JPH08106307A - Programmable controller - Google Patents

Abstract

PURPOSE: To modify a user program during its execution without causing malfunction. CONSTITUTION: A RAM 2 includes a user program storage part 21, a last value storage area 22, and an area 23 for a device. When the user program is modified, the user program stored in the user program storage part 21 is rewritten into a modified user program and a write inhibition/permission control part 5 places the area 23 for the device in a write inhibited state. In this state, a CPU 6 makes one scan on the modified user program stored in the user program storage part 21, and then the device information stored in the device area 23 is stored as a last value in the last value storage area 22. Then the write inhibition/permission control part 5 places the device area 23 in a write permitted state and the CPU 6 continuously executes the modified user program.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a programmable controller for controlling the case of a controlled device.

[0002]

2. Description of the Related Art A programmable controller is used to sequentially control a controlled device.
FIG. 3 is a block diagram showing the configuration of a conventional programmable controller.

Programmable controller 100 of FIG.
Includes a CPU (central processing unit) 11, a RAM (random access memory) 12, a ROM (read only memory) 13, an input unit 14, an output unit 15 and a communication interface 16.

Input devices such as switches and sensors are connected to the input unit 14, and an electromagnetic switch, a relay, and an output unit 15 are connected to the output unit 15.
Output devices such as solenoids and motors are connected. ROM
In 13, a system program for controlling the overall operation of the programmable controller 100 is stored.

The RAM 12 is a user program storage unit 1
21 and a data storage unit 122. The user program storage unit 121 stores a user program for sequentially controlling the controlled device. The data storage unit 122 stores device information and other various data. Here, the device information includes an input state from the input device to the input unit 14, an output state from the output unit 15 to the output device, and an internal relay (input relay, output relay and auxiliary relay) set on the user program, It is information indicating the states of timers, counters, data memories, etc. (hereinafter referred to as internal states), and the device is a name indicating an area on the memory provided for storing the device information.

The CPU 11 controls each part in the programmable controller 100 according to the system program stored in the ROM 13, and executes the user program stored in the user program storage unit 121. The user program is created by the user using a program creating device (not shown), and then stored in the user program storage unit 121 of the RAM 12 via the communication interface 16.

FIG. 4 shows a programmable controller 100.
3 is a flowchart showing the basic operation of FIG. First, the state of the input device is input to the input unit 14, and the input state is R
Write to the data storage unit 122 of the AM 12 (step S
1). This is called input refresh.

Next, the user program stored in the user program storage unit 121 is executed for one scan based on each device information in the data storage unit 122 (step S).
2). Here, one scan means executing one instruction of the main routine. The execution of the user program updates each device information in the data storage unit 122.

Thereafter, the output state of the data storage section 122 is read and the output state is output to the output device via the output section 15 (step S3). This is called output refresh.

The above input refresh (step S
By repeating 1), one scan of the user program (step S2) and output refresh (step S3), the controlled device is sequentially controlled.

[0011]

In the programmable controller 100 described above, when the user program stored in the user program storage section 121 is changed, the operation of the programmable controller 100 is temporarily stopped and then the user creates the program. The user program is modified using the device, and the modified user program is written to the user program storage unit 121 of the RAM 12 via the communication interface 16. In this case, since the programmable controller 100 is reset by stopping the operation of the programmable controller 100, it is not possible to continuously execute the control operation from the middle of the sequence after changing the user program.

Therefore, it is considered that the changed user program is created by using the program creating device and the changed user program is written in the user program storage unit 121 between one scan of the running user program. To be In this case, the user program can be changed during execution of the user program.

However, when a differential instruction for detecting the rising or falling of the input state, the output state or the internal state is present in the user program, the following problem occurs.

In order to detect the rising or falling of the input state, the output state or the internal state, the input state, the output state or the internal state at the previous scan and the input state, the output state or the internal state at the current scan are detected. Need to compare with. Therefore, the data storage unit 122 of the RAM 12 stores the input state, output state, and internal state (hereinafter referred to as the previous value) at the time of the previous scan. When reading the previous value during the next scan, the RAM 12 stores the previous value based on the number and length of instructions.
Calculate the address of.

Therefore, when the number and length of instructions are changed due to the change of the user program, it is not possible to calculate the address where the previous value is stored.
In this case, there is no alternative but to use the value stored in the address where the previous value was saved in the user program before the change as it is, or to use the value after clearing the previous value to the initial state. The value used in this way is not the original previous value in the changed user program.

Therefore, when such a method is used,
The execution result of the instruction to detect the rising or falling may not be obtained correctly, and erroneous processing may be performed or erroneous output may be derived. As a result, the sequence control may malfunction. Therefore, conventionally, the operation of the programmable controller is not guaranteed when the user program is changed during execution of the user program.

It is an object of the present invention to provide a programmable controller capable of changing a user program during its execution without causing a malfunction.

[0018]

A programmable controller according to the present invention comprises a state storage means, a previous value storage means,
A program storage means, a write prohibition means, and a control means are provided.

The state storage means stores an input state, an output state and an internal state. The previous value storage means stores the previous value of the internal state. The program storage means stores a program for performing sequence control in relation to the input state, output state and internal state stored in the state storage means and the previous value stored in the previous value storage means. The write inhibit means puts the state storage means into a write inhibit state. After changing the program stored in the program storage means, the control means sets the state storage means to the write-protected state by the write prohibition means, executes the changed program for one scan, and then writes the state storage means by the write prohibition means. Cancel the prohibited state.

[0020]

In the programmable controller according to the present invention, the state storage means for storing the input state, the output state and the internal state and the previous value storage means for storing the previous value of the internal state are separately provided, and the program storage means is provided. After changing the program stored in, the state storage means is put into the write-protected state, and the changed program is executed for one scan in that state. As a result, the internal state stored in the state storage means as the current value before the program change is stored in the previous value storage means as the previous value in the changed program.

Therefore, after that, by releasing the write-protected state of the state storage means, the changed program can be continuously executed by using the previous value obtained by the changed program. Therefore, the execution result of the instruction for detecting the rise or fall of the internal state can be accurately obtained.

[0022]

1 is a block diagram showing the configuration of a programmable controller according to an embodiment of the present invention.

The programmable controller 1 shown in FIG.
RAM2, ROM3, communication interface 4, write prohibition / permission control unit 5, CPU 6, input unit 7 and output unit 8
including.

Input devices such as switches and sensors are connected to the input unit 7, and output devices such as electromagnetic switches, relays, solenoids and motors are connected to the output unit 8. The ROM 3 stores a system program for controlling the entire programmable controller 1.

The RAM 2 is a user program storage unit 2
1. Previous value storage area 22 and device area 23
including. The user program created by the user using the program creating device 9 is stored in the user program storage unit 21 of the RAM 2 via the communication interface 4.

In the device area 23, the input state from the input device to the input unit 7, the output state from the output unit 8 to the output device, the internal relay (input relay, output relay and auxiliary relay), timer, counter, A current value of information (hereinafter, referred to as device information) indicating an internal state of a data memory or the like is stored. The previous value storage area 22 stores device information (hereinafter referred to as a previous value) at the time of the previous scan.

The write prohibition / permission control section 5 has a function of setting the device area 23 of the RAM 2 in the prohibition state and the permission state. The write prohibition / permission control unit 5 sets the device area 23 to the write prohibition state by software when the user program is changed.

The CPU 6 controls each part of the programmable controller 1 in accordance with the system program stored in the ROM 3 and also stores the user program storage unit 2.
The user program stored in 1 is executed.

Next, the operation of the programmable controller 1 of FIG. 1 will be described with reference to the flowchart of FIG. Typically, a conventional programmable controller 100
Similarly, the input refresh (step S1), the execution of one scan of the user program (step S2) and the output refresh (step S3) are repeated.

When the user program is changed (step S4), first, the user program created by the user using the program creating device 9 is transferred to the user program storage section 21 of the RAM 2 via the communication interface 4,
The user program before the change is rewritten with the user program after the change (step S5). And write protect /
The permission control unit 5 puts the device area 23 of the RAM 2 in a write-protected state (step S6). As a result, the current value of the device information stored in the device area 23 is held.

In this state, the CPU 6 executes one scan of the changed user program stored in the user program storage section 21 (step S7). This is called a dummy scan. By this dummy scan, the device information stored in the device area 23 is stored in the previous value storage area 22 as the previous value.

After that, the write prohibition / permission control unit 5 causes the R
The device area 23 of AM2 is set to the write-enabled state (step S8). As a result, the device area 23
The device information stored in can be rewritten.

Then, returning to the normal cycle, the input refresh (step S1), the execution of one scan of the user program (step S2) and the output refresh (step S3) are performed. In this case, when the changed user program has an instruction to detect the rising or falling of the device information in step S2, the previous value obtained by the dummy scan of the changed user program is used. As a result, the execution result of the instruction to detect the rising or falling of the device information can be accurately obtained in the changed program.
Therefore, the changed user program can be continuously executed without causing a malfunction.

The write prohibition / permission control unit 5 may set the device area 23 in the write-prohibited state and the write-permitted state in response to a signal given from the program creating device 9 when the user program is changed, Alternatively, the device area 23 may be set to the write-protected state and the write-enabled state in response to the switch operation by the user.

[0035]

As described above, according to the present invention, when a program is changed during execution, the input state, output state and internal state obtained by the program before the change are fixed and the changed program is changed. By executing one scan, the previous value of the internal state in the changed program can be obtained, and the rise or fall of the internal state can be accurately detected. Therefore, the program can be changed during execution without causing a malfunction.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a programmable controller according to an embodiment of the present invention.

FIG. 2 is a flowchart showing the operation of the programmable controller of FIG.

FIG. 3 is a block diagram showing a configuration of a conventional programmable controller.

FIG. 4 is a flowchart showing a basic operation of a conventional programmable controller.

[Explanation of symbols]

 1 Programmable Controller 2 RAM 3 ROM 4 Communication Interface 5 Write Protect / Permission Control Unit 6 CPU 7 Input Unit 8 Output Unit 9 Program Creation Device 21 User Program Storage Unit 22 Previous Value Storage Area 23 Device Area

Claims (1)

[Claims] 1. A state storage means for storing an input state, an output state and an internal state, a previous value storage means for storing a previous value of the internal state, and an input state, an output state and an internal state stored in the state storage means. A program storage means for storing a program for performing sequence control in relation to a state and a previous value stored in the previous value storage means; a write prohibition means for setting the state storage means in a write-protected state; After changing the stored program, the write prohibiting means sets the state storing means to the write prohibiting state, the changed program is executed for one scan, and then the write prohibiting means cancels the write prohibiting state of the state storing means. And a control means for controlling the programmable controller.