BECKHOFF BK7500 User Manual

SERCOS Coupler

( Serial Real Time Communication System )

BK7500

Valid for all BK75xx Bus Coupler

Technical Hardware Documentation

Version 1.1
2006-10-30

Contents

Contents

1. Foreword 3

Notes on the documentation 3

Liability Conditions 3
Delivery conditions 3
Copyright 3

Safety Instructions 4

State at Delivery 4
Description of safety symbols 4

2. Basic information 5

The Beckhoff bus terminal system 5
The interfaces 7

Power supply 7
Power supply to the power contacts 7
Power contacts 7
Fieldbus connection 8
Configuration interface 8
K-bus contacts 8
Supply isolation 8

The operating modes of the bus coupler 9
Mechanical construction and mounting 11
Electrical data 13
The peripheral data in the process image 14
Starting operation and diagnostics 17

Terminal bus error 18
Fieldbus error 18

Setting the Transmission Rate 19
Setting the Cable Length 19
Setting the Station Address 20

3. SERCOS interface Coupler BK7500 21

Introduction to the SERCOS Interface System 21
The I/O Data Channel 23
The transfer medium: plugs and cables 27

4. Appendix 28

Example: composition of a process image in the Bus Coupler 28

The hardware configuration: 28
Configuration of the SERCOS master 29

5. Index 31

6. Support and Service 32

Beckhoff's branch offices and representatives 32

Beckhoff Headquarters 32

2 Buskoppler BK7500

Foreword

Foreword

Notes on the documentation

This description is only intended for the use of trained specialists in control and automation engineering
who are familiar with the applicable national standards. It is essential that the following notes and
explanations are followed when installing and commissioning these components.

Liability Conditions

The responsible staff must ensure that the application or use of the products described satisfy all the
requirements for safety, including all the relevant laws, regulations, guidelines and standards.
The documentation has been prepared with care. The products described are, however, constantly under
development. For that reason the documentation is not in every case checked for consistency with
performance data, standards or other characteristics. None of the statements of this manual represents a
guarantee (Garantie) in the meaning of § 443 BGB of the German Civil Code or a statement about the
contractually expected fitness for a particular purpose in the meaning of § 434 par. 1 sentence 1 BGB. In
the event that it contains technical or editorial errors, we retain the right to make alterations at any time
and without warning. No claims for the modification of products that have already been supplied may be
made on the basis of the data, diagrams and descriptions in this documentation.

Delivery conditions

In addition, the general delivery conditions of the company Beckhoff Automation GmbH apply.

Copyright

©

This documentation is copyrighted. Any reproduction or third party use of this publication, whether in

whole or in part, without the written permission of Beckhoff Automation GmbH, is forbidden.

BK7500 3

Foreword

i

Safety Instructions

State at Delivery

All the components are supplied in particular hardware and software configurations appropriate for the
application. Modifications to hardware or software configurations other than those described in the
documentation are not permitted, and nullify the liability of Beckhoff Automation GmbH.

Description of safety symbols

The following safety symbols are used in this documentation. They are intended to alert the reader to the
associated safety instructions..

This symbol is intended to highlight risks for the life or health of personnel.

Danger

This symbol is intended to highlight risks for equipment, materials or the

Attention

Note

environment.

This symbol indicates information that contributes to better understanding.

4 BK7500

Basic information

Up to 64 bus terminals

each with 2 I/O channels
for any form of signal

Decentralized wiring of the
I/O level

IPC as control unit

Bus couplers for all current
bus systems

Standard C rail assembly

Modularity

Display of channel status

The K-bus

End terminal

The Beckhoff bus terminal system

The bus terminal system is the universal connecting link between a
fieldbus system and the sensor/actor level. A unit consists of a bus coupler,
which is the interface to the fieldbus, and up to 64 electronic terminals, of
which the last is an end terminal. Terminals, each with two I/O channels,
are available for any form of technical signal and can be combined as
desired. The various types of terminal are all constructed in the same way,
so that the planning costs are kept extremely low. The height and depth of
the construction are calculated for compact terminal cabinets.

Fieldbus technology makes it possible to use compact control
architectures. The I/O level does not need to be taken right up to the
control unit. Sensors and actors can be connected decentrally with minimal
lengths of cable. You can position the control unit at any convenient
location in the installation. Using an industrial PC as control unit makes it
possible to implement the operating and monitoring element as part of the
control hardware, so the control unit can be located on an operating desk,
control point or similar. The bus terminals constitute the decentralized
input/output level of the control unit in the switch cabinet and its
subordinate terminal cabinets. As well as the sensor/actor level, the power
unit of the equipment is also controlled via the bus system. The bus
terminal replaces a conventional terminal as the cabling level in the switch
cabinet; the switch cabinet can be made smaller.

The Beckhoff bus terminal system combines the advantages of a bus
system with the functionality of compact terminals. Bus terminals can be
used on all current bus systems and serve to reduce the diversity of parts
in the control unit, while behaving like the conventional standard units for
the relevant bus system and supporting the entire range of functionality of
the bus system.

The simple and compact assembly on a standard C rail, and the direct
cabling of actors and sensors without cross connections between the
terminals, serve to standardize the installation, as does the uniformly
designed labeling.

The small size and great flexibility of the bus terminal system mean that
you can use it anywhere that you could use a terminal and use any type of
connection – analog, digital, serial or direct sensors.

The modular construction of the terminal row, using bus terminals with
various functions, limits the number of unused channels to at most one per
function. Two channels to a terminal is the optimum solution for the number
of unused channels and the cost per channel. The possibility of using
power input terminals to provide separate power supplies also helps to
minimize the number of unused channels.

The integrated light-emitting diodes close to the sensor/actor indicate the
status of each channel.

The K-bus is the path taken by data within the terminal row. The bus
coupler carries the K bus through all the terminals by means of six contacts
on the side walls of the terminals, and the end terminal terminates the K
bus. The user does not need to know anything about the function of the K
bus or the internal operation of terminals and bus couplers. There are
numerous software tools available which provide for convenient planning,
configuration and operation.

Basic information

BK7500 5

Basic information

Potential

Power supply

End terminal

SERCOS interface

Power input terminals
for
separately powered groups

The principle of the bus
terminal

Three power contacts pass the operating power to the following terminals.
You can use power input terminals to subdivide the terminal row as desired
into groups, each with a separate power supply. These power input
terminals are not taken into account for addressing the terminals, you can
insert them at any position along the terminal row.

You can install up to 64 terminals on a terminal row, including power input
terminals and the end terminal.

Bus coupler
BK7500

for the
Bus coupler

supply
bus terminal

K-Bus

0201

24V

0V

+ +

PE PE

Bus couplers for various
fieldbus systems

Power
contacts

Potential
isolation

You can use a variety of bus couplers to attach the electronic terminal row
quickly and easily to the various fieldbus systems, and you can also
subsequently convert to a different fieldbus system. The bus coupler deals
with all the necessary monitoring and control tasks for operating the
attached bus terminals, indeed all the operation and configuration of the
bus terminals is carried out via the bus coupler. The fieldbus, K bus and I/O
level are electrically isolated.

If the exchange of data across the fieldbus is temporarily interrupted, logic
states are preserved, digital outputs are cleared and analog outputs revert
to a reset value which can be individually configured for each output when
the equipment is set up.
The default for the analog outputs is 0V or 0mA. Digital outputs assume an
inactive state. The bus couplers' timeouts correspond to the usual times for
the field bus system. When changing over to a different bus system, pay
attention to the change in timeouts in the event of larger-scale bus system
cycle times.

6 BK7500

The Beckhoff-SERCOS ­coupler BK7500

The interfaces

There are six ways of making a connection to a bus coupler. These
interfaces are designed as plug connections and spring terminals.

Basic information

24 V DC on the topmost
terminals

Lower 3 terminal pairs for
power input

maximum 24 V

maximum 10 A

Spring contacts at the side

Power supply

The bus couplers need an operating power of 24 V DC which is connected
via the topmost spring terminals, labeled "24 V” and "0 V”. This power
supply serves not only the electronic components of the bus coupler but
(via the K bus) also the bus terminals. The power supply of the bus coupler
circuitry and that of the K-bus (Terminal bus) are electrically isolated from
the voltage of the field level.

Power supply to the power contacts

The six lower connections with spring terminals can be used to supply
power to the peripherals. The spring terminals are connected in pairs to the
power contacts. The power supply to the power contacts has no
connection to the power supply of the bus couplers. The power input is
designed to permit voltages up to 24 V. The pair-wise arrangement and the
electrical connection between the feed terminal contacts makes it possible
to loop through the wires connecting to different terminal points. The load
on the power contact may not continuously exceed 10 A. The current
capacity between two spring terminals is the same as the capacity of the
connecting wires.

Power contacts

On the right-hand side face of the bus coupler are three spring contacts
which are the power connections. The spring contacts are recessed in slots
to prevent them from being touched. When a bus terminal is connected,
the blade contacts on the left-hand side of the bus terminal are connected
to the spring contacts. The slot and key guides at the top and bottom of the
bus couplers and bus terminals ensure reliable location of the power
contacts.

BK7500 7

Basic information

Periphery level

Bus terminals

Bus coupler

24 V DC

SERCOS Fibre optic

Plug SERCOS Z1003

Serial interface under the
front flap

6 contacts at the side

3 supply groups:
fieldbus
K-bus
peripheral level

Setting up the power levels
in the bus terminal system

Fieldbus connection

There is a recessed front face on the left hand side. The typical SERCOS
connecting plugs can be inserted here. SERCOS consists of a fiber-optic
conductor ring into which the bus coupler is inserted. You need a fiber­optic conductor connector type SERCOS Z1003 for connection.

Configuration interface

On the lower part of the front face you will find the standard bus couplers
which are fitted with an RS232 interface. The miniature plug can be
attached to a PC by means of a connection cable and the configuration
software KS2000. This interface enables you to configure the bus terminals
, e.g. setting the amplification factor of the analog channels. The mapping
of the bus terminal data to the process view in the bus coupler can be
changed via the interface. You can also access the functionality of the
configuration interface via the fieldbus by means of the ADS
communications.

K-bus contacts

The connections between the bus coupler and the bus terminals are
effected by gold contacts at the right-hand side of the bus coupler. When
the bus terminals are plugged together, these gold contacts automatically
complete the connection to the bus terminals. The K bus is responsible for
the power supply to the electronic components of the K bus in the bus
terminals, and for the exchange of data between the bus coupler and the
bus terminals. Part of the data exchange takes place via a ring structure
within the K bus. Disengaging the K bus, for example by pulling on one the
bus terminals, will break this circuit so that data can no longer be
exchanged. However, there are mechanisms in place which enable the bus
coupler to locate the interruption and report it.

Supply isolation

The bus couplers operate with three independent supplies. The input
power supplies the electrically isolated K-bus circuitry in the bus coupler
and the K-bus itself. The power supply is also used to generate the
operating power for the fieldbus.

Note: All the bus terminals are electrically isolated from the K bus, so that
the K-bus is completely electrically isolated.

Terminal bus

8 BK7500

Field bus

Power on selftest

Initialisation of the coupler

Start-up behavior of the bus
coupler

The operating modes of the bus coupler

When it is first switched on the bus coupler carries out a self-test to check
the functions of its components and the communications of the K bus, and
while this is going on the red I/O LED will flash. When the self-test has
been completed successfully, the bus coupler will begin to test the
attached bus terminals (the "bus terminal test”) and read in the
configuration from which it constructs an internal structure list, which is not
accessible from outside. If an error occurs the bus coupler will enter the
operating mode "STOP”. If the start-up sequence is completed without
errors the bus coupler will enter the mode "fieldbus start”.

The BK7500 is now in phase 0 (P0). In this phase it sends telegrams that it
has received to the next device in the ring (repeater function). In phase 0,
the master sends master sync. telegrams (MST). If these are received ten
times without interruption, the master switches to communication phase 1
(P1). Master data telegrams are now also sent. Each slave has its own
station address. The slave answers with a drive telegram (AT), and in this
way indicates its readiness for changing the phase to communication
phase 2 (P2). After the master has switched to phase 2, the SERCOS
interface is now in the stage of non-cyclic data exchange. Each cycle now
only involves communication with a device in the SERCOS ring. The time
slots required for cyclic data exchange are calculated, and are checked by
the connected devices. When all the slave devices have reported that they
are ready to switch-over, the master can switch to phase 3 with the MST.
In phase three (P3), the communication is already almost like that of phase

4. The only difference is that valid cyclic data is still not being transferred.
The time slots defined in phase 2 are valid, and are monitored. If the
communication is proceeding without error, phase 4 is entered.

Basic information

Cyclic data exchange

BK7500 9

Bus terminal test Structure list

Master Sync. Telegram (MST)

At the beginning of each cycle an MST is sent by the master to all the
slaves. The broadcast address is used for this. Each connected slave uses
this telegram to determine its send window.

Basic information

Master Data Telegram (MDT)

The MDT is sent by the master as a broadcast to all devices. It contains
the data for all the slave devices. Because of different configurations, the
data length can vary.

Drive Telegram (AT)

Each slave sends its output data in the appropriate time slot. The telegram
contains its station address, so that the master can identify it.

t

Scyc

(CP4)

MST

t

1.1

AT AT

1

t

1.2

2

t

1.n

AT

t

1.n+1

AT

n

n+

t

2

MDT

MST
(CP4)

10 BK7500