products		Rubidium Series 1 & 3: Module GT Reference Time Input

This document specifies the reference time input of a RUB GT module. If the reference input signals are within the limits of the following "general specifications" of the RUB GT module, it can operate in the reference time mode without constraints.

1. Serial data receive

• Common asynchronous serial data interface.
• RUB GT only has a receive line, no handshake shall be used.
• Formats: 7/8 bits, parity odd/even/none.
• Baud rates: 2400/4800/9600/19200/38400/115200.
• Protocol: see below.

Electrical specifications:

• General purpose unbalanced input.
• Input "Low": -15.0 to +1.0 V
• Input "High": +3.0 to +15.0 V
• Input accepts RS232 and TTL levels.

2. PPS input

Input a positive or negative going pulse each second.

Electrical specifications:

• General purpose unbalanced input.
• Input "Low": -15.0 to +1.0 V
• Input "High": +3.0 to +15.0 V
• Input accepts RS232 and TTL levels.

3. Time, date and status string of the serial data interface

The data string shall be sent periodically (every second). The HH:MM:SS time information shall be in an up-counting sequence without time jumps. The complete data string shall fit between two timing reference signals (see below). RUB GT can receive the following data strings:

• Meinberg Standard Time.
• Meinberg Uni Erlangen.
• NMEA 0183: GPRMC.
• NMEA 0183: GPZDA.
• Wharton ASCII.
• Wharton Status.
• Gorgy.
• Hopf Status.
• Computime Time Telegram.
• ABB-SPA Time Telegram.
• SAT Time Telegram.

This list will be updated when new data strings are added.

4. Timing reference

RUB GT needs a timing reference. This can be the PPS signal or - if no PPS signal is available - the start word of the serial data string. The time between the two timing reference signals shall be one second and shall not vary more than 1%.

5. List of recommended devices

• Meinberg GPS167 GPS receivers.
• Meinberg LANTIME devices (GPS, PZF).
• Meinberg DCF77 receivers with RS232 and PPS output.
• Hopf DCF77 receivers with RS232 and PPS output.
• Garmin GPS35.
• SYSTEM 2000 (Datum/Symmetricom/Efratom).

This list is to be continued.

6. Application diagrams

Reference time input with PPS and serial data. Stand-alone unit.

Reference time input with PPS and serial data. Unit receives power from the GT module.