JP2023168186A - Display device and display method - Google Patents

Abstract

To perform logging in a programmable logic controller including a plurality of arithmetic processing sections.SOLUTION: A programmable logic controller comprises a plurality of arithmetic processing sections, which distribute and execute control processing for controlling an external device, and executes a user application program for the control processing. Any of the arithmetic processing sections collects values of a plurality of respective variables used in the user application program at predetermined collection timing and performs logging processing for generating collection data. The display device for displaying the collection data includes a display control section and a display section. The display control section checks which of a value of the variable and defect information indicating a defect of the value of the variable is included in the collection data for each of the plurality of variables. The display section displays the value of the variable for the variable of which the value is included in the collection data, and displays defect display information indicating the defect of the value of the variable for the variable of which the defect information is included in the collection data.SELECTED DRAWING: Figure 1

Description

The present invention relates to a programmable logic controller (PLC) technology.

PLC is a controller that controls manufacturing equipment, transport equipment, and inspection equipment in factory automation. PLCs control various control devices by executing user application programs created by users, such as ladder programs.

When an abnormality occurs in the control of equipment by a control device such as a PLC, it is desirable to identify the cause of the abnormality. In addition, there is a desire to record information related to control of equipment and to verify the information afterward, not only in the case of occurrence of such an abnormality. Therefore, the user may set conditions in the control device in advance for keeping a data history, and based on these conditions, the control device may log data indicating the operating status of the equipment and the control device itself. .

In connection with data logging, a PLC is known that facilitates specifying the temporal relationship between various data input from monitoring equipment and device values (for example, see Patent Document 1).

This PLC collects device values stored in any one of a plurality of devices, associates information regarding the collection time of the device values with the device values, and stores them in a first buffer. The PLC collects data input from the monitoring equipment, associates the data with information regarding the acquisition time at which the data was acquired, and stores the data in a second buffer. When a predetermined storage condition is met, the storage unit stores information related to the device value and collection time stored in the first buffer in association with information related to the data stored in the second buffer and acquisition time. do.

A programmable controller including a plurality of interface units and a plurality of CPU (Central Processing Unit) modules is also known (see, for example, Patent Document 2).

In this programmable controller, the interface unit is connectable to the CPU module and can send out a first potential signal having a plurality of different potential states to the connected CPU module. The CPU module is connectable to the interface unit and other CPU modules, and includes a CPU for executing arithmetic processing and a memory for storing determination bits and definition information.

The determination bit has binarized information. The binarized information determines whether the CPU in the CPU module is the main CPU or the sub CPU based on the potential state of the first potential signal input to the CPU module from the interface unit to which the CPU module is connected, which has a determination bit. Indicates whether The definition information includes setting information indicating whether the CPU in the CPU module having the definition information is set in advance as a main CPU or a sub CPU.

There is also known a program creation support device for a programmable controller that allows a user to declare global variables without being aware of the assignment of programs to processors (see, for example, Patent Document 3).

JP2020-13526A International Publication No. 2014/080457 Japanese Patent Application Publication No. 2012-164178

In a PLC with a multi-CPU configuration that includes multiple CPU modules, the high-load processing performed by one CPU module is distributed to multiple CPU modules, increasing the memory capacity of the entire PLC and speeding up control processing. can be converted into

Even in a PLC with a multi-CPU configuration, logging can be easily performed on data stored in a memory in a CPU module that performs logging and data input to that CPU module. However, in such a PLC, a shared memory may be used as a shared resource between CPUs. There are no known techniques for logging data stored in shared memory.

Note that this problem occurs not only in PLCs that include multiple CPU modules, but also in various PLCs that include multiple arithmetic processing units.

In one aspect, the present invention aims to perform logging in a PLC that includes a plurality of arithmetic processing units.

According to one embodiment, a programmable logic controller that controls an external device includes a plurality of removable arithmetic processing units that perform distributed control processing to control the external device. The programmable logic controller executes a user application program for control processing. The plurality of arithmetic processing units include a first arithmetic processing unit and a second arithmetic processing unit.

The first arithmetic processing section includes a collection section. The collection unit performs a logging process that collects the values of each of a plurality of variables used in the user application program at a predetermined collection timing, and generates collected data. In the logging process, if access to the value of a predetermined variable used by the second arithmetic processing section among the plurality of variables fails, the collection section sets missing information indicating the missing value of the predetermined variable in the collected data. do.

According to another embodiment, a programmable logic controller that controls an external device includes a plurality of arithmetic processing units that distribute and execute control processing for controlling the external device. The programmable logic controller executes a user application program for control processing. One of the plurality of arithmetic processing units collects the values of the variables to be collected that are used in the user application program at a predetermined collection timing based on the setting information, and generates collected data. Performs logging processing.

The programmable logic controller support device includes a program analysis section, a display section, a specification section, and an output section. The program analysis unit analyzes the user application program and extracts a plurality of variables used in the user application program.

The display section displays variables used by each of the plurality of arithmetic processing sections among the plurality of variables. The specifying unit specifies a variable selected from among the variables used by each of the plurality of arithmetic processing units as a variable to be collected. The output unit outputs information indicating variables to be collected as setting information.

According to yet another embodiment, a programmable logic controller that controls an external device includes a plurality of arithmetic processing units that perform distributed control processing to control the external device. The programmable logic controller executes a user application program for control processing. One of the plurality of arithmetic processing units performs a logging process that collects the values of each of the plurality of variables used in the user application program at a predetermined collection timing and generates collected data.

A display device that displays collected data includes a display control section and a display section. The display control unit checks, for each of the plurality of variables, whether the collected data includes a value of the variable or missing information indicating a missing value of the variable. The display section displays variable values for variables whose values are included in the collected data, and displays missing display information indicating missing variable values for variables whose missing information is included in the collected data. do.

According to one aspect, logging can be performed in a PLC including a plurality of arithmetic processing units.

It is a diagram showing an example of the configuration of a PLC system. FIG. 3 is a diagram illustrating an example of an execution period P of each process executed by a CPU module. FIG. 3 is a diagram showing an example of the hardware configuration of a CPU module. It is a diagram showing an example of the hardware configuration of a PC. It is a figure showing an example of functional composition of a support device. FIG. 3 is a diagram illustrating a method of setting conditions for executing logging processing. This is an example of a UI screen. FIG. 3 is a diagram showing an example of a data structure of logging setting data. FIG. 3 is a diagram illustrating an example of a data structure of collection target setting information. It is a figure showing an example of functional composition of a CPU module. FIG. 3 is a diagram illustrating a logging execution method by a CPU module. 3 is a flowchart showing details of processing contents of logging processing and storage processing. FIG. 3 is a diagram illustrating an example of a data structure of logging collection data. FIG. 3 is a diagram showing an example of a data structure of collected data. FIG. 3 is a diagram showing an example of a data structure of variable data. 7 is a flowchart showing details of the processing content of collection processing. It is a diagram showing an example of the hardware configuration of a collected data display device. FIG. 2 is a diagram showing an example of a functional configuration of a collected data display device. FIG. 3 is a diagram illustrating an example of a method of displaying collected data. FIG. 3 is a diagram illustrating details of program display processing. This is an example of a warning screen. FIG. 3 is a diagram illustrating details of waveform display processing. FIG. 3 is a diagram illustrating details of logging file analysis/conversion processing. It is a flowchart which shows the processing content of a logging file analysis/conversion process. 3 is a flowchart showing details of the processing contents of variable value generation processing. FIG. 3 is a diagram illustrating details of display control processing. This is an example of a display drawing of collected data. This is an example of a waveform display screen of collected data.

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

FIG. 1 shows an example of the configuration of a PLC system. The PLC system in FIG. 1 includes a PLC 1, a personal computer (PC) 2, input/output modules 3-1 to 3-M (M is an integer of 2 or more), and communication modules 4-1 to 4-M. including.

The PLC 1 centrally controls various control devices installed in factories and the like. The PLC 1 is a PLC with a multi-CPU configuration, and includes CPU modules 7-1 to 7-M and a shared memory 8. The CPU module 7-i (i=1 to M) and the shared memory 8 are connected via a bus 9. The CPU module 7-i accesses the shared memory 8 via the bus 9. The shared memory 8 operates as a storage unit that stores the values of variables.

The CPU module 7-i is a removable hardware module, and may be removed from the PLC 1 for maintenance or the like. The CPU module 7-i operates as an arithmetic processing section.

The CPU module 7-1 performs logging processing, which will be described later. The CPU module 7-1 and the PC 2 are connected via a communication cable 5. The PC 2 may be connected to another CPU module 7-i via the communication cable 5. Two or more CPU modules 7-i including the CPU module 7-1 may perform the logging process. For example, the CPU module 7-1 operates as a first arithmetic processing section, and the other CPU module 7-i operates as a second arithmetic processing section.

The PC2 provides a function as a support device that supports the PLC1. The PC 2 is used, for example, to edit a user application program. Note that in the following description, the user application program may also be referred to as a "user program." The user program may be created using, for example, a ladder language compliant with IEC (International Electrotechnical Commission) 61131-3. The user program may be created using a graphical programming language such as a motion program in a flowchart format such as a Sequential Function Chart (SFC). The user program may be created using a high-level programming language such as the C language.

Furthermore, as will be described later, the PC 2 also provides a function for setting conditions for executing logging processing.

The CPU module 7-i, input/output module 3-i, and communication module 4-i are connected via a communication bus 6-i. A plurality of input/output modules 3-i and a plurality of communication modules 4-i may be connected to the communication bus 6-i. The input/output module 3-i and the communication module 4-i are removable.

The input/output module 3-i converts a signal from a servo amplifier, an encoder, or a sensor into an electrical signal, and may also input/output a digital signal or an analog signal.

The communication module 4-i provides a communication interface with other devices.

FIG. 2 shows an example of the execution period of each process executed by the CPU module 7-1 in the PLC system of FIG.

The CPU module 7-1 repeatedly executes a cycle of control processing including input processing, program execution processing, output processing, logging processing, and system processing. The input process is a process of taking in input data received from the input/output module 3-1, which is an external device. The program execution process is a process of executing a user program created by a user. In the execution of this user program, input data captured through input processing is used. The output process is a process of controlling the input/output module 3-1 by outputting the execution result of the user program and reflecting the execution result in the output of the input/output module 3-1.

The logging process is a process of collecting values of variables used in a user program and generating collected data. The logging process is also a process of recording data indicating the operating state of each component of the PLC system including the PLC 1 and saving it as a history. System processing is processing for managing the operation of the CPU module 7-1 itself and maintaining proper operation.

The CPU module 7-1 executes the logging process at a predetermined collection timing after the output process in each control cycle so as not to interfere with the execution of the user program. The control cycle is the total execution period of input processing, program execution processing, output processing, logging processing, and system processing. The CPU modules 7-2 to 7-M also repeatedly execute a cycle of control processing including input processing, program execution processing, output processing, and system processing.

Next, PLC1 and PC2 in the PLC system will be explained in more detail.

First, the hardware configuration of the CPU module 7-i will be described with reference to the example hardware configuration shown in FIG. The CPU module 7-i in FIG. 3 includes a communication I/F 11, a CPU 12, a bus controller 13, a memory 14, a storage device I/F 15, and a bus I/F 16. These components are all hardware, connected to the internal bus 17, and can exchange data with each other. "I/F" is an abbreviation for interface. A CPU is sometimes called a processor.

The communication I/F 11 is connected to the communication cable 5 and manages the exchange of various data with the PC 2.

The CPU 12 executes various programs such as a user program, a system program for managing the operation of the CPU module 7-i itself, and a logging execution program.

The bus controller 13 is connected to the communication bus 6-i, and manages the exchange of various data with the input/output module 3-i and the communication module 4-i, which are external devices.

The memory 14 is, for example, a semiconductor memory, and includes a RAM (Random Access Memory) area and a ROM (Read Only Memory) area. The RAM area is used as a storage area for temporarily storing various data when the CPU 12 executes various programs. The ROM area is an area where various programs and data are stored, and for example, nonvolatile memory is used.

The RAM area can also be used as a shared memory for the CPU modules 7-1 to 7-M. When the RAM area is used as a shared memory, the shared memory 8 in FIG. 1 may be omitted. The memory 14 used as a shared memory operates as a storage unit that stores the values of variables used by the CPU module 7-i.

The storage device I/F 15 manages writing and reading processing of various data to and from an external storage device 18 such as a memory card.

The bus I/F 16 is connected to the bus 9 and manages the exchange of various data with the shared memory 8. The CPU 12 accesses the shared memory 8 via the bus I/F 16. When the memory 14 of the other CPU module 7-i is used as a shared memory, the CPU 12 can also access the memory 14 of the other CPU module 7-i via the bus I/F 16. The bus I/F 16 operates as an interface for accessing a storage section that stores variable values.

Next, the hardware configuration of the PC 2 will be described with reference to the example hardware configuration shown in FIG. 4. The PC 2 in FIG. 4 includes a CPU 21, a memory 22, an input device 23, a display device 24, an auxiliary storage device 25, and a communication I/F 26. All of these components are hardware and are connected to the internal bus 27, so that they can exchange data with each other.

The CPU 21 provides a user program editing function and a function for setting conditions for executing logging processing, for example, by executing a predetermined program using the memory 22.

The input device 23 is, for example, a keyboard, a pointing device, or the like, and is used to input instructions or information from the user.

The display device 24 is used, for example, to make inquiries or instructions to the user, and to display and output processing results.

The auxiliary storage device 25 is a magnetic disk device, an optical disk device, a magneto-optical disk device, etc., and may be, for example, a hard disk drive or a flash memory. The PC 2 can store programs and data in the auxiliary storage device 25 and load them into the memory 22 for use.

The communication I/F 26 is connected to the communication cable 5 and manages the exchange of various data with the PLC 1.

<Logging settings>

Next, a method of setting conditions for executing logging processing in the PLC 1 in the PLC system of FIG. 1 will be described.

First, FIG. 5 will be explained. FIG. 5 is a diagram showing an example of the functional configuration of the support device 30. As shown in FIG. This configuration example is an example in which the support device 30 provides a function of setting conditions for execution of logging processing by the PLC 1. In the PLC system, the PC 2 provides the functions of the support device 30 by causing the PC 2 to execute a predetermined setting tool program.

In FIG. 5, the support device 30 includes a program analysis section 31, a display section 32, a specification section 33, and an output section 34.

The program analysis unit 31 analyzes a user program to be executed by the PLC 1 and extracts a plurality of variables used in the user program. The display section 32 displays variables used by each CPU module 7-i among the variables extracted by the program analysis section 31.

The specifying unit 33 specifies a variable selected from among the variables used by each CPU module 7-i as a variable to be collected. The output unit 34 outputs information indicating variables to be collected as setting information.

According to the support device 30, the user can easily generate setting information by selecting variables to be collected in the logging process from among the variables used by each CPU module 7-i. can. Therefore, it becomes possible to perform logging in a PLC including a plurality of CPU modules 7-i.

A method for setting conditions for executing logging processing, which is an example of a support method performed by the support device 30 having the configuration shown in FIG. 5, will be described in more detail with reference to FIG. 6.

The support device 30 is equipped with a setting tool 40. In the PC 2, the function of the setting tool 40 is provided by causing the CPU 21 to execute a predetermined setting tool program.

Project data 41 is input to the setting tool 40 . The project data 41 includes information on the system configuration of the PLC system, a user program to be executed on the PLC 1, and function setting information for external devices included in the PLC system, such as the input/output module 3-i and the communication module 4-i. It is information. Here, it is assumed that the project data 41 has already been created by the user by executing a predetermined project data editing program on the PC 2, and is already stored in the auxiliary storage device 25, for example.

The setting tool 40 first performs collection target setting processing on the project data 41 in S110. This process is a process that sets variables to be logged from variables used in the user program, and is a process that provides the functions of the program analysis unit 31 and identification unit 33 in the support device 30 in FIG. be.

The process of S110 includes the program analysis process of S111. The program analysis process is a process of analyzing a user program included in the project data 41 and extracting a plurality of variables used in the user program. In the collection target setting process of S110, a process is further performed in which the user selects a variable to be collected by the logging process performed by the PLC 1 from the variables extracted by executing the program analysis process.

FIG. 7 will now be described. FIG. 7 shows an example of a UI (User Interface) screen 100 used in the collection target setting process of S110.

In the screen example of FIG. 7, the UI screen 100 includes a program selection section 101, an extracted variable display section 102, and a target variable display section 103. When the PC 2 in FIG. 4 provides the functions of the support device 30, the display device 24 operates as the display unit 32 and displays the UI screen 100.

Information indicating the user program included in the project data 41 is displayed in the program selection section 101. Note that in this embodiment, a task is configured as a collection of multiple programs, a CPU process is configured as a collection of multiple tasks, and a user program is configured as a collection of multiple CPU processes and global variables. shall be taken as a thing.

In the screen example of FIG. 7, "application name" is the name of the user program, and "CPU1" and "CPU2" are the names of each CPU process. "CPUi" represents a process executed by the CPU module 7-i. "Task 1" is the name of each task belonging to each CPU process, and "Program" and "Program N" are the names of each program belonging to each task. A "global variable" is a variable that can be accessed by multiple programs and is defined by the user. In this screen example, the relationship between the user program, each CPU process, each task, each program, and global variables is expressed in a tree format.

When the user performs an operation to select one of the program names displayed in the program selection section 101, the program analysis process of S111 is performed on the program corresponding to the selected name. The variables that are specified are extracted.

Note that when an operation is performed to select a task name instead of a program name, variables are extracted from each of the programs belonging to the task corresponding to the selected name. Furthermore, when an operation for selecting the name of a CPU process is performed, variables are extracted from each of the programs belonging to the task included in the CPU process corresponding to the selected name. At this time, the names of the extracted variables are displayed in a list on the extracted variable display section 102.

When the user selects one or more of the variable names displayed in the extracted variable display area 102 and presses the registration button 104, the variable corresponding to the selected name is added to the collection target. Identified as a variable. At this time, the names of the identified variables to be collected are displayed in a list on the target variable display section 103.

Note that when the user selects one or more of the names of the variables to be collected displayed in the target variable display section 103 and presses the release button 105, the name corresponding to the selected name is selected. The variable is excluded from the variables to be collected.

Furthermore, when the user presses the batch registration button 106, all the variables whose names are displayed in the extracted variable display section 102 are selected as variables to be collected, and their names are displayed in the target variable display section 103. A list will be displayed. On the other hand, when the user presses the batch release button 107, all variables whose names are displayed in the target variable display section 103 are excluded from the variables to be collected.

Returning to the explanation of FIG. 6. In S120, collection operation setting processing is performed. This process is a process for creating information for setting the operation of the logging process. With this information, for example, settings can be made to the PLC 1, such as the collection timing of variable values that are data to be collected, the period for data collection, and the storage timing at which the PLC 1 saves the collected data to the external storage device 18. be exposed.

Following the processes of S110 and S120 described above, the setting file creation process of S130 is performed. This setting file creation process is a process that provides the function of the output unit 34 in the support device 30 shown in FIG.

The configuration file creation process is a process that outputs, as logging configuration data 42, the information specifying the variable to be collected selected in the process of S110 and the operation setting information of the logging process set in the process of S120. The logging setting data 42 corresponds to setting information output by the output unit 34. The logging setting data 42 is transferred to the PLC 1, and in the PLC 1, operation settings for logging processing are performed based on the contents of the logging setting data 42.

The logging setting data 42 will be further explained. FIG. 8 shows an example of the data structure of the logging setting data 42.

The logging setting data 42 includes project data information 51, collection operation setting information 52, and collection target setting information 53.

The project data information 51 is information that specifies the user program to be executed by the PLC 1, and includes information such as the name (project name) given to the object code obtained by compiling the user program and the execution date and time of the compilation. include. Note that the project data information 51 is included as part of the project data 41.

The collection operation setting information 52 is information created by the collection operation setting process in S120. The collection operation setting information 52 includes, for example, the data collection timing, the period during which data is collected, the storage timing at which the PLC 1 stores the collected data in the external storage device 18, and the storage destination external storage device 18 in which the collected data is stored. Contains identifying information.

The collection target setting information 53 is information about the collection target variable selected by the collection target setting process in S110. An example of the data structure of the collection target setting information 53 is shown in FIG.

In the example of FIG. 9, the collection target setting information 53 includes information on the total size of collected data at the data collection timing. Furthermore, the collection target setting information 53 includes information on the number of variables to be collected.

Furthermore, the collection target setting information 53 includes information on memory type, data type, memory address, and data size as information about each variable to be collected. The memory type may include identification information of the shared memory 8, and may include identification information of the memory 14 that stores the value of the variable to be collected among the memories 14 included in each of the CPU modules 7-1 to 7-M. May contain information. These pieces of information make it possible to specify the location of the storage area used to hold the values of the variables to be collected when the user program is executed in the PLC 1.

Setting of the conditions for execution of the logging process by the PLC 1 is performed by the support device 30 by using the setting tool 40 described above.

<Execution of logging>

Next, a logging process performed by the PLC 1 in accordance with conditions set by the PC 2 as the support device 30 in the PLC system of FIG. 1 will be described.

First, FIG. 10 will be explained. FIG. 10 is a diagram showing an example of the functional configuration of the CPU module 7-1 that performs logging processing.

In the configuration example shown in FIG. 10, the CPU module 7-1 includes a processing execution section 61, a collection section 62, a ring buffer 63, and a storage section 64.

As described above, the CPU module 7-1 repeatedly executes a cycle of control processing including input processing, program execution processing, output processing, logging processing, and system processing. In the functional configuration example shown in FIG. 10, the processing execution unit 61 executes input processing, program execution processing, output processing, and system processing, and the collection unit 62 executes logging processing. In the hardware configuration example shown in FIG. 3, the CPU 12 operates as a processing execution section 61 and a collection section 62.

The ring buffer 63 is a storage area that stores collected data in which the collection time of the variable value through logging processing is associated with the variable value collected at that collection time, each time the variable value is collected. In the hardware configuration example shown in FIG. 3, a ring buffer 63 is configured by a part of the storage area of the memory 14.

When the collection unit 62 fails to access the value of a predetermined variable used by another CPU module 7-i in the logging process, it sets missing information indicating the missing value of the predetermined variable in the collected data. For example, if there is a difference between the system configuration of the PLC system indicated by the project data 41 and the actual system configuration of the PLC system, access to the value of the predetermined variable may fail. For example, such a difference may occur if another CPU module 7-i is removed from the PLC 1 for maintenance or the like.

The storage unit 64 sequentially reads out the collected data stored in the ring buffer 63 and stores it in the external storage device 18 . In the hardware configuration example shown in FIG. 3, the storage device I/F 15 provides the function of the storage unit 64 under the control of the CPU 12. For example, the collection unit 62 provided by the CPU 12 may control the storage device I/F 15 as part of the logging process.

The other CPU module 7-i has, for example, a configuration in which the collection section 62, ring buffer 63, and storage section 64 are removed from the CPU module 7-1 in FIG.

According to such a PLC 1, when each CPU module 7-i successfully accesses the value of a variable used, the value of the variable is recorded in the collected data. In addition, even if a CPU module 7-i other than the CPU module 7-1 that performs logging processing fails to access the value of a variable, a loss indicating the missing value of the variable due to the failure Information is recorded in the collected data. Therefore, it becomes possible to perform logging in a PLC including a plurality of CPU modules 7-i.

The logging execution method performed by the CPU module 7-1 including the components shown in FIG. 10 will be described in more detail using FIG. 11.

The program execution process of S210 is a process of executing a user program using the input data sent from external devices such as the input/output module 3-1 and the communication module 4-1, which are captured in the input process. This execution result is output by output processing for controlling external equipment. In the hardware configuration example shown in FIG. 3, the CPU 12 that executes this program execution process uses the storage area of the memory 14 to execute the user program. The storage area used at this time will be referred to as the program use area 14a.

The logging process of S220 is a process of collecting the values of the variables to be collected among the variables used in the user program executed by the program execution process of S210. The logging setting data 42 including information about variables to be collected and operation setting information for logging processing is created as described above in the support device 30 (PC2) and provided to the CPU module 7-1 in advance. It is assumed that there is

The CPU 12 of the CPU module 7-1 performs time management processing in S230 and collection timing detection processing in S240 in parallel with the control processing. The time management process is a process of measuring the current time. The collection timing detection process is a process of detecting the arrival of the data collection timing indicated by the collection operation setting information 52 included in the logging setting data 42.

In the logging process of S220, the process of collecting each value of the variable to be collected is performed in response to the detection of the arrival of the collection timing by the collection timing detection process. In addition, in the logging process, a process is performed in which the collection time of the variable value is acquired from the time measurement result by the time management process, and the collected data in which the variable value and the collection time are associated with each other is stored in the ring buffer 63.

Further, the CPU 12 of the CPU module 7-1 executes the storage process of S250. This storage process includes a process of detecting the arrival of the storage timing indicated by the collection operation setting information 52 included in the logging setting data 42. In addition, this storage process is performed by controlling the storage device I/F 15 to read the collection data stored in the ring buffer 63 in response to the detection of the arrival of the storage timing. This includes processing for saving the data in the external storage device 18, which is the storage destination.

Here, the logging process in S220 and the storage process in S250 will be explained in more detail using the flowchart shown in FIG.

In FIG. 12, the processes in S251 and S252 represent the details of the logging process, and the processes in S253 and S254 represent the details of the storage process.

The process shown in FIG. 12 is started when the logging process start timing arrives in each cycle of the control process.

First, in S251, a process is performed to determine whether or not the arrival of the collection timing has been detected by the collection timing detection process in S240 described above. In this determination process, when it is determined that the arrival of the collection timing has been detected (when the determination result is YES), the collection process of S252 is performed. On the other hand, in this determination process, when it is determined that the arrival of the collection timing is not detected (when the determination result is NO), the process shown in FIG. 12 ends.

The collection process of S252 is a process of collecting the values of the variables to be collected, and storing the collected values in the ring buffer 63 as collected data 73, which will be described later. Details of this collection process will be described later.

Following the collection process in S252, in S253, a process is performed to determine whether the storage timing indicated by the collection operation setting information 52 included in the logging setting data 42 has arrived. In this determination process, when it is determined that the storage timing has arrived (when the determination result is YES), the process advances to S254. On the other hand, in this determination process, when it is determined that the storage timing has not arrived (when the determination result is NO), the process shown in FIG. 12 ends without performing the process of S254.

In S254, the collected data 73 saved in the ring buffer 63 by the collection process in S252 in the currently executed logging process is read out, and the logging collected data 73 is stored in the external storage device 18 at the storage destination indicated by the collection operation setting information 52. The process of saving it as .

The logging collection data 70 will be further explained. FIG. 13 shows an example of the data structure of the logging collection data 70.

The logging collection data 70 includes project data information 51, the number of collection data 71, the collection data size 72, and one or more collection data 73.

The project data information 51 is information that specifies the user program executed by the PLC 1, and includes, for example, the name given to the object code obtained by compiling the user program, and information on the execution date and time of the compilation. That is, the project data information 51 included in the logging collection data 70 is similar to the project data information 51 included in the logging setting data 42. In the collection process of S252, the CPU 12 reads the project data information 51 from the logging setting data 42 and incorporates it into the logging collection data 70.

The number of collected data 71 is information representing the number of pieces of collected data 73 included in the logging collected data 70. Further, the collected data size 72 is information representing the total amount of collected data 73 included in the logging collected data 70.

The logging collected data 70 includes, as collected data 73, data about the values of collected variables in the order in which they were collected. An example of the data structure of this collected data 73 is shown in FIG.

In the example of FIG. 14, the collected data 73 includes time stamp 74 information. This timestamp 74 represents the time when the values of the variables were collected.

The collected data 73 also includes variable data 75 representing the values of one or more variables collected at the time of the timestamp 74. An example of the data structure of this variable data 75 is shown in FIG.

In the example of FIG. 15, the variable data 75 includes information on a variable validity flag 76, a variable size 77, and a variable value 78.

The variable validity flag 76 indicates whether the variable value 78 is valid or invalid. When the variable value 78 is valid, the variable valid flag 76 is set to ON, and when the variable value 78 is invalid, the variable valid flag 76 is set to OFF. The variable validity flag 76 set to OFF is an example of missing information indicating a missing value of the variable. By providing the variable validity flag 76, it becomes possible to record missing values of variables in the variable data 75.

Variable size 77 represents the amount of data of variable value 78. Variable value 78 represents the value of the collected variable.

In the process of S254, the logging collection data 70 having such a data structure is created using the logging setting data 42 and the collection data stored in the ring buffer 63, and is stored in the external storage device 18. .

Thereafter, when the process of S254 ends, the process shown in FIG. 12 ends.

Note that when the logging process shown in the flowchart of FIG. 12 is completed, the CPU 12 also performs a process to further save the logging setting data 42 in the external storage device 18. This logging setting data 42 is used when displaying collected data 73, which will be described later.

Next, the collection process of S252 in FIG. 12 will be described in more detail using the flowchart shown in FIG.

First, in S291, a process is performed in which the current time measured by the time management process in S230 described above is obtained as a timestamp, and the obtained timestamp is written into the ring buffer 63 as the timestamp 74 of the collected data 73. .

Next, in S292, a determination process is performed to determine whether access to the value of the variable to be collected is successful. Access to the value of the variable in the CPU module 7-1 that is performing the logging process will be successful unless a failure occurs in the CPU module 7-1. On the other hand, access to the shared memory 8 or other CPU module 7-i performed via the bus I/F 16 may fail due to circumstances such as the absence of an access target. For example, if another CPU module 7-i is removed from the PLC 1 for maintenance or the like, access to the value of a variable stored in the memory 14 of that CPU module 7-i may fail.

When it is determined that the access to the value of the variable is successful (when the determination result is YES), the variable validity flag 76 of that variable is set to ON in S293.

Next, in S294, the current value of the variable whose variable validity flag 76 is set to ON is acquired, and the acquired value is written into the ring buffer 63 as the variable value 78 of the variable data 75.

The values of the variables to be collected are stored in the shared memory 8 or the memory 14 included in each of the CPU modules 7-1 to 7-M. The storage area for the value of the variable is specified based on information on the memory type, data type, memory address, and data size regarding the variable to be collected, which is included in the collection target setting information 53 of the logging setting data 42. Therefore, in the process of S294, the value of the variable to be collected is acquired by reading the data held in the specified storage area.

When it is determined that the access to the value of the variable has failed (when the determination result is NO), the variable validity flag 76 of that variable is set to OFF in S296.

Next, in S295, a process is performed to determine whether values have been collected for all the collection target variables whose information was included in the collection target setting information 53 of the logging setting data 42. In this determination process, when it is determined that values have been collected for all variables to be collected (when the determination result is YES), the current collection process ends. On the other hand, in this determination process, if it is determined that there are variables to be collected whose values have not yet been collected (when the determination result is NO), the process returns to S292 and the values have been collected. For variables to be collected that do not exist, processing is performed to collect their values.

When the above collection process is completed, the storage of the collected data 73 in the ring buffer 63 is completed, and then the process of S253 in FIG. 12 is performed.

<Display of collected data by logging>

Next, a method of displaying the collected data 73 obtained by the logging process performed by the PLC 1 in the PLC system of FIG. 1 will be described.

First, the hardware configuration of the device that displays the collected data 73 will be described. FIG. 17 shows an example of the hardware configuration of the collected data display device 80.

In the configuration example of FIG. 17, the collected data display device 80 includes a CPU 81, a memory 82, an input device 83, an auxiliary storage device 84, a display device 85, and a storage device I/F 86. All of these components are hardware, connected to an internal bus 87, and can exchange data with each other.

The CPU 81 provides a function of controlling various displays such as display of collected data, waveform display of collected data, and indefinite value display when data is missing, by executing a predetermined program using the memory 82, for example. .

The input device 83 is, for example, a keyboard, a pointing device, or the like, and is used to input instructions or information from the user.

The auxiliary storage device 84 is a magnetic disk device, an optical disk device, a magneto-optical disk device, etc., and may be a hard disk drive or a flash memory, for example. The collected data display device 80 can store programs and data in the auxiliary storage device 84 and load them into the memory 82 for use.

The display device 85 is used, for example, to make inquiries or instructions to the user, and to display and output processing results.

The storage device I/F 86 manages reading processing of various data from the external storage device 18 such as a memory card.

The collected data display device 80 has the above hardware configuration. Note that since such a hardware configuration is a standard configuration of a general computer, the collected data display device 80 may be configured using such a computer. Further, the collected data display device 80 may be configured by further using the PC 2 that functions as the support device 30 in the PLC system of FIG.

Next, FIG. 18 will be explained. FIG. 18 is a diagram showing an example of the functional configuration of the collected data display device 80.

In FIG. 18, it is assumed that the above-mentioned logging collection data 70 is stored in the external storage device 18 by the PLC 1. As explained using FIGS. 13 and 14, the logging collection data 70 includes collected data 73 in which the values of the variables to be collected collected by the logging process of S220 executed by the PLC 1 are associated with the collection time. They are arranged in chronological order.

In the configuration example of FIG. 18, the collected data display device 80 includes a display control section 91 and a display section 92. The CPU 81 in FIG. 17 operates as a display control section 91, and the display device 85 operates as a display section 92.

The display control unit 91 checks whether each variable data 75 included in the collected data 73 includes a value of the variable or missing information indicating a missing value of the variable.

The display unit 92 displays variable values for variables whose values are included in the collected data 73, and displays missing values for variables whose missing information is included in the collected data 73, indicating that the value of the variable is missing. Display information. The display unit 92 may display, for example, indefinite value information indicating that the value of the variable is an indefinite value as the missing display information.

According to the collected data display device 80, the values of the variables included in the collected data 73 collected from the CPU modules 7-1 to 7-M are displayed, and the values of the variables are not included. In this case, missing display information indicating that the value of the variable is missing is displayed. Therefore, it becomes possible to perform logging in a PLC including a plurality of CPU modules 7-i.

An example of a method for displaying collected data performed by the collected data display device 80 having the configuration shown in FIG. 18 will be described in more detail with reference to FIG. 19.

The collected data display device 80 performs program display processing in S310, waveform display processing in S320, logging file analysis/conversion processing in S330, and display control processing in S340. Each of these processes is performed by the display control section 91. A program that causes the CPU 81 to perform each of these processes is sometimes referred to as engineering software.

The program display process in S310 displays the user program included in the project data 41 described above, and also displays the values of variables to be collected for the user program using display data created from the logging collection data 70. It is processing. The display data includes collection time and variable values. Here, it is assumed that the project data 41 has already been created by the user by executing a predetermined project data editing program on the PC 2, and is already stored in the auxiliary storage device 84, for example.

The waveform display process of S320 is a process of displaying the relationship between the collection time and the value of the variable to be collected using a waveform using the display data created from the logging collection data 70.

The logging file analysis/conversion process at S330 analyzes the logging setting data 42 and the logging collection data 70, and converts the collected data 73 into display data that is input to each of the program display process at S310 and the waveform display process at S320. This is the process of converting it into Note that here, it is assumed that the logging setting data 42 and the logging collection data 70 are provided by the external storage device 18. In the logging file analysis/conversion process, these data are read from the external storage device 18 and used.

The display control process of S340 includes a process of providing the display data created by the logging file analysis/conversion process of S330 to the program display process of S310 and the waveform display process of S320. The display control process also includes a process of linking the display of the program display process and the waveform display process.

The details of each process shown in FIG. 19 performed by the collected data display device 80 will be further explained below.

First, details of the program display process in S310 will be explained using FIG. 20.

As shown in FIG. 20, the program display process in S310 includes the operation UI process in S311, the variable value display control process in S312, the user program display process in S313, the collation process in S314, and the warning process in S315. processing.

The operation UI process in S<b>311 is a process of accepting input according to an operation on the input device 83 by the user of the collected data display device 80 .

The variable value display control process in S312 receives the input information accepted by the operation UI process in S311 and the interlocking information from the display control process in S340, and controls the display of variable values included in the display data. It is processing.

The user program display process of S313 displays the user program included in the project data 41, and also displays the value of the variable to be collected on the display of the user program under the control of the variable value display control process of S312. It is processing.

The verification process in S314 is a process of verifying the project data 41, the logging setting data 42, and the project data information 51 of the logging collection data 70.

The warning process of S315 is a process of issuing a predetermined warning when the project data information 51 of each data does not match as a result of the collation process of S314.

FIG. 21 shows an example of a warning screen displayed on the display device 85. A predetermined warning in the warning process of S315 is performed by displaying such a warning screen on the display device 85, for example. This example screen includes a warning dialog 130 that warns the user that the project data information 51 does not match. Note that, since this is useful when debugging a user program, for example, the collected data display device 80 allows the function of displaying variable values to be used even if the project data information 51 does not match.

Next, details of the waveform display processing in S320 will be explained using FIG. 22.

As shown in FIG. 22, the waveform display process in S320 includes the operation UI process in S321, the variable value display control process in S322, and the waveform creation process in S323.

The operation UI process of S321 is similar to the process of S311, and is a process of accepting input according to the operation on the input device 83 by the user of the collected data display device 80.

The variable value display control process in S322 is similar to the process in S312, and receives input information accepted by the operation UI process in S321 and the above-mentioned linked information from the display control process in S340, and displays This process controls the display of variable values included in the data.

The waveform creation process of S323 is a process of creating and displaying a waveform representing the relationship between collection timing and variables based on the display data provided by the display control process of S340.

Next, details of the logging file analysis/conversion process in S330 will be explained using FIG. 23.

As shown in FIG. 23, the logging file analysis/conversion processing in S330 includes the logging setting data acquisition processing in S331, the logging collection data acquisition processing in S332, the variable data missing determination processing in S333, and the display processing in S334. Contains data creation processing.

The logging setting data acquisition process of S331 is a process of importing the logging setting data 42 from the external storage device 18.

The logging collection data acquisition process of S332 is a process of reading and importing the logging collection data 70 from the external storage device 18.

The variable data missing determination process in S333 is a process for determining whether or not variable values are missing in the logging collection data 70 read from the external storage device 18. More specifically, this variable data missing determination process refers to the variable data 75 included in the logging collected data 70 acquired by the logging collected data acquisition process of S332 to determine if missing variable values have occurred. This is a process to determine whether or not there is.

The display data creation process in S334 is a process for creating display data including collection times and variable values from the logging setting data 42 and the logging collection data 70. If it is determined by the variable data missing determination process in S333 that a missing variable has occurred, indefinite value information indicating that the value of the variable is an indefinite value is created in place of the missing variable value.

Next, FIG. 24 will be explained. FIG. 24 is a flowchart showing the processing contents of the logging file analysis/conversion processing in S330.

In FIG. 24, first, in S401, a process of reading and importing the logging setting data 42 and the logging collection data 70 from the external storage device 18 is performed. This process corresponds to the logging setting data acquisition process in S331 and the logging collection data acquisition process in S332 in FIG.

In S402, variable value generation processing is performed to create display data including collection time and variable values from the collected data 73 included in the logging collected data 70. The process in S402 corresponds to the display data creation process in S334 in FIG. 23.

In S403, a process is performed to increment (increase by 1) a counter that counts the number of times the collected data 73 is retrieved by the process in S402.

In S404, a process is performed to determine whether the current value of the counter has reached the value indicated by the number of collected data 71 included in the logging collected data 70. In this determination process, when it is determined that the value of the counter has reached the value indicated by the number of collected data 71 (when the determination result is YES), this logging file analysis/conversion process is ended. On the other hand, in this determination process, when it is determined that the value of the counter has not yet reached the value indicated by the number of collected data 71 (when the determination result is NO), the process returns to S402. At this time, the remaining collected data 73 that has not yet been extracted from the logging collected data 70 is processed from S402 onwards.

The above process is the logging file analysis/conversion process of S330.

Next, the variable value generation process in S402 in FIG. 24 will be described in more detail using the flowchart shown in FIG.

First, in S411, a process is performed to determine whether the variable validity flag 76 of the variable data 75 included in the collected data 73 is ON. In this determination process, when it is determined that the variable validity flag 76 is ON (when the determination result is YES), the variable value 78 is used as it is as the variable value of the display data. On the other hand, in this determination process, when it is determined that the variable validity flag 76 is OFF (when the determination result is NO), in S412, the indefinite value information of the amount of data indicated by the variable size 77 is added to the variable of the display data. Processing to create it as a value is performed. Note that the collection time associated with the collection data 73 including the variable data 75 is used as the collection time of the display data.

In S413, processing is performed to increment (increase by 1) a counter that counts the number of variable data 75 determined in S411.

In S414, a process is performed to determine whether the current value of the counter has reached the number of variable data 75 included in the collected data 73. In this determination process, when it is determined that the value of the counter has reached the number of variable data 75 (when the determination result is YES), this logging file analysis/conversion process is ended. On the other hand, in this determination process, when it is determined that the counter value has not yet reached the number of variable data 75 (when the determination result is NO), the process returns to S411. At this time, the processing from S411 onward is performed on the remaining variable data 75 that has not yet been determined.

Next, details of the display control process in S340 will be explained using FIG. 26.

As shown in FIG. 26, the display control process in S340 includes the variable value providing process in S341, the reproduction control process in S342, and the collected data acquisition process in S343.

The variable value providing process in S341 uses the display data created by the logging file analysis/conversion process in S330 as the value of the variable associated with the collection timing, and performs the program display process in S310 and the waveform display process in S320. This is a process provided to Note that the provided display data may include indefinite value information created by logging file analysis/conversion processing.

The playback control process in S342 is a process in which, upon receiving a predetermined linkage instruction, the program display process in S310 and the waveform display process in S320 are controlled to link the contents of the screen displayed by each process.

The collected data acquisition process at S343 is a process for acquiring display data created by the logging file analysis/conversion process at S330 and providing it to the variable value providing process at S341.

As described above, the display control process in S340 provides the display data created by the logging file analysis/conversion process in S330 to the program display process in S310 and the waveform display process in S320. Next, the screens displayed on the display device 85 by the program display process and the waveform display process will be described.

First, FIG. 27 will be explained. FIG. 27 is an example of a display screen for collected data. This display screen is displayed on the display device 85 when the CPU 81 executes the program display process in S310.

The example screen in FIG. 27 shows a state where the UI screen 120 obtained by the operation UI process in S311 is displayed over the user program display screen 110 obtained by the user program display process in S313.

Through the user program display process in S313, a diagram (for example, a ladder program) representing the contents of the user program included in the project data 41 is created and displayed as the user program display screen 110.

The UI screen 120 includes a frame advance button 121 and a seek bar 122 that give instructions to sequentially update the display of the values of the variables being collected at each collection timing, and a time input button that allows you to directly input the collection timing of the variable values to be displayed. It has columns 123 and the like. Note that the time input field 123 also has a function as a display field that displays the time of the collection timing specified by operating the frame advance button 121 or the seek bar 122.

Through the operation UI process in S<b>311 , the collection timing specified in response to the operation of the frame advance button 121 or the seek bar 122 is acquired, and the time of this timing is displayed in the time input field 123 . Further, when a time input operation is performed in the time input field 123, the input time is acquired as the specified collection timing by this operation UI process.

Through the variable value display control process in S312, the value of the variable associated with the collection timing in the logging collection data 70 and the designation of the collection timing acquired through the operation UI process in S311 are acquired. Also, through this variable value display control process, the value of the variable at the specified collection timing is sent to the user program display process in S313, and the user program display process causes the value of the variable to be displayed on the user program display screen 110. It will be done.

In the screen example of FIG. 27, ON/OFF display 111, ON/OFF indefinite display 112, variable display 113, variable display 114, and variable indefinite value display 115 display values of variables to be collected.

The ON/OFF display 111 displays elements in different colors depending on the state indicated by the variable value when the state of a program component that has either an ON or OFF state is selected as a variable to be collected. Variable values are represented by a filled-in display. In the screen example of FIG. 27, elements in the user program are displayed in black as the ON/OFF display 111, but in reality, for example, in the case of "ON", they are displayed in red, and in the case of "OFF", elements in the user program are displayed in black. ”, the element is displayed in blue.

An unfilled ON/OFF indefinite display 112 indicates that the state of a program component that has either an ON or OFF state has been selected as a variable to be collected, and the variable value is missing. This is the display when there is. The ON/OFF indefinite display 112 is an example of indefinite value information.

The variable display 113 and the variable display 114 directly display the numerical value as a variable value when a numerical value regarding a program component is selected as a variable to be collected.

The variable indefinite value display 115 includes a display of "???" as a display of a numerical value regarding a program component. This variable indefinite value display 115 is a display when a numerical value related to a program component is selected as a variable to be collected, and the value of the variable is missing. The variable indefinite value display 115 is an example of indefinite value information.

When the variable valid flag 76 of the variable data 75 is OFF, an ON/OFF undefined display 112 and a variable undefined value display 115 are displayed on the user program display screen 110. This display is performed by the user program display process in S313.

As described above, through the processes of S311, S312, and S313, the collection time and the value of the collected variable are correlated and displayed on the display device 85, as shown in the screen example of FIG. .

Next, FIG. 28 will be explained. FIG. 28 is an example of a waveform display screen 140 of collected data. This waveform display screen 140 is displayed on the display device 85 when the CPU 81 executes the waveform display process in S320.

The waveform 141 included in the waveform display screen 140 is created by the waveform creation process in S323. In the screen example of FIG. 28, the waveforms 141 for each of "variable 1," "variable 2," and "variable 3" are displayed using a solid line, a broken line, and a dashed-dotted line, respectively. Further, a time display 142 included in the waveform display screen 140 represents the collection timing whose relationship with the variable value is expressed by the waveform 141, and is displayed on the waveform display screen 140 by the waveform creation process of S323. .

Furthermore, when an instruction to move the collection timing range is accepted through the operation UI process in S321, a waveform 141 for the post-move collection timing range is displayed on the waveform display screen 140 through the waveform creation process in S323. Further, the collection timing time indicated by the thick line 143 displayed on the waveform display screen 140 is displayed in the time display column 144 by the waveform creation process of S323.

The variable value display control process of S322 acquires the value of the variable with which the collection timing is associated in the variable value display data provided by the display control process of S340. Furthermore, the time of the collection timing displayed in the time display column 144 is acquired through the variable value display control process of S322. Further, by this variable value display control process, the value of the variable at the acquired collection timing is displayed in the variable value display column 145 as the value of the variable represented by the intersection of the waveform 141 and the thick line 143.

The variable indefinite value display 146 in the variable value display field 145 is a display when the value of the variable is missing, similar to the variable indefinite value display 115 in FIG. The waveform indefinite display 147 that partially covers the waveform 141 of the variable 3 is a display when the value of the variable is missing, similar to the variable indefinite value display 146.

When the variable valid flag 76 is OFF, such a waveform indefinite display 147 is displayed in place of the waveform 141 at a position corresponding to the collection timing on the waveform display screen 140. This display is created by the waveform creation process in S323.

As described above, through the processes of S321, S322, and S323, the collection time and the value of the collected variable are correlated and displayed on the display device 85, as shown in the screen example of FIG. .

Through the playback control process in S342, for example, the collection timing specified by the operation on the UI screen 120 in the screen example of FIG. 27 and the collection timing indicated by the bold line 143 in the screen example of FIG. 28 are set to be the same time. It will be done.

Although the disclosed embodiments and their advantages have been described in detail above, those skilled in the art can make various changes, additions, and omissions without departing from the scope of the present invention as clearly stated in the claims. Will.

1 PLC
2 PCs
3-1 to 3-M Input/output module 4-1 to 4-M Communication module 5 Communication cable 6-1 to 6-M Communication bus 7-1 to 7-M CPU module 8 Shared memory 9 Bus 11, 26 Communication I /F
12, 21, 81 CPU
13 Bus controller 14, 22, 82 Memory 14a Program use area 15, 86 Storage device I/F
16 Bus I/F
17, 27, 87 Internal bus 18 External storage device 23, 83 Input device 24, 85 Display device 25, 84 Auxiliary storage device 30 Support device 31 Program analysis section 32 Display section 33 Specification section 34 Output section 40 Setting tool 41 Project data 42 Logging setting data 51 Project data information 52 Collection operation setting information 53 Collection target setting information 61 Process execution section 62 Collection section 63 Ring buffer 64 Storage section 70 Logging collection data 71 Number of collection data 72 Collection data size 73 Collection data 74 Timestamp 75 Variable Data 76 Variable valid flag 77 Variable size 78 Variable value 80 Collected data display device 91 Display control section 92 Display section 100, 120 UI screen 101 Program selection section 102 Extracted variable display section 103 Target variable display section 104 Registration button 105 Cancel button 106 Bulk Registration button 107 Batch release button 110 User program display screen 111 ON/OFF display 112 ON/OFF undefined display 113, 114 Variable display 115, 146 Variable undefined value display 120 UI screen 121 Frame advance button 122 Seek bar 123 Time input field 130 Warning dialog 140 Waveform display screen 141 Waveform 142 Time display 143 Thick line 144 Time display field 145 Variable value display field 147 Waveform indefinite display

Claims (3)

A display device that displays collected data generated by a programmable logic controller that controls external equipment,
The programmable logic controller includes a plurality of arithmetic processing units that distribute and execute control processing for controlling the external equipment, and executes a user application program for the control processing,
One of the arithmetic processing units among the plurality of arithmetic processing units collects the values of each of the plurality of variables used in the user application program at a predetermined collection timing, and generates the collected data. and
The display device includes:
a display control unit that checks, for each of the plurality of variables, whether the value of the variable or missing information indicating a missing value of the variable is included in the collected data;
Missing display information that displays the value of the variable for a variable whose value is included in the collected data, and indicates that the value of the variable is missing for a variable for which the missing information is included in the collected data. a display section that displays;
A display device comprising: The collected data includes a flag indicating whether each of the plurality of variables is valid or invalid,
The display control unit determines that the value of the variable for which the flag indicates valid is included in the collected data, and for the variable for which the flag indicates invalid, the missing information is determined to be included in the collected data. The display device according to claim 1, wherein the display device determines that the information is included in the collected data. For each of the plurality of variables used in the user application program for the control processing, which is executed by a programmable logic controller that includes a plurality of arithmetic processing units that distribute and execute control processing for controlling external equipment, Check whether the collected data contains missing information indicating the value of the variable or the missing value of the variable,
Displaying the value of the variable for a variable whose value is included in the collected data;
Displaying missing display information indicating a missing value of the variable for a variable for which the missing information is included in the collected data;
The display device executes the processing,
The collected data is generated by one of the plurality of arithmetic processing units performing a logging process of collecting values of each of the plurality of variables at a predetermined collection timing. display method.

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