to...
  • Page 31 The phase controller value is the current value of the phase controller used to adjust the local 1 PPS to UTC. In the GPS8 Plus this phase control is always set to zero because following initialization the 1 PPS is maintained in phase with the satellite 1 PPS by frequency control.
  • Page 32 DAC is ±32767 counts, where a positive increase indicates an increase in oscillator frequency. At switch on the GPS8 Plus frequency control system starts with a fast time constant to achieve frequency correction of the oscillator in the shortest possible time.
  • Page 33 3.6.6.7 Frequency Trend The frequency trend is the movement in the average phase over a specified measurement period. The measurement period is dependent on the oscillator option fitted and the time elapsed since start up. For example, a general purpose ovened oscillator period starts at 1 second, after ten samples of 1 second the period increases to 10 seconds, and after ten samples the period increases to 100 seconds, at which point the measurement resolution is 1 x 10 -...
  • Page 34 DESCRIPTION Valid Time Set to 1 when the GPS8 Plus has synchronized to the satellite receiver. It is reset to 0 if 8 hours elapsed without satellite reception or after the user re- enters time from the keypad until the GPS 8000 has re-synchronized to the GPS time.
  • Page 35 Positive LPFRS opt A 48 hours 01 – 07 AS PER TABLE ABOVE FOR LINKS 001 – 111 Standard grade plain XTAL Positive Brandywine High Stability Positive 9 hours OCXO (SC) Table 17 EEPROM Code MANUAL P/N 900000007 REV 2.0...

  • Page 36: Health Status Of Satellites

    3.6.7 Health Status of Satellites Requested by h<CR><LF> Field $PFEC, GPanc, YYMMDDhhmmss, XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX*CK<CR><LF> FIELD CONTENTS OF FIELD GPanc Fixed text identifier YYMMDDhhmmss Almanac date/time Where YY = year, MM = month, DD = day, hh = hour, mm = minute, and ss = seconds 32 columns being the status of satellite PRN 1 –...

  • Page 37: Leap Second Information (Firmware 13+)

    3.6.8 Leap Second Information (Firmware 13+) Requested by j<CR><LF> Field $PRCCG, J, YYMMDDhhmmss, +1, dd*CK<CR><LF> FIELD CONTENTS OF FIELD Fixed text identifier “J” YYMMDDhhmmss Leap second date Where YY = year, MM = month, DD = day, hh = hour, mm = minute, and ss = second 000000000000 The leap second date information has not been acquired.

  • Page 38: Nd Pulse Output Data And Command (Pcb Con6 Pin 3)

    Remember that if the checksum is omitted in the user command to the GPS8 Plus, the ‘*’ must be omitted from the end of the message so that the GPS8 Plus recognizes that no checksum is available. Two forms exist as seen below: •...

  • Page 39: Location And Signal Noise Ratio Of Satellites

    Refer to the ‘c’ command description above for more pulse command examples. The ‘c’ command is almost identical to the ‘k’ command except the ‘c’ command specifies the 1 pulse output instead of the 2 pulse output. Since ‘k’ replaces ‘c’...

  • Page 40: Firmware Version Number

    3.6.11 Firmware Version Number Requested by n<CR><LF> The software version number is only outputted. Field $PRCCG, N, nnn, ppppppp-vvv, t*CK<CR><LF> FIELD CONTENTS OF FIELD Fixed text letter “N” 3 digit decimal firmware serial number with leading zeros included 7 digit engine program and 3 digit version number Test result If the firmware version is EGPS13 and the engine is 4850102 version 009, the example message will be $PRCCG, N, 013, 4850102-009, 1*CK<CR><LF>.

  • Page 41: Offset Of Local Time Data And Command

    (not used). Remember that if the checksum is omitted, the ‘*’ must be omitted from the end of the message so that the GPS8 Plus recognizes that no checksum is available.

  • Page 42: Position Of Gps Antenna

    3.6.13 Position of GPS Antenna Requested by p<CR><LF> Field 5 6 7 10 11 12 13 14 $GPGGA, hhmmss, DDMM.MMMM, N, DDDMM.DDDD, E, s, NN, 00.00, AAAAAA.A, M, GGGG.G, M,.,*CK<CR><LF> FIELD CONTENTS OF FIELD hhmmss Time (UTC) of position update DDMM.MMMM Latitude (degrees, minutes, and decimal fraction of minutes) “N”...

  • Page 43: Additional Information (Including Magnetic Declination)

    3.6.14 Additional Information (Including Magnetic Declination) Requested by s<CR><LF> Field $GPRMC, hhmmss, A, DDMM.MMMM, N, DDDMM.DDDD, E ,000.0, 000.0, DDMMYY, MMM.M, W*CK<CR><LF> FIELD CONTENTS OF FIELD hhmmss Time (UTC) of position update A or V A = positioning V = positioning interrupted or known position DDMM.MMMM Latitude (degrees, minutes, and decimal fraction of minutes) “N”...

  • Page 44: Software Reset Command

    (ASCII code 30 hexadecimal) and describes the type of reset to use. If the message corresponds correctly to the reset command and the checksum is valid, the GPS8 Plus returns the message as an acknowledgment and waits 160 ms and then restarts the initialization as though the unit had just been switched on.

  • Page 45: Txd2/Rxd2 Messages (Rear Panel J12)

    TxD2/RxD2 Messages (Rear Panel J12) The GPS8 Plus second serial output is configured to output serial data in the user’s chosen format automatically after initialization. The format selection can be changed by entering a simple command into the TxD1/RxD1 command port at J13.
  • Page 46 Leap year Table 18 Status Bit Allocation • Valid time is set to 1 when the GPS8 Plus has synchronized to the satellite receiver. It is reset to 0 if 8 hours elapsed without satellite reception or after the user re-enters time from the keypad until the GPS 8000 has re- synchronized to the GPS time.

  • Page 47: Type 3 Format (Gps4 Format)

    3.7.3 Type 3 Format (GPS4 Format) Field YYYY, DDD:HH:MM:SS, T, S<CR><LF> FIELD CONTENTS OF FIELD Year (UTC) Day of year (January 1 = 001), hours, minutes, and seconds TFOM Status of time Please note that TFOM refers to Time Figure of Merit and S refers to Status. TFOM DESCRIPTION 10 ms <...

  • Page 48: Irig B And Afnor Nf 2 87-500 Time Code Output

    IRIG B and AFNOR NF 2 87-500 time code is the generated standard by the GPS8 Plus. This time code consists of a 1 KHz carrier, which is modulated in the pattern described below. The carrier and time code is synchronized precisely to the GPS time by the GPS8 Plus.

  • Page 49: Irig B And Afnor Nf 2 87-500 Time Code Bit Allocation

    There are 100 bits total in one second with bit 0 (an 8 ms marker) starting at the second’s edge. The GPS8 Plus allows the selection of IRIG B time code without the AFNOR extensions (TC1 = 1 in the ‘e’ command) or with AFNOR (TC1 = 5 in the ‘e’...
  • Page 50 MANUAL P/N 900000007 REV 2.0...

  • Page 51: Nasa36 Time Code Output

    NASA36 Time Code Output NASA36 time code can be selected by the user using the ‘e’ command. NASA36 time code operates in a similar manner to IRIG B with the bit allocations described below. 1 KHz is the standard carrier for NASA36 time code. To select the desired time code, use the NMEA style ‘e’...
  • Page 52 WEIGHT WEIGHT Reference always 0 Position identifier Seconds 1 Hours 10 Seconds 2 Hours 20 Seconds 4 Always 0 Seconds 8 Always 0 Always 0 Always 0 Always 0 Always 0 Always 0 Always 0 Always 0 Always 0 Always 0 Always 0 Marker Position identifier...

  • Page 53: 2137 Time Code Output

    3.10 2137 Time Code Output The 2137 time code can be selected by the user. 1 KHz is the standard carrier frequency for 2137, which otherwise resembles the code known as XR3. To select the desired time code, use the NMEA style ‘e’ command described in section 3.6.5.

  • Page 54: Vela Time Code Output (Slow Code)

    3.11 VELA Time Code Output (Slow Code) VELA time code can be selected by the user. To select the desired time code, use the NMEA style ‘e’ command described in section 3.6.5. The type of code in operation is queried by sending e<CR><LF> to the command port. The VELA logic level time code output is a positive pulse commencing at the second's edge with a duration of 200, 500, or 800 ms according to the details below.

  • Page 55: Alarm Contacts (J14)

    3.12 Alarm Contacts (J14) The status output is provided by relay RL1, which has a normally open and a normally closed contact with changeover to a common terminal. LK5 inside of the unit allows jumpers to be placed which provides optional connection to 0 V and 5 V for Alarm_Open and Alarm_Closed respectively as shown below.

  • Page 56: Gps8 Plus Keypad And Display Operation

    GPS8 Plus Keypad and Display Operation Scope of Section Section 4 provides a description of the GPS8 PLUS keypad and display operation. General Principles of Operation of Keypad and Display The display has two lines of 24 characters and its function is organized as a series of two line screens displaying information to the user.

  • Page 57: Messages After Power On

    POWERUP 00:00:07 001 UTC THU JAN1 2004 At power down the GPS8 Plus does not retain the time and date. At power up it increments the time from switch on. The screen with the time indicates the status of the time as seen in the POWERUP screen above. Other screens are selected by pressing the Up Arrow and Down Arrow keys, which are described below.

  • Page 58: Operating Mode Selection

    FREERUN Operation of the GPS8 Plus as a free running time and frequency source. In this mode the user can enter the time and date and press ENTER to run from that time. No corrections are applied from the GPS. If the selection of FREERUN is confirmed...

  • Page 59: Free Run Mode

    GPS8 Plus to the reference 1 PPS update. NO 1PPS The GPS8 Plus is in PPSLOCK mode, but no 1 PPS is being detected. Time and date continue to be maintained from the free-running GPS8 Plus internal frequency standard.

  • Page 60: Position Screen

    The day of week is calculated by the GPS8 Plus and does not require data entry. For PPSLOCK mode, pressing ENTER starts a synchronization process that synchronizes the entered time to the 1 PPS reference.

  • Page 61: Pps Status Screen

    The 1 PPS instantaneous phase measurement is rejected because the value exceeds the limit accepted for the GPS8 Plus frequency reference. LOOP FROZEN The user has initiated a GPS8 Plus test (such as centering the DAC) so the frequency controller is disabled. SAMPLE USED The instantaneous phase measurement has been used in the phase averager and for frequency estimation.

  • Page 62: Mean Phase Screen

    No data entry is possible for this screen. Calculation of the mean phase of the GPS8 Plus 1 PPS from the received 1 PPS is carried out for the 1 PPS samples that have been accepted as valid. The samples are placed in a buffer to allow a moving average calculation of the phase.

  • Page 63: Estimated Mean Frequency

    In this screen the number after FRQ CTRL: is the value of the 16 bit DAC that controls the GPS8 Plus oscillator frequency. The center frequency of a particular oscillator is not necessarily at zero and the calculated DAC position includes an offset for the oscillator calibration, which is updated after the unit has been switched on and allowed to discipline the oscillator for at least several hours.

  • Page 64: Test Configuration Of Frequency Controller

    The screen shows the current positioning mode and in the case of the position average mode the number of current position samples. The position averaging is the default mode of operation for the GPS8 Plus. The mode can be changed to suit dynamic applications in which averaging cannot be used.

  • Page 65: Position Mode Selection

    From the position mode configuration screen, pressing the Up Arrow key once selects the local time configuration screen. At this screen the user can select whether the GPS8 Plus outputs are in UTC or local time and the magnitude of the offset of the local time from the UTC.

  • Page 66: Time Code Configuration

    4.12 Time Code Configuration From the local time configuration screen, pressing the Up Arrow key once selects the time code configuration screen. On selection its function is displayed in the top line for 2½ seconds. TIMECODE CONFIGURATION IRIG B TIMED TYP2 TYP3 The description TIMECODE CONFIGURATION in the top line is then replaced by the names of the output ports as headers to their current settings in line 2 of the screen.

  • Page 67: J13 Txd1 Configuration

    After confirmation of the J10 mode, pressing ENTER places the cursor next to J13. The description ‘TYP2’ is fixed for this port and cannot be changed by the arrow keys. J13 is the GPS8 Plus asynchronous serial interface RxD1/TxD1 which provides time, position, and status data on request from the user (see section 3.5).

  • Page 68: J10 Pulse Output Configuration

    4.13 J10 Pulse Output Configuration From the time code configuration screen, pressing the Up Arrow key once selects the J10 pulse output configuration screen. On selection the function of the screen is shown in the top line for 2½ seconds. J10 PULSE CONFIGURATION CODE: IRIG B (TC1 AS DC) The function message is replaced by a line describing the output from J10.

  • Page 69: J10 Pulse Period Configuration

    Press ENTER to edit the minute field and choose the minute count at which the pulse is outputted from 00 to 59. Again an extra count XX is included for selection when the minutes are not used in the time of day comparison. With hours similarly selected the pulse will be outputted once per minute.

  • Page 70: J10 Pulse Time Code Configuration

    Only when pressing ENTER for the final time are the values applied. The first pulse to be outputted is synchronized with the GPS8 Plus time. 4.13.3 J10 Pulse Time Code Configuration J10 : TIMECODE (DC)

  • Page 71: Status Screen And Alarm Configuration 1

    For outputs which are judged faulty, FLT is displayed. Any output that is FLT will cause the GPS8 Plus status relay to be deactivated signaling an alarm that turns on the red Fault LED on the GPS8 Plus front panel.

  • Page 72: Status Screen And Alarm Configuration 2

    4.15 Status Screen and Alarm Configuration 2 From the J10 pulse output configuration screen, pressing the Up Arrow key once selects the alarm configuration 2 screen. The function of the screen is displayed in the top line of the screen for 2½ seconds followed by a list of the alarm sources and their statuses.

  • Page 73: Status Screen 3

    NRM when the procedure has been successfully completed. Set to FLT if the GPS8 Plus is unable to discipline its oscillator to follow the GPS. It will automatically be cleared to NRM when the GPS8 Plus succeeds in controlling the oscillator.

  • Page 74: Principles Of Operation

    Principles of Operation Scope of Section Section 5 provides a functional description of the GPS8 Plus and a general description of the Global Positioning System. Theory of Operation Operation of the Global Positioning System is based on the principle that the position of an object can be determined by measuring the distance to three or more satellites of known positions.
  • Page 75 GPS as a timing reference caused by the possibility of selective availability, which may be introduced to deny the highest positioning accuracy to non-military users. The drift while the GPS8 Plus is operating without satellite synchronization (a period known as “holdover”) will depend on the quality of the oscillator, ambient temperature changes, and the period with no satellite visibility.
  • Page 76 The complete unit is normally powered by an AC supply, which uses a high efficiency toroidal transformer to provide two independent low noise supplies regulated to +5 V for the processor and digital support circuitry and +15 V for the analog circuits and output distribution circuits.

  • Page 77: Maintenance And Calibration

    The only component which will degrade with time and may need replacement during the life of the unit is the battery, which powers the GPS receiver and GPS8 Plus' RAM when the main power supply is switched off or disconnected.

  • Page 78: Fault Finding

    CAUTION: In the case of equipment malfunction or failure, it is recommended that the GPS8 Plus is returned to the factory for repair. If this is not practical, fault finding and repair must only be undertaken by a qualified test engineer.

  • Page 79: Diagrams

    Diagrams FIGURE DESCRIPTION GPS8 Plus Front Panel GPS8 Plus Rear Panel GPS8 Plus Mechanical Outline GPS8 Plus Link Locations Table of Link Settings 0180BN GPS8 Plus Block Diagram MANUAL P/N 900000007 REV 2.0...
  • Page 83 GPS8 Plus Link Locations MANUAL P/N 900000007 REV 2.0...
  • Page 84 Notes Setting OPEN NOT TESTING GPS8 Plus executes main program from flash memory; EPROM is still required for key I/O management and ‘flash’ programming. Must be open to allow flash programming. TESTING FROM EPROM GPS8 Plus uses EPROM only; Flash need not be programmed.
  • Page 85 GPS8 Plus Block Diagram TIMECODE T1 OR E1 T1 OR E1 POWER RS232/RS422 OUTPUTS ALARM G703 SECTION 6 (2,37Vpp INTO 75R) G703 SECTION 10 (set 3Vpp max sinewave into 75R) PULSES TIMECODE OR 1/5/10MHz SINE 1Vrms into 50R 8kHz FRAME...

  • Page 86: Appendix I Output Alarm Masks

    Appendix I Output Alarm Masks The GPS8 Plus uses hardware detectors to measure the presence or absence of its outputs. The detectors are monitored by the processor, which turns on the red Fault LED and activates the alarm contacts in the event of an output failure.
  • Page 87 The alarm masks are contained in two bytes corresponding to the 16 bits in the table above. Each byte is stored as its true value, where ‘1’ means the alarm is enabled and its complement (all bits inverted) in EEPROM at address 4 and 5. There are 16 bits of data at each of these addresses and the masks are organized as F1MSK and its complement at address 4 and F2MSK and its complement at address 5.
  • Page 88 Enter 4<RETURN> 4 Addr=04 Enter Hex Data 0000-FFFF Enter 0FF0<RETURN> 0FF0 Data=0FF0 GPS8 Plus confirms location has been programmed Prog time=02ms Value Saved=0FF0 P Program EEPROM location Enter Hex Addr (ESC=quit) 00-37 User can just press <RETURN> for the next address...
  • Page 89 Press <ESC> to quit programming function of the EEPROM menu 6. Edit/View EEPROM <SPACE> Display All EEPROM F TxD2 Format 1 to 3 O Enter Osc 0 to 9 P Program EEPROM location U Unlock PRESS <ESC> again to quit test menu QUIT 6 For the new values to take effect the unit must be powered on again.

  • Page 90: Appendix Ii Phase Noise

    Appendix II Phase Noise The standard GPS has been designed for low phase noise. The precision ovened crystal oscillator and the analog distribution is separately powered and opto-isolated from the digital processor section. However, the standard unit with telecom outputs shows some expected cross-talk between the telecom outputs and the standard frequency outputs, primarily visible in the form of a substantial peak at 16 KHz in the phase-noise spectrum.

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