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Brandywine GPS4 User Manual

Satellite synchronized time frequency standard
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GPS4 Satellite Synchronized Time & Frequency
User Guide
Standard
Model GPS4
P/N 001-0045
Revision 2.2
November 2004
Brandywine Communications
1153 Warner Avenue
Tustin, CA 92780
(714) 755 1050
(714) 755 0175
http://www.brandywinecomm.com
1
MANUAL P/N 900000038 REV 2.2

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  • Page 1 User Guide GPS4 Satellite Synchronized Time & Frequency Standard Model GPS4 P/N 001-0045 Revision 2.2 November 2004 Brandywine Communications 1153 Warner Avenue Tustin, CA 92780 (714) 755 1050 (714) 755 0175 http://www.brandywinecomm.com MANUAL P/N 900000038 REV 2.2...
  • Page 2 Revision History REVISION DATE COMMENTS 08-29-03 Preliminary release of GPS4 user guide. 11-02-04 Revision of entire GPS4 user guide. MANUAL P/N 900000038 REV 2.2...

  • Page 3: Table Of Contents

    Operation......................... 17 Serial Data Communication .................... 20 Control TxD1/RxD1 ......................20 4.4.1 TxD1 / RxD1 User Commands and GPS4 Responses ........... 21 Message Formats ......................24 4.5.1 Time and Date with Status, Position Averager Status, and Output Status....24 4.5.2 Pulse Output Data and Command................
  • Page 4 4.5.7 Leap Second Information..................40 4.5.8 Location and Signal-Noise Ratio of Satellites............41 4.5.9 Firmware Version Number ..................42 4.5.10 Offset of Local Time Data and Command ............... 43 4.5.11 Position of GPS Antenna ..................45 4.5.12 Software Reset Command..................46 4.5.13 Additional Information ....................

  • Page 5: Introduction

    Introduction The GPS4 disciplined time and frequency standard is a device that offers many desirable features. Utilizing signals from the Global Positioning System, the unit provides highly accurate time, synchronization, and frequency functions. The unit may operate in either GPS or UTC time mode. Local time offsets may be programmed into the unit in resolutions of minutes.

  • Page 6: Product Specifications

    Product Specifications Power Requirements CONNECTOR DESCRIPTION Connector Type MR series locking type AMP 1-640508-0 Connector Pin Pin 1 Positive Pin 2 Chassis ground Pin 3 Negative 2.1.1 Standard STANDARD DESCRIPTION Input Voltage/Current 15 VDC @ 1.4 A maximum and 0.5 A steady state Isolation None 2.1.2 Power Option 1...

  • Page 7: 10 Mhz

    2.2.2 10 MHz 10 MHz DESCRIPTION Frequency 10 MHz Period 100 ns Waveform Sinusoid (standard) or square (link selectable) Drive Level 1 Vrms (minimum) into 50 ohm load Harmonics < 30 dB Phase Noise 100 Hz -140 dBc/Hz 1000 Hz -150 dBc/Hz 10 KHz -155 dBc/Hz...

  • Page 8: Status Indicators

    2.2.4 Status Indicators INDICATOR COLOR DESCRIPTION POWER GREEN Indicates the system power is available LOCKED GREEN Indicates the system time locked status HOLDOVER YELLOW Indicates the system is in holdover operation ALARM Indicates the system fault Inputs 2.3.1 System Reset SYSTEM RESET DESCRIPTION Function...

  • Page 9: Control Port

    2.6.1 Control Port CONTROL PORT DESCRIPTION Baud Rate 75 – 19200 baud selectable by the DIP switch 4800, N, 8, and 1 is factory setting 2.6.2 TOD Port TOD PORT DESCRIPTION Protocol Time of day (ASCII) Baud Rate 19.2 K 2.6.3 Serial Option 1 SERIAL OPTION 1 DESCRIPTION...

  • Page 10: Connectors And Indicators

    Connectors and Indicators The GPS4 provides access to the power, I/O, and signal connectors on the front panel of the chassis. These various connectors and indicators are described below. LABEL FUNCTION DETAIL Power input connector Pins are numbered from left to right so...

  • Page 11: Installation

    Installation To maximize the performance of the GPS4, please consider the following guidelines Thermal Considerations This unit is designed to operate over a temperature range of -10°C to +60°C, but optimum performance will be achieved when the unit is allowed to operate at a relatively constant temperature.

  • Page 12: Power Supply Connections

    CHASSIS In all cases the maximum power required by the GPS4 is 20 watts. The maximum power consumption will be experienced when power is first applied to the unit and/or when the unit is operating at low temperatures (0°C to -10°C).

  • Page 13: Unit Mounting

    In general, keep the GPS4 away from the system power supply, particularly if the power supply is AC-DC linear or switching type.

  • Page 14: Serial Interface Connections

    ‘HWRESET’ signals. These three signals provide open collector outputs used as a hardware status indicator that reports the basic usability of the GPS4 and as a system reset. It is not necessary to use these signals so these signals may be left disconnected.

  • Page 15: Txd2 Ascii Time Of Day Output

    GPS RF signals (1575.42 MHz) that are received from the GPS antenna to the GPS4 and to conduct the DC bias voltage (5 VDC) provided by the GPS4 to the LNA (low noise amplifier) contained inside of the GPS antenna.

  • Page 16: Lightning Protection

    (antenna gain – cable loss) be between 10 dB and 33 dB. Thus, using an antenna with 30 dB of gain allows for about 20 dB of cable loss. The GPS4 is shipped with 100’ of antenna cable. Additional cable configurations are possible.

  • Page 17: Operating Instructions

    Satellite tracking is automatic, provided that at least one is visible and the GPS4 already has a valid position in its battery backed receiver. The time and frequency control can start within approximately 1 minute. If three or more satellites are visible, 3-D position information will also be processed.
  • Page 18 GPS4 is improved by a factor of 3 when the GPS4 has averaged its position. The vertical scale on the graphs is the 1 PPS deviation in nanoseconds.
  • Page 19 MANUAL P/N 900000038 REV 2.2...

  • Page 20: Serial Data Communication

    Serial Data Communication The GPS4 has two asynchronous serial ports that communicate with the user. These serial ports may be connected to other units such as printers, computers, and terminals. These serial ports can be factory configured to be RS232 or RS422.

  • Page 21: Txd1 / Rxd1 User Commands And Gps4 Responses

    If there is no time delay between the characters sent to the GPS4, the maximum baud rate for the user commands is 4800. The requested record will be directed to the GPS4 serial port TxD1 output. All characters transmitted by the GPS4 are consistent with the ASCII character or control code.
  • Page 22 If the checksum is attached by the user, it will be checked by the GPS4 and the message will be rejected if an error is detected. Errors in the format of the message will also cause a rejection.
  • Page 23 The time at which the request character was received is logged at the next whole millisecond and the GPS4 transmits as soon as the serial port is free. This special message is not in the NMEA format but in the industry standard Type 2 Serial Data Format.

  • Page 24: 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 the GPS4 firmware 000 to 999 Hours, minutes, and seconds Day of the month, month, and year The status is the ASCII representation of a hexadecimal character between 0 and F.
  • Page 25 BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0 (LSB) One or more Reserved Oscillator Frequency Reserved Rubidium Reserved OP failures satellites for frequency error oscillator detected 8 hours control near oscillator status shows its limit cannot be Rubidium...

  • Page 26: Pulse Output Data And Command

    GPS. Remember that if the checksum is omitted in the user command to the GPS4, then the ‘*’ must also be omitted from the end of message so that the GPS4 recognizes that no checksum is available.
  • Page 27 GPS4 and its own checksum is added to its message output. Illegal commands are ignored except when the pulse length is commanded to be greater than the pulse period, in which case the pulse length is reset to 1 ms.
  • Page 28 Four examples of the pulse commands and responses are given below when the period of the pulse is specified instead of the UTC or Local time. Pulse Period + Pulse Active The pulse period may be a minimum of 2 ms to a maximum of 9999 ms. The pulse width is a minimum of 1 ms to a maximum of 9998 ms.

  • Page 29: Dilution Of Precision Values And Satellites Used

    4.5.3 Dilution of Precision Values and Satellites Used Requested by d<CR><LF> Field 1 2 3 10 11...15 $GPGSA, A, 1, NN, NN, NN, NN, NN, NN, NN, NN,…,PP.PP, HH.HH, VV.VV*CK<CR><LF> FIELD CONTENTS OF FIELD “A” or “M” Operational Modes: “M” = 2-D mode only “A”...

  • Page 30: Time Code And Serial Data Output Formats

    GPS4 that describes its time code outputs and serial data formats. The same message format transmitted to the GPS4 can be used to set the time code and serial data formats. The pulsed output is reported only. You must use the ‘c’...
  • Page 31 Message Examples $PRCCG, E, 1, 1, 1, 1*2C<CR><LF> TC1 modulated time code output is IRIG B (1 kHz carrier). TC2 pulse output is IRIG B (0 and 5V from 50R). TxD1 is type 2 serial data requested only (this output is not currently changed by the command). TxD2 is type 1 format data that automatically outputs once per second until ‘t’...
  • Page 32 To change TC2 to a timed pulse output, the ‘c’ command must be used because the specification of pulse time or period and pulse duration is required. For example, make the TC2 output a 1 ms positive pulse with a 2 ms period (500Hz, +ve edge on time).

  • Page 33: Frequency And Phase Controller Data

    Instantaneous phase (ns) -499999999 to +500000000 (signed decimal integer) Typically +0 2 characters to 10 characters +XXX Phase controller value (ns) Will always be ‘+0’ in GPS4 (signed decimal integer) controller output 2 characters +XXX Average phase (ns) -32768 to +32767...
  • Page 34 The current value of the phase controller is used to adjust the local 1 PPS to UTC. In the GPS4 this phase control value is always set to zero because following initialization the 1 PPS is maintained in phase with the satellite 1 PPS by the frequency control.
  • Page 35 DAC is ± 32767 counts where a positive increase indicates an increase in oscillator frequency. At switch on the GPS4 frequency control system starts with a fast time constant to achieve frequency correction of the oscillator in the shortest possible time.
  • Page 36 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, for a general purpose ovened oscillator the period starts at 1 second and after ten samples of 1 second it increases to 10 seconds and after ten samples it increases to 100 seconds at which point the measurement resolution is 1 x 10 - .
  • Page 37 DESCRIPTION Valid Time The valid time is set to 1 when the GPS4 has synchronized to the satellite receiver. It is reset to 0 if 8 hours elapsed without satellite reception or the user re-enters time from the keypad, until the GPS4 has resynchronized to the GPS time.
  • Page 38 The oscillator type is determined by a parameter stored in the EEPROM. Refer to the table below. EEPROM CODE High grade rubidium/cesium positive LPFRS opt A 48 hours 01 TO 07 RESERVED Standard grade plain XTAL positive Brandywine High Stability positive 9 hours OCXO (SC) MANUAL P/N 900000038 REV 2.2...

  • Page 39: Health Status Of Satellites

    4.5.6 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 with date and time, where YY = year, MM = month, DD = day of the month, hh = hours, mm = minutes, and ss = seconds 32 columns containing the status of satellites PRN 1 –...

  • Page 40: Leap Second Information

    4.5.7 Leap Second Information 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 of the month, hh = hours, mm = minutes, and ss = seconds.

  • Page 41: Location And Signal-Noise Ratio Of Satellites

    4.5.8 Location and Signal-Noise Ratio of Satellites Requested by l<CR><LF> Please note that the response to the l request contains a maximum of three records. Field 1 2 3 11 12 13 14 15 16 17 18 $GPGSV, N, n, NN, SS, XX, XXX, XX, SS, XX, XXX, XX, SS, XX, XXX, XX, SS, XX, XXX, XX*CK<CR><LF> FIELD CONTENTS OF FIELD The number of messages (1 to 3)

  • Page 42: Firmware Version Number

    4.5.9 Firmware Version Number Requested by n<CR><LF> 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.

  • Page 43: Offset Of Local Time Data And Command

    UTC switch for time and time code outputs. However, the sign and number of the hours offset of local time is programmed by the ‘o’ command alone. The user can set the GPS4 time code output to UTC, but generate pulse outputs which follow local time.
  • Page 44 When a command has been accepted by the GPS4 the message is echoed, but the contents of the response are recalculated from the data used by the GPS4 to implement the user request. A checksum is always returned.

  • Page 45: Position Of Gps Antenna

    4.5.11 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 46: Software Reset Command

    ‘Z’, ‘0’, and the correct checksum. The ‘0’ is the number of zeros (ASCII code 30 hexadecimal) and it describes the type of reset. If the message corresponds correctly to the reset command and the checksum is valid, the GPS4 returns the message as an acknowledgment, waits 160 ms, and restarts the initialization as though the unit had just been switched on.

  • Page 47: Additional Information

    4.5.13 Additional Information 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 the 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 48: Request Precision Time

    DESCRIPTION Valid Time The valid time is set to 1 when the GPS4 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 resynchronized to the GPS time.
  • Page 49 Example Message (Fixed Format 31 Characters Including Spaces) The example message below is seen when a request is made thirty four minutes, three seconds, and 123 milliseconds past eight in the evening on Tuesday the . Furthermore, the GPS Synchronized Master Clock is reporting valid time, the GPS is locked, and UTC is in a leap year.

  • Page 50: Txd2/Rxd2 Messages

    TxD2/RxD2 Messages The GPS4 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. The three formats are shown below. Other customer specific outputs and protocols are available.
  • Page 51 Type 3 Format (GPS4 Format) Field 1 YYYY, DDD:HH:MM:SS, T, S<CR><LF> FIELD CONTENTS OF FIELD Year (UTC) Day of the year (January 1 = 001), hours, minutes, and seconds TFOM Status of the time An example message (fixed format 23 characters including commas and termination) is given below.

  • Page 52: Irig B And Afnor Nf 2 87-500 Time Code Output

    IRIG B and AFNOR NF 2 87-500 Time Code Output IRIG B/AFNOR NF 2 87-500 time code is generated as a standard by the GPS4. This time code consists of a 1 kHz carrier which is modulated in the pattern described below.
  • Page 53 – 10 dB. There are 100 bits total in one second with bit 0 (8 ms marker) starting at the second’s edge. The GPS4 is normally configured to send the full AFNOR specification time code contents when IRIG B is selected.
  • Page 54 MANUAL P/N 900000038 REV 2.2...

  • Page 55: Nasa36 Time Code Output Option

    NASA36 Time Code Output Option NASA36 time code must be specified at time of ordering. NASA36 time code operates in a similar manner to IRIG B with the bit allocations described below. 1 kHz is the standard carrier for the NASA36 time code. SPECIFICATION DESCRIPTION Time...
  • Page 56 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 57: 2137 Time Code Output Option

    2137 Time Code Output Option 2137 time code must be specified at time of ordering. 1 kHz is the standard carrier frequency for 2137. SPECIFICATION DESCRIPTION Time Universal time (UTC) Time Frame 1.0 second Code Digit Weighting BCD: Binary Coded Decimal time of day code word is 20 binary digits. (1) Hours, minutes, and seconds (2) Recycles every 24 hours Code Word Structure...

  • Page 58: Vela Time Code Output Option

    4.10 VELA Time Code Output Option VELA time code must be specified at time of ordering. 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. SECOND FUNCTION DURATION...

  • Page 59: Maintenance And Calibration

    CAUTION: In the case of equipment malfunction or failure, it is recommended that the GPS4 be 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 60: Diagrams

    Diagrams FIGURE DESCRIPTION GPS4 Front Panel GPS4 Mechanical Outline GPS4 Link Settings Table MANUAL P/N 900000038 REV 2.2...
  • Page 63 LINK STANDARD BUILD CONSEQUENCE NO FIT EMULATOR PORT NO FIT TXD2– (TOD) RS422 CONNECTION OPEN NO FIT TXD2+ (TOD) RS422 CONNECTION OPEN TXD2 (TOD) RS232 OUTPUT CONNECTED NO FIT RXD1 RS422 INPUT BUFFER OUTPUT CONNECTION OPEN NO FIT RXD1+ RS422 CONNECTION OPEN NO FIT TXD1–...
  • Page 64 714 755 1050 Tel 714 755 0175 Fax Please take a moment to help us improve your experience with Brandywine Communications. When you’re done, please either email this form to lisap@brandywinecomm.com or fax this form to 714 755 0175. PRODUCT QUALITY...

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