JP2024011240A - Communication apparatus and communication method - Google Patents

Abstract

To achieve normal operation while maintaining the specifications of a token-passing bus method even when communication apparatuses having variations in communication processing time are mixed.SOLUTION: A communication apparatus 1-1 connected to a network using a token-passing bus method includes a normality determination unit 21 that determines the normality of a processing time for a token, when the received token is addressed to its own apparatus, based on the time difference between the time when the current token was received by itself and the time when the token addressed to another communication apparatus was received immediately before that; a response processing unit 22 that transmits a response frame to a communication apparatus that is the transmission source of the current token when the normality determination unit 21 determines that the token is normal; and a token processing unit 24 that transmits the token to a next transmission destination communication apparatus when the normality determination unit 21 determines that it is normal.SELECTED DRAWING: Figure 2

Description

The present invention relates to communication equipment connected to a token passing bus type network.

Conventionally, a token passing bus method has been known as an access control method for a LAN (Local Area Network) (see Patent Document 1). In networks where many devices share a single signal line, it is necessary to avoid collisions in which multiple devices transmit data at the same time. In the token-passing bus system, a device attempting to transmit data obtains the right to transmit by capturing a token. Therefore, only one device having the right to transmit exists at a time, and no data collision occurs.

In conventional communication devices (hereinafter referred to as nodes), communication functions are realized using dedicated hardware and firmware, but dedicated hardware has the problem of running out of parts. Therefore, the communication function is implemented using general-purpose hardware and software rather than dedicated hardware and firmware, but this increases processing time and increases the variation in processing time.

In conventional systems, a timeout period is provided for token transmission. A node retransmits the token if the destination party does not respond to the token within the timeout period. This timeout period is set relatively short because it affects communication performance, and traditional nodes that use dedicated hardware and firmware cannot change the timeout setting.

When a new node whose communication function is implemented using general-purpose hardware and software is connected to the network, the processing may not be completed within the timeout period due to the processing time delay described above. In this case, a collision may occur between the token retransmitted by the conventional source node and the frame to which the new node responds late, and when a collision occurs, the token is lost.

Conventional systems can dynamically add or remove nodes on a network. Therefore, even if some kind of check is provided, it is difficult to set the check limit value to a fixed value. For example, in the system shown in FIG. 4, tokens are transmitted in the order of nodes 100-1 → 100-2 → 100-3 → 100-4 → 100-5 → 100-1 → . Here, if node 100-2 stops, there will be no response from node 100-2, so node 100-1 transmits a token to node 100-3. Therefore, the processing time required for communication changes. In this way, processing time changes not only depending on the mix of old and new nodes but also depending on the situation, so it is difficult to set a fixed limit value for checking the dispersion of processing time.

Japanese Patent Application Publication No. 3-106145

The present invention has been made to solve the above problems, and even when communication devices with varying communication processing times are mixed, normal operation can be achieved while maintaining the specifications of the token passing bus method. The purpose of the present invention is to provide a communication device and a communication method that can realize the following.

The present invention provides a communication device connected to a token-passing bus network that, when a received token is addressed to itself, sends a token addressed to another communication device at the time when the device received the current token and immediately before that. a normality determining unit configured to determine the normality of the processing time for the token based on the time difference from the time of reception; and a normality determining unit configured to determine the normality of the processing time for the token; a response processing unit configured to transmit a response frame to a next communication device; and a response processing unit configured to transmit a token to a next destination communication device when the normality determination unit determines that the frame is normal. The present invention is characterized in that it includes a token processing section.

Further, in one configuration example of the communication device of the present invention, the normality determination unit is configured to determine whether the communication device that is the source of the current token is the same as the communication device that is the source of the token that was received last time, and the time difference between the is smaller than the average value of the time differences plus a predetermined tolerance value, it is determined to be normal, and the average value of the time differences is determined so that the current time difference is reflected in the average value of the time differences. It is characterized by updating.
Further, in one configuration example of the communication device of the present invention, the normality determination unit determines the average value of the time difference when the communication device that is the source of the current token is the same as the communication device that is the source of the previously received token. If the value obtained by subtracting a predetermined tolerance value from the above is smaller than the current time difference, and the current time difference is smaller than the sum of the average value of the time differences and the tolerance value, it is considered normal. The average value of the time differences is updated so that the current time difference is reflected in the average value of the time differences.

Further, in one configuration example of the communication device of the present invention, the normality determination unit is configured to detect the current time difference in the case where the communication device that is the source of the current token is different from the communication device that is the source of the previously received token, and is larger than a predetermined minimum time difference, the source node determines that the time difference is normal, updates the average value of the time difference to the current value of the time difference, and indicates the communication device from which the previously received token was sent. The feature is that the information is updated to information indicating the communication device that is the source of the currently received token.
Further, in one configuration example of the communication device of the present invention, when the normality determination unit determines that there is an abnormality, the normality determination unit clears the average value of the time difference to 0, and indicates the communication device that is the source of the last received token. This is characterized by deleting the source node information and discarding the currently received token.

Furthermore, in the communication method of the present invention, when a received token is addressed to itself, a communication device connected to a token-passing bus type network receives another communication at the time when it received the current token and immediately before that. a first step of determining the normality of the processing time for the token based on the time difference from the time when the token addressed to the device was received; and determining that the communication device that received the token addressed to itself is normal in the first step. In this case, the second step is to send a response frame to the communication device that sent the current token, and if the communication device that received the token addressed to itself is determined to be normal in the first step, the following steps are performed: and a third step of transmitting the token to the destination communication device.

According to the present invention, by providing a normality determination unit in a communication device, even if there are communication devices with varying communication processing times, the specifications of the token passing bus method can be maintained and normality can be maintained. It is possible to realize the following actions.

FIG. 1 is a block diagram showing the configuration of a communication system according to an embodiment of the present invention. FIG. 2 is a functional block diagram of a communication device according to an embodiment of the present invention. FIG. 3 is a flowchart illustrating the operation of the communication device according to the embodiment of the present invention. FIG. 4 is a diagram illustrating the conventional problem.

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of a communication system according to an embodiment of the present invention. The communication system of this embodiment is composed of communication devices (hereinafter referred to as nodes) 1-1 to 1-3 connected to a network 2. The node 1-1 includes an Ethernet board 10 equipped with an LSI (Large Scale Integration) that performs physical layer, data link layer, and network layer protocol processing for Ethernet (registered trademark) communication, and an OS (Operating System) 11. , and an application function unit (APP) 12. An Ethernet driver 13 is installed in the OS 11. A CPU (Central Processing Unit) 14 of the node 1-1 executes processes of the OS 11 and the APP 12 according to programs stored in the memory 15.

FIG. 2 is a functional block diagram of node 1-1. Node 1-1 has a reception processing unit 20 that receives frames from other nodes, and when the received token is addressed to itself, the time when it received the current token and the token addressed to other nodes immediately before that. The normality determining unit 21 determines the normality of the processing time for the token based on the time difference from the time when the token was received, and if the normality determining unit 21 determines that the processing time is normal, A response processing unit 22 that sends a response frame to a node, a data processing unit 23 that sends data to other nodes, and a token sent to the next destination node when the normality determination unit 21 determines that the node is normal. and a transmission processing section 25 that transmits frames to other nodes.

The configuration of the node 1-1 shown in FIG. 2 is realized by the Ethernet board 10, the OS 11, and the APP 12. In particular, it is desirable that the normality determination unit 21, response processing unit 22, and token processing unit 24, which require fast responses, be implemented by the Ethernet driver 13. Although FIGS. 1 and 2 only show the configuration of node 1-1, the configurations of nodes 1-2 and 1-3 are also similar to node 1-1. Further, in FIG. 1, the number of nodes is three for the sake of simplicity, but it goes without saying that the number of nodes may be two or three or more.

Although not shown in FIG. 1, since the nodes 1-1 to 1-3 in this embodiment internally perform protocol processing in the Ethernet format, these nodes 1-1 to 1-3 are connected to the token-passing bus system. When connecting to the network 2, a relay device for performing protocol conversion may be provided between each node 1-1 to 1-3 and the network 2. The relay device converts the token-passing bus frame from the network 2 into an Ethernet frame, and converts the Ethernet frame from the nodes 1-1 to 1-3 into a token-passing bus frame.

FIG. 3 is a flowchart illustrating the operations of nodes 1-1 to 1-3 in this embodiment. It is not possible to determine whether token processing is delayed or not based only on the own node's data. Therefore, in this embodiment, information on other nodes on the network is used as reference. In an IEEE802.4 (token passing bus system) network, the transmission order of frames is determined by the node configuration, as explained with reference to FIG. When other nodes operate regularly, the time difference between the reception time of a token addressed to the own node and the reception time of the immediately preceding token addressed to another node is constant. This time difference is used to detect fluctuations in the processing time of the own node.

When the reception processing unit 20 receives a token from another node, the normality determination unit 21 of each node 1-1 to 1-3 saves the latest reception time as the previous reception time, The current time is saved as the latest reception time (step S100 in FIG. 3). Then, the normality determining unit 21 determines whether the token received this time by the receiving processing unit 20 is a token addressed to the own node (step S101 in FIG. 3). If the token is not addressed to the node itself, the process ends without responding to the token.

In the case of a token addressed to its own node, the normality determining unit 21 determines whether the source node of this token is the same as the source node of the previously received token (step S102 in FIG. 3). If the source node of the current token is different from the source node of the previously received token (NO in step S102), the normality determination unit 21 determines the time when the local node received the current token and the time immediately before that when the node addressed to the other node. It is determined whether the time difference Cur_diff from the time when the token was received is larger than a predetermined minimum time difference Min_diff (step S103 in FIG. 3). The time difference Cur_diff is a value obtained by subtracting the previous reception time from the latest reception time saved in step S100.

The minimum time difference Min_diff is a time difference that always occurs due to design, and includes the frame transmission time and the like. The determination process in step S103 is a process that takes into consideration changes in the node configuration on the network.

If the current time difference Cur_diff is less than or equal to the minimum time difference Min_diff (NO in step S103), the normality determination unit 21 determines that there is an abnormality, and receives a token addressed to another node at the time when the token addressed to the own node is received and immediately before that time. The average value Ave_diff of the time difference from the time when the token was received is cleared to 0, the source node information indicating the source node of the token received last time is deleted, the token received this time is discarded (step S104 in FIG. 3), and the process ends. shall be. Since the source node information has been deleted, the next time a token is received, the determination in step S102 will be NO.

Further, if the current time difference Cur_diff is larger than the minimum time difference Min_diff (YES in step S103), the normality determination unit 21 determines that the current time difference is normal, updates the average value of the time differences Ave_diff to the value of the current time difference Cur_diff, and updates the previous time difference The source node information indicating the source node of the received token is updated to the information indicating the source node of the token received this time (step S105 in FIG. 3).

When the normality determining unit 21 of its own node determines that the node is normal, the response processing unit 22 transmits a response frame to the source node of the current token via the transmission processing unit 25 (step S106 in FIG. 3).

After transmitting the response frame, if a data transmission request is generated from the APP 12 within the own node (YES in step S107 in FIG. 3), the data processing unit 23 transmits the requested data to the requested destination node. It instructs the transmission processing section 25 to transmit the data to the destination, and passes the data to the transmission processing section 25. In response to an instruction from the data processing unit 23, the transmission processing unit 25 transmits the data to the destination node (step S108 in FIG. 3).

If there is no data transmission request or if data transmission is completed, the token processing unit 24 transmits the token to the next destination node via the transmission processing unit 25 (step S109 in FIG. 3). As mentioned above, in a token passing bus type network, for example, the destination of a token from node 1-1 is node 1-2, the destination of a token from node 1-2 is node 1-3, and the destination of a token from node 1-3 is node 1-3. The destination of the token is determined in advance, such as node 1-1.

On the other hand, if the source node of the current token is the same as the source node of the previously received token (YES in step S102), the normality determination unit 21 determines a predetermined fluctuation tolerance value α based on the average time difference Ave_diff. It is determined whether the value obtained by subtracting Ave_diff-α is smaller than the current time difference Cur_diff (step S110 in FIG. 3).

The allowable value α is a fixed time set based on a value verified by actual measurement. If Ave_diff-α is greater than or equal to the current time difference Cur_diff (NO in step S110), the normality determining unit 21 determines that it is abnormal, proceeds to step S104, and ends the process.

The determination process in step S110 is a process that takes into consideration the case where the processing of the token transmission source node is delayed, and is a determination process that also considers the case where the processing of the transmission source node is delayed as an abnormal case.

If Ave_diff-α is smaller than the current time difference Cur_diff (YES in step S110), the normality determination unit 21 determines whether the current time difference Cur_diff is smaller than the value Ave_diff+α, which is the sum of the average value Ave_diff of the time differences and the tolerance value α. It is determined (step S111 in FIG. 3).

If the current time difference Cur_diff is equal to or greater than Ave_diff+α (NO in step S111), the normality determination unit 21 determines that it is abnormal, proceeds to step S104, and ends the process.

Further, if the current time difference Cur_diff is smaller than Ave_diff+α (YES in step S111), the normality determination unit 21 updates the average value of time differences Ave_diff so that the current time difference Cur_diff is reflected in the average value of time differences Ave_diff. (Step S112 in FIG. 3). Specifically, the normality determination unit 21 adds the current time difference Cur_diff to the denominator of the calculation formula used when calculating the average time difference Ave_diff last time, adds 1 to the numerator of the calculation formula, and calculates the average time difference Ave_diff by adding 1 to the numerator of the calculation formula. Just recalculate.

The processing in steps S106 to S109 is as described above. Through the determination process in step S111, it is possible to determine whether or not the processing of the own node is delayed with respect to the token.

Note that after transmitting the token (step S109), the token processing unit 24 resends the token if the destination node does not respond to the token within the timeout period. Furthermore, if the destination node does not respond to the retransmission of the token a predetermined number of times, the token is transmitted to the next node after the destination node. For example, when node 1-1 sends a token to node 1-2, if node 1-2 does not respond, node 1-1 skips node 1-2 and sends the token to node 1-3. do. Such token processing is in accordance with the specifications of the token passing bus method.

If the judgment is NO in any of steps S103, S110, or S111 and the node does not respond to the token, this node will be skipped and the token will be sent to the next node, but when the next token comes around, If the determination in step S103 or step S111 is YES, token processing is performed normally.

The present invention can be applied to a token passing bus type communication system.

1-1 to 1-3...Communication equipment, 2...Network, 10...Ethernet board, 11...OS, 12...Application function unit, 13...Ethernet driver, 14...CPU, 15...Memory, 20...Reception processing unit, 21 ...Normality determination section, 22...Response processing section, 23...Data processing section, 24...Token processing section, 25...Transmission processing section.

Claims (6)

In communication equipment connected to token passing bus network,
When the received token is addressed to itself, determine the normality of the processing time for the token based on the time difference between the time when it received the current token and the time when it received a token addressed to another communication device immediately before that. a normality determination unit configured to
a response processing unit configured to transmit a response frame to a communication device that is a source of the current token when the normality determination unit determines that the token is normal;
A communication device comprising: a token processing unit configured to transmit a token to a next destination communication device when the normality determination unit determines that the communication device is normal. The communication device according to claim 1,
The normality determination unit determines that when the communication device that is the source of the current token is the same as the communication device that is the source of the token that was received last time, and the current time difference is a predetermined tolerance value for the average value of the time differences. If the communication device is smaller than the sum of , the communication device determines that the communication device is normal, and updates the average value of the time differences so that the current time difference is reflected in the average value of the time differences. The communication device according to claim 1,
The normality determination unit determines that when the communication device that sent the current token is the same as the communication device that sent the token received last time, a value obtained by subtracting a predetermined tolerance value from the average value of the time difference is determined. , is smaller than the current time difference, and if the current time difference is smaller than the sum of the average value of the time differences and the tolerance value, it is determined to be normal, and the current time difference is the average value of the time differences. A communication device that updates the average value of the time difference so that it is reflected in the time difference. The communication device according to claim 1,
The normality determination unit determines whether the communication device sending the current token is different from the communication device sending the token received last time, and if the current time difference is larger than a predetermined minimum time difference. , determines that the time difference is normal, updates the average value of the time difference to the current value of the time difference, and updates the source node information indicating the communication device that sent the token received last time to the communication device that sent the token received this time. A communication device characterized by updating to information indicating. The communication device according to any one of claims 2 to 4,
When the normality determination unit determines that there is an abnormality, the normality determination unit clears the average value of the time difference to 0, deletes the source node information indicating the communication device of the source of the previously received token, and uses the currently received token. Communication equipment characterized by being discarded. When a communication device connected to a token-passing bus network receives a token addressed to itself, it determines the time when it received the current token and the time when it received a token addressed to another communication device just before that. a first step of determining the normality of the processing time for the token based on the time difference;
a second step of transmitting a response frame to the communication device that is the source of the current token when the communication device that has received the token addressed to itself is determined to be normal in the first step;
and a third step of transmitting the token to the next destination communication device if the communication device that has received the token addressed to itself is determined to be normal in the first step. .

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