JP2907233B2 - Upper link system of programmable controller - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an upper link system of a programmable controller for controlling communication between a programmable controller and an upper computer.

[0002]

2. Description of the Related Art In a programmable controller system, a higher-level computer such as a personal computer or a mini computer executes an application program such as system monitoring by an upper-level computer. Conventionally, communicative connection is performed.

[0003] As a transmission path interface for communication between the programmable controller and the host computer, RS
232C, RS422, etc. are used, and as a communication control procedure, a non-procedural method is widely used to reduce the load on the communication software of the host computer.

[0004]

The transmission of a function request (command) from the higher-level computer to the programmable controller by non-procedural communication and the response (response) of the processing result of the programmable controller to the higher-level computer are as follows. When a response does not reach the application program of the host computer due to a communication failure or the like, a command is generally retransmitted to the programmable controller by time-over control by the application program.

[0005] In this case, the retransmission command is processed twice and twice by the programmable controller, and there is a problem that one request command from the application program is processed twice. This double processing is not a problem when the host computer reads the state variables from the programmable controller, but when writing or changing data, it causes a malfunction in the application system of the host computer and the programmable controller. become.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems in the conventional link system of the programmable controller, and the programmable controller is not required to have a complicated communication control procedure program. It is an object of the present invention to provide an upper link system of a programmable controller having a processing function for preventing a request command from a computer application program from being processed twice.

[0007]

SUMMARY OF THE INVENTION According to the present invention, there is provided a programmable controller upper link system for controlling communication between a programmable controller and a host computer. Storage means for storing one request command, adding retransmission identification information to a command data format transmitted from the host computer to the programmable controller, and determining whether the command transmission from the host computer to the programmable controller is retransmission based on the retransmission identification information. Is determined, and if retransmitted, the request command stored in the storage means is compared with a new received command. If they are the same, the fact that processing has been completed is transmitted from the programmable controller to the host computer. Notifies the host computer as a result code scan Pons data format, the host computer is accomplished by the programmable controller upper link system, characterized in that it is configured to stop the retransmission of the command.

[0008]

According to the upper link system of the programmable controller according to the present invention, one request command processed immediately before by the programmable controller is stored in the storage means, and the retransmission added to the command data format transmitted from the upper computer to the programmable controller. Based on the identification information, it is determined whether or not the command transmission from the host computer to the programmable controller is retransmission, and if the request command stored in the storage means is the same as the new reception command at the time of retransmission, The host computer is notified by a response that processing has already been completed, and the host computer stops resending the command.

[0009]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of an embodiment of the present invention.

FIG. 1 shows an example of a programmable controller system to which an upper link system of a programmable controller according to the present invention is applied. In FIG. 1, reference numeral 1 denotes a host computer, and 2 denotes N programmable controllers. The host computer 1 and the N programmable controllers 2 are communicably connected to each other by a transmission line 3.

The host computer 1 is a computer having a general configuration such as a personal computer or a mini computer, and executes an application program such as system monitoring such as monitoring of the operating state of a programmable controller and the operating state of each relay. A function request (command) is transmitted to the programmable controller 2 according to an application program, and a response (response) of a processing result is received from the programmable controller 2.

The programmable controller 2 may be a programmable controller having a known structure including an upper link unit, receives a command from the upper computer 1, performs a process in response to a command request, and sends a response to the command. To be sent to.

FIG. 2 shows a communication processing flow of the host computer 1 in the host link system according to the present invention. In this communication processing flow, first, the count value N of the retransmission counter is reset to 0 (step 10), and then a command is transmitted to the programmable controller 2 (step 2).
0).

FIG. 4 shows an example of the data format of this command. The command data format includes a start delimiter section indicating the beginning of a command, a programmable controller number section of a request destination, a retransmission identification information section, a command section including a code or a number corresponding to a function requested to the programmable controller, a data section, and a command. Is constituted by a delimiter unit indicating the end of the process. The retransmission identification information in the retransmission identification information section of the command data format is the retransmission identification information for the same request set by the application of the host computer 1,
In this embodiment, it is given by the count value N of the retransmission counter whose initial value is set to 0.

The host computer 1 sets a timer in synchronization with the transmission of the command (step 30), and monitors whether a response is received from the programmable controller 2 within a predetermined time from the transmission of the command (step 40).
If no response is received within the predetermined time, the count value N of the retransmission counter is incremented by one (step 5).
0), and then whether the count value N is a predetermined value, for example, 4
A determination is made as to whether or not this is the case (step 60). If the count value N is abnormal, the communication abnormality process is performed (step 70). If the count value N is equal to or less than the predetermined value, the process returns to step 20 and the command is transmitted again.

When a response is received from the programmable controller 2 within a predetermined time from the command transmission,
It is determined whether or not the processed result code is set in the result portion of the data format of the response from the programmable controller 2 (step 8).
0). 1 if the processed result code is not set
This is the time when a response is normally obtained by transmitting the command twice, and in this case, processing based on the result data of the received response is performed (step 90), and if a processed result code is set for this, This is when command transmission by the same request command is performed in multiplex, and in this case, command transmission by the same request command is stopped (step 100).

FIG. 3 shows a communication processing flow of the programmable controller 2 in the upper link system according to the present invention. This communication processing flow is started when the programmable controller receives a command from the host computer 1. First, the count value of the retransmission counter is determined based on the retransmission identification information in the retransmission identification information section of the command data format. If N is 0,
It is determined whether or not it is (step 200).

When the count value N is 0, it is the time of the first command reception. In this case, the received request command is processed as a processed command, such as a work memory of the programmable controller 2. The storage in the storage means is performed (step 210). Next, the request command is processed (step 220), and a response is transmitted to the host computer 1 (step 230).

FIG. 5 shows an example of the data format of this response. The response data format includes a start delimiter section indicating the beginning of a response, a requestable programmable controller number section, a retransmission identification information section, a command section, a result section, a result data section, and a delimiter section indicating the end of the response. .

When the count value N is not 0, it means that the command has been received two or more times. In this case, the processed command stored in the storage means, that is, one of the commands processed by the programmable controller 2 immediately before A determination is made as to whether the request command is the same as the request command newly received this time (step 240), and one request command processed immediately before by the programmable controller 2 and a request command newly received this time. If the requested command is not the same, the process proceeds to steps 210 and 220, where the request command is newly stored as a processed command in the memory of the programmable controller 2, and then the requested command is processed. Is one request command processed by the programmable controller 2 immediately before,
If the newly received request command is the same as this time, a result code indicating that processing has been completed is set in the result portion of the response data format, and the response in which the result code indicating processing has been set is ranked higher. Sent to computer 1.

Thus, the programmable controller 2
Does not duplicately process the request command from the application program of the host computer 1 twice.

FIG. 6 shows a transition example of communication between the host computer 1 and the programmable controller 2.
In this example, a communication failure occurs in the process of transmitting the response B of the command B, and the host computer 1 transmits the same command B to the programmable controller 2 after a predetermined time. In this case, since the processed result code is set in the result portion of the response B by the second transmission of the command B as described above, the host computer 1 stops transmitting the command B, The process proceeds to the stage for transmitting C.

[0023]

As can be understood from the above description, according to the host system of the programmable controller according to the present invention, one request command processed immediately before by the programmable controller is stored in the storage means. The host computer determines whether or not the command transmission to the programmable controller is a retransmission based on the retransmission identification information added to the command data format to be transmitted to the command data format. At the time of retransmission, the request command stored in the storage means If the new received command is the same as the new received command, the host computer is notified by a response that the command has already been processed, and the host computer stops resending the command. It is prevented from being processed twice request command from Tsutomu program. This is because the management program of the retransmission identification information is simply added to the application program without the need for a complicated communication control procedure program by adding the retransmission identification information that can be set and read by the application program in the host computer. Is easily realized.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an example of a programmable controller system to which an upper link system of a programmable controller according to the present invention is applied.

FIG. 2 is a flowchart showing an example of a communication processing flow of a host computer in the host link system according to the present invention.

FIG. 3 is a flowchart showing an example of a communication processing flow of the programmable controller 2 in the upper link system according to the present invention.

FIG. 4 is an explanatory diagram showing a data format example of a command.

FIG. 5 is an explanatory diagram showing an example of a data format of a response.

FIG. 6 is a time chart showing a transition example of communication between a host computer and a programmable controller.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Upper computer 2 Programmable controller 3 Transmission line

Claims (1)

(57) [Claims] An upper link system of a programmable controller for controlling communication between a programmable controller and a host computer, wherein the programmable controller is provided with storage means for storing one request command processed immediately before, and the host computer sends the command to the programmable controller. Retransmission identification information is added to the command data format to be transmitted to, and it is determined whether or not the command transmission from the host computer to the programmable controller is retransmission based on the retransmission identification information. The request command and the new received command are compared, and if they are the same, the fact that they have already been processed is indicated by the result code in the response data format sent from the programmable controller to the host computer. Programmable controller upper link system that notifies the computer, the host computer is characterized by being configured so as to stop the retransmission of the command.