JP2010287034A - Address display system of modbus protocol communication between external equipment and plc - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a communication system by which Modbus master external equipment can transmit a Modbus function code which PLC can recognize and a Modbus address, without computating address when memory location of PLC is specified and accessed by a Modbus protocol communication from external equipment. <P>SOLUTION: As a Modbus master, for example, a programmable display 11 accesses a device address in a memory in a PLC 12 by Modbus protocol communication for obtaining device information. A communication system in which a Modbus function code corresponding to a device address and a Modbus address are sent to the PLC is configured such that on an address picker screen called on the tool screen for programming in the PLC, a list in which all device addressing can be assigned to all Modbus addresses and all Modbus functional codes. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a Modbus protocol communication method for an external device to obtain in-memory information of a PLC (programmable controller, programmable logic controller) as a Modbus master.

  The PLC is installed in a production facility, executes a sequence program, and performs sequence control of control devices such as various machines and devices in the production facility connected to the PLC. The PLC inputs ON / OFF information of input devices such as switches and sensors corresponding to the state of the control target, and stores the input ON / OFF information in a memory, while a sequence program written in a ladder language or the like In addition to executing logical operations according to the above, storing the information of the obtained operation results in a memory and outputting the stored information to output devices such as relays, valves, actuators, etc. Is supposed to run.

  In a control system in which an external device such as a temperature controller, a programmable display, or another PLC is connected to such a PLC, the external device obtains information in the memory of the PLC and controls the entire control system having the PLC. May be performed. And when an external apparatus communicates with PLC, generally the communication by Modbus protocol is employ | adopted (refer patent document 1). MODBUS is a Modicon. This is a communication protocol developed by Inc for PLC. The MODBUS communication method is a single master / multi-slave method. Only the master can issue a request, and the slave returns a response message in response to the request. The request from the master is a device address, function code, request data, and error check in the slave, and the response from the slave is a check device address, check function code, response data, and error check.

  In the above communication, the external device is a Modbus master device, the PLC is a slave device, the external device designates a memory location (device address = Modbus address) in the PLC, and accesses the memory location (Modbus address). In order to obtain ON / OFF information of input devices such as switches and sensors and ON / OFF information of output devices such as relays, valves, actuators, etc., the software on the external device side can recognize the Modbus that the PLC can recognize. It is necessary to transmit the function code and the Modbus address to the PLC.

  In this case, since the Modbus address in the PLC is different for each PLC manufacturer, on the external device side, in order to obtain the Modbus address from the PLC, the Modbus function code of the memory location and the specification provided by each PLC manufacturer are used. It is necessary to know the Modbus address. In this case, the address only needs to be directly described in the specification provided to the user. However, depending on the PLC, only the top address may be described as the Modbus address. It is necessary to calculate the address, for example, by adding the address that the side addresses from the top address. However, when the number of Modbus address calculations becomes enormous, the user is very troublesome. The Modbus function code is, for example, a numerical value such as 01, 02,..., Whether access to the PLC is read or write, whether the access target is one data point, or a group thereof. It is a code for deciding what it is.

Special Table 2002-528980

  The problem to be solved in the present invention is to eliminate the need for the user to perform a complicated Modbus address calculation when the external device communicates with the PLC via the Modbus protocol.

  In the present invention, when an external device as a Modbus master accesses a position (device address) in a memory of a PLC as a Modbus slave to obtain device information, the external device sends a Modbus function code and Modbus corresponding to the device address to the PLC. In the Modbus protocol communication method for transmitting an address, a screen operation by the user calls a predetermined screen on the screen of the PLC programming tool, and all device addresses in the PLC memory are all displayed on the called predetermined screen. A list associated with the Modbus address and all the Modbus function codes can be displayed.

  The predetermined screen is an address picker screen in the embodiment, but is not limited to this name in the present invention.

  According to the present invention, when the user designates and accesses the memory location of the PLC from the external device by Modbus protocol communication according to the above list, the Modbus function code that can be recognized by the PLC without performing address calculation, the Modbus address, Can be transmitted by the Modbus master external device.

FIG. 1 is a diagram showing a schematic configuration of a control system according to an embodiment of the present invention. FIG. 2 is a diagram showing each device address in the internal memory of the PLC and ON / OFF information corresponding to each device address. FIG. 3 is a diagram showing the procedure of Modbus protocol communication from the programmable display to the PLC. FIG. 4 is a diagram showing an address picker screen when the memory location of the PLC is not designated. FIG. 5 is a diagram showing an address picker screen in Modbus protocol communication of HEX notation by specifying the memory location of the PLC. FIG. 6 is a diagram showing an address picker screen in Modbus protocol communication of 984 notation by specifying the memory location of the PLC.

  Hereinafter, a communication method according to an embodiment of the present invention will be described with reference to the accompanying drawings. However, the embodiment described below exemplifies one method for embodying the technical idea of the present invention, and the present invention is not limited to the following method.

  In FIG. 1, 10 is a computer, 11 is a programmable display as an example of an external device, 12 is a programmable controller (PLC), 13a to 13d are input / output devices, 14 is a controlled device, and 15 is a bus.

  The computer 10 is a general-purpose personal computer used for a ladder program creation / editing tool of the PLC 12, and includes a CPU 10a, a memory 10b, a display unit 10c, an operation unit 10d, an external storage device 10e, a communication interface 10f, and the like.

  The CPU 10a performs control and arithmetic processing of each unit when operating various application programs including a ladder program editing program on an OS (operating system) installed in the computer 10. The memory 10b includes a memory such as a RAM and a ROM, and has a memory configuration capable of providing a work area during data storage, temporary data storage, and arithmetic processing of the CPU 10a.

  The display unit 10c of the computer 10 includes a flat monitor screen such as a CRT, LCD, liquid crystal panel, or EL panel. The operation unit 10d is a device for performing an input operation such as a keyboard and a mouse. In particular, a pointing device such as a mouse is suitable for an input operation using a ladder program editing program that operates in a GUI environment. The external storage device 10e is a device such as a magnetic disk drive such as a hard disk device or an optical disk drive such as a CD-ROM drive, and includes at least a device that can read information such as a ladder program editing program recorded on a recording medium. It is out. The interface 10 f is an input / output unit that performs data communication with the PLC 12. The ladder program created by the ladder program editing program is transferred to the PLC 12 via the interface 10f and downloaded to the memory in the PLC 12. The ladder program editing program installed and executed on the computer 10 is executed by the CPU 10a of the computer 10.

  The programmable display 11 is provided with an interface with the PLC 12, and displays operation statuses of the input / output devices 13a-13d connected to the PLC 12 and operation inputs for giving control instructions to the input / output devices 13a-13d. It has a function to accept from the screen. A display program is installed in the programmable display 11. This installation can be performed from the computer 10. The programmable display 11 performs a display operation according to the display program.

  As the HMI device, the programmable display 11 displays, on its display screen 11a, components 11b1-11b4 that display the operation status of the input / output devices 13a-13d and operate the input / output devices 13a-13d. Yes.

  Each component 11b1-11b4 has various properties such as various shapes, colors, characters, fonts, and the like. The components 11b1-11b4 are HMI (Human Machine Interface) components that form an interface between the input / output devices 13a-13d and the operator. The components 11b1-11b4 correspond to the input / output devices 13a-13d.

  The PLC 12 includes a CPU 12a that executes a ladder program, a system control memory 12b that stores a system control program (firmware), a ladder program memory 12c that stores a ladder program, an internal memory 12d that stores data such as variables used for control, There is an input / output interface 12e, which are interconnected by an internal bus 12f. Connected to the input / output interface 12e are various input / output devices 13a-13d such as sensors and actuators and various controlled devices 14 such as machines and devices. The internal memory 12d of the PLC 12 includes an input memory X, an output memory Y, an internal relay memory C, a timer T, a counter CT, a data memory D, and the like. The PLC 12 having the above configuration can control the operations of the input / output devices 13a to 13d according to the procedure defined by the ladder program created by the ladder program editing program according to the system control program by the built-in CPU 12a. It can be done.

  FIG. 2 shows device addresses X001, X002, X003, X004... In the internal memory 12d of the PLC 12 and ON / OFF information corresponding to each device address. In FIG. 2, the ON / OFF information of the device address X001 is ON, the ON / OFF information of X002 is OFF, the ON / OFF information of X003 is ON, and the ON / OFF information of X004 is ON. It has been shown. In the embodiment, for the sake of understanding, FIG. 2 shows device addresses X001 to X004 in the PLC 12 in a state corresponding to the input / output devices 13a to 13d.

  Referring to FIG. 3, programmable display 11 designates device address X001-X004 of internal memory 12d of PLC 12 for storing ON / OFF information of input / output devices 13a-13d, and stores them in device addresses X001-X004. In order to obtain ON / OFF information of the input / output devices 13a-13d, Modbus protocol communication is performed with the PLC 12. The device addresses are X0001, X0002, X003, and X004. In order to obtain data to be stored at the device address X001 of the PLC 12, the programmable display 11 transmits a Modbus address 0000 in HEX notation and a Modbus function code 02 as a request signal from the Modbus master. When the PLC 12 recognizes that the Modbus address 0000 in HEX notation corresponding to the device address X001 and the Modbus function code 02 are transmitted from the programmable display 11, the PLC 12 stores the response signal from the Modbus slave in the device address X001. The ON / OFF information (ON in the embodiment) of the component 11b1 is transmitted to the programmable display 11. Next, in order to obtain data to be stored in the device address X002 of the PLC 12, the programmable display 11 transmits a Modbus address 0001 in HEX notation and a Modbus function code 02 to the PLC 12. When the PLC 12 recognizes that the Modbus address 0001 in HEX notation corresponding to the device address X002 and the Modbus function code 02 are transmitted from the programmable display 11, the PLC 11b2 ON / OFF information stored in the device address X002 is received. (OFF in the embodiment) is transmitted to the programmable display 11. In this way, communication is performed from the programmable display 11 to the PLC 12.

  Referring to FIG. 4, a user interface address picker screen AP is displayed on the computer screen of the display unit 10 c of the computer 10. This address picker screen AP is a screen for displaying the editing information of the ladder program and the address information of the internal memory 12d. The address picker screen AP is a screen used for creating a ladder program, debugging or repairing a ladder program, and the like. In the address picker screen AP, the internal memory address cannot be changed. The user can register or change the nickname and comment, which are information associated with the address. The user can program a ladder program using the nickname and comment. The address accompanying information includes a nickname that is an alias for the address, and the same nickname cannot be registered. Another accompanying information is a comment. The comment supplementally explains the nickname, and a plurality of the same names can be registered. In the ladder diagram, the accompanying information is displayed in a two-stage configuration with a nickname and a comment.

  Since the address picker screen is a display mode (Pickup Mode) in which an address is picked up, “Address Picker: Pick Mode” is displayed in the title bar TB. Another mode is “Edit Mode”. This mode is displayed when a nickname that is address-associated information is registered in the “Nick name” field and a comment that is also address-associated information is registered in the “Comment” field. Mode. A square display area is displayed on the screen, and user operation buttons labeled “All”, “X”, “Y”, “C”, “T”, “CT”,... Are displayed in a vertical line on the left end outside the display area. . “All” is a button for selecting all internal memories, “X” is a button for selecting input memory X, “Y” is a button for selecting output memory Y, “C” is a button for selecting internal memory, “T” Is a button for selecting a timer, and “CT” is a button for selecting a counter. On the left side of the lower end outside the display area, the characters “Data Type Filter” and the check box (□) of “Display All Data Types” are displayed in the rectangular frame area including these characters. “Used / Unused Address” is displayed at the center of the bottom edge outside the display area, and the “Display both used and unused” check box (□) and the “Display only used” check box are displayed in the area within the square frame including the characters. A box (□) and a “Display only unused” check box (□) are displayed. Furthermore, the characters “Display MODBUS Address” are displayed on the lower right side outside the display area, the check box (□) of “MODBUS 984 Addressing” and the check box of “MODBUS HEX Addressing” ( □) and are displayed.

  In the present embodiment, as shown in the Modbus address and Modbus function code non-display state in FIG. 4 to the Modbus address and Modbus function code display state in FIGS. A list in which all device addresses in the internal memory 12d are associated with all Modbus addresses and all Modbus function codes can be displayed.

  In FIG. 4, “Display MODBUS Address” is not required to be displayed, and “Le” is displayed in the “Display All Data Types” check box (□) on the lower left side outside the display area. The check box (□) of “Used / Unused Address” is put in the lower end center side outside the display area, but “Display MODBUS Address” is put on the lower right side outside the display area. Does not have a check box (□). In FIG. 4, among the user operation buttons “All”, “X”, “Y”, “C”, “T”, “CT”..., The user operation buttons “All” corresponding to all the memories are selected and operated. Yes. On the upper side outside the display area, a search term entry area for searching for address information, address associated information, etc., “Find” notation indicating the area name, and the search name in the area are entered, and then the search is performed. The “Find” operation button for executing the above is arranged.

  In FIG. 4, “Address”, “AZ ↓”, “DataType”, “Nickname”, “Used”, “Initial Value”, “Retentive”, “Address Cc” ... Is displayed. Addresses are described in one vertical column of “Address”. This address is automatically described by any selection operation of user operation buttons “All”, “X”, “Y”, “C”, “T”, “CT”,. In FIG. 4, user operation buttons All corresponding to all memories All are selected. “Address” indicates entry of the internal memory location (device address) of the PLC 12, and in the example shown in the figure, the device addresses are X001, X002, X003,. The notation “RW” in the address means that the address can be read and written. The data type is automatically described in the vertical column of “Data type”. The embodiment indicates that the data type is bit by BIT notation. In the vertical row of “Nick name”, an alias of the address is described by a user operation. In the vertical row of “Use”, “YES” is automatically described when the address is used, and “NO” is automatically described when the address is not used. In the vertical column of “Comment”, a comment is described by a user operation.

  In FIG. 5, “Display MODBUS Address” has a check box (□) put in the check box (□) on the lower right side outside the display area, and a display field of “MODBUS Address (Function Code)” is arranged in the display area. In addition, the “MODBUS HEX Addressing” check box (□) is put with “less”, and the Modbus address is expressed in HEX (hexadecimal) notation in the vertical column of “MODBUS Address (Function Code)”.

  As a result, the user knows that the Modbus address corresponding to the PLC device address “X0001” is “0000” in HEX notation and the Modbus function code is “02”. It can also be seen that the Modbus address corresponding to the PLC device address “X0002” is “0001” in HEX notation and the Modbus function code is “02”. The same applies to the following.

  In FIG. 6, “Display MODBUS Address” has a check box (□) placed in the check box (□) on the lower right side outside the display area, and a “MODBUS Address (Function Code)” display field is arranged in the display area. In addition, the “MODBUS 984 Addressing” check box (□) is put with “Le”, and the Modbus address is expressed in 984 (decimal) in one vertical column of “MODBUS Address (Function Code)”.

  As a result, the user knows that the Modbus address corresponding to the device address “X0001” of the PLC is “10000” in 984 notation and the Modbus function code is “02”. Further, it can be seen that the Modbus address corresponding to the device address “X0002” of the PLC is “100002” in 984 notation and the Modbus function code is “02”. The same applies to the following.

  As described above, in the present embodiment, when the programmable display 11 accesses the position (device address) in the memory of the PLC 12 by Modbus protocol communication to obtain device information, the programmable display 11 receives communication software. The Modbus function code corresponding to the device address and the Modbus address are transmitted to the PLC 12 by calling the address picker screen AP on the screen of the computer 10 which is a programming tool of the PLC 12, and this address picker screen. On the AP, as shown in FIGS. 5 and 6, a list in which all device addresses, all Modbus addresses, and all Modbus function codes are associated with each other can be displayed. The table lists the Modbus function codes to PLC12 without the need for Modbus address calculation, it is possible to transmit the Modbus address.

10 Computer 11 Programmable Display 12 PLC

Claims (1)

  When the external device as the Modbus master accesses the location (device address) in the memory of the PLC as the Modbus slave to obtain device information, the external device transmits the Modbus function code and Modbus address corresponding to the device address to the PLC. In the Modbus protocol communication system, the user calls a predetermined screen on the screen of the PLC programming tool by the user's screen operation, and all the device addresses in the PLC memory are displayed on the called predetermined screen. A Modbus protocol communication address display method, characterized in that a list associated with Modbus function codes can be displayed.

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