JP3915313B2 - LAN communication system in PLC - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a LAN communication system in a PLC in which PLCs (programmable logic controllers) are connected to each other via a LAN.
[0002]
[Prior art]
The LAN uses a coaxial cable as a data transmission medium, and enables communication between computers by an interface of a CSMA / CD method (access method of collision detection type carrier multiplexed LAN).
[0003]
In recent years, personal computers have been adopted as monitoring and control systems in plants in place of workstations and minicomputers as host computers, and the most common LAN has been established as the de facto standard for PC upper-level networks and inter-PC networks. May be.
[0004]
These personal computers and PCL have a reliable one-to-one relationship when implementing the TCP / IP protocol when implementing the TCP / IP protocol when implementing the TCP / IP protocol in the interface for communication using the LAN. Communication is realized using TCP / IP.
[0005]
Normally, when a personal computer performs communication using TCP / IP, an application program generally performs all the procedures of establishing a logical line → transmitting / receiving data → releasing a logical line.
[0006]
[Problems to be solved by the invention]
Since the PLC is positioned as a sequence controller, the data handled in the host PC network and the inter-PC network is control data, and prompt exchange is required.
[0007]
Therefore, when communication is performed using TCP / IP, if the procedure of establishing a logical line → data transmission → releasing the logical line is taken, processing delay is caused.
[0008]
The present invention has been made in view of the above problems, and an object of the present invention is to provide a LAN communication system in a PLC that can quickly transmit and receive control data.
[0009]
[Means for Solving the Problems]
The present invention uses a personal computer as a host computer to connect a plurality of PLCs via a LAN, each of which has a physical layer for obtaining an intercommunication function, a data link layer, a LAN interface having IP and TCP, and a user for storing transmission / reception data In a LAN communication system in a PLC having a processor having an application program for performing a memory, logical line establishment, data transmission / reception, and logical line release procedure,
A functional part having a function of controlling data transmission and reception and a function of releasing and establishing a logical line is mounted on a coupling part with the processor of the LAN interface, and a non-volatile memory for storing information for establishing a logical line is mounted. The information for establishing the logical line can be flexibly loaded into the nonvolatile memory by an external man-machine interface.
[0010]
The processor has a key switch for controlling two operation states of the application program, namely, a RUN state and a STOP state, and an operation state storage memory for storing the state of the key switch is mounted on the processor.
[0011]
When the functional part mounted on the LAN interface detects the timing for performing the line establishment process, information for establishing a logical line is downloaded from the man-machine interface to the nonvolatile memory.
[0012]
The functional part implemented in the LAN interface monitors the operating state of the processor and establishes a logical line based on the information in the non-volatile memory when a RUN state change is detected from the STOP of the key switch state. When a STOP state change is detected from the RUN in the key switch state, a logical line release process is performed.
[0013]
In the logical line establishment processing, the functional part implemented in the LAN interface issues an open request to the TCP, and if the open confirmation from the TCP for this open request is “normal”, the line establishment state to the processor To enable transmission and reception of application programs.
[0014]
In the logical line establishment processing, the functional part implemented in the LAN interface is issued, an open request is issued to the TCP, and if the open confirmation from the TCP for the open request is “abnormal”, the processor operating state If it is STOP, the circuit establishment process is terminated, and if it is RUN, an open request is issued again after a predetermined time.
[0015]
The functional part implemented in the LAN interface notifies the processor that the line state has not been established to the processor when a close confirmation or open confirmation “abnormality” notification is received from the TCP, and after a certain time has passed to the TCP. Issue an open request to it.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described with reference to the drawings.
[0017]
(1) System Configuration Referring to FIG. 1, a personal computer 1A is a host computer, and PLCs 2A to 2L are connected to a LAN 9. The personal computer 1A and the PLCs 2A to 2N each have a LAN interface 3 and a processor 4 for obtaining an intercommunication function, as representatively shown by the PLC 2A.
[0018]
In addition to the physical layer 31, the data link layer 32, the IP 33 and the TCP 34, the interface 3 performs logical line establishment and release processing on the application of the processor 4 when performing one-to-one communication between PCs using TCP / IP. A functional part 35 for avoiding the need to execute a program is provided at the joint with the processor 4.
[0019]
This functional part 35 is configured by software in the same manner as the data link layer 32, the IP 33, and the TCP 34. Specifically, the functional part 35 implements a function for establishing and releasing a logical line in addition to a function for controlling data transmission / reception.
[0020]
For this reason, a non-volatile memory 36 that stores information for establishing a logical line in the interface 3 is also mounted. Information such as a destination IP address and a destination port number for establishing a logical circuit can be flexibly loaded into the nonvolatile memory 36 by an external man-machine interface 37.
[0021]
The processor 4 has a user memory 41 for storing transmission / reception data by the functional part 35 and an application program 42 for using it. The processor 4 has a key switch 44 that controls the operating state of the application program 42. The key switch 44 has two states, a RUN state and a STOP state. This RUN state is a state in which the application program 42 operates, and the STOP state is a state in which the application program 42 stops. An operation state storage memory 43 that stores the state of the key switch 44 is mounted inside the processor 4.
[0022]
(2) The logical line establishment interface 3 can always read information for establishing a logical line in the nonvolatile memory 36, and this information indicates the timing at which the functional part 35 performs the line establishment process. Read when detected.
[0023]
The functional section 35 of the interface 3 monitors the operating state of the processor 4 and establishes a logical line based on information in the nonvolatile memory 36 when a change in RUN is detected from the STOP state of the key switch 44. Process. When a STOP state change is detected from the RUN state of the key switch 44, a logical line release process is performed.
[0024]
Thereby, only when the application program 42 is operating, it is possible to flexibly change the establishment information for establishing the logical line and establish the logical line.
[0025]
This line establishment process is performed according to the procedure shown in FIG. By this line establishment process, the application program 42 can realize data transmission / reception using only the transmission / reception control function of the functional part 35 without being conscious of establishment / release of the logical line.
[0026]
However, since the application program is unaware of the establishment / release of the logical line, it cannot cope with the case where the establishment process fails or the logical line is disconnected from the other party. For this reason, the above-described functional portion 35 of the interface 3 has the following functions.
[0027]
(3) Re-establishment of logical line With respect to FIG. 3, in the line establishment process, the functional part 35 issues an open request to the TCP 34.
[0028]
When the open confirmation from the TCP 34 for the open request is “normal”, the functional part 35 notifies the processor 4 of the line establishment state. As a result, the application program 42 can be sent and received.
[0029]
4 and 5, when the open confirmation from the TCP 34 for the open request is “abnormal” (this occurs when the other party does not exist), if the operating state of the processor 4 is STOP, the line establishment process is performed. finish. If it is RUN, an open request is issued again after a predetermined time. While the open confirmation is notified as “abnormal”, the processor 4 is notified of the line unestablished state.
[0030]
As a result, when the application program 42 is operating in the RUN state, even if the line establishment process ends in “abnormal”, the application program 42 is automatically reestablished until the line is established without being aware of it. Is done.
[0031]
This line re-establishment process is performed according to the procedure shown in FIG. In FIG. 6, S <b> 1 to S <b> 8 indicate a procedure for performing the abnormal sequence 1, and S <b> 1, S <b> 11 to S <b> 13 indicate a procedure for performing the abnormal sequence 2.
[0032]
(4) When a line disconnection request is received from the partner station With respect to FIG. 7, when the disconnection request is received from the partner station in the state where the operation state of the processor 4 is RUN and the line is established, The function part 35 has a close notification. In this case, a close request is issued to the TCP 34 and a response is made to the partner station. When the confirmation from the other party is received, there is a close confirmation from the TCP 34, and the processor 4 is notified that the line state is not established.
[0033]
The functional part 35 issues an open request after a certain time when the line is not established. When the open confirmation is notified as “abnormal”, issuance of an open request after a predetermined time T is repeatedly performed, and when the open confirmation becomes “normal”, the processor 3 is notified of the establishment of the line.
[0034]
Processing when a disconnection request is received from the other station is performed according to the procedure shown in FIG.
[0035]
【The invention's effect】
Since the present invention is configured as described above, the following effects can be obtained.
(1) A PLC application program can transmit and receive data without being aware of establishment and release of a line in one-to-one communication by TCP / IP.
(2) Therefore, transmission / reception of control data can be performed quickly because there is no extra procedure.
(3) By installing means for loading information for establishing a circuit on the Ethernet interface and an operation state key switch in the PLC, the information for establishing the line is flexibly changed to establish and release the line. be able to.
[Brief description of the drawings]
FIG. 1 is a system configuration diagram according to an embodiment.
FIG. 2 is a flowchart of a line establishment process according to the embodiment.
FIG. 3 is a normal sequence diagram of circuit establishment according to the embodiment;
FIG. 4 is a first diagram illustrating a line establishment abnormality sequence according to the embodiment;
FIG. 5 is a circuit establishment abnormality sequence (part 2) according to the embodiment;
FIG. 6 is a flowchart of a line re-establishment process according to the embodiment.
FIG. 7 is a sequence diagram for disconnecting a line from the partner station according to the embodiment;
FIG. 8 is a process flow diagram when a disconnection request is received from the counterpart station according to the embodiment;
[Explanation of symbols]
1A ... PCs 2A-2N ... PLC (Programmable Logic Controller)
3 ... LAN interface 4 ... processor 9 ... LAN (local area network)
31 ... Physical layer 32 ... Data link layer 33 ... IP (network layer protocol)
34 ... TCP (Transmission Control Protocol)
35: Function part for controlling data transmission / reception / Function part for establishing / releasing logical line (function part according to the present invention)
36 ... Non-volatile memory 37 ... Man-machine interface 41 ... User memory 42 ... Application program 43 ... Operation state storage memory (stores key switch state)
44: Key switch SYN, FIN, ACK, RST: Communication code in TCP / IP protocol

Claims (7)

A personal computer is used as a host computer to connect multiple PLCs via a LAN, each of which has a physical layer, a data link layer, a LAN interface having IP and TCP, and a user memory for storing transmission / reception data and a logical line. In a LAN communication system in a PLC having a processor having an application program for performing procedures for establishing data, transmitting / receiving data, and releasing a logical line,
A functional part having a function to control data transmission / reception and a function to release and establish a logical line is mounted on a coupling part with the processor of the LAN interface, and a nonvolatile memory for storing information for establishing a logical line is mounted. ,
A LAN communication system in a PLC, wherein information for establishing the logical circuit can be flexibly loaded into the nonvolatile memory by an external man-machine interface. In claim 1,
The processor has a key switch that controls two operating states of a RUN state and a STOP state of the application program, and an operating state storage memory for storing the state of the key switch is mounted on the processor. LAN communication system. In claim 1 or 2,
A LAN in a PLC, wherein information for establishing a logical line is downloaded from a man-machine interface to the non-volatile memory when the functional part mounted on the LAN interface detects a timing for performing a line establishment process. Communication method. In claim 3,
The functional part implemented in the LAN interface monitors the operating state of the processor and establishes a logical line based on the information in the non-volatile memory when a RUN state change is detected from the STOP of the key switch state. A LAN communication system in a PLC, which performs processing and performs logical line release processing when a STOP state change is detected from a RUN in a key switch state. In claim 4,
In the logical line establishment processing, the functional part implemented in the LAN interface issues an open request to the TCP, and if the open confirmation from the TCP for the open request is “normal”, the line establishment state to the processor LAN communication system in PLC, characterized in that the application program can be transmitted and received. In claim 4,
In the logical line establishment processing, the functional part implemented in the LAN interface issues an open request to the TCP, and if the open confirmation from the TCP for the open request is “abnormal”, the processor operating state is STOP. If so, the line establishment process is terminated, and if it is RUN, an open request is issued again after a predetermined time. In claim 3,
The functional part implemented in the LAN interface notifies the processor that the line status has not been established to the processor when a close confirmation or open confirmation “abnormality” is notified from the TCP, and after a certain period of time, A LAN communication system in a PLC, which issues an open request to a PLC.

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