This catalog is out of date, see note on page 2
TELEPERM M
CS 275 Bus System
Catalog PLT 130 · 1994
This catalog is no longer available in printed form. However, it can still be used to obtain information and for ordering spare parts.
Certain products from this catalog are no longer available. Your Siemens partner will offer appropriate substitutes wherever possible.
Summary
Mode of operation
Design
Modules and ordering data
Appendix |
SY--TRANS 300 CS Gateway |
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Documentation for |
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CS 275 bus system |
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Subject index |
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Conditions of sale and delivery |
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This catalog is out of date, see note on page 2
Summary
The TELEPERM M process control system consists of functionally different components which are optimized for the various problems encountered in process automation. Because of their modular design, these components are also referred to as systems.
The TELEPERM M process control system is divided into 
AS automation systems,
OS operation and monitoring systems and 
CS 275 bus system.
The CS 275 bus system is responsible for communication between all TELEPERM M components and to components of other systems by means of serial data transmission on stranded conductors (local bus) or coaxial cables (remote bus), if applicable also via optical fibers. Data exchange is mainly between the AS automation systems themselves as well as between automation systems, OS operation and monitoring systems and central configuring console and the AS and OS systems.
In order to satisfy the high demands made on data communication in process control technology, the CS 275 bus system has been particularly optimized for the following demands:
Efficient data transmission
High data reliability and availability
Uniform system time
Automatic establishment of communication.
The CS 275 bus system has exceptional real--time properties. Every bus participant is provided with the current process data at all times. The capacity of the bus system is large enough such that sufficient reserve is available for transmitting messages (e. g. process alarms) even with a high cyclic loading.
Automatic test routines guarantee data reliability. The user can configure which messages must be acknowledged by the receiver. The failure of a bus component has no influence on the communication between the other participants.
Fig. 1/1 TELEPERM M, process control system, summary, including system-integrated links to SICOMP computer systems, SIMATIC S5 programmable controllers and the SINEC communication network
1) Not for AS 215 and OS 520 systems.
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Summary
The bus system can be designed in redundant form if extremely high demands are placed on the availability. This does not result in additional configuring requirements.
Events are always recorded with the exact time since the individual bus participants can synchronize their clocks via the bus system.
The simple configuring is one of the most important characteristics of the CS 275 bus system. Convenient system functions are used to establish the connection, intervention by the operator is not required. The parameters to be transmitted (analog/binary values, messages etc.) are already declared when configuring the automation systems and the operation and monitoring systems. The establishment of the connection for the operation and monitoring systems is carried out automatically when starting up, it is merely necessary to enter a coupling command for connections between automation systems.
Optimum utilization of the high performance of the CS 275 bus system is only guaranteed with a large number of participants if certain rules are observed when configuring the bus and if it is ensured that the cyclic bus loading does not exceed 70 % of the bus capacity. Thus 30 % are available for acyclic data transfer (e. g. messages).
In the case of a specific configuration, the cyclic bus loading is independent of
xthe configuration of the transmitter blocks in the automation systems,
xthe transmission mode selected and
xthe processing cycle of the transmitter blocks.
Information on the establishment of data transfer with the coupling blocks for data exchange via the CS 275 bus system is included in the publication ”Configuring guidelines” in the Manual ”CS 275 bus system”. This publication describes the determination of the cyclic bus loading using the bus loading characteristics and lists the cyclic bus loading for a selected configuration.
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Mode of operation
Contents |
Page |
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Transfer control |
2/2 |
Data protection |
2/2 |
Data transfer |
2/2 |
Addressing |
2/3 |
Transmission modes |
2/3 |
Redundant operation mode |
2/4 |
Transmission reliability |
2/4 |
Time synchronization |
2/4 |
Configuring of communication |
2/5 |
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2/1 |
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Mode of operation
Transfer control, data protection and transfer
Transfer control
Sequential data transmission systems require a transfer control unit for organization of the data traffic on the line. This unit organizes and coordinates the data traffic so that only one subscriber transmits data on the bus at a time. This transfer control function is decentralized in the CS 275 bus system. The availability of the data transmission system is therefore mainly determined by the line length.
Data transfer control in the CS 275 bus system operates according to the token principle, i. e. each participant (local bus interface module) accepts the transfer control function (master function) from time to time.
In a system with n participants, there is only one participant in the master condition at any one time, all other (n--1) participants are in the slave condition. The change of the master function from one participant to another is called master transfer. Since every participant can assume the master function, this function has n--times redundancy in a token system.
The ”bus protocol” also specifies how a participant becomes master and how this status is transferred within the system. The protocol complementary methods for the assignment of the master function to a participant are:
Time-out-controlled master transfer
Request-controlled master transfer 
Instruction-controlled master transfer
Data protection
Data protection is achieved in the CS 275 bus system by generating line and column parities and is referred to as block parity.
The following errors are detected by the data protection:
1-bit, 2-bit and 3-bit errors,
Hamming distance d = 4
Odd bit errors, 1-, 3-, 5-, 7- and 9-fold errors, independent of location
Error bursts < 11 bit long
Error pattern (with exception of rectangular format).
The bit error rate of p =10-5 satisfies the requirements of IEC- SC-65-WG6 for process buses. According to this, an undetected transmission error in a message may occur on average once in every 1000 years (at 250 kbit/s).
Data transfer
Blocks in the TELEPERM M system components are available for a cyclic and a sporadic (acyclic) data transfer via the bus system:
Dedicated transmitter and receiver blocks handle all functions associated with data transfer. Thus, the data transfer can be established easily by configuring, just as the automation functions.
The user need only carry out the following to produce communication:
-- The inputs of the transmitter block must be provided with the addresses of the data to be transmitted
-- The transmitter block must be inserted into the processing sequence
-- The outputs of the corresponding receiver block must be linked accordingly in another automation system
-- The receiver block must be inserted into the processing sequence
-- The connection to the transmitter must be established using a coupling instruction.
This presents the following advantages:
Easy configuring of communication (only the transmitter and receiver blocks must be configured, not the interface modules for 20-m local bus)
Messages to several subscribers are simply transmitted on the bus (several receiver blocks can access one transmitter block)
Symbolic addressing (block name and number)
Complete documentation of all connections by self-documen- tation of systems
The communication procedure can be configured in a still simpler manner in full-graphic mode on the screen by means of the configuring tool PROGRAF and can also be documented in the same representation (see page 2/5).
Cyclic data transfer
Analog values are transmitted cyclically with the coupling blocks AKS/AKE, binary values with the BKS/BKE blocks and characters with the ZKS/ZKE blocks.
There are also further functions in addition to the cyclic data transfer.
These functions include image updating in an OS operation and monitoring system. The updating time is < 2 s in the TELEPERM M process control system. In order to guarantee this value, the bus system provides a function ”Read parameters”. This enables up to 30 different parameters per message to be read from one AS system. The functional sequence is as follows:
The OS system sends the request to the bus system to read the corresponding parameters from several AS systems for image updating. The addresses of these parameters have already been converted to on-line-accessible parameters from the symbolic addresses of the configuration during the system start-up. Thus, the bus interface modules can read the desired information out of the automation system memory by DMA, generate corresponding reply messages and return these to the corresponding OS systems.
Fig. 2/1 Cyclic data transfer, example OS/AS and AS/AS
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Mode of operation
Addressing, transmission modes
This method has the following important advantages:
There is far less loading on the bus system since only the information is read from the automation system which is currently displayed on the monitor channels
Data need only be stored at one position as a result of the distributed data base principle. Modifications are therefore only necessary at one position
No special planning for the OS systems is required in the automation systems (exception: curve display)
Acces to information in the automation systems by another computer is possible without additional planning (by using the function ”Read parameters”).
The cyclic data exchange is also used for a life test of all participants connected to the CS 275 bus by an OS operation and monitoring system. Each failure and also the return of a participant is supervised and signalled.
Sporadic data transfer
Sporadic data transfer is necessary to rapidly pass on modifications in the process control system to other participants. Typical examples are faults or changes in status (e. g. motor on/off) which detects the automation system. Messages exchanged between several automation systems are transmitted by means of the coupling blocks MKS/MKE.
A status word is assigned to each function block for processing with standardized operation and monitoring as well as to driver blocks for I/O modules with standardized display. The changes in signal are detected event-controlled by the status word or by the MKS block, provided with the actual time (MKS only) and transferred to the bus system. This then transfers MKS messages to a maximum of 6 participants (typically OS systems and higher-level computers) which have ”registered” themselves for this information when the complete system was started up. This presents the advantage that the automation system need only transmit one message with one or several destination addresses. In addition, only those stations receive the information which actually require it.
Data transfer with OS systems and computers takes place using the functions ”Read parameters” and ”Write parameters”.
Fig. 2/2 Sporadic/acyclic data exchange, example OS/AS and AS/AS
Addressing
The addressing of the participants of the bus system is oriented towards the transmission of messages between several autonomous buses and within a bus.
Each participant is identified by two addresses:
Bus address (0 to 7), i. e. 8 autonomous buses are possible. 7 bus couplers are needed in this case.
Participant address (0 to 99).
These two addresses are set on the local bus interface module using jumpers or DIP switches.
The bus coupler behaves like a participant with respect to each bus. It has an address on each bus.
Transmission modes
A differentation is made between two transmission modes when configuring and defining the AKS and BKS transmitter blocks:
-- Direct coupling (DI)
-- Common data (CD).
Direct coupling (DI)
The registered participants are directly addressed by the transmitter blocks, i. e. each participant only receives the data which is assigned for it. Up to 6 receivers can be registered with a transmitter block and receive the data (analog or binary values) pertaining to it with each transmission cycle of this block.
Any participant on the bus can be a receiver. Transmission can also take place via bus couplers. A receiver is entered as such in the transmitter block in the respective automation system.
The MKS block only operates in direct coupling mode.
Common-Data (CD)
The transmitter block sends the data simultaneously to all connected participants of a particular bus. Thus certain identical data can be planned in a transmitter block for many participants on a bus and many destination addresses can then be reached.
The CD procedure can only be used for subscribers with the same bus address. Addressing via bus couplers is not possible. The participants on a bus connected via a bus coupler can be addressed via their own CD procedure.
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Mode of operation
Redundant operation mode, transmission reliability, synchronization
Redundant operation mode
The CS 275 bus system can be redundant in order to increase the availability. The interface modules for the local bus are already designed for a redundant local bus line. A bus converter UI and a connector board AF are required for connection of a redundant remote bus per remote bus cable. Different remote bus cable lengths are permissible between bus A and the redundant bus B.
The bus system is started up on bus A. Besides this, no preference is given to either bus. The bus system carries out a cyclic test to see whether a changeover criterion is satisfied. An automatic changeover is carried out if this is the case.
Changeover criteria
An image of the local bus is generated through each bus line approx. every 750 ms. If the image of the passive bus contains more entries than that of the active bus, the system switches to the passive bus.
If the images on the two bus lines are the same, but the master detects a transfer request on the passive bus, a changeover also takes place to the passive bus. A slave sends transfer requests on the passive bus if transfers are no longer possible for it on the active bus.
If the current master fails because of a fault, the slave with the smallest participant address assumes the master function on the previously passive bus (if one exists).
The bus changeover is signalled to all bus participants.
Time synchronization
The real-time clocks of the particular TELEPERM M subsystems are synchronized by signals from an OS operation and monitoring system. This can be synchronized by a radio clock (DCF 77 radio transmitter) or a standard clock.
The subscribers on the CS 275 bus system must be synchronized with high accuracy. Because of it, the transit time of the synchronization message is corrected within the milliseconds range by the internal buffers of the local bus interface modules of the automation systems and programmable controllers or by bus couplers.
Date and time transmission program
Remote bus 1
Time receive memory
Intermediate time counter ' t (ms)
Transmission buffer
Remote bus 2
Fig. 2/3 Time generation, time synchronization
Transmission reliability
In addition to data security of the transmission method, the following measures ensure high transmission reliability in the physical transmission path:
Noise immunity to IEC 255-4 
Triple screened cable, redundant
Coarse overvoltage protection in the building entry (option)
Fine overvoltage protection in the connector board AF (option)
Deflection of noise using braided screens and metal front plugs
Passive line without amplifier
Non--reactive inductive coupling
Appropriate signal coding on the remote bus (bipolar current signals)
Automatic signal equalization independent of location 
Balanced (to earth) transmission
High signal voltages
Electrical isolation of participants on remote bus 
Distributed transfer control.
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Mode of operation
Configuring of communication
Configuring of communication
Since the communication via the CS 275 bus system is handled like the automation functions via function blocks, they can also be configured in full-graphic mode on the screen by means of the configuring tools PROGRAF. Examples for AS/AS communication are shown in Figs. 2/4 and 2/5.
Fig. 2/4 Connection of an analog value out of an adder block to the transmitter block AKS (e. g. as subscriber 3 on bus 1 in an automation system)
Fig. 2/5 Take-off of the transmitted analog value from the receiver module AKE/GA (e. g. as subscriber 7 on bus 1 in an automation system) and connection to a divider block
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Design
Contents |
Page |
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General notes |
3/2 |
Local range |
3/2 |
Remote range |
3/3 |
Bus components |
3/3 |
Technical data |
3/5 |
Bus configurations |
3/6 |
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3/1 |
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Design
General notes, local range
The CS 275 bus system is physically divided into
-- a local range up to 20 m (local bus) and
-- a remote range up to 4 km, or up to 12 km with bus couplers.
Each participant requires a local bus interface module to enable bus communication, redundant systems such as the AS 235 H automation system require two modules. These interface modules convert the various internal system bus interfaces of the participants into the uniform local bus interface. The transfer control function for the complete bus is transferred from participant to participant. This function is also handled by the local bus interface module of the respective participant which currently possesses the master function.
The design of the local bus interface modules depends on the participant system to be connected. Thus the modules e. g. for connection of the automation systems are of double ”EUROPE” format, and those for connection of SICOMP industral PCs are of AT format. In the local range, the local bus interface modules are connected together into a ”local bus island” using cables.
Systems not belonging to TELEPERM M require additional coupling software to match their internal communication interface to that of the CS 275 bus system. This software is available, amongst others, for the connection of personal computers with MS-Windows or UNIX operating systems, for workstations and for SIMATIC S5 programmable controllers.
In the remote range, individual participants or complete local bus islands are connected to the remote bus via inductive bus couplers UI. Different designs of coaxial cable are available for the connection depending on the associated mechanical stress.
The local bus is always redundant, the remote bus can be either single or redundant.
Local range
The transmission is on multi-conductor cables with a max. total length of 20 m.
Three line signals are used. The data themselves are transmitted sequentially on one data line. A second line transmits the clock, the third is used for synchronization.
It is necessary to differentiate between electrical participants and (bus) participants when determining the maximum possible number of participants. Electrical participants are the local bus interface modules, the bus converter modules UI and connection multiplexers AV (for connection of a local bus interface module).
(Bus) participants are e.g . an AS 215 automation system (1 electrical participant) or an AS 235 H automation system (2 electrical participants). Up to 9 electrical participants are
permissible on a local bus. For example, this means 7 bus participants for a local bus island connected to a redundant remote bus via two bus converters UI (cf. Figs. 3/1 and 3/2.)
Depending on their type, the local bus interface modules can be either floating or non-floating. Certain design guidelines must be observed when connecting into a local bus island in order to prevent interferences (also refer to Manual ”TELEPERM M, Information and Guidelines for Planning, Installation and Operation”, Order No. C79000-G8076-C417).
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AS |
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Automation system |
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AG |
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SIMATIC S5 programmable controller |
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AV |
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Connection distributor for local bus |
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N-AT, N-AS, |
} Interface modules for 20-m local bus |
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N-V.24, |
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OS |
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UI |
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Fig. 3/1 CS 275 bus system, example for interconnection of local bus and remote bus (non-redundant remote bus); local bus island (left) with 2 communication subscribers and 4 electric participants.
AS |
Automation system |
AG |
SIMATIC S5 programmable controller |
AV |
Connection distributor for local bus |
N-AT, N-AS, |
} Interface modules for 20-m local bus |
N-V.24, |
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Operation and monitoring system |
UI |
Bus converter unit |
Fig. 3/2 CS 275 bus system, example for interconnection of local bus and remote bus (redundant remote bus); local bus island (left) with 2 communication subscribers and 5 electric participants.
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