Meinberg UA32S User Manual

Technical Information
Operating Instructions

UA32S

Meinberg Funkuhren GmbH & Co. KG
Lange Wand 9
D-31812 Bad Pyrmont

Phone: ++49 52 81 / 9309-0
Fax: ++49 52 81 / 9309-30

Internet : http://www.meinberg.de
E-Mail : [e-mail]

January 16, 2007

Table of Contents

General Information about DCF77 ....................................................... 5

UA32S Overview................................................................................. 7

Antenna and LF Receiver ........................................................... 8

Mounting the Antenna................................................................. 8

Microprocessor Circuit................................................................ 8

Buffered Real Time Clock .......................................................... 9

Display........................................................................................ 9

Control LEDs.............................................................................. 9

Asynchronous Serial Port............................................................ 9

Optocoupler and Relay Outputs .................................................. 9

Default Configuration................................................................ 10

Customizing the UA32S Configuration.............................................. 11

Serial Port.................................................................................. 11

Cyclic Output Pulses ................................................................. 11

Programming Turn-On And Turn-Off Times............................ 11

Listing of Default Configuration ............................................... 12

Setting the Clock Manually ................................................................ 17

Technical Specifications UA32S ........................................................ 18

CE Label ................................................................................... 19

Component Layout.................................................................... 21

UA32S Connector Pin Assignments ......................................... 23

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General Information about DCF77

The radio remote clocks made by Meinberg receive the signal from the long wave
transmitter DCF77. This long wave transmitter installed in Mainflingen near Frankfurt/
Germany transmits the reference time of the Federal Republic of Germany. This time
reference is either the Central European Time (Mitteleuropäische Zeit, MEZ) or the
Central European Summer Time (Mitteleuropäische Sommerzeit, MESZ). The transmit­ter is controlled by the atomic clock plant at the Federal Physical Technical Institute
(PTB) in Braunschweig/Germany and transmits the current time of day, date of month
and day of week in coded second pulses. Once every minute the complete time
information is available.

At the beginning of every second the amplitude of the high precision 77.5 kHz carrier
frequency is lowered by 75% for a period of 0.1 or 0.2 sec. The length of these time
marks represent a binary coding scheme using the short time mark for logical zeroes and
the long time mark for logical ones. 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.

Our radio remote clocks decode the highly accurate information on date and time
within a wide range around Germany. So some of our clocks are installed in Bilbao/
Spain as well as in the city of Umeå in northern Sweden - fully satisfying the require­ments of the users. The radio remote clocks automatically switch to summertime and
back. The reception of the time information is free of charge and does not need to be
registered.

Generally it is important to position the antenna in an optimal way. It should be
mounted at least 30 centimeters away from the clock unit and from solid steel. The
antenna should be aligned at a right angle to the direction of the transmitter (Frankfurt).

Figure: Decoding Scheme

M Start of Minute (0.1 sec)
R RF Transmission via secondary antenna
A1 Announcement of a change in daylight sa-

ving

Z1, Z2 Time zone identification
A2 Announcement of a leap second
S Start of time code information
P1, P2, P3 Parity bits

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6

UA32S Overview

The hardware of UA32S is a 100mm x 160mm microprocessor board. The 20mm wide
front panel contains three LED indicators ,only the100,8mm wide front panal contains
an 7-digit LED display and a time/date switch. An asynchronous serial port is available
which can be used to read out information on date, time, and status. The Meinberg
standard time string can be sent automatically whenever a new second begins (default)
and/or the host has sent a request character. Four optocoupler outputs and 3 relay outputs
are available which can be used to switch external components or generate periodic
pulses. The outputs can be programmed using data tables residing at specified addresses
in the on-board EPROM.

4HP 20HP

Frontview UA32S

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Antenna and LF Receiver

An external ferrit antenna is used to receive the signal from DCF77. Optionally, a
weather-proof antenna is available which can be mounted outdoor. A coaxial cable
which can be up to more than 100 meters in length is used to pass the antenna's output
signal to the on-board LF receiver where it is demodulated by a synchronous detector
with automatic gain control. The demodulated time marks are fed to the clock´s micro­processor.

Mounting the Antenna

The antenna case should be installed at least 30 cm away from the board and from steel
girders or plates. The brighness of the LED “Mod” in the front panel depends on the
signal strength of the 77.5 kHz carrier. In order to get the maximum signal, the antenna
should be aligned in two steps. First it should be turned slowly until the “Feld” LED is
mostly dimmed. Finally the antenna must be turned by 90° from this position to obtain
maximum signal.

If the antenna is installed properly and the signal from DCF77 can be received without
strong distortions, the LED labeled "Mod" starts blinking exactly once per second,
corresponding to the time marks from DCF77. If this LED flashes intermediately, there is
some electrical noise around which prevents the microprocessor from decoding the time
message. In this case, a better location for the antenna must be found.

After reset, the LED labeled “Freil.” indicates that the clock is running on xtal and has
not synchronized with DCF77 yet. Due to the plausibility checks, it can take up to three
minutes after power-up until the clock is synchronized and this LED is turned off. The
state of this LED only changes when a new minute begins.

Microprocessor Circuit

Time marks from the receiver circuit are filtered and decoded by the microprocessor. If
no errors are detected in the current time message an additional plausibility check against
the previous time message is performed. If that plausibility check passes, too, the real
time clock on the board is adjusted corresponding to the decoded time and date. The real
time clock is read periodically and it's date and time are passed to the display driver and
the serial port drivers. Additionally, the microprocessor controls the switch outputs. An
on-board microprocessor supervisory circuit provides a watchdog timer which lets the
microprocessor recover from malfunction, along with a power-fail comparator which
resets the microprocessor if the supply voltage drops below a specified threshold.

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