Master unit communication system and method for operation thereof

European).

53 / 55P24210PL00

EP 1 869 836 B1

Description

The invention relates to a station and a master unit in a communication system with many stations that are connected to each other by means of a counter-acting double-ring structure, a communication system with a Master-Slave configuration and the way the station or communication system works.

Serial communication bus systems are increasingly used in manufacturing and automation technology, with the help of which decentralized peripherals such as I / O modules, measuring transducers, drives, valves and operator terminals can communicate in efficient real-time communication systems with automation, engineering or visualization systems. All stations are connected via a serial bus, in particular by means of a fieldbus, whereby data exchange is carried out on the bus in the slave master mode.

Active bus stations, as a rule, control devices, have bus access rights and set the data transfer on the bus. Active bus stations in a serial bus system are called master units. On the other hand, passive bus stations are usually peripheral devices. They do not have bus access rights, i.e. they can only respond to information signals received or, at the request of the parent unit, transmit information signals to it. Passive stations in the serial bus system are called slaves.

Fieldbus slaves with master structure are usually, in order to reduce costs sequentially through cabling, made in ring topology, with all bus stations connected to the ring data bus. The information signal received from the master unit is fed into the annular data transfer bus by the master unit and the slaves go through, connected to the ring data transfer bus, and then they are again received by the master unit and are used by it. Master-slave systems can also be systems with many master units.

Information signals are usually organized by the master unit into data packets, which are composed of control data and user data, in particular the Ethernet standard allows the use of data packets up to 1500 bytes in length, with a high transmission speed of approximately 100 Mbit / second . Each slave connected to the annular data transfer bus exchanges the Ethernet telegram introduced by the master to the annular transmission bus as it passes, the user data specified for it with the telegram data.

Master-slave communication systems with a ring configuration are usually constructed in such a way that the master unit is the transmitting unit as the data entry and the receiving unit as the data receiving in the data center. Individual units are subordinated in a data transmission bus in a chain, with each subscriber connected to two neighbors, with the first and last subscribers in the chain being associated with the superior unit. The data packet is sent in the direction from the master unit through its transmitting unit to the first connected slave unit, from it to the next, until the last slave unit in the chain is reached, and then to the receiving unit of the master unit. Each subordinate unit contains, in order to receive a transmitted data packet from an earlier station, an interface with the receiving unit, and for sending to the next station - an interface with the transmitting unit, with a processing unit located between the receiving unit and the transmitting unit that processes the data packet , transferred by the subordinated entity, i.e. it exchanges with the data packet user data related to the subordinated entity.

Ring communication systems with a master-slave configuration are organized in such a way that the master unit with slave units assigned to it forms a physical line, with the transmission center forming a two-wire structure, and each slave unit has two ports with one combined transceiver unit , while at the output port of the last slave unit in the transmission chain, the transmitting and receiving units are compact. The data packet, which is inserted into the first line by the sending unit of the master unit, is processed by the slave units in one direction, and the other line is simply sent back to the receiving unit on the return path.

The main requirement for a superior - subordinate communication system, in particular when used in the automation of production and processes, is a high tolerance to errors, as well as the ability of the communication system, despite the occurrence of errors, to perform the desired function, e.g. production of semi-finished products. Errors in the communication system, which must be tolerated without disrupting the process, are in addition to errors in data packets, in particular also caused by the loss of entire sections of the data bus, for example by physical intersection of the transmission medium.

In order to achieve a fault-tolerant master-slave communication system, in particular in the case of bus sections, i.e. when entire bus sections fall out, double-ring structures with counter-rotation are often installed. Such a master-slave communication system is described in US 4,663,748, in which the master unit is connected in series with numerous slave units by means of two counter-acting communication routes, the master unit sending the data packet simultaneously by both communication routes. The slave unit in this case contains two processing units that are switched on between two communication routes to process transmitted data telegrams. In addition, subscribers include activated coupling units to ensure that in the event of a route error, e.g. interruption of the communication connection, by monitoring the signals in both transmission rings and appropriate switching, so that the configuration of the communication system is changed so that the cut-off of the large sections of the communication system, resulting from an error, can be avoided, or even completely turned off.

DE 103 12 907 A1 proposes the organization of a subordinate unit that in each communication route in the direction of data transmission, first there is a processing unit, and then a multiplexer with two inputs and one output. The multiplexer is connected with its inputs to both processing units of the subordinate unit, and with its output it is connected to the assigned communication route. During normal, smooth operation, each of the two multiplexers switches the given processing unit to its assigned communication route. During emergency operation, when route errors occur in the assigned communication route, the processing unit is switched to the second communication route. This organization of the subordinate unit enables reconfiguration of the communication system in the event of disturbances, in principle in real time.

Error-tolerant master slave communication systems with a double-ring configuration in which individual slaves contain two processing units for processing transmitted data telegrams, increase the number of devices and switches in slave units, and thus increase costs. In addition, each slave must, in normal operation, decide which of the two data packets sent by the two processing units should be used to control the device, which, at the high speed required for data transfer, greatly limits the performance of such a communication system. At the same time, in the case of known fault tolerant communication systems with double ring topology, it is required that the parent unit react separately to the route error and switch from normal operation to emergency mode.

From the description of US 2004/0008719 a master is known for a master communication system - slave with the features given in claim 1 and a way of working the master communication system - slave with the features given in general claims 9. A communication system with error tolerant double ring configuration is further disclosed in US 4,527,270, EP 0 605 795 A2 and GB 2 348 782, as well as in EP 1 271 854.

The purpose of the invention is to provide a master unit for a master - slave communication system and a method of operation of a slave master communication system, which, with a minimum cost of equipment and switches in the master unit, allow obtaining real reconfiguration means in the event of faults occurring in error tolerant double ring topology.

This object is achieved by means of a master unit according to claim 1 and a method according to claim 9. Preferred embodiments are set out in the dependent claims.

According to the present invention, a station in a communication system with a plurality of stations that are connected to one another, a first communication route and a second communication route, said communication lines operating in opposite directions in a double ring, is constructed in such a way that the station includes a receiving unit for each communication route, used to receive information signals from the assigned communication route and the sending unit, used to transmit information signals assigned to a communication route. In addition, a single processing unit is provided, including input and output, intended for processing the information signals transmitted by the station, as well as an activated coupling unit. Said activated coupling unit connects during the normal operation the first receiving unit and the first transmitting unit assigned to the first communication route, wherein the processing unit is switched on for processing the transmitted information signals, with the second route of the communication configuration route assigned to the second route and the second transmitting unit . In the event of an error of the first transmitting unit and / or the second receiving unit, i.e. in the event of a route error for the station, the activated coupling unit connects the first receiving unit to the second transmitting unit via the processing unit, and in the event of the first receiver unit and / or second sending unit, i.e. again in the event of a route error for an adjacent station, the second receiving unit is connected to the first transmitting unit by a processing unit.

With this design of the station in a fault tolerant communication system with double ring topology, you can, in the event of route errors for neighboring stations in one or both communication routes, perform real-time reconfiguration of the station and, despite route errors, obtain interference-free operation. The operation of the station, and thus the operation of the communication system to which the station is connected, can be obtained in this way, despite route errors. The design according to the present invention has the advantage that only one processing unit is provided in each station, which reduces the number of devices and thus the costs. In addition, the station's behavior in the event of redundancy, also in the event of route errors, does not differ from the behavior during normal operation, as the transmitted information signals are still interpreted and processed by the existing processing unit. This also ensures high dynamics when switching, as well as limiting real-time requirements imposed on the communication system.

It is advantageous to make the activated subscriber coupling unit in the form of a first multiplexer whose first input is associated with the first receiving unit, whose second input is associated with the second receiving unit, and whose output is associated with the processing unit and the second multiplexer, whose first input is associated with a second receiving unit, whose second input is associated with the processing unit and whose output is associated with the second transmitting unit, whereby the first multiplexer in its normal operation connects its first input to its output, and in case of erroneous operation of the first receiving unit and / or the second transmitting unit, it combines its the second input with its output and the second multiplexer in the case of normal operation connects its first input with its output, and in case of erroneous operation of the first transmitting unit and / or the second receiving unit, it connects its second input with its output.

The design of the activated coupling device according to the present invention with two 2-1 multiplexers that connect to the processing unit on one or the other side thereof ensures, in the event of an error, when a route error occurs that the information signal is still transmitted by the station that the information signal after transmission by the processing unit, it is returned. Installing 2-1 multiplexers involves only a small expansion of the equipment and allows a simple and highly dynamic way to switch between normal and emergency operation.

According to the present invention, the master unit in a communication system of the slave master configuration, which includes a plurality of stations as slave units, is constructed so that the slave units are connected in series with the master unit by the structure of a counter-acting double ring formed from the first and second communication routes . The design of the master unit comprises a transmitting and receiving unit assigned to each communication path, the transmitting units being associated with a transmitting control unit and the receiving units being associated with a receiving control unit. The transmission control unit forwards the information signal with the data field and the counter field, with a set value, to both the transmitting units of the master unit to a separate, upward and downward communication path.

each station's processing information, value, value fields. The control unit then uses the values ​​of the counter fields of the information signals received by both receiving units from the first and second communication routes.

According to the innovative design of the communication system, the master unit can easily keep it free in the communication system when reconfiguring the transmission system

Units during the transmission of meters with signals determined from interference, especially the transmission of communication after the occurrence of route errors.

After analyzing sent identical counter fields following the opposite directions of information signals, find out how many receiving both communication units, the master unit can work from among the connected slave units. The processing units of active subordinate units change namely the values ​​of the counter fields in transmitted information signals by means of their processing units, as a result of which, when analyzing the counter fields of both information signals received by the master unit, the functionality of the subordinate units can be determined. By correlating the values ​​in the counter fields of both received information signals, it can also be determined between which stations a route error occurred or whether or where the station is completely excluded.

Preferably, the analysis of the counter fields of both information signals transmitted on the first and second communication routes is performed by adding the value of the counter fields. The sum immediately indicates whether all connected subordinated units are active, as their number is reflected in the sum value.

According to the present invention, the communication tolerance for errors is simply increased due to the fact that in read mode, i.e. when the slave units should send data to the master unit, the transmission control unit in the master unit sends an information signal to both transmitting units a data field which, for each station connected to the communication system, contains a data fragment assigned to it. Both information signals are then separated and counter-transmitted by the first and second communication routes, whereby the station, when transmitting information signals, stores the assigned data fragment. The master receiving control unit then compares the data fields of both information signals received from the first communication route and the second communication route.

Using this procedure, the functionality of the communication system easily ensures reliable operation, in particular also in the case of redundancy, as well as when the communication system has been reconfigured as a result of route errors and individual stations have been switched to emergency mode. By comparing the data fields of both received information signals, i.e. in particular by subjecting them to the logical operation "or", namely a combined data field is obtained, which shows whether the information signals returning via communication routes to the master unit contain all the data transmitted to them by the stations. The procedure according to the invention thus makes it possible to easily obtain a large tolerance of errors, in particular in the case of route errors in double-ring topology. Still, the way of using the master unit after reconfiguration does not differ from the normal work case.

The invention will be explained with reference to the attached drawings. Wherein:

Figure 1 schematically shows a communication system according to the invention with a superordinate structure, whereby

Figure 1A illustrates normal operation

Figure 1B shows the first reconfiguration of the communication system after a double route error occurred, while

Figure 1C shows the second reconfiguration of the communication system after excluding one slave unit, while

Figure 2 schematically shows a station according to the invention.

In the automation technique, fieldbus systems are increasingly used, thanks to which distributed peripherals can communicate with automation, engineering and visualization systems. Fieldbus systems are basically a serial bus, which can be, for example, an electric cable, optical fiber or radio link. All fieldbus stations are connected to the fieldbus, with the stations being active and passive. The active stations in the fieldbus system are master units that generate data transmissions on the bus. Such a parent unit is, for example, an industrial computer that works as a process controller in production procedures. The master has bus access permission and can transfer data to the fieldbus without external commands. Passive bus stations in the bus system are peripheral devices, for example, input / output devices, valves, drives and measuring transducers. They serve as slave units and do not have bus access rights, i.e. they can only confirm receipt of information signals or transmit information signals at the request of the superior unit.

As a communication standard for data transmission in a master - slave type system, the Ethernet concept can be used in particular. In the Ethernet communication system, the transmitted data are placed in a specific format in data packets, also called telegrams below. At the same time, Ethernet telegrams can reach a data length of up to 1500 bytes, but in addition to the user data, they contain control data forming the origin, destination and source address, data packet type and error correction mechanism.

Ethernet communication systems with a master-slave type structure are preferably constructed in such a way that individual slave units are connected by means of a transmission medium into a chain, with each slave unit connected to two neighbors, with the first and last stations in the chain connected to the unit superior so that a ring structure is obtained. The data is transferred from the master unit to the first neighbor slave unit, from it to the next, up to the last slave unit, and then back to the master unit.

In order to ensure high tolerance for errors, in particular in the event of a route error in the communication system, i.e. when all slave units, cable are excluded, the communication system with a transmission section with e.g.

Counter-rotating due to the counter-rotating units of the ring.

In the event of a double-ring structure, it is possible to reconfigure the communication system in the event of route errors to maintain the functionality of the communication system despite the route error.

Figure 1 shows a schematic diagram of such a fault tolerant communication system in an embodiment of the invention. The communication system contains one master 1, which is connected in series with N slaves 3 by means of a double ring structure 2. The structure of the double comprises two unidirectional communication routes 21, 22, which run in opposite directions through the attached slaves 3. The master unit 1 is connected to the first communication route 21 as a station sending data via the coupling circuit by means of the first transmission unit TX11, and by means of the second transmission unit TX12 is connected to the second communication route 22 as the station sending data via the coupling circuit. In addition, master 1 includes a first receiving unit RX13 as a station receiving data via the coupling circuit from the first communication route 21 and a second receiving unit RX14 as a station receiving data via the coupling circuit from the second communication route 22. The first transmitting unit TX11 and the second transmitting unit TX12 are, via the first control link 15, connected to the broadcast control unit 16. The first receiving unit RX13 and the second receiving unit RX14 are connected to the receiving control unit 18 by means of the second control link 17.

Each slave 3 contains, for receiving telegrams from the previous station, the first communication route 21, an interface with the first receiving unit RX31, and for sending telegrams to the next station, the first communication route 21, an interface with the first transmitting unit TX32. In addition, each slave 3 includes, for receiving Ethernet telegrams sent on the second communication route 22 from the previous station, an interface with the second receiving unit RX33, and for sending telegrams to the next station, an interface with the second transmitting unit TX34. Between the first receiving unit RX31, the second receiving unit RX32, the first transmitting unit TX33 and the second transmitting unit TX34 is connected in each slave 3 the processing unit 35 and the coupling device 37 activated.

The schematic diagram of the slave 3 is shown in more detail in Figure 2. In the slave 3, the first receiving unit RX31, which is connected to the first communication route 21 and the second transmitting unit TX34, which is connected to the second communication route 22, are grouped as Port 0 . The second receiving unit RX33, which is attached to the second communication route 22, and the first sending unit TX32, which is attached to the first communication route 21, are organized as Port 1.

The activated coupling device 37 has a first switch 38 and a second switch 39 that are connected as a 2-1 multiplexer. The receiving and transmitting units 31, 32, 33, 34, the multiplexers 38, 39 of the activated coupling device 37 and the processing unit 35 are connected to each other, as shown in Figure 2, by an energy network 40.

The output of the first receiving RX31 unit is connected to the first input of the first multiplexer 38. The second input of the first multiplexer 38 is connected to the second unit of the multiplexer 38 processing 35 receiver RX33

The output of the first unit is further connected to the Second multiplexer 39 is connected by the first input to the second receiving unit RX33, and the second input to the output of the processing unit 35. The output of the second multiplexer 39 is connected to the second transmitting unit TX34. In addition, the output of the processing unit 35, via the power network 40, is connected to the first transmitting unit TX32.

During the interference-free, normal operation of the communication system, as shown in Figure 1A, the transmit control unit 16 of the master unit transmits a telegram to the first TX11 sending unit and the second TX12 sending unit, which is then sent in opposite directions by the first communication route 21 and the second communication route

22. Slave telegrams pass 3, when activated identical by the attached units, all activated coupling devices 37 in the slave units 3 are so switched on that the input of the processing unit 35 is connected to the first receiving unit RX31, the output of the processing unit 35 is connected to the first sending unit TX32, and the second RX33 receiving unit is connected to the second TX34 sending unit.

In this mode of operation of the slave unit 3, the coupling device 37 ensures that the messages circling in opposite directions of the first communication route 21 and the second communication route 22 are so forwarded by the slave unit that only the telegram sent on the first communication route 21 is processed by the processing unit 35. The telegram sent via the second communication route 22 is only forwarded by the slave 3 and reaches the master 1 unprocessed again. Both telegrams circulating in opposite directions of the first and second communication routes 22 are recognized by the first receiving unit RX13 and the second receiving unit RX14 of the master unit 1 and are transmitted to the receiving control unit 18 for analysis by the second control link 17.

In the embodiment of the invention, the activated coupling device 37, consisting of both 2-1 38, 39 multiplexers is also controlled such that from both identical telegrams that circulate on both communication routes 21, 22 simultaneously, but in opposite directions, always only the telegram from the first communication route 21 is processed by the processing unit 35 of the slave unit. The telegram sent via the second communication route 22 is used for redundancy purposes and is returned unchanged to the parent unit 1.

The communication system according to the invention, having a structure of the type in which the parent unit - slave connected to the unit - is subordinated in series to the master by two counter-acting double-ring structures, with only one processing unit 35 provided in each slave 3, in case of interference, ie. in the event of route errors, it is possible to reconfigure the communication route in individual subordinate units in order to preserve the functionality of the entire communication system.

Figure 1B shows a double route error between slave M and slave M + 1. Figure 1C shows the complete exclusion of slave unit M, which is equivalent to two double route errors, between slave unit M-1 and slave unit M and between slave unit M + 1 and slave unit M. In the event of such a double route error, the activated coupling devices 37 in the slave units 3 are controlled in such a way that the telegram sent by either the first communication route 21 or the second communication route 22 is returned by a different communication route to the master unit 1, whereby the telegram passes earlier by the processing unit 35 slave 3.

In the case of the double route error shown in Figure 1B between slave unit M and slave unit M + 1, switching is carried out so that slaves 1 to M-1 and M + 2 to M operate in normal mode, and slaves M and M +1 is reconfigured. In the case of the error shown in Figure 1C, as a result of which slave unit M is completely excluded, slaves 1 to M-2, and slave units M + 2 to M operate in normal mode. Slave units M-1 and M + 1 are reconfigured.

The reconfiguration is preferably carried out by both ports 0 and 1 of the slave unit 3. Both ports 0 and 1 check using a known method of checking whether the slave unit can communicate with the neighboring slave unit. When a route error is detected by Port 0 or Port 1, appropriate operation in emergency mode is performed and the activated coupling device 34 of the slave unit is controlled accordingly.

In the event of a Port 1 emergency operation, as in the case of the double route error shown in Figure 1B in slave unit M or in the case of the device exclusion shown in Figure 1C in slave unit M-1, the activated coupling device 37 is controlled such that the input of the processing unit 35 is connected to the first receiving unit RX31 and the output of the processing unit 35 is connected to the second transmitting unit TX34. The telegram sent via the first communication route 21 is then returned by the processing unit 35 via the second communication route 21. In the system of the activated coupling device 37 shown in Figure 2, the slave 3 with the first multiplexer 38 and the second multiplexer 39 switches so that the second input of the second multiplexer 39 is connected to the multiplexer output. The first multiplexer 38 remains in the normal operating mode.

In the event of emergency operation of Port 0 in subordinate unit 3, i.e. when the first receiving unit RX31 and / or the second transmitting unit TX34 detected a communication route interruption with the neighboring slave, which occurs in the double route error shown in Figure 1B in the slave unit M + 1 and in the case of the device exclusion shown in Figure 1C +1, the coupling device 34 activated is controlled in slave unit 3 in this way, that the input of the processing unit 35 is connected to the second receiving unit RX33 and the output of the processing unit 35 is connected to the transmitting TX32 so, communication 22, the first unit that the telegram transmitted on the second route after processing by the processing unit 35 is routed the first communication route 21 back to the unit parent 1. In the embodiment of the activated coupling device 34 shown in Figure 2, there is a switch such that the first multiplexer 38 connects its second input with particular output processing, while the second multiplexer 39 remains in the normal operating mode.

In the method of operation according to the invention, it is therefore possible to obtain in a simple way in a slave unit with only one processing unit, in cooperation with the structure of the double ring and the activated coupling device, reconfiguration means in the communication system, in order to ensure the functionality of the communication system in the event of a route error, operation of subordinated entities, regarding the processing of telegrams in the case of redundancy is no different from normal operation.

The method of operation according to the invention makes it possible to detect, in addition to the double route errors shown in Figures 1B and 1C, at which both communication routes are interrupted in a section to the neighboring subscriber, also a single route error at which only one communication route is interrupted and by means of appropriate reconfiguration of the neighboring station with error location, maintaining the functionality of the communication system.

In slave units 3, only single processing units 35 are also envisaged, so that compared to slaves with two processing units, it is not necessary to decide which processing unit is appropriate for processing the telegram.

In order to obtain a high tolerance for communication system errors with a small development of the equipment, also in the master unit 1, the telegrams sent in the opposite direction via the first communication route 21 and the second communication route 22 are implemented in such a way that the processing in the case of interference-free normal operation does not differ significantly from emergency work, in which the functionality of the system also constructed in the possibility of communication with route errors is preserved by reconfiguration of individual slave units. A subordinate unit can be an innovative way. There are, however, installations of subordinate units of a different design that can be used as part of a subordinate master with a double ring configuration.

According to the present invention, at the master 1, both telegrams received at the master 1 by the first receiving unit RX13 from the first communication route 21 and by the second receiving unit RX14 from the second communication route 22 are forwarded to the receiving control unit 18 to form a single telegram. This is preferably done so that the user data of both telegrams are binary subjected to the logical operation "or".

In addition, if the telegrams contain counting fields among the control data, their values ​​are used, preferably they are added together to assess the operational state of the communication system, in particular the occurrence of route errors. This is carried out in accordance with the invention so that the transmission control unit 16 of the master unit 1 transmits to the first TX11 sending unit and the second TX12 sending unit an identical telegram with the data field and the counter field each time, with a set value set, for separate, backward transmission via the first communication route 21 and the second communication route

22. The processing unit 35 of each connected processing unit 3 is further constructed in such a way that when transmitting telegrams, the value is changed by a certain value.

the reception 18 analyzes the values ​​of the counter fields of both telegrams received by the first receiving unit RX13 from the first communication route 21 and by the second counter field is in the control unit the receiving unit RX14 from the second communication route 22. Based on the values ​​of both counter fields, it can be easily determined , whether all slave units connected are active.

Preferably, it is possible that the counter telegram counter field is set to 0 for reverse transmission, and each processing unit 35, when transmitting the telegram by slave 3, increases the counter field value by 1. Because by performing the station according to the invention, both during normal operation and during emergency operation after reconfiguration of station connections, only one telegram is still processed by the processing unit, the sum of the count fields of both telegrams returned to the master 1 provides the number of active stations. Thus, it can be determined whether all attached stations are active or whether station exclusion has occurred, for example as a result of double occurrence of a double route error, as shown in Figure 1C. In addition, by comparing the values ​​in both counter fields, based on the known number of slave units connected, the exact location of the route errors can be determined, e.g. between slave unit M and slave unit M + 1 in Figure 1B.

The error-tolerant operation of the communication system, in particular also during reconfiguration of the communication system by changing the signal path in stations when route errors occur, is further achieved by the fact that both identical telegrams, transmitted in the opposite direction by the first communication route 21 and the second communication route 22, are constructed in such a way. that a data range is assigned in the user data field of each connected slave unit. The processing unit 35 of each slave 3 performs with the sent or emergency all units in the assigned data. The control unit receiving the logical operation with the telegram data exchange in the assigned data fragment. In the receiving control unit 16 of the master unit 1, the user data fields of both telegrams received by the first receiving unit RX13 from the first communication route 21 and by the second receiving unit RX14 from the second communication route 22 are superimposed on each other so that a common telegram is created. The resulting telegram is always the same, regardless of whether the communication system is operating normally, the occurrence of route errors, as long as slaves 3 are still active.

When reading, when the slave units 3 should send data to the master unit 1, the transmission control unit 16 of the master unit 1 sends the first control link 15 to both transmission units TX11, TX12 a telegram, which contains the value 0 in the whole field. The processing units of 35 slave units 3 then save the user data fragments of the required master 1 subject or "data fields" of both telegrams received by the first receiving unit RX13 from the first communication route 21 and by the second receiving unit RX14 from the second communication route to create a common telegram. Regardless of whether the communication system is operating normally or in reconfigured mode, the logically operated "or" telegram contains all data required by the master 1 from the connected slave 3.

In recording mode, when the master unit 1 through the first control link 15, can forward e.g. control commands to the slave units 3, the transmission control unit 16 of the master unit 1 transmits to the TX11, TX12 transmission units a telegram with a usable field that contains data to be transferred to subordinate units 3, for simultaneous, backward sending on both communication routes 21, 22. Processing units of 35 subordinate units then charge regardless of whether they work in reconfiguration.

assigned data from normal mode, logical operation

Submitting a telegram, whether after or "usable fields" of both telegrams returned to the master 1, received by the first receiving unit RX13 and by the second receiving unit RX14, is in principle no longer required. Such a logical operation "or" results in a joint telegram with a usable field that corresponds to the field of user data of the transmitted telegrams.

In the case of a master-assigned communication system according to the invention, the master unit has the option, with any construction of individual slave units, in particular, however, when the slave units are made and operate according to the invention, to maintain interference-free operation of the communication system, in particular also when reconfiguring the waveform in a double ring structure after a route error has occurred. In addition, in the communication system, also in the case of redundancy, as well as when individual stations in the communication system are switched to emergency mode, you can ensure reliable read and write operation by superimposing the user data fields of both returned telegrams.

EP 1 869 836 B1