DE10004425A1 - Network with subscriber device, esp. field device, enables transmitter, receiver transmission, reception time delays to be taken into account for time synchronisation - Google Patents

Abstract

The network has a first subscriber device for transmitting a first message for time synchronisation to a second subscriber device in which the physical transition time for the message over the physical transmission path between the subscriber devices is stored. The first message contains a time corrected by a transmission time delay for the first subscriber device and the second subscriber device measures the delay since receiving the first message and corrects the time received in the first message by the transition time and the receiver delay time.

Description

The invention relates to a network according to the preamble of Claim 1 and a network participant, in particular a Field device, for such a network.

Such a network is, for example, from the DE 197 10 971 A1 known. In a network with more number of network participants, for example sensors and Actuators using the network for data transmission interconnected, for time-critical applications, for example for simultaneous acquisition of measured values in the rule operations, a synchronization can be made. For syn Chronization of participants is done by one participant Telegram sent to the other participants, for example can be used as a simultaneous acquisition of measurements by certain participants. It is taken into account that in the transmission of Tele gram through times between sender and receiver the physical transmission link arise that under among other things by the distance and the physical transfer speed of the signals on the transmission medium be determined. So that runtime differences of Telegrams to different participants are not negative the synchronization accuracy will affect the run times automatically by a telegram sequence detected. Especially in networks, their topology and spatial expansion is variable, brings an automatic Determining lead time benefits. Changes can for example, occur when participants are only temporarily or can be connected to different locations. A possibility to synchronize the participants is that a Participant sent his time in a telegram to the others Participant transmits. The previously determined throughput time of the  Telegram is stored in the other participants. This correct the time received in the telegram by respective throughput time of the telegram and synchronize this way their internal clock to the time of day of the transmitter.

The invention has for its object a network as well a subscriber, in particular a field device, for a derar to create a network that is characterized by an improved Characterize accuracy with regard to time synchronization.

The new network instructs the to solve this task gangs mentioned in the characterizing part of the An claim 1 specified characteristics. A network participant, in particular a field device for such a network and advantageous embodiments of the invention are claimed 11 or described in the subclaims.

The invention has the advantage that a transmission time delay in the transmitter as well as a reception time delay in the receiver, which can be changeable in the time synchronization be taken into account.

For this purpose, a first network participant sends a first telephoto grams to a second network participant, which is the one Transmission time delay corrected time of the first network work participant contains. The second participant is the tele Gram transit time over the physical transmission path between the first network participant and the second network Worker saved as lead time. You can at for example, entered manually or by another Telegram traffic must have been measured beforehand. The second network Worker measures the time delay since receiving the first telegram and corrects those in the first telegram received time by the throughput time and the measured Reception time delay. The second network participant is thus advantageously able to synchronize at any time Time from the sum of the time received in the telegram  and the reception time delay supplemented by the transit time determine. Variable transmission and reception time delays do not affect the result of the synchronization.

If the second network participant is further trained to a second telegram for time synchronization to one to send third network participants, the one around the barrel time and the delay time between receiving the first Telegram and sending of the second telegram corrected received time contains an iterative continuation send the corrected time from the network part Participants to network participants possible. In the receiving Network participants can make identical corrections mechanisms are applied. Each in a network The saved runtime corresponds to the run time over the physical transmission path between the the last sending and the receiving network Attendees.

As an alternative to sending a telegram for time synchronization sation from a first network participant to a second can also do time synchronization with two telegrams respectively. For this purpose, the first network participant sends a first one Telegram for time synchronization to a second network participant and saves one at the same time time delay corrected time of the first network part customer. The runtime is in the second network participant of the telegram over the physical transmission path between the first network participant and the second network Workers saved. The second network participant measures the time delay since receiving the first telegram, but without stopping the timer. The first Network participants now send a second telegram that the time of the first corrected by the transmission time delay 3 network participants contains, to the second network participants mer. Corrected the time received in the second telegram the second network participant about the runtime and the  Reception time delay that is related to the reception of the first telegram is measured. This procedure with two Telegrams have the same advantages as with the Procedure for time synchronization with only one telegram are connected.

For a network with more than two network participants the procedure with two telegrams also in an itera tive process to be continued. The second leads Network participants send the first telegram to a third network participant and measures its delay time of the Telegram forwarding. The sends in a third telegram second network participants one about the runtime and the delays Delivery time of the forwarding of the first telegram corrected received time to the third network part participants.

The actual transmission is advantageous time delay in time synchronization when the first network participant has a first timer to determine the transmission time delay that he has at Enter a telegram in a list of send jobs starts and after the telegram to physika is provided transmission as the value of the transmission time delay reads by which to correct the time of the telegram entry is greed.

Likewise, the actual delay in reception during transmission sees if the second network participant a second Has a timer for determining the reception time delay, which he receives when receiving a first telegram from a physi calic transmission path starts.

The duration of the telegram via the physical transmission distance between the first network participant and the second network participant can be used as a starting value in the second  The timer must be saved before it starts. That has the Advantage that the sum of the transit time and the reception time delay can be determined by only one timer.

In further training, the start and end of the term can be of a telegram can be determined as the point in time to which a characteristic field of a telegram with fixed distance from the beginning of the telegram a media independent Interface of the first network participant leaves or in one Media independent interface of the second network participant enters. Measurements of the transmission time are advantageous here Delay, runtime and receive time delay independent on the length of the respective telegram.

The network components meet the ethernet, fast ether net or gigabit ethernet specification, so can be an advantage as the characteristic field of the telegram, the type field ver be applied. The second network participant is receiving the Type field known that it is a telegram acts, which is used for time synchronization, and it can the necessary mechanisms are put in place. The data field is located behind the type field and can be in the transmitter until the type field is output to the media Indepen dent interface can be changed. So it is possible already in the same telegram the time delay to transmit the corrected time.

The runtime of a telegram via the physical transmission distance can be determined exactly by the first Network participants receive a first telegram at runtime sends to a second network participant and one Response time timer after the telegram is provided physical transmission starts. The second network Participant starts after receiving the first telegram Runtime determination a timer to measure the stay time and stops the timer after providing a second Telegram for physical transmission to the first  Network participants. The measured stay time is in the second telegram to determine the runtime to the first network transfer participants. After receiving the second tele of the physical transmission stops the first Network participants the response time timer and calculates the Runtime of a telegram via the physical transmission distance as half the difference between the measured Response time and the time spent in the second part of the network participants.

A network participant, in particular a Field device with several ports, in particular four ports, for Connection of other network components. An interface, a so-called micropro processor interface, for connecting the ports with a participant internal processor bus and a control unit, a so-called called switch control, which is a tele routing between the ports and the microprocessor Interface. This has the advantage of being part of the network participants, in particular field devices, in which the user of Fieldbuses are boarded as usual in a line structure can be tet. A separate switch, like that of a star-shaped structure would be required. Insbeson with a network based on Ethernet, Fast Ethernet or Gigabit Ethernet specification is invented by the The construction of a network of large dimensions enables it to be single Lich the distance between two network components determined The length of the line structure must not exceed limits However, the structure is unlimited. It also has integration of switch functions in the network participants the advantage that especially with Ethernet the CSMA / CD access control can be deactivated and the network is a determinist behavior. The application area of the Network participants and the network on use cases expanded in which real-time behavior is required.  

If there are four ports on the network participants for connection other network components can be provided, part to a two- or three-dimensional network structure be interconnected, since these two ports are for integration the network participant in a line two more each used to connect the line to another line can be.

An execution of the cut realized by the ports according to the Ethernet or Fast Ethernet specification has the advantage that in the implementation, for example a field bus with such network components Technology knowledge already available from other areas can be used. You get one in this way end-to-end network for office, control, cell and field level, which provides transparent access to any data allows. A gateway for coupling network areas with different physics and different protocols is in advantageously not required. Also stand out Networks based on the Ethernet specification through a high performance of data transmission. they offer Cost advantages through a widely available technology and Components that are available in large quantities. It is possible a large number of network participants in a network to connect the plant. The advantages of the invention the preferred line or bus structure in the field Network, e.g. B. the advantage of a simple connection of the Participants, with the advantages of networks mentioned above based on the Ethernet specification according to IEEE 802.3 connected. The switch integrated in the network participants Functions take over the function of a previously separate installed network component, for example a switch, which is thus eliminated.

Another improvement in automation applications tion technology, especially when used in time-critical Applications, is achieved when the control unit of the  Switch function is designed such that a transfer priority of the telegrams to be sent evaluated and telegrams with high priority over telegrams with lower priority are sent.

A microprocessor to correct an internal clock based on in Telegrams received time information has the advantage that the time synchronization largely without additional Hardware effort can be realized.

Using the drawings, in which embodiments of the Invention are shown below, the invention as well as configurations and advantages explained in more detail.

Show it:

Fig. 1 shows a communication structure of a technical system automation,

Fig. 2 is a block diagram of an interface of a network subscriber,

Fig. 3 is a series connection of network devices with line-shaped network topology,

Fig. 4 is a series connection of network devices with two communication channels,

Figure 5 participants. A two-dimensional interconnection network,

Fig. 6 is a two-dimensional interconnection with redundant design,

Fig. 7 is a two-dimensional network after redundancy management,

Fig. 8 is a three-dimensional network after redundancy management,

Fig. 9 shows the basic structure of a telegram and

Fig. 10 shows the structure of a job list.

Fig. 1 shows the structure of a communication structure in an automated system. Communication takes place consistently at the control, cell and field level through a network, the data transmission of which complies with the Fast Ethernet standard according to IEEE 802.3u. At the field level, a sensor 1 , for example a pressure transducer, a sensor 2 , here an ultrasonic flow transducer, an actuator 3 , a control valve for setting a flow, and a programmable logic controller 4 with twisted-pair lines 5 , 6 and 7 are bus-shaped connected. The memory programmable controller 4 forms together with the two sensors 1 and 2 and the actuator 3, a control circuit in which the position of the control valve is predetermined depending on the measured values of the pressure transducer and the Durchflußmeßumfor mers. The programmable logic controller 4 is connected to a switch 9 via a twisted pair line 8 . A cell computer 10 , a master computer 11 and a firewall 12 , with which a secure Ethernet access is implemented, are also connected to the switch 9 in a star-shaped topology. With a line 13 further, in the figure for clarity not shown cell computers of neighboring cells of the automation system are connected to the switch 9 . The example shown in FIG. 1 shows in particular the advantage of high data transparency across all levels. The same transmission standard is used for the control, cell and field level. The field devices 1 , 2 and 3 are connected to the programmable logic controller 4 in a linear topology in the manner familiar to the user. Another advantage is the consistent use of uniform addresses for the individual network participants. An address implementation, as would be required when using different standards in the different levels, can be omitted in the new network and the new network participants in an automation system.

FIG. 2 shows the basic structure of the communication interface of a network participant, for example sensor 2 in FIG. 1. Application-specific circuit parts, such as, for. B. a mechanical-electrical transducer element, a device for signal preprocessing and a voltage supply are not shown for reasons of clarity. The parts summarized in a rectangle 20 can be integrated in an ASIC (Application Specific Integrated Circuit). Communication with the application-specific circuit parts of the network participant takes place via a microprocessor bus 21 , to which a RAM 22 , a microprocessor 23 and a microprocessor interface 25 are connected. With broken lines is indicated in the presen- tation of the microprocessor 23 that the integration into the ASIC is optional. Its functions could be taken over by an external processor. The task of the microprocessor 23 is to execute user programs and communication functions, for example the handling of TCP / IP. Another task can be the management of send and receive lists of telegrams of different priority in the external RAM 22 . The microprocessor 23 selects an order 3 from a transmission list in the external RAM 22 and starts a DMA controller 26 , which is referred to as DMA 1 control, via a microprocessor interface 25 after having previously entered the number of the DMA controller 26 data bytes to be sent and a pointer that points to the data byte to be sent. If the send job is completely transferred into a transmit buffer 27 by the DMA controller 26 , the microprocessor 23 removes this send job from the send list in the RAM 22 and processes the next send job if the send list is not empty and in the transmit buffer 27 free space is still available.

Four Ethernet controllers 28 , 29 , 30 and 31 are also integrated in the ASIC 20 . Each of these Ethernet controllers enters the data bytes of a completely received telegram via a multiplexer 32 , a DMA controller 33 , which is also referred to as DMA 2 control, and the microprocessor interface 25 in a reception list in RAM 22 . The microprocessor 23 accesses the reception list and evaluates the received data in accordance with an application program.

The microprocessor interface 25 forms the essential interface between the Ethernet controllers 28 . , , 31 and the microprocessor bus 21 . It controls or arbitrates the write and read accesses that are made to the RAM 22 via the DMA controller 33 or the DMA controller 26 . If both DMA controllers 26 and 33 have DMA requirements at the same time, the microprocessor interface 25 decides on the access rights of the two DMA channels. Via the micro processor interface 25 , the micro processor 23 can continue to write parameter registers 34 , which are necessary for operating the communication interface of the network participant. Examples are a pointer to the start of the high-priority memory area in a transmit buffer of an Ethernet controller, a pointer to the start of the high-priority memory area in each of the receive buffers of the Ethernet controller, an operating mode register for general control bits, an address of the Series to which the network participant belongs, called a cycle time for so-called port select telegrams and settings for various monitoring time intervals.

The transmit buffer 27 has a size of more than three kilobytes and is divided into a memory area for high priority and a memory area for low priority telegrams. The ratio of the two memory areas can be parameterized. The memory areas of the transmit buffer for high and low priority data are each implemented as a ring buffer. When the data is sent from the transmit buffer 27 via one or more Ethernet controllers 28 . , , 31 is started when the number of bytes entered in a telegram is greater than the parameterizable fill level, or when a complete telegram has been copied from the RAM 22 into the transmit buffer 27 and at least one Ethernet controller 28 . , , 31 is free for broadcasting.

The ethernet controller 28 . , , 31 are constructed identically. Their structure is explained in more detail using the example of the Ethernet controller. A device 40 , which is referred to as Trans with Control, contains a control unit which is responsible for sending telegrams, for repetitions, sending abort, etc. It forms the interface between the internal controller clock and the send clock. A transmit status register is provided in the device 40 for storing transmit status information for low-priority and high-priority telegrams. If a telegram was sent without errors via the port, an appropriate interrupt is generated.

A Media Independent Interface 41 (MII) integrates the MAC sublayer of layer 2 according to the seven-layer model, ie the data link layer. This forms an interface to a module 36 for physical data transmission. The MII 41 also contains a transmit function block 42 and a receive function block 43 . In addition, a MAC control block, not shown in FIG. 2, an address filter, a statistics counter and a host interface are integrated. Control and configuration data can be transmitted to the module 36 and status information can be read from it via the media-independent interface. The individual functions of the transmit function block 42 are: mapping of the bytes to be sent, detection of collisions in half-duplex operation and execution of a back-off algorithm, provision of transmit status information to the device 40 after a send operation has ended , Compliance with the idle time inter-packet gap (IPG) between two telegrams, supplementing the send data with a preamble, a start-off-frame delimeter (SFD) and a parameterizable cyclic redundancy check word (CRC), filling a telegram with pad bytes, if the telegram length would be <60 bytes, and abort of a send process on request.

The receive function block 43 makes the received bytes available to a device 44 , which is referred to as receive control. The receive function block 43 recognizes the start-of-frame delimeter and a VLAN frame. It checks the length field and the CRC word in telegrams. After the reception process has ended, receive status information is made available to the device 44 . Block 43 recognizes and removes preambles and start-of-frame delimeters in the case of telegrams. If the free memory space in a receive buffer 45 of the Ethernet controller 28 falls below a predetermined threshold in full duplex mode, the MAC control block sends a pause control telegram for flow control via the module 36 . This telegram causes the connected network subscriber to send no data telegrams to the Ethernet controller 28 until the time interval sent with the pause control telegram has expired. The address filter carries out a telegram filtering according to unicast, multicast and broadcast addresses. To do this, the target address (DA) received in a telegram is compared with filter addresses. The statistics counters store statistical information about send and receive operations. The host interface allows access to parameter registers and statistics counters of the Ethernet controller 28 by the neighboring network participants.

The device 44 contains a control unit which is responsible for receiving telegrams. It forms the interface between the internal clock of the Ethernet controller 28 and the receive clock.

The receive buffer 45 has a size of more than 3 kilobytes. It is divided into a memory area for high priority and a memory area for low priority telegrams. The ratio of the two memory areas can be parameterized. The memory areas are each implemented as a ring buffer.

The DMA controller 33 controls the DMA transfer from one of the receive buffers in the Ethernet controllers 28 . , , 31 to RAM 22 . The DMA transfer begins when in one of the receive buffers, for example in receive buffer 45 , the number of data bytes received has reached a parameterizable minimum fill level or a telegram has been completely received. At the same time, this receive buffer must be selected for the DMA transfer by a module 46 , which is referred to as switch control.

The device 40 is preceded by a multiplexer 47 which is controlled by a control unit 46 , which is referred to as switch control.

Switch control 46 controls the forwarding of data between the ethernet controllers 28 . , , 31 and the storage of received data if it is intended for the respective network participant. Since the application of the invention is not limited to networks according to the Ethernet specification, the Ethernet controllers 28 . , , 31 hereinafter also generally referred to as port 1, port 2, port 3 or port 4. Which ports are released for forwarding received data depends on the network structure in which the subscriber is integrated. Switch-Control 46 controls the following actions as a function of the operating status, the network structure, the received destination address and the telegram priority:

• - If the received destination address is the same as the subscriber's own subscriber address, the received telegram is transmitted via the microprocessor interface 25 into the RAM 22 without forwarding it to other ports.
• - If a broadcast telegram is received at one port, the telegram is transferred to RAM 22 and made available to the other released ports for transmission.
• If a telegram with a multicast address is received at a port that matches one of the multicast addresses stored in a filter table 48 , the telegram is transferred to RAM 22 and made available to the other released ports for transmission.
• - If the destination address received is different from your own Subscriber address and the multicast addresses, so it will Telegram to the other released ports for sending made available without deducted for further processing to be saved.
• - In the case of telegrams with so-called VLAN bytes, for example, eight priority levels are available. Stand If several telegrams are to be sent simultaneously, the transmission order of the telegrams according to their Transfer priority set.
• - In an operating mode monitor mode, all telegrams that meet the parameterized filter conditions are transferred to RAM 22 .
• - The telegram forwarding taking into account a modified spanning tree algorithm.

Switch control 46 contains further parameters, the meanings of which will be explained in more detail later: a row address R _P3 , which corresponds to the row connected to port 3, a row address R _P4 , which represents the address of the row connected to port 4, a number N _{R1 of} the transmission paths up to port 1, a number N _{R2 of} the transmission paths up to port 3, a value | N _R1 - N _R2 | _{S of} the respective network participant, a value | N _R1 - N _R2 | _Sender from the sender of a received port select telegram, an amount | N _R1 - N _R2 | _min as the smallest value received so far, a source address A _{sender of} a received telegram, a source address A _{Stored of} the telegram with the smallest value of amount | N _R1 - N _R2 | _min , a best received combination (Root_ID.Cost.Transmitter_ID.Port_ID) _P3 for port 3 , a best received combination (Root_ID.Cost.Transmitter_ID.Port_ID) _P4 for port 4, a best received combination (Root_ID.Cost.Transmitter_ID.Post_ID ) _{R of} the series, a message interval counter for a cycle time of port select telegrams, a timeout counter for a timeout interval on port 1, a timeout counter for a timeout interval on port 2, a timeout Counter for a timeout interval on port 3, an active time counter for a time interval that begins with the last receipt of a port select telegram on port 4, a combination aging counter for a maximum time interval within which a configuration telegram must be received, otherwise the stored combination Root_ID.Cost.Transmitter_IC.Port_ID is deleted, a counter for a time interval Δt _rowdelay , after which a port 3 of a row switches from inactive to active tet that corresponds to twice the worst case throughput time of a port select telegram through the series, and a counter for a time interval Δt _netdelay , after which a port is switched from potentially active to active and which is twice the worst case throughput time a configuration telegram through the network.

The user can enter multicast and virtual LAN identification addresses, so-called VLAN addresses, in the filter table 48 . A multicast or VLAN telegram is only accepted if the received address matches one of the addresses in the filter table 48 .

A device 50 for redundancy control is intended to ensure in a network that detected physical errors do not impair communication between the network components. On the one hand, there is redundancy within each row formed with network participants. To do this, the network participants connected in series must form a ring that is open at one point in the event of a fault, but can be closed in the event of an error. On the other hand, redundancy with several communication channels between the rows is possible. To do this, a number of network participants must be connected to an adjacent row via at least two ports. Only one communication channel is active between two rows at a time, ie data telegrams are only exchanged via this communication path. If an active communication channel between two rows is identified as faulty, it is deactivated and switched to another communication channel. In order to implement the redundancy, a cycle time register with a parameterized cycle time for test telegrams, a cycle time counter for generating a cycle time interval, a control unit for switching over to a redundant communication channel and for initiating sending of so-called link-up are implemented in the device 50 or link-down telegrams, a row runtime register with a parameterized worst case throughput time of a telegram through a row and a row runtime counter are used to generate a row runtime.

Certain events are communicated to the microprocessor 23 via a device 51 for interrupt control, which is also referred to as interrupt control. These are essentially messages from telegrams sent or received and error messages. The device 51 contains an interrupt request register, an interrupt mask register, an interrupt register and an interrupt acknowledge register. Every event is stored in the interrupt request register. Individual events can be suppressed via the interrupt mask register. Only events that are not masked by the interrupt mask register appear in the interrupt register. In contrast, the entry in the interrupt request register is independent of the interrupt mask in the interrupt mask register. Bits in the interrupt request register can be reset with write access to the interrupt acknowledge register. A module 52 contains special user functions which are to be integrated in the communication interface of the network participant. A partial function is implemented with a module 53 for time synchronization, another with a module 54 for equidistance, which will be explained in more detail later. A delay timer 1 to 4 with the reference symbols 57 , 58 , 59 and 60 is provided for each of the ports 1 to 4, which determines the transmission time between the respective network subscriber and the network subscriber connected via the respective port. The respective delay timer is also used as a lead time timer (DLZ timer) for the respective port. Furthermore, an equidistance timer, an auxiliary timer for a transmission time Δt _i via the respective port and a parameter Δt _DLZ are provided for each port, which are the sum of the throughput times in the send and receive direction and the cable runtime between the communication interface and the network participants connected via the respective port. There is also a local clock 37 in the network subscriber, the time of which can be read and set via the microprocessor bus 21 .

An integrated serial-peripheral interface (SPI) 55 is a simple but powerful serial bus system for connecting peripheral components, e.g. B. EEPROMs. An integrated I / O interface 56 is a parallel interface with 12 configurable inputs and outputs. LEDs for status display can be controlled via this interface, for example.

Each port of the communication interface can be parameterized bar can be operated in half-duplex or full-duplex mode. While half-duplex mode is set on a port, can be simultaneously on another port of the full duplex mode be parameterized. In full duplex mode you can simultaneously Telegrams are sent and received. In half duplex mode is this not possible.

An application-specific application program, which can be stored on the RAM 22 , for example, enters data to be sent in an order list in the RAM 22 . The DMA controller 26 copies data from this job list into the transmit buffer 27 . Compiled telegrams are sent to the released Ethernet controller 28 . , , 31 passed on. If a transmission conflict occurs because other telegrams are currently being routed through the communication interface, controlled by switch control 46 , the transmit buffer 27 should be able to store two complete Ethernet telegrams. Sending the data from the transmit buffer 27 begins when a number of data bytes to be parameterized or a complete telegram has been transferred from the RAM 22 to the transmit buffer 27 and at least one Ethernet controller is free. The telegram remains stored in the transmit buffer 27 until it is via all released Ethernet controllers 28 . , , 31 was sent. The number of data bytes of a telegram, which must be stored in the transmit buffer 27 at least before being sent, must be parameterized so that the telegram is sent without gaps. Otherwise the telegram will be received incorrectly by other network participants. If telegrams of different priority are stored in the transmit buffer, the telegrams are sent according to their transmission priority.

FIG. 3 shows an example of an interconnection of three network participants 61 , 62 and 63 in a linear structure. For better clarity of the representation, the ports 1 to 4 of the communication interface of the network participants 61 , 62 and 63 are divided into circuit parts T1 to T4 for the transmission direction and circuit parts R1 to R4 for the reception direction. For example, port 2 can also be referred to as port T2 / R2. For a linear structure, port T2 / R2 of network participant 61 are connected to port T1 / R1 of network participant 62 and port T2 / R2 of network participant 62 to port T1 / R1 of network participant 63 in the manner shown. The data transmission takes place with a twisted pair cable for each direction of transmission. The ports involved can thus be operated in full duplex mode. Terminals can optionally be connected to the ports T3 / R3 and T4 / R4 in FIG. 3 as well as to the T1 / R1 port of the network subscriber 61 or the port T2 / R2 of the network subscriber 63 and thus coupled to the network.

Fig. 4 shows a number of network participants 70 , 71 , 72 and 73 , each of which can exchange data with one another via two communication channels. The communication channels are in each case implemented by connecting the port T2 / R2 to the port T1 / R1 of the adjacent network subscriber and the port T4 / R4 to the port T3 / R3 of the adjacent network subscriber in the manner shown. For example, a high-priority and a low-priority communication channel can be set up and data throughput doubled. A data exchange between the communication channels does not take place, ie a telegram received at the circuit part R1 can - if necessary - only be forwarded by the circuit part T2. Both communication channels are operated in full duplex mode.

FIG. 5 shows an example of a two-dimensional interconnection of the network subscribers. Network subscribers 80 , 81 and 82 are interconnected in a row in the manner already described with reference to FIG. 3. Furthermore network participants 83 , 84 and 85 form a series and network participants 86 , 87 and 88 form a series. Terminals 89 , 90 and 91 are connected to ports T4 / R4 of network participants 80 , 81 and 84 , respectively, and terminals 92 , 93 and 94 are connected to ports T3 / R3 of network participants 83 , 84 and 87 . By connecting the port T4 / R4 of the network participant 82 with the port T3 / R3 of the network participant 85 , a communication channel between the respective rows is realized. In a corresponding manner, two communication channels are formed between the network participants 83 and 86 and between the network participants 85 and 88 . To ensure that there is no loop in the network, only one communication channel may be activated at a time.

The rows formed from the subscribers 80 to 82 , 83 to 85 and 86 to 88 are each assigned a unique row address R _k , which is stored in a parameter register "row address".

A further two-dimensional network is shown in FIG. 6 to clarify the redundancy control. 8 network participants 100 each. , , 107 , 110 . , , 117 , 120 . , , 127 and 130 . , , 137 are connected in a row. Both the broken lines and the solid lines between the network participants represent communication channels. However, it must be ensured that only one communication path is used between any two network participants in the entire network. If there were several possible communication paths, loops would occur, ie telegrams would multiply and circulate. To avoid such situations, the spanning tree algorithm has been developed. Data telegrams are only received by ports, forwarded to ports and sent by ports that are contained in the spanning tree. The remaining ports are deactivated. Deactivated communication channels are shown in Fig. 6 with broken lines, activated with solid lines. For redundancy within a row, the two line ends are connected to one another, for example at network participants 100 and 107 . In the event of an error, the communication channel created in this way is deactivated and, in the event of an error, set to the active state. This redundancy requires an uninterrupted line structure. Since the spanning tree algorithm would also interrupt a connection via ports T1 / R1 and T2 / R2, it cannot be used unchanged. In the following, a method is presented that ensures loop freedom for a network of interconnected rows of network participants without having to interrupt a row. If necessary, only ports T3 / R3 are deactivated. Only one communication channel may be active between two rows at a time, ie data telegrams are exchanged via this communication path. There is no data exchange via the other communication paths between two rows. The selection of the only active communication channel between two rows is made with the help of port select telegrams. These are telegrams that are only forwarded within a row. There is no exchange between the rows.

The task of these port select telegrams is to create a network to find a device that is connected to port T3 / R3 with a adjacent row is connected and based on the number the network participants from both ends of the line structure is as far away as possible, d. H. the smallest Distance from the middle of the row. Defi these properties kidney the only network participant in the series that over Port T3 / R3 is actively connected to an adjacent row. All other connections via ports T3 / R3 of the network part Participants in the same row to this neighboring row are disabled fourth. There will be no communication channels deactivated Data telegrams exchanged.

Port select telegrams are identified by an identifier in the type field clearly marked.

Fig. 7 shows the result of the redundancy control in a two-dimensional network in a different representation. The number entered in the individual boxes corresponds to the respective address of the network participant. Port T1 / R1 is on the left side, port T2 / R2 on the right side, port T3 / R3 on the upper side and port T4 / R4 on the lower side of the network participants. An active communication channel operated in full duplex mode is shown by two solid parallel lines between two participants. The communication channels marked with two broken lines are deactivated.

The data area of port select telegrams that are received by a network subscriber via port T2 / R2 contains information about the number N _{R2 of} the transmission links between port T1 / R1 of the network subscriber on the “right” edge of the row and the port T2 / R2 of the respective network participant and contains the number N _{R1 of} the participant who was the last to forward or send the received port select telegram.

The data area of port select telegrams that are received via port T1 / R1 contains the number N _{R1 of} the transmission links between port T2 / R2 of the network subscriber at the "left" edge of the row and port T1 / R1 of the respective network subscriber and the number N _R2 , which is valid for the network subscriber who was the last to forward or send the received port select telegram.

Regardless of the port via which a port select telegram was received, it contains the value | N _R1 - N _R2 | _Initiator at the initiator of the received port select telegram, the 16-bit address R _k (0 ≦ k ≦ p, p number of rows) of the row to which the initiator of the port select telegram belongs, and a valid bit V for the received value of | N _R1 - N _R2 | _Initiator and for the row address R _k . V = 0 means that the received values are invalid. Such a port select telegram was fed into the row by a network subscriber who is not connected to its neighboring row via an operational port T3 / R3. If V = 1, the received values are valid. The port select telegram was fed into the row by a network participant who is connected to an adjacent row via an operational port T3 / R3. A connection to the neighboring row is ready for operation if a port select telegram is received at port P3 / R3 within a parameterizable time interval Δt _timeout (timeout interval). This is only possible if port T3 / R3 of the network subscriber in its own row and port T4 / R4 of the network subscriber in the adjacent row are each in a "link-pass" state. In this state, telegrams can be transmitted in both directions.

In the steady state, only the network participant in each row sends cyclically, ie in every reporting interval Δt _M , port select telegrams, which is the only one actively connected to the next row via port T3 / R3. This shows whether this connection between two rows is still active. A method is described below according to which this network participant can be determined:

• 1. Network participants send to be forwarded or themselves Compiled port select telegrams additionally via their port T3 / R3.
• 2. Upon receipt of a port select telegram via port T3 / R3, each network participant recognizes whether it is connected to another row via this port.
  Network participants set the valid bit V to one if a port select telegram has been received via port T3 / R3.
• 3. Port select telegrams received on port T3 / R3 are sent back to the sender unchanged. The network subscriber previously saves the address R _n received with the port select telegram of the row connected via port T3 / R3.
• 4. A timeout counter is assigned to port T3 / R3, which is incremented with an adjustable clock. Each port select telegram received on port T3 / R3 resets this counter. The network participant sets the valid bit V to zero if no port select telegram is received within a parameterizable time out interval Δt _timeout .
• 5. Network participants send to be forwarded or themselves Compiled port select telegrams additionally via Port T4 / R4.
• 6. At the receipt of a port select telegram via port T4 / R4 a network participant recognizes that it is using this port is connected to another row.
• 7. Port select telegrams received on port T4 / R4 are sent back to the sender unchanged. The network participant previously saves the address R _n received with the port select telegram of the row connected via port T4 / R4.
• 8. Network participants send their own, ie self-made, port select telegrams
  • 1. 8.1 via port T1 / R1 with N _R2 = 1 and port T2 / R2 with N _R1 = 1 during initialization with amount | N _R1 - N _R2 | _Initiator = FFH and valid bit V = 1 if a port select telegram has already been received via port T3 / R3, or valid bit V = 0 if no port select telegram has been received via part T3 / R3 ;
  • 2. 8.2 via T1 / R1 with N _R2 = 1 and port T2 / R2 with (N _R1 + 1) if no port select telegram or data telegram was received within a parameterizable time interval Δt _timeout at port T2 / R2. The port T2 / R2 is assigned a timeout counter, which is incremented with an adjustable clock. Every port select telegram or data telegram received at port T2 / R2 resets this counter;
  • 3. 8.3 via port T1 / R1 with (N _R2empf + 1) and port T2 / R2 with (N _R1 + 1), if a port select telegram is received at port T2 / R2 with the received value N _R2empf not equal the stored value of N _R2 . In addition, N _{R2empf is} saved.
  • 4. 8.4 via part T2 / R2 with (N _R1 + 1), if a port select telegram is received at port T2 / R2 with N _R1LastSender not equal (N _R1 + 1).
  • 5. 8.5 via port T2 / R2 with N _R1 = 1 and port T1 / R1 with (N _R2 + 1), if no port select telegram or data telegram was received within a parameterizable time interval Δt _timeout at port T1 / R1 , A timeout counter is assigned to port T1 / R1, which is incremented with an adjustable clock. Each port select or data telegram received on port T1 / R1 resets this counter.
  • 6. 8.6 via port T2 / R2 with (N _R1empf + 1) and port T1 / R1 with (N _R2 + 1), if a port select telegram is received at port T1 / R1 with a received value NRlempf not equal to the saved one Value of N _R1 . In addition, N _{R1empf is} saved.
  • 7. 8.7 via port T1 / R1 with (N _R2 + 1) if a port select telegram is received at port T1 / R1 with N _R2lastSender not equal (N _R2 + 1).
• 9. Network nodes which are connected to another row via an operational communication channel via port T3 / R3 and which receive a port select telegram with a valid bit V set to one, compare | N _R1 - N _R2 | _{Initiator of} the received port select telegram with amount | N _R1 - N _R2 | _s of your own station:
  • 1. 9.1 Is | N _R1 - N _R2 | _Initiator <| N _R1 - N _R2 | _s , then | N _R1 - N _R2 | _Initiator in the data field of the port select telegram not changed during forwarding. The network participant stores | N _R1 - N _R2 | _min = | N _R1 - N _R2 | _Initiator and sets the address A _Stored = A _initiator . A _initiator is the source address of the received port select telegram. The value | N _R1 - N _R2 | _s is the distance from the receiving station to the center of the row.
  • 2. 9.2 Is | N _R1 - N _R2 | _Initiator = | N _R1 - N _R2 | _s , A _{initiator is} compared with its own station address A _s :
    With A _initiator <A _s , the port select telegram is changed without changing the data field with | N _R1 - N _R2 | _Initiator forwarded. The network participant stores | N _R1 - N _R2 | _min = | N _R1 - N _R2 | _s and A _stored = A _initiator .
    If A _initiator = A _s , the received port select telegram is filtered out, since this case is only possible in the event of an error.
    If A _initiator <A _s , the received port select telegram is filtered out and a separate port select telegram with | N _R1 - N _R2 | _Initiator set to | N _R1 - N _R2 | _{s sent} via ports T1 / R1 and T2 / R2. The network participant stores | N _R1 - N _R2 | _min = | N _R1 - N _R2 | _s , and A _stored = A _s .
  • 3. 9.3 Is | N _R1 - N _R2 | _Initiator <| N _R1 - N _R2 | _s , the received port select telegram is filtered and a separate port select telegram with | N _R1 - N _R2 | _Initiator set to | N _R1 - N _R2 | _{s sent} via ports T1 / R1 and T2 / R2. The network participant stores | N _R1 - N _R2 | _min = | N _R1 - N _R2 | _s and A _stored = A _s .
• 10. Network participants that are not connected or connected to another row via a non-operational communication channel via port T3 / R3 and receive a port select telegram with a valid bit V = 1 route the telegram with the received valid bit V and the value | N _R1 - N _R2 | _{Initiator continues} within the series. The network subscriber stores | N _R1 - N _R2 | _min = | N _R1 - N _R2 | _Initiator and A _stored = A _initiator .
• 11. Network participants that receive a port select telegram with a valid bit V = 0 route the telegram with V = 0 and the value | N _R1 - N _R2 | _{Initiator continues} within the series. The stored values of | N _R1 - N _R2 | _min and A _stored remain unchanged.
• 12. An operational port T3 / R3 is activated when | N _R1 - N _R2 | _min = | N _R1 - N _R2 | _s and A _stored = A _{s is} stored. This applies to a period of time Δt _rowdelay that _corresponds to at least twice the worst case throughput time of a port selection telegram through a row.
• 13. An active port T3 / R3 of a network participant is deactivated if the network _participant does not _receive a port select telegram from another row within the timeout interval Δt timeout. In addition, the communication channel via port T3 / R3 to the other row is marked as not ready for operation.
  An active port T3 / R3 is also deactivated when the network participant receives a port select telegram with | N _R1 - N _R2 | _Initiator <| N _R1 - N _R2 | _s or | N _R1 - N _R2 | _Initiator = | N _R1 - N _R2 | _s and A _initiator <A _s . This network participant stores the received values | N _R1 - N _R2 | _Initiator and A _initiator and forwards the received telegram. The communication channel via port T3 / R3 to the other row remains operational.
• 14. Network nodes that are connected to another row via an operational communication channel via port T3 / R3 send their own port select telegrams cyclically in every message interval Δt _M.
  • 1. 14.1 via port T1 / R1 with (N _R2 + 1) and port T2 / R2 (N _R1 + 1), if an active port T3 / R3 is deactivated, with | N _R1 - N _R2 | _Initiator = FFH and valid bit V = 1 until a port select telegram from another network participant is received;
  • 2. 14.2 via port T1 / R1 with (N _R2 + 1) and port T2 / R2 with (N _R1 + 1), if within a parameterizable time interval Δt _timeout neither on port T1 / R1 nor on port T2 / R2 Port select telegram or data telegram was received by the network participant with the only active communication channel to the neighboring row, ie a telegram with the source address A _stored ;
  • 3. 14.3 via port T1 / R1 with (N _R2 + 1) and port T2 / R2 with (N _R1 + 1) if | N _R1 - N _R2 | _min = | N _R1 - N _R2 | _s and A _stored = A _{s is} stored.

In the steady state of the process, each network subscriber in the row knows the network subscriber who is connected to an adjacent row via his port T3 / R3 and has the smallest distance from the center of the row. Data telegrams are only exchanged between the two rows via this active communication channel. The connections of the other network participants to the next row are deactivated. Fig. 7 shows a network in this steady state.

If, in deviation from this exemplary embodiment, the only active communication channel of a row to the adjacent row is to be at the edge of the row, then | N _R1 - N _R2 | are in the described method _min through | N _R1 - N _R2 | _max | N _R1 - N _R2 | _Initiator <| N _R1 - N _R2 | _s by | N _R1 - N _R2 | _Initiator <| N _R1 - N _R2 | _s to replace.

Fig. 8 shows a network in a three-dimensional structure. The arrangement of the ports on the individual boxes, which each represent a network participant with the entered address, is the same as in the illustration according to FIG. 7. The communication channels are also shown in the same way. In the case of a three-dimensional structure, a row is built up in a linear structure with several network participants by connecting the ports T1 / R1 and T2 / R2. Several of these rows are interconnected to form a three-dimensional structure, as shown in FIG. 8. To do this, at least one communication channel must be available between ports T3 / R3 and T4 / R4 between two rows. Multiple communication paths between two rows are permitted. Terminals can be connected to ports T3 / R3 and T4 / R4 of the network nodes that are not used for communication channels between rows. Each row is assigned a unique row address R _k with 0 ≦ k ≦ p, where p is the number of rows of the selected network structure. The respective row addresses are indicated on the left side of FIG. 8 next to the respective row. The associated address of the row is stored in the "Row address" parameter register in each network node.

However, it must be ensured that between any two network participants in the entire network only one Communication path is used. With several communica loops would occur, d. H. telegrams could multiply and circulate. To avoid Loops become port select telegrams in combination used with a modified spanning tree algorithm.

For this purpose, the data area of the port select telegrams is expanded by the address R _{n of} the adjacent row to which the port T3 / R3 or the port T4 / R4 of the network subscriber who compiled the telegram is connected.

The task of the port select telegrams expanded by the row address R _{n of} the adjacent row is to find a network subscriber who is connected to a row with the address R _n via port T3 / R3 and based on the number of network subscribers from both ends its row is as far apart as possible, ie it has the smallest distance from the middle of the row. This defines the only network participant in the series that is potentially actively connected to the neighboring series with the address R _n via port T3 / R3. Port T3 / R3 is switched from potentially active to active if the modified spanning tree algorithm also switches this port active. Data telegrams are only exchanged via active communication channels between the rows. With the method previously described for the two-dimensional network structure, the network participant can be found who has the smallest distance to the center of the row and whose port T3 / R3 is connected to the row with the address R _N. The port select telegrams ensure that between two rows that are directly connected to each other via communication channels, only one communication channel via port T3 / R3 is potentially active at any time. So that loops that are closed over more than two rows are reliably prevented, a modified spanning tree method ensures that no loop occurs across the entire three-dimensional network. Characteristics of the modified spanning tree method are that each row is regarded as a virtual switch, with the potentially active communication channels via ports T3 / R3 or via ports T4 / R4 to other rows as ports of the virtual switch, and that a communication channel via a port T4 / R4 is potentially active if it is connected to a potentially active port T3 / R3 of another row, which is also regarded as a virtual switch. The following entries are also provided in the data field in configuration telegrams:

• 1. Root_ID: A 64-bit address R _{R of} the virtual switch that is assumed to be "root".
• 2. Transmitter_ID: A 64-bit address R _{T of} the virtual switch to which the sending network participant belongs. The addresses R _R and R _T each correspond to the address of the row that is regarded as a virtual switch.
• 3. Cost: Smallest number of rows that a telegram of one Sender must go through to Root_ID.
• 4. Port_ID: A 16-bit address P _{ID of} the port via which the sending virtual switch sends the configuration message. R _PID is equal to the address R _{n of} the row connected to the port over which the virtual switch with the Transmitter_ID sends.

With these definitions, the spanning tree algorithm can be applied to a network of virtual switches. It is based on the described configuration telegrams, sent and received by virtual switches.  

Only the potentially active or active ports T3 / R3 or T4 / R4 in a row, i.e. H. of a virtual switch received configuration telegrams. The deactivated Ports T3 / R3 or T4 / R4 evaluate the configuration telegrams and then filter them. The spanning tree process switches ports T3 / R3 or T4 / R4 from potentially active actively order to ensure that between every two only one of any network participants in the network Communication path exists and therefore no loops occur. The remaining ports T3 / R3 or T4 / R4 remain potentially active or deactivated. Only through active communication channels between the rows, data telegrams are output exchanges.

A virtual switch is always ready to receive configuration telegrams at its ports and stores the configuration message for each port with the "best" combination of Root_ID.Cost.Transmitter_ID.Port_ID. Not only are the combinations received compared for each port, but also the combination that the virtual switch would send to this port is compared. A combination K1 is "better" than another combination K2 if

• 1. Root_ID of K1 <Root_ID of K2,
• 2. Root_ID of K1 = Root_ID of K2 and
  Cost of K1 <Cost of K2,
• 3. Root_ID of K1 = Root_ID of K2 and
  Cost of K1 = Cost of K2 and
  Transmitter_ID of K1 <Transmitter_ID of K2 or
• 4. Root_ID of K1 = Root_ID of K2 and
  Cost of K1 = Cost of K2 and
  Transmitter_ID of K1 = Transmitter_ID of K2 and
  Port_ID of K1 <Port_ID of K2.

The root port of a virtual switch is the port with the "best" combination received K _R = K _E = Root_ID.Cost.Transmitter_ID.Port_ID.

The root port is the port of a virtual switch with the shortest distance to Root_ID.

The combination of the root port is via port select tele gram all network participants of the virtual switch communicated. So every network participant owns the necessary information to decide whether a port of is potentially to be switched actively to active. A potentially active port is switched to active if Root_ID. (Cost + 1) .Transmitter_ID.Port_ID from the root port "better" is than Root_ID.Cost.Transmitter_ID.Port_ID from considered port.

The condition that leads to the activation of a port of a virtual switch must be valid for a period of time Δt _netdelay that corresponds to at least twice the worst case throughput time of a configuration _message through the network before the relevant port is actually activated. Only configuration telegrams received from the root port are forwarded to the active ports of the virtual switch. Configuration telegrams are only sent or forwarded via the active ports T3 / R3. The only receivers of these telegrams are the potentially active ports T4 / R4 of the connected virtual switches. In addition, configuration telegrams are only sent or forwarded via the active ports T4 / R4. The only receivers of such telegrams are the potentially active ports T3 / R3 of the connected virtual switches. A so-called combination aging counter is assigned to each port of a virtual switch. This counter is reset and restarted with every received or forwarded configuration telegram. The combination aging counter is therefore only activated for the potentially active or active ports in a row and is incremented with a parameterizable time cycle. If the combination aging counter for a potentially active or an active port reaches the parameterizable threshold "maximum age", the combination Root_ID.Cost.Transmitter_ID.Port_ID saved for this port is deleted and recalculated.

The exchange of information within a virtual switch, ie within a number of network participants with a linear structure, takes place with port select telegrams that are similar to the above described port select telegrams of a network with a two-dimensional structure. The data area of the port select telegrams of a network with a three-dimensional structure is expanded by a 16-bit address R _n des via port T3 / R3 regardless of the receiving port compared to the data area of the port select telegrams for a network with two-dimensional structure connected virtual switches, ie the neighboring row, the validity of which is indicated by the valid bit V already described. If V = 0, the received value of the row address R _{n is also} invalid. The port select telegram was fed into the virtual switch by a network participant, which is connected to the virtual switch via an operational port T4 / R4. If V = 1, the address R _{n is} valid. In addition, a potentially active bit P _{pA is} inserted in the data area of the port select telegram. Depending on the receiving port, this bit has two meanings:

• _{1.P pA} in port select telegrams received at port T4 / R4 informs the network subscriber whether port T3 / R3 of the sending network subscriber of the connected virtual switch is potentially active or active (P _pA = 1) or deactivated ( P _pA = 0).
• 2. P _pA in port select telegrams received on port T1 / R1 or port T2 / R2 informs the network subscriber whether port T4 / R4 of the initiator of the port select telegram is potentially active or active (P _pA = 1) or deactivated (P _pA = 0).

Furthermore, the data area of the port select telegram is expanded by a 16-bit address R _{i of} the virtual switch connected via port T4 / R4. The value of the address is only necessary if P _pA = 1 is set.

In addition, a value of an active timer is transmitted in the port select telegrams at the time of transmission. The active timer measures the time that has elapsed since the last receipt of a port select telegram via port T4 / R4 with the potential active bit set, ie with P _pA = 1. The value of the active timer is only valid if P _pA = 1.

Furthermore, the data area of port select telegrams for three-dimensional network structure contains the best received combination for this port
K _E = Root_ID.Cost.Transmitter_ID.Port_ID,
that was sent or forwarded in the data field of a configuration telegram from a row connected to a potentially active or active port T3 / R3 or T4 / R4 with the address R _n or R _i .

In addition, the best combination known to date is transmitted to the potentially active or active ports T3 / R3 and T4 / R4 in the series, ie the virtual switch, in the data field of port select telegrams:
KR = Root_ID.Cost.Transmitter_ID.Port_ID.

A network participant that receives a port select telegram from a potentially active or active port T3 / R3, ie a port select telegram with P _pA = 1, from another row on a deactivated port T4 / R4, switches port T4 / R4 to potentially active or active and sends a parameterizable number of port select telegrams with P _pA = 1.

An active timer is assigned to each of the ports T4 / R4, which is incremented with an adjustable clock. The active timer measures the time since the last receipt of a port select telegram with the potential active bit P _pA = 1. Each port select telegram received via port T4 / R4 with the potential active bit P _{pA set} = 1 resets the active timer and restarts it. Received port select telegrams with P _pA = 0 reset the active timer without starting it.

A network participant with a potentially active or active port T4 / R4 deactivates this port if

• 1. a port select telegram with P _pA = 0 is received via port T4 / R4,
• 2. A port select telegram is received via port T1 / R1 or T2 / R2 with P _pA = 1 and a received value of the active timer that is less than the own active time, whereby the own active timer in this case reset without restarting, or
• 3. The time measured by the active timer is a parameterizable one Maximum value reached.

In the steady state, in each virtual switch, ie in each row, all network participants with a potentially active T3 / R3 connection to an adjacent row connected via ports T3 / R3 send a port select cyclically in each reporting interval Δt _M Telegram via the ports T1 / R1 and T2 / R2.

In addition, the following network participants send a port select telegram in each virtual switch via ports T1 / R1 and T2 / R2:

• 1. each network participant during initialization with K _R = K _E = source address. 0. Source address. Port_ID,
• 2. each network participant with a potentially active communication channel via the port T3 / R3 to a row with the address R _n when it receives a configuration telegram via port T3 / R3,
• 3. each network participant with a potentially active communication channel via port T4 / R4 to a row with the address R _i when receiving a configuration telegram via port T4 / R4,
• 4. Each network participant at which the combination aging counter of a potentially active or active port reaches the "maximum age" threshold value, the combinations K _E and K _R stored for this port being deleted and recalculated, and first of all a port select Telegram with
  K _R = K _E = source address.O. source address.Port_ID
  is sent
• 5. each network subscriber with a potentially active or active port, the stored combination K _{R of which is} "better" than the combination K _R in the received port select telegram, the combination K _R stored for this port being deleted and recalculated, and wherein a port select telegram with the best combination received so far for this port
  K _E = Root_ID.Cost.Transmitter_ID.Port_ID and with
  K _R = min {K _E , received value of K _R } is sent and
• 6. Each network participant, whose port T4 / R4 is switched from deactivated to potentially active or active, sends a parameterizable number of port select telegrams with P _pA = 1.

All receivers of a port select telegram with a deactivated communication channel to another row store the values K _E and K _R sent by the associated potentially active or active port of the virtual switch.

Fig. 8 shows the result of applying the port select messages in combination with the modified Spanning Tree shows process on each row of the three-dimensional network shown.

Redundancy in the network should ensure that physika mical errors, electromagnetic interference, network expansions communications or an exchange of components  between the network components. The prerequisite for this is not just quick detection of errors or network modifications and a quick Network reconfiguration, but also the smallest possible network factory area, which during the reconfiguration period of the Effects of the error or network modification is affected.

Redundancy management means that there is redundancy within every row of a network, in terms of communication channels between two connected rows and redundancy with respect to the entire network is possible. There is no loops due to the modified spanning Tree algorithm guaranteed.

This type of redundancy advantageously enables short reconfiguration times with minimal hardware expenditure and can therefore be implemented with little effort. In addition, the network area limited that during the reconfigura time of the effects of an error or of a Network configuration is affected.

In order to ensure redundancy in a row of network participants connected in a linear fashion, a ring is formed, as is shown in FIG. 6, for example, with network participants 100 . , , 107 is the case. A network participant, for example the network participant 100 , which is located at one end of the row, must be operated in redundancy mode. It acts as a redundancy manager.

By setting a redundancy bit in the parameter register this network participant is switched to the redundancy mode. To check the row, it sends in at port 1 cyclically Telegram Test1 with the MAC address of port 1 as the source address. The cycle time is 10 ms, for example. On port 2, a telegram Test2 with the MAC address of the Ports 2 sent as the source address. The cycle time is  also for example 10 ms. The Test2 telegram is changed to half the cycle time is sent offset, 5 ms after the Telegram Test1. If the row is not interrupted, the Test1 telegrams sent at port 1 are received again at port 2 catch and also the Test2 telegrams in the opposite direction tung. In this case, the communication channel between the two ports 1 and 2 within the network participant, the is operated as a redundancy manager, so that all data telegrams received at port 2 are filtered out and of the telegrams received at port 1 only those to own station address directed are accepted.

The network participant operated as a redundancy manager closes the ring, d. H. it routes received telegrams between port 1 and 2 if within a para metrable time interval of, for example, 100 ms no test telegram is received on one of the two ports or if a telegram "link-down" from a network participant the respective row is received, which is an interruption of the communication channel to the next network participant Has been established. The port affected by the interrupt of the network participant is deactivated. requirement for reactivating this port is restoring the Connection to the other network participant for a specific Minimum time of 1.6 s, for example, or the reception of a "Link-up" telegram from the redundancy manager. With the closing of the ring is on ports 1 and 2 of the redundancy manager a "link-down" telegram is sent to all other network series members about the new series structure inform. Test telegrams will continue to be cyclically versed det.

The network participant operated as a redundancy manager opens the ring when another test telegram is sent via the previously interrupted route is received or if a Telegram "link-up" from the network participant of the emp will catch whose communication channel to the neighboring  Network participants for a certain minimum time of for example 1.6 s is no longer interrupted. With the The ring is opened at ports 1 and 2 of the redundancy Managers sent a telegram "link-up" to everyone else Network participants in the series about the new ring structure inform. Test telegrams will continue to be cyclically versed det. Each network participant in the series continues with the reception a "link-up" or "link-down" telegram for the tele necessary register forward.

A redundant execution of the communication channels between two rows requires at least two separate communication paths. However, a maximum of one path may be used for data exchange between the rows. The selection of this potentially active communication channel between two rows is made with the help of port select telegrams. If a potentially active communication channel is identified as faulty, it is deactivated and another communication path is switched to potentially active. The following applies to the switchover time from deactivated to potentially active:
Switchover time ≧ Δt _timeout + Δt _rowdelay , where Δt _{timeout is} the timeout interval and Δt _{rowdelay corresponds} to twice the worst case throughput time of a port select telegram through the row. The switchover time therefore depends on the number of network participants that form a row. It lies z. B. for a series of 50 network participants in the order of 200 ms if a timeout interval of 150 ms is assumed.

Redundancy in a three-dimensional network is also possible. If the loop structure already provides freedom from loops, ie there is no network redundancy, every potentially active communication path between two rows is also active. In this case, it is not necessary to use the modified spanning tree algorithm described. With network redundancy, the modified spanning tree algorithm ensures loop freedom between the rows. A reconfiguration of a network with the modified spanning tree algorithm is only necessary for errors or network modifications that are not processed by the redundancy within a row or the redundancy of the communication channels between two rows. In the case of a network with such network participants, the transmission time from the transmitter to the receiver depends on the number of network participants via which a telegram is forwarded and cannot be neglected. The transmission time of a telegram increases for each network participant that forwards the telegram by a participant-specific delay time Δt _i , which is composed of the following times:

• 1. Throughput time through the physical layer block, for example block 36 in FIG. 2, in the receiving direction from the reception of the first bit of a nibble until the nibble on the MII with "RX_DV = 1" is output as valid. This time is, for example, 21 T _bits for DP83843 PHYTER from NSC, T _bits corresponding to 100 ns at 10 Mbaud transmission rate and 10 ns at 100 Mbaud transmission rate.
• 2. Time spent in the network participant from receiving a nibble to sending the same nibble. If the subscriber is sending its own telegram and a telegram has already been entered in the receive buffer, data forwarding can be delayed by up to (3k × 8) × T _bit compared to undisturbed operation.
• 3. Throughput time through the physical layer module, via which the telegram is forwarded in the transmission direction, from the first rising edge of a transmit clock signal after the provision of a nibble on the MII to the first transmitted bit of this nibble. This lead time is 6 T _bits for example for DP83843 PHYTER from NSC.
• 4. Runtime over the lines between two neighboring ones Network participants.

The sum of the times specified under 1, 3 and 4 is a fixed quantity and is referred to as the throughput time Δt _DLZ . It can either be parameterized or measured by the network participants. This throughput time Δt _DLZ can only be changed if a network participant is removed from the network or added to the network or if the cabling is changed.

The throughput time Δt _DLZ can be determined with the following sequence of telegrams, which network participants execute after initialization or on request:

• 1. Each network participant who is new to the network is taken, sends its four neighboring network participants each receive a so-called DLZ telegram, d. H. a first telegram to determine the runtime. That tele grams is clearly identified in the 16-bit type address records.
• 2. The new network participant starts a DLZ timer 1, after the last nibble of the type field of the DLZ-Tele the media independent interface (MII) of port 1 was made available for dispatch. Corresponding he starts a DLZ timer 2, 3 and 4 for sending via ports 2, 3 or 4.
• 3. Each of the maximum of 4 neighboring network participants starts after receiving the last nibble of the type Field of the DLZ telegram on his MII his DLZ timer of the respective port. The received DLZ telegram is not forwarded, but supplemented by the transmitter Residence time in the respective Ethernet controller of the Network participant sent back. Has this neighboring network participants the last nibble of the Type field of the DLZ-Tele modified in this way gramms his to the newly added network participant When the MII is sent, it stops the DLZ timer and sends the stay time saved in the DLZ timer  with the data field of the telegram to the newly connected network participants.
• 4. The new network participant added to the network stops with the reception of the last nibble of the type Field on his MII of the respective port DLZ timers 1, 2, 3 and 4.
• 5. For example, for port 1 of the newly connected network participant, the throughput time Δt _DLZ1 can be calculated using the formula: Δt _DLZ1 = (T _DR - T _DA ): 2, with T _DR - response time measured with DLZ timer 1 and T _DA - measured time spent in the neighboring network participants.
  The throughput times .DELTA.t _DLZ2 , .DELTA.t _DLZ3 and .DELTA.t _{DLZ4 are calculated} in a corresponding manner for the other ports of the network _subscriber newly inserted into the network. The throughput times determined in this way are stored in the module 52 ( FIG. 2) as parameters.
• 6. The newly connected network participant sends with one the measured throughput times via another telegram the assigned port to the neighboring network factory participants.

The described determination of throughput times is at Initialization of a network only every second network work participants required.

The task of clock synchronization is the clocks synchronize several or all network participants. The communication channels between Network participants operated in full duplex mode, so that Transmission of telegrams deterministic behavior shows.

The transmission time from a transmitter to a receiver is in a network from the number of network participants, over which the telegram is routed depends on and cannot be ignored.  

Time synchronization can be carried out with two special telegrams, for example. Fig. 9 shows the general structure of a telegram. A first field 140 contains a destination address, ie an address of the subscribers to whom the telegram is directed, for example 48 bits in length. A second field 141 contains a source address, the address of the sending network participant, the length of which is also 48 bits, for example. In a type field 142 with, for example, 16 bits, a identifier of the telegram is transmitted 11991 00070 552 001000280000000200012000285911188000040 0002010004425 00004 11872. The user data of the telegram are sent in a data field 143 of variable length. The telegram is ended by a check sequence of 144 , which essentially serves to check the transmission quality. Telegrams for time synchronization can be identified by a special multicast address as destination address 140 and / or by a new type address to be defined in type field 142 .

FIG. 10 shows an order list which can be stored, for example, in the RAM 22 in FIG. 2. Telegrams that are to be transmitted via the network are entered in such an order list. If the transmission is not prioritized, the telegram below is transmitted next. It can therefore happen that, for example, a completed telegram 151 is only transmitted when two telegrams 152 and 153 previously entered in the job list have been transmitted. Depending on the number of pending orders, the transmission delay time of a telegram in a network participant can be varied after it has been entered in the order list. The following describes a way in which the influence of the transmission time delay in time synchronization can be avoided:

• 1. With a time master, d. H. a network participant, on whose clock the clocks of the other network participants syn chronized, carries an SM-Time0 telegram, an ers telegram for time synchronization, in a job list  on, starts for each port P, P = 1, 2, 3, 4, a delay timer and remembers the start time of this Timer.
• 2. The delay timer of each port P, P = 1, 2, 3, 4, will stopped at the time master after the last nibble of the type field of the SM-Time0 telegram to the MII of the respective ports provided for sending has been. The transmission delay time is thus determined. On Nibble is defined as half a byte, i.e. that is a sequence of 4 bits.
• 3. After receiving the last nibble of the type field of the SM-Time0 telegram on the MII of its port P, P = 1, 2, 3 or 4, each neighboring network participant starts its delay timer with the value of the respective _{transit time} Δt _DLZp previously measured by the method described above or entered by an operator. In addition, the address of the time master that was received as the source address in the SM-Time0 telegram is saved.
• 4. At the point in time at which the neighboring network subscriber creates the last nibble of the type field of the SM-Time0 telegram for forwarding to the MII of another port, the value of the delay timer that corresponds to the port P, P = 1 , 2, 3 or 4, is stored. However, the delay timers continue to run. The stored delay times of the ports each correspond to the transmission time Δt _i defined above for this network participant. The running time of the telegram via the physical transmission is already added by the start value Δt _{DLZp of} the delay timer.
• 5. The time master then carries an SM-Time1 tele gram, the start time of the delay timer in the data field contains, in the order list. Before this SM- Sends Time1 telegram via a port P, P = 1, 2, 3, 4, it replaces the start time of the delay timers with the clock time at which the last nibble of the type field of the SM Time0 telegram to the MII of this port for sending  Was made available, d. H. by the sum of the start time of the delay timer and the measured delay time of the respective ports P. In the SM-Time1 telegram the time corrected for the transmission time delay wear.
• 6. Each neighboring network participant that receives an SM-Time1 telegram adds the stored delay time Δt _{i of} the SM-Time0 telegram previously forwarded via port P, P = 1, 2, 3 or 4 to the one in the SM- Time1 telegram received time and sends the time received in this way with an updated SM-Time1 telegram via another port to the next neighbor. SM-Time1 telegrams are only accepted by the network participant who previously sent an SM-Time0 telegram.

When the SM-Time1 telegram is received, the time Slave, i.e. H. the neighboring network participant, the start time of its delay timer. The synchronized time results from the sum of the time received in the SM-Time1 telegram and the delay time of the time slave for each received port. The neighboring network part thus corrects the time received in the second telegram at Runtime and the reception time delay.

As an alternative to the option described above, the following procedure enables time synchronization with just one telegram:

• 1. A time master starts the ports assigned Delay timer and carries the time telegram with the start time this timer in the order list.
• 2. The delay timer of each port P, P = 1, 2, 3, 4, is at Time master stopped after the last nibble of the Type field of the time telegram to the media independent Interface provided by port P for sending was, d. H. after the last nibble of the type field for physical transmission was provided. The network The work participant then adds the ones in the time telegram  specified start time of the delay timers at the value of the delay Timers of the respective port P and sends this sum as the time corrected for the transmission time delay with a first telegram for time synchronization via the respective port P.
• 3. After receiving the last nibble of the type field of the first telegram for time synchronization at a port P, P = 1, 2, 3 or 4, each neighboring network participant starts its assigned delay timer with the value of the respective throughput time Δt _DLZP . It therefore measures the time delay since the first telegram was received.
• 4. At the point in time at which the neighboring network subscriber creates the last nibble of the type field of the first telegram for time synchronization for forwarding to the MII of a port, the value of the delay timer which is assigned to this port is stored. However, the delay timers continue to run. The stored delay times assigned to the individual ports each correspond to the transmission time Δt _{i of} this network subscriber. It is added to the received start time of the delay timer and forwarded with a second telegram for time synchronization via another port to the next, ie a third, network participant.

With the receipt of a first or second telegram for The time slave knows the start time by time synchronization of its delay timer. The synchronized time results from the sum of those in a first or second telegram received time and the delay time of the time slave for the receiving port P.

The described time synchronization options can synchronize Equi serve distance timers in the network participants. Abandonment of Equidistance timers is to multiple or all network part to enable participants to take predefined actions equidistantly respectively. This function is common in control systems  referred to as "electronic wave". It should be with everyone Network participants that ver are bound to generate a beat with which Pass the target values and the actual values queried become. An application example is the measurement of the elec trical performance if the required electricity and Voltage measured values from separate transmitters recorded and over a network can be queried.

It is assumed that an equidistant cycle of only is controlled by an equidistance master. The network part participant who takes on the function of an equidistance master, has a timer that starts with the parameterizable Value of the equidistance interval is loaded. The timer is free running and is decremented with every bit clock. Is the Timer has expired, it will return to the parameterized value of the equidistance interval loaded and a new cycle starts. A difference from an equidistance timer a clock is therefore the direction of rotation. To correct a with Telegrams transmitted timer status must therefore Time delays are not added as with the time, but be subtracted. The term "time Synchronization "should therefore be understood so that it too includes synchronization of equidistance timers.

The following options are available for synchronizing equidistant actions:

• 1. The equidistance master enters the equidistance telegram in the job list. It stores the value of the equidistance timer each time the last nibble of the type field of the equidistance telegram is transferred to the MII of the four ports P, P = 1, 2, 3, 4, ie provided for physical transmission becomes. This value Δt _equi stored for each port P, which corresponds to the remaining time until the equidistance interval expires, is sent with the equidistance telegram via port P to the neighboring network subscriber.
• 2. After receiving the last nibble of the type field of the equidistance telegram at the MII of a port, ie when receiving the equidistance telegram from the physical transmission _link, each network participant starts an auxiliary timer with the value of the throughput time Δt _DLZP .
• 3. The value of the auxiliary timer is saved at the point in time at which the neighboring network subscriber creates the last nibble of the type field from the equi-distance telegram for forwarding to the MII of another port. The stored value of the auxiliary timer corresponds to the transmission time Δt _{i of} this network participant for port P. This stored time Δt _i is subtracted from the received remaining time Δt _equi until the next cycle _begins . The neighboring network participant forwards the corrected remaining time (Δt _equi - Δt _i ) with the equidistance telegram via the other port to the next neighboring network participant. In addition, he loads the corrected remaining time into his equidistance timer, which is decremented with every cycle.
• 4. If the equidistance timer of an equidistance slave has expired, it is first loaded with the parameterized value of the equidistance interval and decremented with each bit clock. As soon as a new equidistance telegram is received from the equidistance master, the equidistance slave loads the remaining time determined in the manner described (Δt _equi - Δt _i ) into the equidistance timer until the next cycle _begins .

For the described synchronization of equidistance timers should be the maximum transmission time between a transmitter and a receiver in the network must be smaller than the length of the equidistance interval.

In the exemplary embodiment, a network according to the Ethernet specification described. However, the invention is easily on Fast Ethernet, Gigabit Ethernet or other types of networks applicable.

Claims (14)

1. Network with a plurality of network participants, a first network participant being designed to send a first telegram for time synchronization to a second network participant in which the transit time of the telegram is stored over the physical transmission path between the first network participant and the second network participant, characterized in that the first telegram contains a time corrected by a transmission time delay of the first network participant, and that the second network participant is designed to measure the time delay since receipt of the first telegram and the time received in the first telegram by the throughput time and correct the reception delay. 2. Network according to claim 1, characterized records that the second network participant continues is designed to sync a second telegram send chronization to a third network participant, the one about the lead time and the delay time between receiving the first telegram and sending the second Received time corrected in the telegram. 3. Network with several network participants, one the first network subscriber is designed to be a first Telegram for time synchronization to a second To send network participants in which the lead time of the telegram over the physical transmission path between the first network participant and the second Network subscriber is stored, thereby ge indicates that the first network participant is further trained to one by one broadcast time delay of the first telegram corrected time of the first Store network participant that the second network participant  is designed to delay the time since Receiving the first telegram to measure, the first Network participants continue to be trained second telegram, which is about the transmission time delay contains corrected time of the first network participant, to send to the second network participant and the second network participant is further trained to Time received in the second telegram at the throughput time and correct the reception time delay. 4. Network according to claim 3, characterized records that the second network participant continues is designed to send the first telegram to a third Network participants forward its delay time to To measure telegram forwarding and a third telegram to send the third network participant, the one around the Processing time and the delay time of the telegram further Received time corrected in the first telegram contains. 5. Network according to one of the preceding claims, characterized in that the first network participant has a first timer ( 57 ) for determining the transmission time delay, which it starts when a telegram is entered in a list of send orders and after the telegram is made available for physical transmission as a value reads the transmission time delay by which the time at which the telegram was entered in the list of transmission orders is to be corrected. 6. Network according to claim 5, characterized records that the second network participant second timer for determining the reception time delay which he receives when receiving a first telegram from a physical transmission link starts.   7. Network according to claim 6, characterized ge indicates that the throughput time of the telegram over the physical transmission path between the first network participant and the second network participant as the starting value in the second timer before it started stores. 8. Network according to one of the preceding claims, there characterized by that beginning and end the throughput time of a telegram as the time for which a characteristic field of a A media with a fixed distance from the beginning of the telegram Independent interface of the first participant leaves, or in a media independent interface of the second network participant mer runs in. 9. Network according to claim 8, characterized records that the network is ethernet, fast ether net or Gigabit Ethernet specification met and that characteristic field of the telegram is the type field. 10. Network according to one of the preceding claims, characterized in that the first network subscriber is further configured to send a first telegram for determining the runtime to an adjacent subscriber after inclusion in the network and a response time timer after providing the telegram for physical Start transmission that the second network participant is further trained to start a timer to determine the residence time after receiving a telegram to determine the runtime from the physical transmission and to stop the timer after providing a second telegram for physical transmission and the measured Transfer time t _DA in a second telegram to determine the runtime to the first network participant that the first network participant is further trained to receive the Ant after receiving the second telegram to determine the runtime from the physical transmission Word timer to stop, evaluate the measured response time t _DR and the measured stay time t _{DA of} the second network participant and to determine a transit time t _{DLZ of} the physical transmission
11. Network subscriber, in particular field device, for a network according to one of the preceding claims, characterized in that a plurality of ports, in particular four ports ( 28 ... 31 ), are provided for connecting further network components that an interface ( 25 ), a So-called microprocessor interface, is provided for connecting the ports to an internal processor bus ( 21 ) that a control unit ( 46 ), a so-called switch control, is provided for routing the telegram between the ports and the microprocessor interface and that Network subscriber is designed to send a first telegram for time synchronization to a second network subscriber as the time master, which contains a time corrected by a transmission time delay of the network subscriber, and / or that the throughput time of a telegram in the network subscriber as a time slave over the physical transmission link between the network eilnehmer and a second network participant is stored and that the network participant is trained to measure the time delay since receipt of a telegram for time synchronization and to correct a time received in a telegram by the throughput time and the reception time delay. 12. Network subscriber according to claim 1, characterized in that the ports ( 28 ... 31 ) meet the Ethernet, Fast Ethernet or Gigabit Ethernet specification. 13. Network subscriber according to claim 12, characterized in that the control unit ( 46 ) is designed such that a transmission priority of the telegrams to be sent is evaluated and that telegrams with high priority are sent before telegrams with low priority. 14. Network subscriber according to one of claims 11 to 13, characterized in that a microprocessor ( 23 ) is present for correcting an internal clock on the basis of time information received in telegrams.