JPH05298220A - Lan system - Google Patents

Abstract

PURPOSE:To realize the instantaneous switching between a control programmable controller and a back-up programmable controller by providing a data selecting function part to decide to take out the data on one of a pair programmable controllers and to output the data to the outside. CONSTITUTION:For instance, when a control programmable controller 11 has a trouble during its control operation, an output data selecting circuit 18 of an input/output device 13 detects the trouble of the controller 11 based on the operating state information on the controller 11 and a back-up programmable controller 12. Then the controller 12 is switched to the controller 11 with the immediate switching of the ON/OFF states between the switched 18a and 18b. At the same time, the reading destination of the output data is switched to a writing area 17b of the controller 12. Then the output data are read out of the area 17b and outputted to the outside.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a LAN system.

[0002]

2. Description of the Related Art Conventionally, a LAN system in which a programmable controller for control and backup, and an input / output device are tightly coupled by a LAN has a configuration as shown in FIG. That is, a control programmable controller (PLC) 1, a backup programmable controller (PLC) 2, and an input / output device that outputs data from any of these programmable controllers to the outside and inputs data to these from the outside. 3 and 3 are connected to the LAN 4, and the memory 5 is further connected to the LAN 4. In the control programmable controller 1 and the backup programmable controller 2, the control programmable controller 1 normally operates, and when the failure or abnormality occurs, the operation is switched to the backup programmable controller 2 exclusively. The programmable controllers 1 and 2 are provided with operating switches 6a and 6b, and the memory 5 is a common write area in which data can be written from either the control programmable controller 1 or the backup programmable controller 2. 7 is provided. The input / output device 3 is also provided with an input / output circuit 8 for controlling input / output of data.

[0003]

However, in the conventional LAN system having such a configuration, each programmable controller has a determination function, and the control output is provided to a predetermined writing area 7 of the memory 4 on the LAN 4. Since the data is written, the control programmable controller 1 writes the control output data to the writing area 7 in the normal state, and if the control programmable controller 1 fails, it switches to the backup programmable controller 2 and the same program The control output data obtained under this condition is written in the same write area 7. Therefore, the control programmable controller 1 and the backup programmable controller 2 are made to execute the same program in parallel at the same time. , Of failure or abnormality Since it is not possible to instantaneously switch the programmable controller to output the data at the time of live, the data of the backup programmable controller 2 is written to the common writing area 7 and then output, which requires time for switching. There was a problem.

The present invention has been made in view of such conventional problems, and an object thereof is to provide a LAN system in which the control programmable controller and the backup programmable controller can be switched instantaneously.

[0005]

According to the present invention, there is provided a LAN including at least one pair of programmable controllers connected by LAN, an input / output device, and a common memory.
In the system, the same program is loaded into a pair of programmable controllers, the write area of each programmable controller is assigned to the memory, and the operating state of the pair of programmable controllers is monitored in the input / output device. A data selection function unit for determining whether to take out the data of the controller from the memory and output the data to the outside is provided.

[0006]

In the LAN system of the present invention, normally,
A pair of programmable controllers execute the same program at the same time in parallel, and output each output data to LAN.
Writing in their own dedicated writing area on the memory. Then, the data selection function unit of the input / output device selects and outputs the output data in the write area assigned to the predetermined programmable controller for control.

However, if a trouble occurs in the preset programmable controller, the data selection function unit reads the data to be output to the outside from the write area of the control programmable controller for backup programming. Control is performed so that the writing area of the controller is switched to read.

In this way, if a trouble occurs in one of the pair of programmable controllers, the read destination is instantly switched to the writing area assigned to the other programmable controller operating in parallel, and the data is written from there. It can be read and output to the outside.

[0009]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 is a circuit block diagram of an embodiment of the present invention. A pair of programmable controllers 11 and 12 loaded with the same program and operating in parallel at the same time.
And the input / output device 13 that controls the input / output of data
LAN memory 15 and L connected to AN14
The LAN control device 16 that controls the entire AN 14 is L
It is connected to the AN 14.

The memory 15 has dedicated write areas 17a, 1 for the programmable controllers 11, 12, respectively.
7b is assigned. Further, to the input / output device 13, an output data selection circuit 18 for switching and selecting which of the write areas 17a and 17b assigned to the programmable controllers 11 and 12 is to be read, and the read data is output to the outside. In addition, an input / output circuit 19 for inputting data from the outside is provided. The switches 18a and 18b are switches that are switched by the output data selection circuit 18, and operate exclusively with each other.

Next, the operation of the LAN system having the above configuration will be described.

A pair of programmable controllers 11,
12 simultaneously executes the same program in parallel, and writes the output data of the respective execution results to the write areas 17a and 17b in the memory 15 which are allocated to each of them. The write data also includes abnormal / normal status information of each programmable controller.

Usually, one of the programmable controllers 11 and 12, for example, the programmable controller 11 is used as a control programmable controller, the programmable controller 12 is used as a backup programmable controller, and the output data selection circuit 18 of the input / output device 13 is also switched. 18a is turned on and the switch 18b is turned off to set the data in the write area 17a to be output from the input / output circuit 19 to the outside.

However, with such an initial setting, LA
If trouble occurs in the programmable controller 11 for control for some reason while operating the N system, the output data selection circuit 18 of the input / output device 13 can be programmed from the operation state information of these programmable controllers 11 and 12. When an abnormality of the controller 11 is detected, the switches 18a and 18b are immediately turned on and off so that the programmable controller 12 that has been used for backup is switched to control, and the read destination of the output data is the programmable controller 1.
The writing area 17b on the second side is switched to, and the output data is read from the writing area 17b and output to the outside.

When the trouble of the programmable controller 11 is recovered and the status information of the write area 17a returns to normal, the output data selection circuit 18 detects this and uses the programmable controller 11 side for control again, and the programmable controller 12 The side is switched for backup, and the data is read from the writing area 17a on the programmable controller 11 side and output to the outside.

In this way, the pair of programmable controllers 11 and 12 are caused to simultaneously execute the same program in parallel, and their dedicated write areas 17a and 17b are respectively written.
If the programmable controller on the side that outputs data to the outside for control has an error, the data is immediately written to the outside from the writing area on the side of the programmable controller that is operating for backup. By switching so as to output, the programmable controller for control can be switched to bumpless.

The switching determination process of the control programmable controller based on the state information is performed not only at the time of outputting the data but also when the input / output device 13 has finished outputting all the data. If the programmable controller is selected according to the latest state information of the programmable controller before the control output on the LAN 14 is read,
The reliability of output data can be improved.

In the above embodiment, the case of two programmable controllers 11 and 12 and one input / output device 13 was described, but the present invention is not limited to the above embodiment and is essential. If the programmable controllers for control and backup have a 1: 1 relationship, the number of units is not limited, and, for example, as shown in FIG.
Programmable controllers 11 that form a pair,
12, programmable controllers 11 ', 12',
Input / output devices 13 and 13 'corresponding to each of these groups are set to L
It is also possible to configure a system connected to the AN 14.

[0020]

As described above, according to the present invention, normally, a pair of programmable controllers simultaneously execute the same program in parallel, and each output data is written in its own dedicated memory on the LAN memory. The data selection function unit of the input / output device selects the output data in the write area assigned to the preset programmable controller for output and outputs the data. When a problem occurs in the programmable controller, the data selection function unit reads the data to be output to the outside by switching the write area of the backup programmable controller from the previous write area of the control programmable controller. I have a pair of programmers If a problem occurs in one of the two controllers, it is possible to instantly switch the read destination to the write area assigned to the other programmable controller operating in parallel, read the data from there, and output it to the outside. Even if a trouble occurs in one programmable controller, the input / output device can continuously output the data to the outside with almost no time delay, and the reliability of the operation can be improved.

[Brief description of drawings]

FIG. 1 is a circuit block diagram of an embodiment of the present invention.

FIG. 2 is a circuit block diagram of another embodiment of the present invention.

FIG. 3 is a circuit block diagram of a conventional example.

[Explanation of reference signs] 11, 12, 11 ', 12' Programmable controller 13, 13 'Input / output device 14 LAN 15 Memory 17a, 17b Write area 18 Output data selection circuit 18a, 18b Switch 19 Input / output circuit

Claims (1)

[Claims] 1. A LAN system comprising at least one pair of programmable controllers coupled by LAN, an input / output device, and a common memory, wherein the same program is loaded into the pair of programmable controllers, and The write area of each programmable controller is assigned to the memory, the operating state of the pair of programmable controllers is monitored in the input / output device, and the data of which programmable controller is taken out from the memory and output to the outside is determined. A LAN system provided with a data selection function unit.