JP2001257696A - Communication method between master and slave - Google Patents

Abstract

(57) [Problem] To provide a plurality of master nodes in a network, and enable each master node to communicate with all slave nodes. SOLUTION: A request message ID is added from a master node 10B by adding a request source station number for identifying the own station and a request message ID for identifying the request message, and a slave node 20C receiving this transmits a request message to the response message to the request message. The request source station number and the request message ID added to the request message are added, and the request message ID is returned to the master node 10B. In the master node 10B, when the request source station number and the request message added to the received response message do not match those added to the request message, the request is not a response message to the request message, but is a request transmitted by another master node 10A, for example. Recognize it as a message.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a master-slave type network system in which a plurality of master nodes are provided in a network and communication is performed between the master nodes and the slave nodes. About the method.

[0002]

2. Description of the Related Art Conventionally, in a master-slave type network system, one node in the network system becomes a master node and performs data transmission. Then, when transmitting data from the master node to the slave node, the master node transmits a data write message including the transmission data to the slave node, and the slave node that has received the data write message notifies that the data write message has been received. ACK for
A message is returned to the master node that transmitted the data write message. Conversely, when the master node receives data from the slave node, the master node transmits a data read message to the slave node, and the slave node that has received the data appends predetermined data to the ACK message. It is sent to the master node.

When the master node requests some processing to the slave node, for example, when the master node receives data specified from the slave node, that is, when a transaction message is transmitted, the master node first transmits a data write message. , The request information indicating the processing contents requested to the slave node is transmitted to the slave node, whereby the slave node generates predetermined response data according to the request information, and then a data read message is notified from the master node. Then, the generated response data is added to the ACK message and transmitted.

[0004]

In the slave node, predetermined response data is generated based on the request information notified by the data write message, and when the data read message is received next, the slave node generates the response data. The response data is transmitted to the transmission source. For this reason, for example, when a data write message for notifying the request information to the slave node is received from a plurality of nodes, the previously received data write message is validated, and a predetermined data write message is specified according to the request information specified in the message. Response data will be generated. Then, when the slave node receives the data read message, the slave node transmits response data to the master node of the transmission source.

[0005] At this time, even if the slave node receives the data read message from the master node, the slave node will transmit response data even if the master node has invalidated the data write message.
Response data that is not response data to the request information requested by itself will be transmitted to the invalidated master node. For this reason, the master node may execute processing based on the received response data although the master node does not actually respond to the request information requested by itself.

[0006] Therefore, a plurality of master nodes cannot be provided in the network, and only one master node is provided in the network, thereby performing communication with each slave node. Also, a communication method that can have multiple master nodes is being considered,
In this case, one slave node can communicate only with a certain master node, and the master node and the slave node are restricted by the communication destination node even in the same network. There is.

Accordingly, the present invention has been made in view of the above-mentioned conventional unsolved problem, and even when a plurality of master nodes are provided in a network, the master node and the slave nodes are not connected to each other. An object of the present invention is to provide a communication method between a master and a slave that can perform communication without being restricted by a communication destination.

[0008]

In order to achieve the above object, according to the first aspect of the present invention, there is provided a communication method between a master and a slave, wherein a slave node receiving a request message transmitted by a master node responds to the request message. In a communication method between a master and a slave, wherein a response message is generated and a slave node that has received a data read message transmitted by a master node transmits the response message to a master node that has transmitted the data read message, The node transmits the request message with identification information for identifying the request message added thereto, and the slave node adds the identification information added to the request message to the response message and transmits the response message, The node identifies the response message received It is characterized by being adapted to determine the correspondence between the response message to the request message received from the identification information added to the broadcast and the request message.

According to the first aspect of the present invention, when the master node transmits a request message such as a transaction message to the slave node, the request message includes identification information for identifying the request message, for example, an ID number. Add and send. On the other hand, the slave node receiving the request message generates a response message specified by the request message, and when receiving the data read message from the master node,
The previously generated response message is transmitted to the master node that has transmitted the data read message. At this time, the slave node adds the identification information added to the request message to the response message and transmits it.

In the master node, the identification information added when transmitting the request message is stored in advance, and when the response message is received, the identification information added to the response message is stored in advance. It is determined whether or not the identification information added to the request message matches, and if they match, it is recognized as a response message to the previously transmitted request message. Conversely, if they do not match, it recognizes that this is not a response to the previously transmitted request message, but a response to, for example, a request message transmitted by another master node.

Here, for example, when a plurality of master nodes are provided in a network system, and the plurality of master nodes transmit a request message to one slave node, the slave node receives a request message from any one of the master nodes. A response message to the request message is generated, and when the data read message is received, the response message is transmitted to the source of the data read message. Therefore, when each master node transmits a request message and then transmits a data read message, a response message to a request message from a certain master node is transmitted to all master nodes. The master node can recognize whether or not the response is to the request message transmitted by the own node. Therefore, even when a plurality of master nodes exist in the network system, each master node can communicate with a desired slave node.

Further, in the communication method between the master and the slave according to the present invention, when the identification information added to the received response message coincides with the identification information added to the request message, the master node responds to the response message. A reception completion message is transmitted to a slave node that has transmitted the message, and the slave node holds the response message until the reception completion message is received.

According to the second aspect of the present invention, when the identification information added to the received response message matches the identification information added when the request message was transmitted earlier, the master node completes the reception. The message is transmitted to the slave node that has transmitted the response message.
On the other hand, when the slave node generates a response message to the request message, it holds this response message and deletes it when it receives the reception completion message.

That is, since the master node transmits a reception completion message when receiving a response message to the request message, the slave node surely receives the response message from the master node which is the transmission source of the request message. Since the response message is deleted when the message exchange between the master node and the slave node has been securely completed, the master node that has received the response message with different identification information may send the response message to another slave node. It is possible to recognize that the processing is being performed on the request message.

According to a third aspect of the present invention, there is provided a communication method between a master and a slave, wherein the identification information is station identification information for identifying a master node of a transmission source of the request message. According to the third aspect of the present invention, the station identification information for specifying the master node of the transmission source of the request message is set as the identification information. Therefore, the master node that has received the response message with the different identification information can recognize with which master node the slave node that is the source of the response message is communicating.

According to a fourth aspect of the present invention, in the communication method between a master and a slave, the identification information specifies the station identification information and a task that has generated the request message in a station identified by the station identification information. And task identification information for performing the task. In the invention according to claim 4, as identification information, a station identification information for specifying a master node of a transmission source of a request message, and a task for specifying a task that has generated the request message in a station specified by the station identification information And identification information. Therefore, a master node that receives a response message with different identification information can recognize which slave node of which response message is transmitting / receiving a message to / from which task of the master node. Becomes

According to a fifth aspect of the present invention, there is provided the communication method between the master and the slave, wherein the slave node receives a new request message after receiving the request message and before receiving the reception completion message. It is characterized in that when it is done, it is discarded. According to the fifth aspect of the present invention, after receiving the request message, the slave node discards the new request message until it receives the reception completion message, even if a new request message is received, and responds to other request messages. No processing is performed. Therefore, even if the master node that has transmitted another request message subsequently transmits a data read message, a response message to the request message being processed is transmitted as a response, and the request message is transmitted later. The master node
It is possible to recognize that the slave node to which the request message is to be transmitted is executing a process for another request message.

In the communication method between a master and a slave according to claim 6 of the present invention, the master node does not match the identification information added to the request message with the identification information added to the received response message. Sometimes, after a lapse of a predetermined time, the request message is retransmitted. In the invention according to claim 6, in the case where the identification information added to the received response message does not match the identification information added to the request message, the master node transmits the request message again when a predetermined time has elapsed. . Therefore, for example, when the identification information added to the received response message does not match the identification information added to the request message, after the transmission / reception time of the message of the slave node when the communication is normally performed, If the request message is transmitted again and the identification information added to the response message is still different, it can be considered that the message exchange between the slave node and the master node of the communication destination is not normally performed.

Further, in the communication method between master and slave according to claim 7 of the present invention, the master node is capable of re-transmitting the request message even when re-transmitting the identification information added to the response message and the identification information added to the request message. When the information does not match, the state of the node specified by the identification information added to the received response message is checked, and when the node is abnormal, the reception completion message is transmitted instead of this node. 7. The communication method between a master and a slave according to claim 6, wherein:

In the invention according to claim 7, in the master node, when the identification information added to the request message does not match the identification information added to the received response message even if the request message is retransmitted, the master node receives the request message. Check the state of the node specified by the identification information added to the response message. Here, when any abnormality occurs in the node, that is, when the node itself is abnormal or the task of the source of the request message is abnormal, the reception completion message is not transmitted. For example, when an error occurs, the slave node may not accept another request message.

However, when a master node or a task in which an abnormality has occurred is detected, another master node transmits a reception completion message instead, so that the slave node can receive another request message.

[0022]

Embodiments of the present invention will be described below. FIG. 1 shows an example of a network system to which the present invention is applied.
For example, a master node 10A and a master node 10B that operate as masters and a plurality of slave nodes 20 that operate as slaves are connected by a communication line L, and messages are transmitted between the master node and the slave nodes by a master-slave method. It has become.

The master node 10 (10A, 10B)
Transmits and receives a message to and from the slave node 20, and executes a predetermined process based on the message received from the slave node 20. And the master node 10
When the master node 10 transmits and receives a message between the slave node 20 and the slave node 20, the master node 10 transmits a request message for requesting processing to the slave node 20, and in response to the request message, sends a response message from the slave node 20. Receives and transmits a reception completion message for notifying that this response message has been received. With this procedure, a series of processes accompanying the transmission of the request message is completed.

The master node 10 generates a data write message of a predetermined format including a transmission message when transmitting and receiving each message with the slave node 20 and transmitting a message from the master node 10. This is transmitted to the destination slave node 20, and an ACK response is received as a response. Conversely, when a message is received from slave node 20, a data read message is transmitted to slave node 20, and an ACK response is received together with a predetermined message as a response.

When a status check request is made from another master node, the master node 10 performs a status check on its own station and a designated task on the master node 10, and returns the result. On the other hand, the slave node 20 is the master node 1
A message is exchanged with the master node 10 in response to the access from 0. When the data write message is received from the master node 10, an ACK response for notifying that the data write message has been received is returned to the master node of the transmission source of the data write message. When the data read message is received, a response message stored in a predetermined storage area is added to the ACK response and returned to the transmission source master node. And
When the request message is notified by the data write message, a predetermined process is executed according to the request message, the response message is generated as a response to the request message, and the response message is stored in a predetermined storage area. When a reception completion message is notified by the data write message, the response message stored in the storage area is removed.

FIG. 2 shows a message frame format of a data write message for transmitting a request message, a response message, a reception completion message, and an ACK response with data. As shown in FIG. 2, each message frame includes a frame code m1 indicating a type of the message frame such as a data write message or an ACK response with data that is a response to the data read message, and a transmission destination of the message. Destination station number m2 for specifying the node of
And the source station number m3 for specifying the source node of the message, and a message type indicating the type of the message to be transmitted in this message frame such as a request message, a response message, or a reception completion message m4, a request source station number m5 for specifying the source node of the request message, a request message ID m6 for identifying the request message, and message data m7 for transmitting request message data or response message data. It is configured.

The request source station number m5 corresponds to the station identification information, and the request message ID m6 corresponds to the task identification information. FIG. 3 shows the state of the master node 10.
9 is a flowchart illustrating an example of a processing procedure when a message is exchanged with the slave node 20. That is, the master node 10 first generates a data write message for transmitting a request message in step S2. That is, as shown in FIG. 2A, the data write message is used as the frame code m1, the station number specifying the transmission destination node as the destination station number m2, the station number specifying the own node as the transmission source station number m3, and the message type m4 as " Request message ", a station number for specifying the own node as the request source station number m5, an identification number as the request message ID m6, and request message data m7 comprising a process requesting the slave node 20, for example. A request message frame including a data write message for transmitting the request message is generated. The request message frame is stored in a predetermined storage area.

Next, the process proceeds to step S4, in which a request message frame is transmitted via the communication line L, and an ACK response is received as a response. Next, the process proceeds to step S6, where a data read message is transmitted to the slave node 20 to which the request message frame is transmitted, and a response message receiving process for receiving the response message is performed. The data read message has, for example, the same format as the message format shown in FIG. 2 described above, and includes a “data read message” as a frame code, a station number specifying a slave node to receive a response message as a destination station number, and a local node number as a source station number. And a "reception request message" as a message type.

Then, the flow shifts to step S7 to determine whether or not an ACK response with data has been received as a response to the data read message. It is determined whether or not a retry for transmitting the data read has been performed. If the retry has not been performed, the process returns to step S6, and the data read message is transmitted again.

ACK with data even if retry
If no response is received, the process ends. On the other hand, when an ACK response with data is received in step S7, the process proceeds to step S10, and the request source station number m5 and the request message ID m6, which are added to the response message and notified in the ACK response with data, are added to the data in step S2. In the process, it is determined whether or not the request message frame stored in the predetermined storage area matches the request source station number m5 and the request message ID m6. If they match, the process proceeds to step S12,
A data write message including the reception completion message shown in (c) is generated. That is, the data write message is used as the frame code m1, and the source station number m notified by the received ACK response with data is received as the destination station number m2.
3. A station number for identifying the own node as a source station number m3, a reception completion message as a message type m4,
A reception completion message frame composed of a data write message for transmitting the reception completion message composed of these is generated. Then, this is transmitted, and the process ends.

On the other hand, in step S10, the request source station number m5 and the request message IDm of the ACK response with data are
When the request source station number m5 and the request message ID m6 stored in advance do not coincide with each other, step S14
Move to Then, it is determined whether or not a retry to transmit the request message again has been performed. If no retry has been performed, the process returns to step S4.

On the other hand, when a retry is performed in step S14, the process proceeds to step S16, and the request source station number m notified in the ACK response with data received in step S6.
A status check request is made to the master node specified in 5 to check the status of the master node.
Then, if the result is normal, the process is terminated. On the other hand, if it is determined in step S16 that the status is abnormal as a result of the status check, the process proceeds to step S18, and a data write message including a reception completion message shown in FIG. Is transmitted to the slave node 20 that is the transmission destination of the request message. Then, the process ends.

FIG. 4 is a flowchart showing an example of a processing procedure when a message is exchanged with the master node 10 in the slave node 20. Slave node 20
Then, upon receiving the request message frame, after returning an ACK response in response to the request message frame,
Then, control goes to a step S24. The ACK response includes, for example, an ACK response as a frame code, a source station number of a data write message as a destination station number, and a station number specifying its own node as a source station number, similarly to the respective message formats of FIG.

In step S24, a process specified by the request message notified by the data write message is performed, and a response message is generated as a response to the process. Then, an ACK response frame with data including the response message is generated. That is, as shown in FIG. 2B, an AC with data is used as the frame code m1.
K response, a station number that identifies the own node as the source station number m3, a response message as the message type m4, a request source station number m5 and a request message ID m6, and the request source station number m5 and the request message added to the request message received in step S22. IDm6 is copied, response message data including response data to the process specified by the request message is set as message data m7, and an ACK response frame with data is generated from these. Then, the ACK response frame with data is stored in a predetermined storage area.

Then, the flow shifts to step S26, and if a data read message is received from the master node 10, the flow shifts to step S28, where the ACK response frame with data stored in a predetermined storage area and the data read message as the destination station number m2. Is set, and this data-added ACK response frame is transmitted. Then, control goes to a step S30.

On the other hand, when the data read message is not received in step S26, the process proceeds to step S30.
Move to In this step S30, the master node 1
From 0, it is determined whether a reception completion message frame has been received. If the reception completion message frame has not been received, the process returns to step S26, and if the reception completion message frame has been received, the process proceeds to step S32. Then, the ACK response frame with data stored in the predetermined storage area in the process of step S24 is deleted, and the process ends.

FIG. 5 is a state transition diagram of the master node 10. That is, when the master node 10 requests the slave node 20 to transmit a transaction message from the idle state (state st1), the state st
Go to 2 and generate a request message and send it.
It is in a state to perform request message transmission processing. When the request message transmission processing is completed, the state is changed to the state st3, the reception processing of the response message, that is, the ACK with data.
Performs response reception processing. Then, when the response message is received, the state shifts to state st4, where the response message is checked, that is, the request source station number and the request message ID.
Check. On the other hand, when the response message cannot be received in the state st3, the process proceeds to the state st5, and the data read message is transmitted again to try to receive the response message. When the response message is received, the flow shifts to the state st4 and the response message is checked.

When the response message cannot be received even if the response message is received again in the state st5, the process returns to the state st1 as a retry failure and enters the idle state. Then, as a result of checking the response message in the state st4, if the response message is normal, the process proceeds to the state st6, a reception completion message is transmitted, and the state becomes the idle state st1.

On the other hand, as a result of checking the response message in the state st4, if the response message is abnormal, the flow shifts to the state st2 and the request message transmission processing is performed again. Then, a response message receiving process is performed in state st3,
As a result of checking the response message in step 4, if the response message is normal, the process proceeds to state st6 and the transmission processing of the reception completion message is performed. The status check is performed for the task that is the master node that is performing the communication processing with the slave node 20 and that is communicating with the slave node 20 and that is specified by the request source station number and the message ID added to the response message. When the result is normal, the state shifts to the state st1 and becomes the idle state.

On the other hand, as a result of the status check in the state st7, if the in-process task is abnormal,
The process proceeds to step 6, where a reception completion message is transmitted in place of the in-process task in which the abnormality has occurred, and thereafter, the process proceeds to state st1 to enter the idle state. FIG. 6 is a state transition diagram of the slave node 20.

That is, when the slave node 20 receives the request message from the master node 10, it shifts from the idle state (state st11) to the state st12, performs processing for the request message, and generates a response message. ACK with data including the response message
When the response frame is generated, the state changes to state st13, and the ACK response frame with data is set in a predetermined storage area. When a data read message is received from the master node 10, this response message, that is, an ACK response frame with data is returned. Then, the state shifts to state st14, and the reception state of the reception completion message as a response to the response message from the master node 10 is waited. When the reception completion message is received, the state shifts to state st15, and the response message stored in the predetermined storage area is stored. Post-processing, such as deleting. And the state st
Return to 11.

The states st12, st13, st
When a new request message is received at step 14 and st15, the process proceeds to state st16, and an ACK response is returned as a response to the request message. However, the received request message is discarded, and each returns to the state before the transfer. . Next, the operation of the above embodiment will be described.

Now, the network system 10 shown in FIG.
0, the master node 10A transmits to the slave node 2
For example, assuming that transmission of specific data is requested to 0B, the master node 10A first generates a data write message for transmitting the request message shown in FIG. That is, the “data write message” as the frame code, and the destination station number is
0B station number “20B”, source station number is master node 10
A station number “10A”, message type is “request message”, request source station number is own station “10A”, request message I
D generates a request message frame as "1" and "request for transmission of specific data" as request message data (step S2), and transmits this request message frame (step S4). At this time, the request message frame is stored in a predetermined storage area.

As a result, as shown in FIG.
_{In step 1} , the request message is transmitted to the slave node 20B of the destination station number "20B", and the slave node 20B that has received the request message returns an ACK response as a response (step S22). Then, processing is performed according to the notified request message, and an ACK response frame with data shown in FIG. 2B is generated (step S2).
4). That is, "ACK response with data" is set as the frame code m1, and the destination station number m2 is not set yet. Then, “20B” that identifies the own node as the source station number m3, “response message” as the message type m4, and the request source station number “10” notified together with the request message as the request source station number m5 and request message ID m6
A ”and a request message ID“ 1. ”Further, data for the process specified by the request message,
That is, the specified specific data is used as the response message,
ACK with data by setting the response message data
Generate a response frame. Then, this is stored in a predetermined storage area.

Then, the master node 10A determines in step S
In the process of No. 6, the station number “20B” of the slave node 20B is set as the destination station number, and the own node “10” is set as the source station number.
When sending data read message at time t ₂ by setting A ", the slave node 20B receives this (step S26), the ACK response frame with data stored in a predetermined storage area, the data lead as the destination codes m2 The source station number "10A" notified by the message is set and transmitted (step S28).

In master node 10A, AC with data
Step S after receiving the K response, that is, the response message
7 to step S10, the request source station number "10A" and the message ID notified together with the response message
“1”, the request source station number “10A” and the message ID “1” stored in a predetermined storage area when transmitting the request message
Compare, because they are consistent, the process proceeds to step S12, generates a reception completion message frame for transmitting a reception completion message shown in FIG. 2 (c), the time t ₃
This is transmitted to the source station number "20B" of the response message.

Since the slave node 20B receives the reception completion message, it proceeds from step S30 to step S30.
32, and deletes the ACK response frame with data stored in the predetermined storage area. As a result, a series of message exchanges shown in FIG.
A is transmitted from the slave node 20B to the master node 10A, and the specific data designated by A is transmitted to the master node 10A.
Will receive the desired specific data.

[0048] At this time, as shown in FIG. 8, sends a request message from the master node 10A at time t ₁₁ the slave node 20B (step S4), and after receiving an ACK response from the slave node 20B to this,
When sending the data read message at t ₁₂ in order to receive the response message (step S6), and if the master node 10A can not receive the data with ACK response by any way, step S8 from step S7
Through the sending data again read message at time t ₁₃ returns to step S6 addressed slave node 20B.

After generating the response message (step S24), the slave node 20B receives the data read message and proceeds from step S26 to step S28.
Then, a response message is transmitted to the transmission source of the data read message. However, since the reception completion message is not received, the process returns to step S26. When the master slave 10A sends the data again read message at time t _13, to receive this in the slave node 20B,
The process shifts from step S26 to step S28 to transmit a response message to the master node 10A again.

[0050] Then, the master node 10A, when receiving a successful response message, and proceeds from step S7 to step S10, if a normal check response message results, received at time t ₁₄ and proceeds to step S12 Send a completion message. Therefore, in the slave node 20B, after receiving the reception completion message, the process shifts from step S30 to step S32, and deletes the ACK response frame with data stored in the predetermined storage area.

As described above, even if the master node 10A fails to receive the ACK response with data, it can surely receive the response message by transmitting the data read message again. For example, as shown in FIG. 9, the master node 10A is connected to the slave node 20C.
If after sending a request message at time t _21, and sends a request message at time t ₂₂ the slave node 20C even the master node 10B respect, the slave node 20C, for the master node 10A, the request message Is received, an ACK response thereto is transmitted to the master node 10A, a predetermined process is performed according to the request message, and a response message to the request message from the master node 10A is generated. And
The request source station number m5 added to the response message and the request message from the master node 10A, in this case, the station number "10A" of the master node 10A and the request message ID "1"
Is added to generate an ACK response frame with data, and this is stored in a predetermined storage area (step S24).

[0052] Then, the master node 10B is requesting station number "10B" at the time point t _22, as a request message ID "11", and send a request message to the slave node 20C, the slave node 20C, the master node 10
B receives a request message and receives an ACK
The response is returned, but the received request message is discarded.

[0053] When the master node 10A transmits a data read message at time t ₂₃ (step S
6) In response, the slave node 20C receives the data and transmits an ACK response with data stored in a predetermined storage area to the master node 10A (steps S26 and S28). On the other hand, the master node 10B even, an ACK response to the request message transmitted at time t ₂₂ the slave node 20C
When receiving from, and sending data read message at time t ₂₄ in order to receive the response message (step S
6) In the slave node 20C, since the data read message is received, steps S26 to S
28, the destination station number m of the ACK response frame with data, which is stored in a predetermined storage area and includes a response message to the request message of the master node 10A.
As 2, the source station number of the data read message, that is, the station number "10B" of the master node 10B is set and transmitted.

Then, the master nodes 10A and 10B that have received the ACK response with data check the response message. At this time, the master node 10
In A, the request source station number “10” added to the request message
A and the request message ID “1” match the request source station number “10A” and the request message ID “1” added to the response message, and thus the master node 10A.
In, and sends a reception completion message at time t ₂₅ (step S12), the response to this, the slave node 20C, the process proceeds from step S30 to step S32, in response to the request message of the master node 10A stored in the storage area The ACK response frame with data consisting of the message is deleted, and a state of waiting for the next request message is entered.

On the other hand, in the master node 10B, the request source station number added to the request message is “10B” and the request message ID is “11”, and the request source station number “10A” and the request message ID “ 1 "
Does not match. Therefore, the process moves from step S10 to step S4 via step S14, and again as request source station number "10B" and request message ID "11" at time t.
_{At 26} , a request message is sent.

At this time t ₂₆ , the slave node 20C
Is waiting for a request message,
This time, the request message from master node 10B is normally received. Then, the slave node 20C generates a predetermined response message in accordance with the request message from the master node 10B, and adds a request source station number “10B” and a message ID “11” to generate an ACK response frame with data. .

[0057] Thus, followed (step S6) when the master node 10B transmits a data read message at time t _27, this request source code "10B", the message ID "11" is added to data with ACK response master Since it is transmitted to the node 10B, the master node 10B
Then, the request source station number "10B" added to the request message
And the message ID “11”, the request source station number “10B” added to the response message, and the message ID “1”.
Shifted from the 1 "and is equal to the step S12, it transmits a reception completion message at time t _28.

In response to this, the slave node 20C deletes the ACK response frame with data including the response message to the master node 10B from the storage area. Thus, in the master nodes 10A and 10B,
Request message I added to the received response message
From D and the request source station number, it can be recognized whether or not the received response message is a response message to the request message transmitted by itself. Therefore, the master node recognizes that even if a response message to a request message transmitted by another master node is received due to a conflict between request messages to the slave node, the response message is not a response message to the request message transmitted by itself. And performing the processing based on the incorrect response message is avoided.

In this case, the master nodes 10A and 10A
Although the case where the request message for the slave node conflicts with the master node 10B has been described, for example, the same applies when the request message conflicts between different tasks of the master node 10A, and one task operates in the same manner as the master node 10B. However, it is possible to prevent one task from executing a process based on an incorrect response message.

Further, for example, as shown in FIG. 10, the master node 10A makes a point of time t _{31 with} respect to the slave node 20C.
In the request message (request source code "10A", the request message ID "2") sends, after receiving the data with ACK response sends a data read message thereto at time t _32, the master node 10A at time t ₃₃ Alternatively, the master node 1 communicating with the slave node 20C
When an error occurs in the task on 0A, the reception completion message is not transmitted from the master node 10A.
The slave node 20C enters a waiting state to wait for a reception completion message from the master node 10A.

[0061] Therefore, the master node 10B at time t ₃₄
Sends a request message (request source station number “10B”, request message ID “12”) to the slave node 20C, the slave node 20 receives the request message from the master node 10B and returns an ACK response. However, the request message from the master node 10B is discarded.

[0062] Therefore, when transmitting the data read message at time t ₃₅ followed master node 10B is the slave node 20C, stored in the predetermined storage area, the response message to the request message from the master node 10A Is transmitted to the master node 10B. However,
In the master node 10B, the request source station number “10A” and the request message ID added to the received response message
"2" and, from the different and requesting station number "10B" was added to the request message and the request message ID "12" at time t _34, the process proceeds to step S4 through step S14 from step S10, at time t ₃₆ Send the request message again.

In the slave node 20C, the master node
Receives a request message from the host 10B and returns an ACK response
To receive, but a reception completion message from the master node 10A.
Since it has not been received, it is discarded. And again
Master node 10B is at time t ₃₇Data read message
When the slave node 20C transmits the message,
The request source station number “10A” stored in a fixed storage area and
ACK with data to which request message ID "2" is added
Reply back.

[0064] In the master node 10B, even if the retry, the requesting station number and the request message ID appended to the response message, and the requesting station number and the request message ID added to the request message transmitted at time t ₃₆ does not match Therefore, the process proceeds from step S10 to step S16 via step S14, and the node of the request source station number “10A” added to the response message, that is, the master node 1
A status check request is made to 0A.

As a result of the status check, the master node 10A returns a task abnormality to the master node 10B if its own task is abnormal, and if the master node 10A itself is abnormal, the check result is transmitted to the master node 10B. Since there is no reply, the master node 10B
In the master node 10A or recognizes abnormality of the task, the process proceeds from step S16 to step S18, in place of the master node 10A, it transmits a reception completion message at time t _38.

Therefore, in the slave node 20C,
Since the reception completion message is received, the ACK with data including the response message to the request message from the master node 10A stored in the predetermined storage area
The response frame is deleted, and a state of waiting for the next request message is entered. Then, again request message master node 10B is at t ₃₉ (the requesting station number "10B", the request message ID "12") when transmitting the slave node 2
At 0C, this is received, and the request message is processed to generate a response message.
_{When the} master node 10B transmits a data read message at ₄₀ , the slave node 20C sends a request source station number “10B” and a request message ID to the master node 10B.
An ACK response with data is returned as "12". The requesting station number "10B" and the request message ID "12" of this data with ACK response, the master node 10B is stored to at t ₄₁ and the request message has been added to the requesting station number "10B" and the request message ID "12 since matching and "sends a reception completion message at time t ₄₁ in the master node 10B.

Then, the slave node 20C deletes the data-added ACK response frame composed of the response message to the request message from the master node 10B, and waits for the next request message. As described above, even when the master node 10A fails during communication with the slave node 20C and the slave node 20C is in a waiting state for waiting for a reception completion message from the master node 10A, the master node 10B is not connected to the master node 10A. When a status check is performed and the abnormality is detected, a reception completion message is transmitted instead of the master node 10A, and the slave node 20C is released from the waiting state. Of the master node cannot communicate with the slave node.

As described above, even when a plurality of master nodes exist in the network system, each master node can surely receive a response message to the request message transmitted by the master node. A plurality of master nodes can be provided in the system, and each master node can communicate with any slave node 20 without any restrictions.

In the above embodiment, the case where two master nodes are provided in the network system has been described. However, the present invention is not limited to this, and it is needless to say that the present invention can be applied to a case where two or more master nodes are provided. Absent.

[0070]

As described above, according to the first aspect of the present invention,
According to the master-slave communication method, the master node adds identification information to the request message and transmits the request message, and the slave node adds the identification information added to the request message to the response message and transmits the response message. Therefore, the master node can recognize whether or not the received response message is a response to the previously transmitted request message. Therefore, even when a plurality of master nodes are provided in the network system, the master node Can reliably exchange messages with desired slave nodes.

According to the communication method between the master and the slave according to the second aspect, the slave node deletes the response message when receiving the reception completion message from the master node. The master node that has received the response message can recognize that the slave node that is the source of the response message is processing another request message.

Further, according to the communication method between the master and the slave according to the third aspect, since the station identification information for specifying the master node of the transmission source of the request message is set as the identification information, the master node having the different identification information can set the identification information. It is possible to recognize which master node this response message is a response message to. According to the master-slave communication method according to the fourth aspect, the identification information includes station identification information and task identification information for identifying the task that generated the request message in the station identified by the station identification information. Is set, the master node that has received the response message having the different identification information can recognize which response message the master node responds to.

According to the communication method between the master and the slave according to the fifth aspect, when the slave node receives a new request message after receiving the request message and before receiving a reception completion message corresponding to the request message, Since this is discarded, it is possible to avoid sending an erroneous response message when transmitting a request message to a slave node that is processing another request message.

According to the communication method between the master and the slave according to the sixth aspect, when the identification information added to the request message and the identification information added to the received response message do not match, the master node determines whether or not the identification information has a predetermined value. After a lapse of time, the request message is retransmitted, so that it is possible to recognize the message exchange state of the transmission source slave node based on the identification information of the response message.

Further, according to the communication method between the master and the slave according to the seventh aspect, when the identification information of the response message does not match even if the request message is retransmitted, the identification information is specified by the identification information added to the received response message. The node confirms the status of the node, and if it is abnormal, sends a reception completion message instead of this node.Therefore, the slave node communicating with the master node in which the abnormality has occurred transmits another request message. It is possible to avoid being unacceptable.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a network system to which the present invention is applied.

FIG. 2 is an example of a message format.

FIG. 3 is a flowchart illustrating a processing procedure when a processing request is issued to a slave node in the master node.

FIG. 4 is a flowchart showing a processing procedure when a processing request is made from a master node in a slave node.

FIG. 5 is a state transition diagram of a master node.

FIG. 6 is a state transition diagram of a slave node.

FIG. 7 is an explanatory diagram for explaining the operation of the present invention;

FIG. 8 is an explanatory diagram for explaining the operation of the present invention;

FIG. 9 is an explanatory diagram for explaining the operation of the present invention;

FIG. 10 is an explanatory diagram for explaining the operation of the present invention;

[Explanation of symbols]

 10A, 10B Master node 20A-20D Slave node

Claims (7)

[Claims] 1. A slave node that has received a request message transmitted by a master node generates a response message to the request message, and a slave node that has received a data read message transmitted by the master node is a source of the data read message. In a communication method between a master and a slave configured to transmit the response message to a master node, the master node transmits the request message by adding identification information for identifying the request message, and the slave node transmits the request message. The master node adds the identification information added to the request message to the response message, and transmits the response message.The master node transmits the identification information added to the received response message and the response message received from the identification information added to the request message. Request message and A communication method between a master and a slave, characterized in that the correspondence between the master and the slave is determined. 2. When the identification information added to the received response message matches the identification information added to the request message, the master node transmits a reception completion message to the slave node that has transmitted the response message. 2. The communication method according to claim 1, wherein the slave node holds the response message until the slave node receives the reception completion message. 3. The master-slave communication method according to claim 1, wherein the identification information is station identification information for specifying a master node that has transmitted the request message. 4. The identification information includes the station identification information and task identification information for identifying a task that has generated the request message in a station specified by the station identification information. The communication method between a master and a slave according to claim 3. 5. When the slave node receives a new request message after receiving the request message and before receiving the reception completion message, the slave node discards the new request message. The communication method between a master and a slave according to any one of claims 1 to 4. 6. When the identification information added to the request message does not match the identification information added to the received response message, the master node retransmits the request message after a predetermined time has elapsed. The communication method between a master and a slave according to any one of claims 1 to 5, wherein: 7. The master node, if the identification information added to the response message does not match the identification information added to the request message even after resending the request message, the identification information added to the received response message. The master-slave according to claim 6, wherein a state of the node specified by the information is confirmed, and when the node is abnormal, the reception completion message is transmitted instead of the node. Communication method between.