DE102019207220A1 - Procedure for operating a field bus - Google Patents

Abstract

The invention relates to a method (16) for operating a field bus (2), in particular an EtherCAT, which has a master (4) and a first slave (6) as well as a second slave (8). A telegram (20) is created by the master (4) and sent to the first slave (6). Using the first slave (6), the telegram (20) is filled with a first value (40) and sent to the second slave (8). Using the second slave (8), the telegram (20) is filled with a second value (50) and sent to the master (4). The first value (40) comprises a request to the second slave (8), and the second value (50) comprises a response to the request. The invention also relates to a field bus (2).

Description

The invention relates to a method for operating a field bus which has a master and a first slave as well as a second slave. The invention also relates to a field bus.

Industrial plants usually have a number of actuators that are operated by means of a process control. In this case, each actuator is usually assigned a separate control which is connected to the process control by means of a communication system, a fieldbus usually being used for communication. By means of the process control, specifications are created for the actuator, which are transmitted to it so that it is actuated based on the specifications. The state of the actuator is transmitted back to the process control, so that further adaptation or coordination with further actuators can take place by means of this.

In addition to the process control of the actuators, there is usually also a safety control. This ensures that in the event of a malfunction or a situation in which injury to a person or damage to an object is possible, the actuator is shut down or can only be actuated in a specific manner. For example, when a person approaches the actuator, this is determined based on the opening of a barrier or the like, and in this case the actuator is shut down. In particular, the safe "STO" function is executed here. However, it is also possible for the actuator to continue to move, usually at a reduced speed. Here it must be ensured that the speed of the actuator does not exceed a certain limit value.

Since there are usually no safety standards for the transmission of the speed to the process control, it is necessary to use an additional fieldbus by means of which the safety control communicates with the actuators. This increases cabling expenditure and manufacturing costs. An alternative to this is to add safety features to the fieldbus used for process control. One possible variant of this is, for example, FSoE (“Fail Safe over Ethercat”). With this type of communication, each telegram that is exchanged between the actuators and the safety controller is based on the previous telegram. It is therefore necessary that the master of the field bus, by means of which the exchanged telegrams are created and organized, also meets the safety standard, since otherwise a corresponding creation of the telegrams is not necessary. The safety controller usually acts as the master for the fieldbus.

The master for the fieldbus is usually exposed to a comparatively high level of continuous stress. It is also necessary that a current standard is always used to create the telegrams, since otherwise communication with newly added actuators is usually not possible. As a result, it is necessary to replace the master of a field bus at certain time intervals. If this now also functions as a safety controller, it must therefore also be replaced, although there are no concerns regarding the continued use of the safety function. As a result, the operating costs of the field bus are increased.

The invention is based on the object of specifying a particularly suitable method for operating a field bus and a particularly suitable field bus, in which in particular a speed of data exchange and / or security is increased and in which production and / or operating costs are expediently reduced.

With regard to the method, this object is achieved according to the invention by the features of claim 1 and, with regard to the field bus, by the features of claim 8. Advantageous further developments and refinements are the subject of the respective subclaims.

The method is used to operate a field bus that has a master and a first slave as well as a second slave. For example, the master, the first slave and the second slave are structurally identical to one another or at least the first slave and the second slave. The assignment as master, first slave or second slave is expediently carried out by means of programming. This means that identical parts can be used, which reduces manufacturing costs. During operation, telegrams are exchanged between the master and the slaves so that communication is possible between them. For this purpose, the master and the two slaves are coupled to one another for signaling purposes, for example by means of a line or wirelessly. In particular, the fieldbus complies with a standard in which the telegrams are described more when they are passed through. In other words, the master sends a single telegram to all slaves on the fieldbus and receives it successively. The slave in which the telegram is currently located is used to process the telegram, which is then sent to another slave. Only after all slaves have processed the telegram is it sent back to the master.

The fieldbus is expediently part of a system, in particular an industrial system. The system is preferably used to process and / or create a workpiece. The first slave and the second slave are assigned to the same actuator or different actuators, for example. In particular, an electric motor is assigned to each of the actuators, for example a specific axis of a portal or a robot arm.

The field bus itself expediently meets a certain standard, for example Sercos, Safetynet, Profibus or Profinet. The EtherCAT fieldbus is particularly preferred, so that a transmission time between the master and the slaves and / or a cycle time is shortened.

The procedure provides that a telegram is created by the master. The telegram has in particular certain sections, for example a heading (header) by means of which the beginning of the telegram is signaled. In particular, a certain time stamp or other data is stored in the heading. Furthermore, the telegram expediently has a termination so that when the telegram is received it is clear when it has ended. It is advisable to have several placeholders between the heading and the conclusion (end), in particular frames or layers. By means of this or otherwise, the placeholders are expediently provided that can be filled with specific values and / or queries. In particular, one of the placeholders is filled with a request from the master to the first and / or to the second slave.

The telegram is sent to the first slave so that it can be processed by the first slave. The telegram is received by the first slave and filled with a first value. For example, the first value includes a response to any request from the master, for example a notification of the status of the first slave. The first value also includes a request to the second slave. For example, the request to the second slave is stored in the same frame or other placeholder of the telegram in which a response to the master is also stored. However, it is particularly preferred to store them in a different area of the telegram, in particular in a further placeholder. A corresponding area of the telegram for such requests from the first slave is preferably made available by means of the master.

The telegram changed in this way is sent from the first slave to the second slave. The telegram is thus received by means of the second slave and filled with a second value. The second value comprises a response to the request from the first slave. In other words, the request of the first slave is answered by means of the second slave, without this being first sent via the master. For example, the second value also has a response to any request from the master. The telegram processed in this way is then sent to the master.

Due to the method, it is thus possible that the answer is already answered in the same clock cycle, that is in the same telegram, by means of the second slave, in which it is created by means of the first slave. It is therefore not necessary to route the request from the first slave via the master to the second slave, which is why the speed of the data exchange is increased.

The first slave functions in particular as a master in a further communication channel of the field bus, which expediently complies with a further standard. The fieldbus is thus operated with two communication channels, one communication channel, namely the communication between the first and second slaves directly, being integrated into the other communication channel that is provided by the master. The first slave thus acts as the master of one communication channel. By means of the master of the field bus, for example two different areas (sections) are provided in the telegram, one area being assigned to the communication channel organized by means of the master of the field bus. The other channel is reserved in particular for the other communication channel that is organized by means of the first slave. There is therefore no overlap, which increases functional reliability. Since the same hardware is also used for the two communication channels, manufacturing costs are reduced. If the master is exchanged, the first slave does not have to be exchanged, and vice versa, which is why the masters of the two communication channels can be exchanged independently of one another. This also reduces operating costs.

The first slave is assigned, in particular, to a safety controller and is preferably part of it. By means of this, the telegrams of the field bus provided by means of the master are used in order to carry out a monitoring of the possible system or other components in this way.

For example, the two communication channels, that is, the requests from the master and the first slave, satisfy the same standard or different standards. In particular, the request from the first slave is verified by means of of the second slave. When the first slave receives the response from the second slave, the response is expediently also verified by means of this. This ensures secure communication between the two slaves. Consequently, the invention also relates to a method for secure communication using a field bus. The communication channel between the first and the second slave preferably complies with a safety standard, for example Fail Safe over Ethercat (FSoE). For example, the complete field bus is operated according to such a safety standard. Particularly preferably, however, the fieldbus is not operated in accordance with such a security standard, so that in particular verification is not required. As a result, a required bandwidth is reduced in the communication in which the master is involved. By means of the communication channel formed between the two slaves, secure communication is nevertheless possible, even if only in a certain part of the fieldbus.

For example, the verification takes place in that a characterizing value of the request is checked. In this communication channel, each message, that is, response and request, is preferably based on the respective preceding message. Since the respective characterizing values can be calculated by the two slaves themselves, verification is possible.

The characterizing value is, for example, a checksum of the request or of the complete telegram that includes the request. For example, an additional value is added to this, for example a specific counter reading. This characterizing value is expediently stored in the response, so that the first slave can be used to verify whether the request was received by the second slave without errors. If a request is now sent again to the second slave by means of the first slave in a further, subsequent work step, in particular the characterizing value of the previous response from the second slave is integrated. This means that the second slave can also verify whether the response was received by the first slave without errors.

For example, the telegram is sent directly from the second slave to the master, or it is sent to the master in particular via the first slave. In this case, however, there is no further reading of the telegram, but rather it is passed through to the master by means of the first slave. In a subsequent work step, the master creates a second telegram which, in particular, is structured in the same way as the telegram. In the second telegram, for example, further requests from the master to the two slaves are integrated. In addition, the response from the second slave is integrated into the second telegram and the second telegram is thus filled with the response, for example the complete second value. The second telegram is sent to the first slave so that the response from the second slave can be read out by means of it. Consequently, the response of the second slave is already available to the first slave in the subsequent work step, which is why the speed of the data exchange is increased. It is also not necessary to modify existing hardware, which is why manufacturing costs are reduced.

In an alternative to this, the telegram is sent from the second slave to the master via the first slave, the response being read out by the first slave. The response is thus available to the first slave before the cycle time has expired, which further increases the speed of data exchange. In this way, the master does not have to intervene in the communication channel of the first and second slave, so that the two communication channels can be set up encapsulated with respect to one another. All that is required here is that the master provides a corresponding section or area in the telegram for communication between the two slaves, that is to say this communication channel. Knowledge of the organization of communication within this area is therefore not required for the master. In particular, this area is also blocked for the master or other participants in the field bus except for the first and second slaves or other participants in this combination channel, which further increases security.

For example, the telegram processed by the second slave is received by the first slave using a suitable interface, for example an FPGA (“Field Programmable Gate Array”). It is thus possible, by means of the first slave, to integrate a further request to the second slave or other participants of the fieldbus into the telegram already processed and filled with the first value, before it is sent to the master. Alternatively or in combination with this, a request to a further subscriber of the fieldbus is integrated into the telegram by means of the first slave, for example, via which the telegram processed in this way is sent to the master. The slave therefore has a total of two interfaces, namely one for receiving the telegram sent by the master and one for receiving the telegram that has already been processed by the second slave. The two interfaces are preferably structurally identical to one another and, for example, are each an FPGA. Because of the two interfaces, the first slave acts in particular as two Participants of the field bus for the master, so that two different addresses or the like are assigned to the first slave, for example. At least the first slave acts as two independent slaves for the master.

In a further alternative, the telegram processed by the second slave is copied from the first slave into a memory. Here, the telegram processed by the second slave and directed to the master is routed via the first slave, the telegram being duplicated by means of the first slave. Here one of the telegrams is copied into the memory of the first slave and the other telegram is forwarded directly to the master. Thus there is no time interruption when the telegram is forwarded to the master by the first slave. The response of the second slave is read from the copied telegram by the first slave. As a result, the hardware requirements of the first slave are reduced, namely no two interfaces are required, and reading out the response from the telegram is not time-critical for the operation of the fieldbus.

For example, the telegram is sent from the first slave to the second slave via a third slave. In other words, the telegram is sent to the second slave via the third slave. The telegram is thus received and, in particular, processed by the third slave. The telegram is expediently filled with a third value by means of the third slave. The third value includes, in particular, a response to a possible request from the master to the third slave. The first value also expediently has a request to the third slave, and the third value includes a response to the request from the master to the third slave. The first slave thus communicates with both the second and the third slave, which expediently only differ in their arrangement with respect to the first slave. In particular, the communication between the first slave and the second slave takes place in the same way as between the first slave and the third slave. Because of the third slave, the one communication channel thus comprises several participants. The communication channel controlled by the master also includes an additional communication participant so that additional data can be exchanged via the fieldbus. The second and third slaves are preferably assigned to different possible actuators of the possible system. For example, the third slave and the second slave are each assigned to different electric motors of the possible system.

For example, there is a fourth, fifth or additional slave, the telegram being sent from the first slave to the second slave via these. The first value here includes requests to the fourth, fifth and / or the additional slaves, so that these slaves are also assigned to the communication channel organized by means of the first slave.

In particular, the telegram is sent to the second slave via further slaves. The telegram is expediently processed by means of each of the further slaves, and by means of this the telegram is thus filled with a respective further value, which in particular includes a response to any request from the master. For example, there is one or more further slaves between the master and the first slave, so that an at least partially processed telegram is already received by the first slave. The first slave thus receives a telegram that has already been at least partially processed. Alternatively or in combination with this, at least one of the further slaves is located between the first slave and the second slave or any third slave or between the third slave and the second slave. As a result, additional processing is carried out by the other slaves, whereas the first value or the third value are not influenced.

The first value itself is free from queries to the other slaves. In other words, these further slaves do not participate in the communication channel that is organized by means of the first slave. For example, the further slaves are not required for the communication channel that is controlled by means of the first slave, or the data generated by means of the further slaves are in particular not required for any safety control that includes the first slave. Since the first value does not include any requests to the other slaves if this is not required, the bandwidth is reduced.

The fieldbus has a master and a first slave as well as a second slave. The master and the slaves are coupled to one another in terms of signaling, for example with a line which comprises a number of cables or at least one cable, that is to say at least one wire. As an alternative to this, the coupling takes place, for example, wirelessly, preferably by radio. The field bus is organized by means of the master, so that telegrams are created by means of it, which are sent to the first and second slave during operation and processed by them and then sent back to the master. This means that the telegrams are processed in transit and then sent back to the master. In particular, the Fieldbus a suitable standard for this, preferably Ethercat.

The fieldbus is operated according to a method in which a telegram is created by the master and sent to the first slave. Using the first slave, the telegram is filled with a first value and sent to a second slave. Using the second slave, the telegram is filled with a second value and sent to the master. The first value here includes a request to the second slave, and the second value has a response to the request from the first slave. To carry out the method, the master and / or the slaves expediently have a control unit which is suitable, in particular provided and set up, to carry out the method. The control unit is formed, for example, by means of a microprocessor or includes this. The microprocessor is expediently designed to be programmable. Alternatively or in combination with this, the control unit comprises an application-specific circuit (ASIC).

The fieldbus is, in particular, part of a system that includes several components. Here, for example, one of the components is assigned to the second slave and a possible safety controller is assigned to the first slave. The field bus is particularly preferably a component of an industrial plant and is used in particular for communication between an actuator and a safety controller. In particular, the safety controller includes the first slave and the actuator the second slave. A speed, other operating data or process parameters of the actuator are preferably integrated in the response. A workpiece is preferably manufactured and / or processed by means of the industrial system. For example, the actuator is operated with a comparatively high power, which is in particular greater than 100 W, 500 W, 1 kW, 5 kW, 10 kW or 20 kW.

If a component is referred to as a first, second, third,... Component, it is in particular only to be understood as a specific component.

In particular, this does not mean that a specific number of such components is present.

The developments and advantages mentioned in connection with the method can also be transferred to the fieldbus and vice versa.

• 1 einen Feldbus mit einem Master, einem ersten Slave, einem zweiten Slave, einem dritten Slave und weiteren Slaves,
• 2 schematisch ein Verfahren zum Betrieb des Feldbusses,
• 3 schematisch einen Aufbau eines Telegramms, das bei dem Verfahren übermittelt wird,
• 4, 5 schematisch jeweils unterschiedliche Ausgestaltungen des ersten Slaves,
• 6 schematisch eine alternative Ausgestaltung des Verfahrens zum Betrieb des Feldbusses, und
• 7 schematisch eine weitere Ausgestaltungen des ersten Slaves.

Exemplary embodiments of the invention are explained in more detail below with reference to a drawing. Show in it:

• 1 a fieldbus with a master, a first slave, a second slave, a third slave and further slaves,
• 2 a schematic of a method for operating the fieldbus,
• 3 schematically the structure of a telegram that is transmitted during the process,
• 4th , 5 schematically different configurations of the first slave,
• 6th schematically an alternative embodiment of the method for operating the field bus, and
• 7th schematically a further embodiment of the first slave.

Corresponding parts are provided with the same reference symbols in all figures.

In 1 is schematically simplified a fieldbus 2 shown being a master 4th having. In addition, the fieldbus 2 a first slave 6th , a second slave 8th and a third slave 10 on. The fieldbus also includes 2 more slaves 12 . All slaves 6th , 8th , 10 , 12 and the master 4th are by means of a line 14th coupled with each other in terms of signaling. One of the other slaves is located here 12 between the master 4th and the first slave 6th , and the third slave 10 as well as the remaining further slave 12 is located between the first and second slave 6th , 8th .

The master 4th is realized by means of a computer, by means of which an organization of the fieldbus 2 ongoing communication takes place. The second, third and the other slaves 8th , 10 , 12 are part of a system of an industrial plant. The system here is a robot arm and each of these slaves 8th , 10 , 12 is assigned to a specific electric motor or other component of the robot arm. The first slave 6th is part of a safety controller that monitors the second and third slaves 8th , 10 he follows. The fieldbus 2 met the Ethercat standard, and the master 4th as well as the slaves 6th , 8th , 10 , 12 are operated accordingly. In addition, the second and third are slaves 8th , 10 identical to each other, as are the other slaves 12 . The assignment as the respective slave is made by programming.

In 2 is a procedure 16 shown, by means of which the fieldbus 2 is operated. For this purpose the master 4th as well as the slaves 6th , 8th , 10 , 12 a corresponding hardware, in particular a control unit in each case. In a first step 18th is by means of the master 4th a telegram 20th created according to the EtherCAT standard. So shows every telegram 22nd , as in 3 shown a headline 22nd (Header) and a graduation 24 on. In the headline 22nd a time stamp is stored as well as the length of the telegram 14th . By means of the degree 24 becomes the end of the telegram 20th signals. In between there is a first area 26th and a second area 28 that are separated from each other.

By means of the master 4th becomes the first area 26th in five separate placeholders 30th divided, each of which is one of the slaves 6th , 8th , 10 , 12 assigned. In the placeholder 30th a corresponding request is sent to the respective slave 6th , 8th , 10 , 12 are stored, for example the request to transmit the current status. The second area 28 however, is done by the master 4th not filled. The telegram 20th becomes the one along the line 14th next slave 6th , 8th , 10 , 12 transmitted and from this in a second step 32 receive. This slave is one of the other slaves 12 , and by means of this the assigned placeholder 30th read out, i.e. those on these other slaves 12 directed request from the master 4th . This request is processed, and the response to it by means of another value in the same placeholder 30th written. The telegram revised in this way 20th becomes the next slave, namely the first slave 6th and from this in a third work step 33 receive.

The first slave 6th is schematically in 4th shown and has a control unit 34 as well as two interfaces 36 which are identical to one another and are each implemented by means of an FPGA. The two interfaces 36 are to each other between the respective connections 38 of the first slave 6th switched, by means of which a signaling coupling to the line 14th he follows. The telegram 20th with one of the interfaces 36 received, which thus has a specific address. Using the first slave 6th becomes the placeholder 30th that for the first slave 6th is intended, read out and filled with a corresponding value. In addition, the second area 28 with a first value 40 filled. The first value 40 contains a request to the second slave 8th as well as to the third slave 10 and meets the FSoE standards. In other words, the first value is based 40 on any previous telegram 20th or at least part of any previous telegram 20th . Especially on the second area 28 of the directly preceding telegram 20th . Alternatively or in combination with this, the first value 40 a characteristic value is stored for the second and third slave 8th , 10 is already known.

The telegram processed in this way 20th is sent to the third slave 10 forwarded and from this in a fourth work step 42 receive. Using the third slave 10 becomes the placeholder 30th of the first area 26th who is the third slave 10 is assigned, read out and with a corresponding response to the master 4th filled. In addition, the first value is first 40 verified. In other words, it is checked whether the first value 40 was received without errors. The verification takes place according to the FSoE standard, for which the means of this first value 40 transmitted characterizing value with that in the third slave 10 already known characterizing value is compared. If they match, the first value is 40 and thus also verified the request. The characterizing value is, for example, the checksum of a previous telegram 20th or at least part of it, such as its second area 28 or its first value 40 .

If the request has been verified, i.e. has already been read, the request of the first slave becomes 6th processed, and by means of the third slave 10 becomes the second area 28 by means of a third value 44 which is a response to the request of the first slave 6th to the third slave 10 includes.

The telegram processed in this way is sent to the remaining slaves 12 forwarded and from these in a fifth step 46 receive. By means of this, the becomes the other slave 12 assigned placeholder 30th read out and filled with another value that has a suitable response. Then the telegram 20th forwarded to the second slave.

In a subsequent sixth step 48 the telegram processed in this way becomes 20th by means of the second slave 8th receive. Thus the telegram 20th from the first slave 6th via the third slave 10 as well as one of the other slaves 12 to the second slave 8th cleverly. Here the first value included 40 a request to the third slave 10 whereas the first value 40 free of requests to the other slaves 12 is. However, the telegram 20th filled with another value. Using the second slave 8th becomes the corresponding placeholder 30th read out and thus the request from the master 4th to the second slave 8th . The appropriate answer is in the same placeholder 30th written. In addition, the second slave 8th the first value 40 read out and verified. This takes place in the same way as with the third slave 10 a check to see if the first value 40 on a previously exchanged telegram 20th based, which is checked by means of the characterizing value. In addition, the telegram 20th , namely the second area 28 , with a second value 50 filled, which is an answer to the request of the first slave 6th to the second slave 8th includes.

The following is the telegram 20th back to the other slaves 12 sent, by means of which the telegram 20th in a seventh step 52 received and sent directly to the third slave 10 is forwarded. This is used in an eighth step 54 receive the telegram and directly to the first slave 6th forwarded by means of which the telegram 20th by means of the remaining of the two interfaces 36 in a ninth step 56 Will be received. the interface 36 corresponds to an address that differs from the address by which the telegram is sent 20th in the third step 34 was received. First are the second and third values 50 , 44 verified what for by means of the first slave 6th a characterizing value is created and with that in the respective values 44 , 50 transmitted characterizing value is compared.

Thus is in the first slave 6th already during the runtime of the same telegram 20th the response of the second and third slaves 8th , 10 known. The following is the telegram 20th over the remaining other slaves 12 to the master 4th directed. Thus the telegram 20th from the second slave 8th via the other slaves 12 , the third slave 10 as well as the first slave 6th to the master 4th sent, being from the first slave 6th the second and third value 44 , 50 and thus the responses of the second and third slaves 8th , 10 when submitting to the master 6th can be read out.

By means of the master 4th become the placeholders 30th read out. This is the status of each slave 6th , 8th , 10 , 12 in the master 4th known. The first step follows again 18th performed and by means of the master 4th a new telegram 20th created. As a result, the individual slaves are continuously checked 6th , 8th , 10 , 12 by means of the master 4th , whereby a further communication channel is also formed, which only the first, second and third slave 6th , 8th , 10 and which meets a certain safety standard, namely FSoE.

In 5 is an alternative embodiment of the first slave 6th shown, in turn, the control unit 14th as well as the connections 38 having. Here the first slave includes 6th but only a single interface 36 so the first slave 6th only a single address is assigned. In addition, the first slave 6th a memory 58 on. In the ninth step 56 becomes the telegram 20th by the slave 6th passed through, additionally creating a duplicate of it and in the memory 58 is deposited. In other words, it is from the first slave 6th the telegram 20th into memory 58 copied. From the one in the store 58 stored telegram 20th which is no longer forwarded, but the forwarded telegram 20th corresponds to the second and third values 44 , 50 and thus the responses of the second and third slaves 8, 10 are read out. This means that the data is read out during the telegram 20th already from the first slave 6th to the master 4th was forwarded. As a result, the telegram is forwarded 20th accelerated and consequently a cycle time of the fieldbus 2 . Also is just a single interface 36 required.

In 6th is an alternative embodiment of the process 16 shown. Here, too, is the first step 18th by means of the master 4th the telegram 20th created, the structure of which is not changed. The following is the second step 32 as well as the third step 34 , the fourth step 42 , the fifth step 46 and the sixth step 48 carried out the previous respective work steps 32 , 34 , 42 , 46 , 48 correspond. In other words, the telegram becomes 20th by means of the slaves 6th , 8th , 10 , 12 received and processed accordingly, for which the values, namely the first value 40 , the second value 44 , the third value 50 or the other values are stored as well as any further adjustments to the placeholders 30th be performed.

The following is a tenth step 60 the telegram 20th from the second slave 8th to the master 4th via the other slaves 12 , the third slave 10 as well as the first slave 6th sent, with the telegram 20th is only passed through. In other words, the telegram is not read out 20th or any values stored in it to be copied into the memory 58 using the in 7th first slaves shown schematically simplified 6th , which is modified in contrast to the previous embodiments. So is the memory 58 and also one of the interfaces 36 omitted. The structure of the first slave is essentially the same 6th the structure of the second, third and further slaves 12 .

In a subsequent eleventh step 62 becomes the telegram 20th from the master 4th received and those in the placeholders 30th stored values or other answers are read out. Also becomes the second area 28 or at least the second and third values 44 , 50 and thus also the responses from the second and third slaves 8th , 10 read out. Furthermore, by means of the master 4th a second telegram 64 created similar to the telegram 20th is built up and is only in the filling of the respective placeholder 30th differs. Here is the placeholder in each 30th again a corresponding status query to the respective slaves 6th , 8th , 10 , 12 deposited. In addition, the master 4th in the second area 28 the second and third value 44 , 50 written, or the full second area 28 of the telegram 20th is in the second telegram 64 copied. The second telegram is thus sent via the master 64 created that the response of the second and third slaves 8th , 10 includes.

The second telegram 64 becomes one more slave 12 sent and from these in a twelfth step 66 receive. The second telegram is processed here 64 in the same way as in the second step 32 . The second telegram processed in this way is shown below 64 to the first slave 6th and guided by them in a thirteenth work step 68 received, the second and third values 44 , 50 can be read out. In addition, verification takes place in accordance with the previous design of the procedure 16 . This means that it is now also in the first slave 6th the response of the second and third slaves 8th , 10 available. A correspondingly adjusted first value is also used 40 in the second area 28 and the corresponding placeholder 30th filled with a suitable value. The following is the fourth step 42 carried out, but instead of the telegram 20th the second telegram 64 is used. Even with this variant of the process 16 is the first slave 6th the response of the second and third slaves 8th , 10 already available after the first clock cycle, i.e. when the second telegram is presented 64 so that a speed of data exchange is increased.

The invention is not restricted to the exemplary embodiments described above. Rather, other variants of the invention can also be derived from this by the person skilled in the art without departing from the subject matter of the invention. In particular, all of the individual features described in connection with the individual exemplary embodiments can also be combined with one another in other ways without departing from the subject matter of the invention

List of reference symbols

2

Fieldbus

4th

master

6

first slave

8th

second slave

10

third slave

12

another slave

14th

management

16

Procedure

18th

first step

20th

telegram

22nd

heading

24

graduation

26th

first area

28

second area

30th

placeholder

32

second step

33

third step

34

Control unit

36

interface

38

connection

40

first value

42

fourth step

44

third value

46

fifth step

48

sixth step

50

second value

52

seventh step

54

eighth step

56

ninth step

58

Storage

60

tenth work step

62

eleventh work step

64

second telegram

66

twelfth work step

68

thirteenth step

Claims (8)

Method (16) for operating a field bus (2), in particular Ethercat, which has a master (4) and a first slave (6) as well as a second slave (8) in which - a telegram (20) is created by the master (4) and sent to the first slave (6), - by means of the first slave (6) the telegram (20) is filled with a first value (40) and sent to the second slave (8), - Using the second slave (8), the telegram (20) is filled with a second value (50) and sent to the master (4), whereby - the first value (40) comprises a request to the second slave (8), and wherein - the second value (50) comprises a response to the query. Method (16) according to Claim 1 , characterized in that the request is verified by means of the second slave (8). Method (16) according to Claim 1 or 2 , characterized in that a second telegram (64) is created by means of the master (4) which includes the response and which is sent to the first slave (6). Method (16) according to Claim 1 or 2 , characterized in that the telegram (20) is sent from the second slave (8) via the first slave (6) to the master (4), the response being read out by the first slave (6). Method (16) according to Claim 4 , characterized in that the telegram (20) is copied from the first slave (6) into a memory (58), and that the response is read from the copied telegram (20). Method (16) according to one of the Claims 1 to 5 , characterized in that the telegram (20) is sent from the first slave (6) via a third slave (10) to the second slave (8) and is filled with a third value (44) by means of this, the first value ( 40) a request to the third salvo (10) and the third value (44) a response to it. Method (16) according to one of the Claims 1 to 6th , characterized in that the telegram (20) is sent via further slaves (12) to the second slave (8) and is filled with a respective further value by means of which the first value (40) is free of queries to the further slaves ( 12) is. Fieldbus (2), in particular Ethercat, which has a master (4) and a first slave (6) and a second slave (8), and which according to a method (16) according to one of the Claims 1 to 7th is operated.

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