Method for identifying and preventing errors by replacement messages and node thereof

FIELD OF THE INVENTION The present invention relates to a method for identifying errors and avoiding errors when transmitting real-time critical data by means of data telegrams in a data network, especially in an automation system.

BACKGROUND A data network is composed of networked data network nodes and makes it possible to communicate between multiple users. The meaning of communication here is to transfer data between users. Here, the data to be transmitted is sent as a data telegram, that is, the data is packaged together in one or more packets and sent in this form to the corresponding recipient through the data network. Therefore it is also called data packet. Here, the concept of data transmission is completely synonymous with the transmission of data telegrams or data packets described above.

For networking, for example, in a switchable high-performance data network (especially an Ethernet network), users are connected to each other through coupling nodes. Each coupling node can be connected to more than two users and can itself be a user. Users have, for example, computers, storable programmable controllers (SPS), or machines that exchange electronic data with other machines, especially machines that process electronic data.

A method of data packet transmission is disclosed in EP0866579A1, in which the data packet is transmitted from the sending station to the receiving station without specifying the respective identification.

In distributed automation systems, such as transmission technology, certain data must reach certain users at certain times and be processed by the recipients. People here call it real-time critical data or real-time critical data exchange, because the data does not arrive at a certain location in time, resulting in undesirable results at the user.

It is also known in the prior art to adopt a synchronous and timing communication system with equal interval characteristics in an automation system. Here, the system is understood to be composed of at least two users who are connected to each other in order to exchange data or transmit data to each other. Among them, the data exchange is carried out periodically in the communication cycle at equal intervals, and the communication cycle is preset by the communication clock used by the system. The user is, for example, a central automation device, such as a programmable controller (SPS, mobile controller) or other control unit, a computer, or a machine that exchanges electronic data with other machines, especially processing data of other machines, and such as input/output Peripherals, transmissions, execution of components

02819037.8 No. device, sensor. Below, the control unit is understood as all types of regulators and control units. The communication systems used to transmit data include, for example, fieldbus, process fieldbus, Ethernet,

02819037.8 No. Industrial Ethernet, Phare bus or PC internal bus system (PCI), etc. Among them, the data telegram is input into the data network by the user at a fixed transmission time in advance. Nowadays, automation components (such as controllers, transmission devices, ...) often have interfaces with periodic timing communication systems. The operation level (fast cycle) of these automation components (such as position adjustment in a controller, transmission speed and torque adjustment) is synchronized with the communication cycle. This determines the communication clock. On the other hand, although a more mantle clock already meets the requirements, the low-performance algorithms (slow cycle) of automation components (such as temperature adjustment) can also only communicate with other components (such as ventilators, ventilators, etc.) through the communication clock. The binary switch of the water pump,...communication. By using only one communication clock to transmit all the information in the system, high requirements are placed on the bandwidth of the transmission distance and the communication connection of the components.

This high requirement cannot always be met, but may lead to transmission errors. The possible transmission errors are:

-Data telegram does not appear or appears delayed;

-Overflow of the data buffer in the coupling node;

-The length of the data telegram is wrong;

-Physical CRC (Cyclic Redundancy Check) error.

In the data network known in the prior art, a problematic data telegram can trigger an error response on all data nodes through which the data telegram is transmitted. Only by using telegrams specially set up for this can error diagnosis be possible. This creates an additional burden on the data network, making error diagnosis difficult and slow.

SUMMARY OF THE INVENTION The technical problem to be solved by the present invention is to avoid error responses on the transmission path of problematic data telegrams and to provide an improved method for error diagnosis.

The technical problem based on the present invention is solved by the features of the independent claims. Specific embodiments of the invention are given in the dependent claims.

In the method according to the invention, problematic data telegrams are basically not transmitted. Here, the advantage is shown that the data telegram in question does not trigger an error reaction on other data nodes. Instead of transmitting a problematic data telegram, if a data telegram with a certain identifier on a data node has no problem until the transmission time corresponding to the identifier has not appeared, or has not appeared during the transmission time, the data node sends a Replacement telegram with this identifier.

02819037.8 The method of saving and forwarding and the short-cut method can be used in the transmission. The data telegram is completely received in the method of saving and forwarding, and the data telegram is temporarily saved before forwarding. In contrast, in the shortcut method, the data is not temporarily saved, but is directly transferred from the receiving port to the sending port.

Data telegrams generally include a logo, security data, and a transmission status. The replacement telegram also includes an identifier, valid data and a transmission status. The identifier of the replacement telegram is the identifier of the data telegram to be replaced. The effective data can be arbitrary. The transmission status indicates the type of the replacement telegram. The transfer status can additionally indicate what kind of transfer error has occurred. Preferably, no additional data telegrams are required for error diagnosis.

At the time of transmission, the coupling node transmits the replacement telegrams received up to the time of transmission through one or more transmission ports corresponding to the identifiers like ordinary data telegrams. In a preferred embodiment of the present invention, a coupling node can receive and transmit multiple data telegrams with the same identity.

The starting point of an application situation is to first receive a data telegram that is not a replacement telegram at the target node, and store the valid data of the data telegram and the assigned timer value. If the target node receives another data telegram with the same identifier, it first verifies whether the data telegram is a replacement telegram. If it is a replacement telegram, the stored valid data and the assigned timer value are not replaced at all. In a preferred embodiment of the present invention, the occurrence of replacement telegrams is collected on the target node. If another data telegram is not a replacement telegram, it will also check whether the stored valid data is still current according to the stored timer value. If the valid data is still current, the valid data can be replaced, but replacement is not necessary. If the valid data is not current, in principle it is replaced by valid data from another data telegram. Before delivering the valid data to the application of the target node, the valid data must be completely received and temporarily saved, because forwarding the valid data of a data telegram that has not been completely received may cause problems in the function of the application.

BRIEF DESCRIPTION OF THE DRAWINGS The preferred embodiments of the present invention will be further described below with reference to the accompanying drawings. In the figure: Fig. 1 shows a network diagram of a data network for transmitting real-time critical data according to the present invention, Fig. 2 shows a schematic connection between a source node and a target node through a coupling node, and Fig. 3 shows the prior art The combination of the DIX Ethernet frame and the Ethernet frame of the present invention,

02819037.8 Fig. 4 shows a flowchart of the method for transmitting real-time critical data on a coupling node in the present invention, and Fig. 5 shows a flowchart of the method for transmitting real-time critical data on a target node in the present invention.

1 shows a data network for transmitting real-time critical data according to the present invention. The source node i is indirectly connected to the target node k through the coupling node j. The transmission of data is carried out through the data bus that connects the data network nodes to each other. For example, a data telegram can be transmitted from the sending port 1 of the source node i=1 through the receiving port 2 and the sending port 3 of the coupling node 1 to the receiving port 4 of the coupling node j=2. However, it can also be directly sent from the sending port 5 of the source node 1 to the receiving port 4 of the coupling node j=2. It can also be seen that the data telegram from the source node 1 can either pass through the coupling node Λ j = 1, or through the coupling node j = = 2 to reach the target node Λ k = h. This shows that the coupling node and the destination node can both pass through different The network path receives the same data telegrams, and these data telegrams therefore also have the same identification.

Figure 2 shows the connection between the source node and the target node through a coupling node. The source node stores such data, which is obtained in the form of a data telegram with a certain identification by means of an application of the source node. At the sending moment predetermined by the identifier, the data telegram is sent to one or more coupling nodes through a sending port. The data telegram is received on a receiving port of the coupling node. Then, either it is temporarily stored in the memory until the transfer time (the method of saving and forwarding), or it is directly transferred to the sending port (the method of short-cutting). At the moment of sending, the data telegram is transferred to other coupling nodes or target nodes through a sending port. The data telegram is received on the receiving port of the target node, and then stored and prepared for the application of the target node. The source node, coupling node and target node are synchronized through a timer.

Fig. 3 shows the structure of the DIX Ethernet frame of the data telegram known in the prior art and the Ethernet frame of the present invention. The settings of title, destination address, source address, real-time type and CRC (Redundancy Check of Shield Ring) are the same and occupy the same four storage spaces. In addition, the DIX Ethernet frame contains application data up to 1.5K bytes. In the same storage space, the Ethernet frame according to the present invention sets application data, data status, and transmission status.

The flowchart in FIG. 4 illustrates the method steps of the present invention for transmitting real-time critical data on a coupling node. The coupling section, account for, first wait for one or more without problems, with specific

02819037.8 The appearance of the first identified data telegram DT A, B -. (step 6) "The number of telegrams is given by the receiving list, and the data telegram DT A, :B that appeared before the transmission time is first temporarily stored (stored) And forwarding method, step 7). Correspondingly, the data telegram received at the time of delivery is directly transferred from the receiving port to the sending port (shortcut method). A replacement telegram with a specific identifier DTA, Β···, is generated instead Every expected data telegram that has not been received until the time of delivery without any problem (step 8). The data telegram is delivered or replaced at the delivery time given by the receiving list (step 9). In a preferred embodiment of the present invention , The occurrence of the transmission error is stored on the node where the transmission error occurred.

Figure 5 illustrates a flow chart of the method of the present invention for transmitting real-time critical data on a target node. The starting point is to first receive a data telegram DTC that is not a replacement telegram (step 10)_oThe situation where a replacement telegram is first received is not important to the present invention. Store the data telegram DTC together with a corresponding timer value (step 11). If another data telegram DTD with the same identification is received at the target node (step 12), it must first be checked whether it is a replacement telegram (step 13). The valid data of the stored data telegram should not in principle be replaced by any valid data of a replacement telegram. If the data telegram DTD is not a replacement telegram, in the next step, check whether the data telegram DTC is still current according to the corresponding timer value (step 14). The current data telegram DT C can be replaced, but it is not necessary to do so. If the data telegram DTC is not current, replace its valid data and its corresponding timer value (step 15). In a preferred embodiment of the present invention, the occurrence of replacement telegrams is collected on the target node. If the data telegram M DTD is a replacement telegram, it does not replace the data telegram DTC in principle (step 16).

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