Meinberg GPS167PC User Manual

FUNKUHREN
Technical Information Operating Instructions
GPS167PC

Impressum

Werner Meinberg Auf der Landwehr 22 D-31812 Bad Pyrmont
Internet: http://www.meinberg.de Email: info@meinberg.de
October 30, 2001
Table of Contents
Impressum ............................................................................................ 2
Driver Diskette for DOS/Windows ...................................................... 4
General Information ............................................................................. 5
GPS167PC Features ............................................................................. 6
Time Zone and Daylight Saving................................................. 6
Asynchronous Serial Ports.......................................................... 7
Time Capture Inputs ................................................................... 7
Pulse and Frequency Outputs ..................................................... 7
DCF77 Emulation ....................................................................... 8
Connectors and LEDs in the Rear Slot Cover ..................................... 9
Installing the Radio Clock.................................................................... 9
Setting The Port Base Address ................................................... 9
Configuring the 9 pin Connector .............................................. 11
Mounting the Board .................................................................. 11
Mounting the Antenna .............................................................. 11
Powering Up the System .......................................................... 12
Files on the Diskette shipped with the Board .................................... 13
Support for other Operating Systems................................................. 13
Copying the distributed Software to the Hard Disk ........................... 13
Using PCPSINFO.EXE...................................................................... 14
The resident driver for DOS/Windows .............................................. 17
Controlling the Resident Driver ............................................... 18
Firmware Updates .............................................................................. 18
Replacing the Lithium Battery ........................................................... 19
CE Label ............................................................................................ 19
Table of Contents (continued)
Technical Specifications GPS167PC ................................................. 21
Technical Specifications of Antenna ........................................ 23
Assembly with CN-UB/E (CN-UB-280DC) ............................ 24
Format of the Meinberg Standard Time String ........................ 25
Format of the Meinberg Capture String ................................... 26
Assignment of the 5 Pin Jumper Block .................................... 26
Component Layout GPS167PC ................................................ 27

Driver Diskette for DOS/Windows

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General Information

The satellite clocks made by Meinberg have been designed to provide extremly precise time to their users. The clocks have been developed for applications where conventional radio clocks can´t meet the growing requirements in precision. High precision available 24 hours a day around the whole world is the main feature of the new system which receives its information from the satellites of the Global Posi­tioning System.
The Global Positioning System (GPS) is a satellite-based radio-positioning, naviga­tion, and time-transfer system. It was installed by the United States Departement of Defense and provides two levels of accuracy: The Standard Positioning Service (SPS) and the Precise Positioning Service (PPS). While PPS is encrypted and only available for authorized (military) users, SPS has been made available to the general public.
GPS is based on accurately measuring the propagation time of signals transmitted from satellites to the user´s receiver. A nominal constellation of 24 satellites together with some active spares in six orbital planes 20000 km over ground provides a minimum of four satellites to be in view 24 hours a day at every point of the globe. Four satellites need to be received simultaneously if both receiver position (x, y, z) and receiver clock offset from GPS system time must be computed. All the satellites are monitored by control stations which determine the exact orbit parameters as well as the clock offset of the satellites´ on-board atomic clocks. These parameters are uploaded to the satellites and become part of a navigation message which is retrans­mitted by the satellites in order to pass that information to the user´s receiver.
The high precision orbit parameters of a satellite are called ephemeris parameters whereas a reduced precision subset of the ephemeris parameters is called a satellite´s almanac. While ephemeris parameters must be evaluated to compute the receiver´s position and clock offset, almanac parameters are used to check which satellites are in view from a given receiver position at a given time. Each satellite transmits its own set of ephemeris parameters and almanac parameters of all existing satellites.
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GPS167PC Features

The hardware of GPS167PC is a plug-in board designed for computers with standard ISA bus architecture. The rear slot cover integrates the antenna connector, two status LEDs, and a 9 pin sub-D female connector.
The antenna/converter unit is connected to the receiver by a 50 ohm coaxial cable with length up to 200m. Power is supplied to the unit DC insulated across the antenna cable. Optionally, an overvoltage protection and an antenna distributor are available. The antenna distributor can be used to operate up to 4 Meinberg GPS receivers using a single antenna/converter unit.
The navigation message coming in from the satellites is decoded by satellite clock´s microprocessor in order to track the GPS system time with an accuracy of better than 250nsec. Compensation of the RF signal´s propagation delay is done by automatical determination of the receiver´s position on the globe. A correction value computed from the satellites´ navigation messages increases the accuracy of the board´s tempe­rature compensated master oscillator (TCXO) to ±5•10 tes the TCXO´s aging. The last recent value is restored from the non-volatile memory at power-up. Optionally, the clock is also available with a higher precision time base.
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and automatically compensa-
A monitoring software shipped with the board can be used to check the clock's status and configure some operational parameters.

Time Zone and Daylight Saving

GPS system time differs from the universal time scale (UTC) by the number of leap seconds which have been inserted into the UTC time scale after GPS has been initiated in 1980. The current number of leap seconds is part of the navigation message supplied by the satellites, so the satellite clock's internal real time is based on UTC. Conversion to local time including handling of daylight saving year by year can be done by the receiver´s microprocessor. For Germany, the local time zone is UTC + 3600 sec for standard time and UTC + 7200 sec if daylight saving is in effect.
The clock's microprocessor determines the times for start and end of daylight saving time by a simple algorithm e. g. for Germany:
Start of DST is on the first Sunday after March, 25th, at 2 o'clock standard time.
End of DST is on the first Sunday after October, 25th, at 3 o'clock daylight time.
The monitoring software shipped with the board can be used to configure the time zone and daylight savings parameters easily. Switching to daylight saving time is inhibited if for both start and end of daylight saving the parameters are exactly the same.
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Asynchronous Serial Ports

Two asynchronous serial interfaces (RS232) called COM0 and COM1 are available to the user. Only COM0 is available at the rear panel slot cover, COM1 must use another submin-D connector which can optionally be connected to the 5 pin jumper block on the board. The monitoring program can be used to configure the outputs. In the default mode of operation, the serial outputs are disabled until the receiver has synchronized after power-up. However, they can be configured to be enabled immediately after power-up. Transmission speed, framing and mode of operation can be configured individually for each port. Both of the ports can be configured to transmit either the Meinberg standard time string (once per second, once per minute, or on request with ASCII ´?´ only), or to transmit capture strings (automatically when available, or on request). The format of the output strings is ASCII, see the technical specifications at the end of this document for details.

Time Capture Inputs

The board provides two time capture inputs called User Capture 0 and 1 (CAP0 and CAP1) which can be mapped to pins at the 9 pin connector at the rear panel. These inputs can be used to measure asynchronous time events. A falling TTL slope at one of these inputs lets the microprocessor save the current real time in its capture buffer. From the buffer, an ASCII string per capture event can be transmitted via COM1 or displayed using the monitoring program. The capture buffer can hold more than 500 events, so either a burst of events with intervals down to less than 1.5 msec can be recorded or a continuous stream of events at a lower rate depending on the transmissi­on speed of COM1 can be measured. The format of the output string is described in the technical specifications at the end of this document. If the capture buffer is full a message "** capture buffer full" is transmitted, if the interval between two captures is too short the warning "** capture overrun" is being sent via COM1.

Pulse and Frequency Outputs

The pulse generator of GPS167PC generates TTL level pulses once per second (P_SEC) and once per minute (P_MIN). A DIL switch on the board can be set up to map one or both of the pulses to pins at the 9-pin connector at the rear slot cover.
A TTL level master frequency of 10 MHz is derived from the TCXO. By default, this frequency is available only at the 5 pin jumper block on the board.
In the default mode of operation, the pulse outputs are disabled until the receiver has synchronized after power-up. However, the monitoring program can be used to enable these outputs immediately after power-up.
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DCF77 Emulation

The GPS167PC satellite controlled clock generates TTL level time marks (active HIGH) which are compatible with the time marks spread by the German long wave transmitter DCF77. This long wave transmitter installed in Mainflingen near Frank­furt/Germany transmits the reference time of the Federal Republic of Germany: time of day, date of month and day of week in BCD coded second pulses. Once every minute the complete time information is transmitted. However, the clock generates time marks representing its local time as configured by the user, including announce­ment of changes in daylight saving and announcement of leap seconds. The coding sheme is given below:
M Start of Minute (0)
R RF Transmission via secondary antenna (0)
A1 Announcement of a change in daylight saving
Z1, Z2 Time zone identification
Z1,Z2 = 0,1: Daylight saving disabled
Z1,Z2 = 1,0: Daylight saving enabled
A2 Announcement of a leap second
S Start of time code information (1)
P1, P2, P3 Even parity bits
Time marks start at the beginning of a new second. If a binary "0" is to be transmitted, the length of the corresponding time mark is 100 msec, if a binary "1" is transmitted, the time mark has a length of 200 msec. The information on the current date and time as well as some parity and status bits can be decoded from the time marks of the 15th up to the 58th second every minute. The absence of any time mark at the 59th second of a minute signals that a new minute will begin with the next time mark. The DCF emulation output is enabled immediately after power-up.
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Connectors and LEDs in the Rear Slot Cover

The coaxial antenna connector, two status LEDs and a 9 pin sub D connector can be found in the rear slot cover. (see figure). The upper, green LED (LOCK) is turned on when after power­up the receiver has acquired at least four satellites and has computed its position. In normal operation the receiver position is updated continuously as long as at least four satellites can be received.
The lower, red LED (FAIL) is turned on after power-up until the receiver has synchronized or if a severe error occurs during operation.
The 9 pin sub D connector is wired to the GPS167PC's serial port COM0. Pin assignment can be seen from the figure beside. This port can not be used as serial port for the computer. Instead, it can be uses to send out Meinberg's standard time string to an external device. A DIL switch on the board can be used to wire some TTL inputs or outputs (0..5V) to some connector pins. In this case, absolute care must be taken if
another device is connected to the port, because voltage levels of -12V through +12V (as commonly used with RS­232 ports) at TTL inputs or outputs may damage the radio clock.
Behind the little hole in the slot cover there is a push button which is needed if the clock's firmware shall be updated. See the chapture about firmware updates for details.

Installing the Radio Clock

Before the clock can be installed in the computer, some configuration may be required if the desired settings differ from the default settings.

Setting The Port Base Address

Programs can read data from or write data to the board using 2 I/O ports from a block of four addresses. The base I/O address can be set up in a wide range using the DIL switch on the board. When being shipped, the board´s address is set to 300h corre­sponding to the default address used by the utility software. If one of the levers 8, 9, or
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