KR19980068492A - Communication method and communication device of Piel City (PLC) - Google Patents

Abstract

The present invention relates to a communication method and communication apparatus of a PLC. A communication method of a PLC is a computer communication unit in which a computer is connected via a communication line and a central processing unit connected to the computer communication unit via a common bus, The computer communication unit generating and sending a predetermined command signal to the central processing unit according to a user command input through the central processing unit; and receiving a response signal of the central processing unit corresponding to the command signal, And causing the computer communication unit to transmit the response signal to the computer for display. Thereby, a communication method of a PLC capable of referring to the contents of a register in the central processing unit using a computer connected to the computer communication unit is provided.

Description

Communication method and communication device of Piel City (PLC)

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a communication method and communication apparatus of a PLC (Programmable Logic Controller).

In general, Pielsi (hereinafter also referred to as PLC) has a computer communication unit (CCU), which is a dedicated communication board for performing communication with a computer, and a computer communication unit (Hereinafter also referred to as a CCU) is controlled by a central processing unit (hereinafter also referred to as CPU).

1 is a schematic diagram of a general PLC and a computer connected thereto. As shown in the figure, a general PLC 10 is composed of boards such as a power supply unit 101, a CPU 102, a CCU 103, an input unit 104, and an output unit 105, They are connected to each other through a common bus on the motherboard. The CCU 103 is connected to the computer A 11 through an RS-232C method to perform serial communication.

During the operation of the PLC 10, it is necessary to refer to the register contents such as the system register in the CPU 102 in order to grasp the current state or the like of the PLC 10. [ In this case, conventionally, a method of monitoring and connecting a separate computer B 13 to the CPU 102 has been used. That is, a predetermined user command is transmitted to the CPU 102 via the computer B 13 connected to the CPU 102, and the computer B 13 receives the response signal of the CPU 102 accordingly and displays it , The user refers to the contents of the necessary registers.

Therefore, in order to refer to the contents of the registers in the CPU 102, it is inconvenient to use a separate computer B (13) to connect to the CPU 102, Even though the computer A 11 is connected to the personal computer 103, it is impossible to use the device directly.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a communication method and a communication apparatus of a PLC capable of reading the contents of registers on a CPU board through a CCU to which a computer is connected.

1 is a schematic diagram showing a connection state between a PLC and a computer,

2 is a flowchart illustrating a communication method of a PLC according to the present invention.

DESCRIPTION OF THE REFERENCE NUMERALS

10: PLC 11: Computer A

13: Computer B 101: Power unit

102: CPU 103: CCU

104: Input unit 105: Output unit

The above object is achieved by a communication method of a PLC having a computer communication unit in which a computer is connected through a communication line and a central processing unit connected to the computer communication unit via a common bus, The computer communication unit generating and sending a predetermined command signal to the central processing unit in response to a user command input via the central processing unit; and receiving a response signal of the central processing unit corresponding to the command signal, And causing the computer communication unit to transmit the response signal to the computer so that the computer communication unit displays the response signal to the computer.

Here, the user command may include a command to read contents stored in at least one of the system registers in the central processing unit. The user command may include a head number of a system register to be read and a final number .

According to another aspect of the present invention, there is provided a computer system having a computer communication unit in which a computer is connected via a communication line and a central processing unit connected to the computer communication unit via a common bus, A computer communication unit transfer unit for transferring the command signal to the central processing unit, and a controller for receiving the command signal and generating a corresponding response signal A communication unit of a PLC including a response signal generation unit, a central processing unit transmission unit for transmitting the response signal to the computer communication unit, and a display control unit for receiving the response signal and displaying the response signal on the computer, / RTI >

Here, the user command may use a command to read contents stored in at least one of the system registers in the central processing unit.

Hereinafter, the present invention will be described in detail with reference to the drawings.

1, the PLC includes a power supply unit 101, a CPU 102, a CCU 103, an input unit 104, and an output unit 102 mounted on a single basic motherboard, And these boards are interconnected via a bus of the basic motherboard, and the CCU 103 can be connected to the computer A 11 through the RS-232C method to perform serial communication.

In the PLC 10 having such a configuration, the communication method according to the present invention is the same as the flowchart shown in Fig. In the flow chart, first, the command program is inputted using the computer A 11 connected in series through the RS-232C port with the CCU 103 (S30). An input of the command program uses an editor executed in the computer A11, and a user command is transmitted from the computer A11 to the CCU 103 by the execution of the command program (S32).

If the user command is an instruction to read the system register in the CPU 102, it can be configured in the format shown in Table 1.

[Table 1]

% Sender # RR 0 Head number Last number BCC cr

Here,% indicates the start of a command signal as a header, the destination indicates a PLC number to be processed by a user command, and # indicates that a command or a message is directly behind. In addition, RR denotes a command to read the contents of the system register, 0 is fixedly used in a format, and the head number and the last number are system registers to be read out from the system registers of the CPU 102 having consecutive numbers And the last number. The BCC (Block Check Code) is a code for checking parity error used for improving the reliability of the transmission signal. The BCC value is an exclusive OR (XOR) from the header of the transmitted command signal to the final character And converting the bit data into an ASCII code character. This BCC value is checked before transmission and after reception, and if the value is different, it can be known that there is an error during communication. Finally, cr represents the end of the command signal.

The CCU 103 receives a user command and analyzes it, generates a corresponding command signal, and transmits the command signal to the CPU 102 (S34). At this time, the reception of the user command and the generation of the command signal are performed by the command signal generating unit in the CCU 103, and the transmission of the command signal is performed by the computer communication unit transmitting unit in the CCU 103.

The CPU 102 receives a command signal transmitted from the CCU 103, analyzes the received command signal, generates a response signal corresponding to the received command signal, and transmits the response signal to the CCU 103, 103). The display control unit of the CCU 102 receives the response signal of the CPU 102 (S36), and transmits the received response signal to the computer A11 so as to be displayed (S38).

If the user command is an instruction to read the system register in the CPU 102, it can be configured in the format shown in Table 1.

At this time, the response signal can be configured in the format shown in Table 2.

[Table 2]

% Source $ RR R [start] ..... R [end] BCC cr

Here,% indicates the start of the response signal, the source indicates the PLC number where the response signal is generated, $ indicates that the response signal is a normal response, RR indicates the response signal according to the RR command, R [start], which is the contents of the system register, which is the head number, R [end], which is the final number, which is the contents of the system register, is sequentially displayed according to the head number and the final number. At this time, the contents of the system register are represented by a 4-digit decimal number, and BCC and cr indicate a code for checking parity error and an end of a response signal, as described above.

If an error occurs during the execution of the user command, the response signal can be configured in the format shown in Table 3.

[Table 3]

% Source ! Error code BCC cr

Here,% and source are as described above, and! Indicates that the response signal is a response when an error occurs. The error code indicates a code corresponding to various errors such as a data error, an over-run error, and a transmission format error, and the user can refer to the error code so as to know the cause of the error.

The computer A 11 having received the response signal displays a response signal corresponding to the monitor or the like (S40). This allows the user to refer to the contents of the desired one of the system registers in the CPU 103. [

By the above-described communication method and apparatus, a user command for the CPU 103 is output through the computer A 11 connected to the CCU 102, and a response signal is received and displayed, The system register contents of the desired CPU 103 can be read.

In the above example, only the case where the system register in the CPU 103 is read is described. However, it is also possible to write the desired contents to the system register in the CPU 103 in the same manner. It is also possible to refer to the contents stored in other resources in the CPU 103 or change the contents thereof by modifying the format.

As described above, according to the present invention, there is provided a PLC communication method and a communication device capable of reading the contents of a register in a CPU through a computer connected to the CCU in a PLC having a CCU and a CPU.

Claims (5)

A communication method of a PLC having a computer communication unit in which a computer is connected through a communication line and a central processing unit connected to the computer communication unit via a common bus, Generating a command signal by the computer communication unit according to a user command input through the computer and transmitting the command signal to the central processing unit; Receiving, by the computer communication unit, a response signal of the central processing unit corresponding to the command signal; And causing the computer communication unit to transmit the response signal to the computer for display. The method according to claim 1, Wherein the user command is a command to read contents stored in at least one of the system registers in the central processing unit. 3. The method of claim 2, Wherein the user command comprises a head number and a final number of system registers to be read. 1. A communication apparatus of a PLC having a computer communication unit in which a computer is connected via a communication line and a central processing unit connected to the computer communication unit via a common bus, A command signal generator for receiving a user command input through the computer and generating a predetermined command signal; A computer communication unit transmitting unit for transmitting the command signal to the central processing unit, A response signal generator for receiving the command signal and generating a corresponding response signal; A central processing unit transmitting unit for transmitting the response signal to the computer communication unit, And a display control unit for receiving the response signal and displaying the response signal on the computer. 5. The method of claim 4, Wherein the user command is a command to read contents stored in at least one of the system registers in the central processing unit.