Meinberg VME31 User Manual

FUNKUHREN

Technical Information
Operating Instructions

VME31

Werner Meinberg
Auf der Landwehr 22
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]

December 17, 1997

Table of Contents

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

Overview ..................................................................................... 6

Configuration............................................................................... 7

Setting the Base Address ............................................... 7

Selecting the I/O Access Mode .....................................8

Installation ................................................................................... 8

Interface Description ...................................................................8

Address Map.................................................................. 9

Using Periodic Interrupts ............................................ 10

Interrupt Vector.............................................10

Interrupt Level............................................... 10

Interrupt Rate ................................................ 10

Technical Specifications............................................................ 11

CE Label...................................................................... 12

Component Layout ...................................................... 13

Pin Assignments .......................................................... 15

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

P3

80

Kalenderjahr

Kalender-

monat

Wochentag

Kalendertag

10

8

4

2

1

10

50

8

4

2

1

4

2

1

40

20

10

8

4

2

1

P2

20

10

Stunde

0

30

P1

8

1

4

2

Kodierung

nach Bedarf

10

R

A1

Z1

Z

2

20

A2

S

1

2

4

8

10

20

40

Minute

M

40

20

M Start of Minute (0.1 sec)
R RF Transmission via secondary antenna
A1 Announcement of a change in daylight saving
Z1, Z2 Time zone identification

Z1,Z2 = 0,1: Daylight saving disabled (MEZ)

Z1,Z2 = 1,0: Daylight saving enabled (MESZ)
A2 Announcement of a leap second
S Start of time code information (0.2 sec)
P1, P2, P3 Even parity bits

5

Overview

The radio remote clock DCF77 VME31 receives the time marks from DCF77 and
makes the decoded time available to VME bus systems. The clock is designed on a 3U
board (euro card size), so it can be used in either 3U systems or 6U systems. An
external ferrit antenna passes the signal from DCF77 to the on-board long wave
receiver. The demodulated time marks are decoded by the clock´s 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 battery buffered real time clock on the board is synchronized corresponding to the
decoded time and date.

Software running on the computer can read out the date/time/status and some more
information from the board's dual port RAM which is updated in 10ms intervals. The
dual port RAM can be configured by a block of jumpers to be mapped to any 1k
boundary in the system's A16 address range. It can be accessed using either Short
Supervisor I/O (2Dh) or Short Non-Priviledged I/O (29H). The radio remote clock can
generate cyclic interrupts at one of the levels IRQ1 through IRQ7 at a rate of 10ms,
100 ms, 1s, 10s, 60s, or 1h.

Frontansicht

6

Configuration

Before the board can be installed in the VME bus rack, some jumpers must be
configured as described below. The location of the jumpers can be seen from the
component layout at the end of this manual.

Setting the Base Address

The base address of the dual port RAM on the board must be configured correspon­ding to the table shown below:

7

Selecting the I/O Access Mode

An additional jumper J1 must be configured to select the access mode: if the jumper is
installed, the board can be accessed using Short Supervisor I/O (2Dh), otherwise the
board is accessed using Short Non-Priviledged I/O (29h).

Installation

After the jumpers have been configured, the board can be installed in the VME bus
rack. When the system is turned on, the clock starts displaying either the on-board date
or time, depending on the position of the date/time selection switch. The LEDs let the
user check the clock's status and proper receiver operation.

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

If the antenna is connected, the brightness of the green LED labeled Feld reflects
the strength of the RF signal. A good way to align the antenna is to turn it slowly until
this LED is mostly dimmed due to minimum signal, finally, the antenna is turned by a
90° angle to obtain maximum signal.

If the antenna is properly installed, the green LED labeled Mod. should be blinking
exactly once per second corresponding to the time marks from DCF77. If this LED
flashes, there is some electrical noise around which prevents the receiver from
decoding the time marks and synchronizing.

The red LED labeled Freil. is on if the clock is running on xtal. This LED can only
change when the minute changes (seconds increment from 59 to 0). After power-up, it
takes at least two up to three minutes until this LED is turned off.

Interface Description

Information on date, time, and status is made available to the VME bus via dual port
RAM. The dual port RAM is mapped into the VME bus' A16 address range correspon­ding to the jumper settings described above. The contents of the dual port RAM is
updated once every 10ms.

Care must be taken not to read an inconsistent block of data due to an update cycle
occurring in the middle of the read loop. For example, the 100th-of-seconds value
could be read twice: as the first byte, and, again, as the last byte. If both of the values
are identical, no update has taken place while the read loop was executed. Another

8

method is to read the clock interrupt driven or poll the 100th-of-seconds until the
value changes: in both of the cases, the software has an interval of 10ms to read the
desired data.

Address Map

The VME31 radio remote clock has a A16:D8 bus interface, so the dual port RAM
must be accessed byte wide on odd address offsets related to the base address. The
address map is shown below:

01h (reserved)

03h (reserved)

05h interrupt vector (default: 0Fh)

07h interrupt level (00h..07h, default: 00h - disabled)

09h interrupt rate (default: 00h, see below)

0Bh EPROM ID

0Dh status (see below)

0Fh year (00h..99h)

11h month (01h..12h)

13h day-of-month (01h..31h)

15h hour (00h..23h)

17h minute (00h..59h)

19h second (00h..59h)

1Bh sec100 (00h..99h)

1Dh day-of-week (01h..07h, 01h = Monday)

1Fh (reserved)

Date and time values are represented in packed BCD numbers.

The bits of the status byte are defined as described below:

bit stands for “1” “0”

D0 clock´s current state: free running DCF77 controlled
D1 daylight saving: enabled disabled
D2 Sync´ed since last Reset: yes n o
D3 dayl. saving going to change: yes n o
D4 interrupt enabled disabled
D5 (reserved, always "0")
D6 (reserved, always "0")
D7 on-board RTC time invalid: yes n o

9

Using Periodic Interrupts

If the clock shall generate periodic interrupts, three bytes must be written to the dual
port RAM:

Interrupt Vector

After power up, this byte is set to 0Fh. The user must take care to set up the vector
number corresponding to the system's exception vector assignments.

Interrupt Level

This byte is set to 00h after power up. The user must supply the desired interrupt level
(01h..07h).

Interrupt Rate

The contents of this byte reflects the rate of interrupts generated by the board. After
power up, its value is 00h. Valid codes are given below:

00h no interrupt

01h once ever 10 milliseconds

02h once every 100 milliseconds

03h once every second

04h on every 10 seconds

05h once every minute

06h once every 10 minutes

07h once every hours

others: (reserved)

10

Technical Specifications

RECEIVER: Narrow bandwidth receiver with automatic gain control

Bandwidth: approx. 40Hz

ANTENNA: Active external ferrite antenna in a plastic case

Length of the cable: up to more than 100m

Standard:
SMB type connector, 5m of RG174 cable

Outdoor:
N type connector, RG58 cable, adapter RG58/RG174

DISPLAY: eight digit LED display shows date or time (selectable by

switch)

RF AMPLITUDE,
MODULATION: Indicated by LEDs

TIMECODE
CHECK: Parity and consistency checking over a period of two minutes

RF distortions indicated by both LED and a bit of the
status register
Without RF signal the clock runs on XTAL
with an accuracy of 10

-5

BATTERY
BACKUP: NiCd accu

when the computer is turned off, the on-board RTC keeps the
time based on XTAL for more than four weeks

RELIABILITY OF
OPERATION: Microprocessor supervisory circuit provides watchdog timer,

power supply monitoring and backup-battery switchover

11

SYSTEM BUS
INTERFACE: VME bus A16:D8, slave

Access: Short Supervisor I/O (2Dh)

Short Non-priviledged I/O (29h)

IRQ levels: 1..7, programmable

DATA FORMAT: packed BCD

PERIODIC
INTERRUPTS: none, 10ms, 100ms, 1s, 10s, 1min, 10min, or 1h

POWER
REQUIREMENT: +5V @ 320mA

PHYSICAL
DIMENSION: 3U Euro card, 6U front panel optional

AMBIENT
TEMPERATURE: 0 ... 50°C

HUMIDITY: max. 85 %

CE Label

This device conforms to the directive 89/336/EWG on the approxi­mation of the laws of the Member States of the European Community
relating to electromagnetc compatibility.

12

Component Lay out

13

14

Pin Assignments

= > ?

1 D0
2 D1
3 D2
4 D3 /BG0IN
5 D4 /BG0OUT
6 D5 /BG1IN
7 D6 /BG1OUT
8 D7 /BG2IN

9 GND /BG2OUT
10 SYSCLK /BG3IN
11 GND /BG3OUT
12
13 /DS0
14 /WRITE

GND
/SYSFAIL
/BERR
/SYSRESET
/LWORD
AM5

15 GND
16 /DTACK AM0
17 GND AM1
18 /AS AM2
19 GND AM3
20 /IACK GND
21 /IACKIN
22 /IACKOUT
23 AM4 GND
24 /IRQ7
25 /IRQ6
26 /IRQ5
27 A4 /IRQ4
28 A3 /IRQ3
29 A2 /IRQ2
30 A1 /IRQ1
31
32 V CC in (+5V) VCC in (+5V)

A15
A14
A13
A12
A11
A10

VCC in (+5V)

15