JP2014052189A - Programmable logic controller, time correction system for the same, and external apparatus for the programmable logic controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a programmable logic controller capable of correcting current time by a simpler and surer method as compared with a conventional method.SOLUTION: When an output voltage of an RTC power supply 40 for supplying electric power to an RTC 37 installed in a body 2 of a PLC is lowered, current time of the RTC 37 is corrected by time data supplied from an RTC of an operation module 3 connected to the body 2. Since the RTC of the operation module 3 can clock the current time without receiving a radio wave indicating time, the current time of the PLC can be corrected even in a site such as a plant where a radio wave does not reach. Further, the current time of the RTC 37 can be corrected by time data supplied from the RTC of the operation module 3 without connecting a terminal device to a GPS receiver via a network. Accordingly, time information of a PLC 1 can be corrected by the simpler and surer method as compared with the conventional method.

Description

  The present invention relates to a technique for correcting the time of a pluggable logic controller.

Programmable logic controller (hereinafter referred to as PLC) is FA (Factory
Automation) is a sequence controller widely used in control systems, and operates according to a dedicated program called a ladder program. The operator (operator) connects input devices such as limit switches, sensors, and thermometers, and output devices such as electromagnetic switches, solenoids, motors, actuators, cylinders, relays, and positioning systems to the PLC. Control the controlled device.

  An operator creates a ladder program on a program creation support device such as a personal computer (hereinafter referred to as a PC), connects the PC and the PLC, and stores the ladder program in the storage unit of the PLC. Various data such as device information is also stored in the storage unit of the PLC. The device information is information indicating an input state from the input device, an output state to the output device, and states of an internal relay (auxiliary relay), a timer, a counter, a data memory, and the like set on the ladder program. A device is a name indicating an area on a memory provided for storing device information. By connecting the program creation support apparatus to the PLC, the device information (device value) held by the PLC can be displayed on the program creation support apparatus for visual recognition.

  By the way, the PLC includes a real-time clock (RTC), acquires time information from the RTC, and performs various controls. The RTC is not supplied with power directly from the main body of the PLC, but is operated with power supplied from a power source such as a battery or a capacitor. Therefore, if the remaining battery level is reduced due to the operation of the RTC while the power of the PLC is turned off, the output voltage of the battery becomes less than the operation limit voltage of the RTC, and the RTC cannot provide correct time information. When the time information is important information for controlling the controlled device, the PLC control may be erroneous. For example, there is a case where it is desired to grasp the time when an abnormality has occurred, or a case where processing is to be executed at a predetermined time of the day. Therefore, it is important to accurately maintain PLC time information. According to Patent Document 1, it is proposed to connect a plurality of terminal devices to a GPS receiver via a network and synchronize the times of the plurality of terminal devices with time data received by the GPS receiver. Patent Document 2 proposes a time synchronization device that receives a standard time signal carried by radio waves such as GPS satellites, AM, FM, and short waves and synchronizes the time of the PLC.

JP 2001-324484 A JP 2007-101306 A

  In the invention of Patent Document 1, it is necessary to connect a terminal device to a GPS receiver via a network so that radio waves from a GPS satellite can be received, and to a PLC that is assumed to be used indoors. It is not easy to apply. Further, the invention of Patent Document 2 is also based on the premise that radio waves can be received, and is not easy to apply to a PLC that is supposed to be used indoors. Also, when the operator recognizes that an error has occurred, it may be troublesome for the operator to prepare the time synchronization device and connect it to the PLC. In addition, it may be difficult to connect a dedicated device such as a time synchronization device to a PLC installed at a site such as a factory. This is because the PLC is installed in a place that is normally out of reach in order to prevent erroneous operation. On the other hand, if it is a program creation support device that creates a ladder program and transfers it to the PLC, the time information of the PLC will be corrected. However, it is still not easy to connect the program creation support apparatus to the PLC in the field. This is because the program creation support apparatus is a personal computer such as a desktop PC.

  Therefore, an object of the present invention is to make it possible to correct PLC time information by a simpler and more reliable method than in the past.

  The present invention is a programmable logic controller time correction system comprising a main body of a programmable logic controller and an external device connected to the main body, wherein the programmable logic controller measures a current time. Regardless of whether or not power is supplied to the main body, a time measuring unit, a power source that supplies power to the first time measuring unit, a voltage monitoring unit that monitors an output voltage of the power source, and an output of the power source A flag control unit that controls a flag to store in a storage unit to indicate that the reliability of the current time measured by the first clock unit may be reduced when the voltage drops below a threshold; A time correction unit that corrects the current time of the first time measuring unit, and the external device stores a second time measuring unit that measures the current time, and a memory of the main body A determination unit that reads out the flag held in the first determination unit and determines whether or not the flag indicates that the reliability of the current time measured by the first time measurement unit may be reduced; When the determination unit determines that the flag read from the storage unit of the main body indicates that there is a possibility that the reliability of the current time measured by the first time measurement unit is reduced, the second A correction command generating unit that acquires time data indicating the current time measured by the time measuring unit, generates a correction command for correcting the current time of the first time measuring unit, and transmits the correction command to the main body together with the time data The time correction unit corrects the current time of the first time measuring unit with the time data received together with the correction command when the main body receives the correction command. The Providing logic controller time correction system.

  In addition, the present invention is a programmable logic controller in which an external device can be connected to the main body, and the first timekeeping section that measures the current time and whether or not power is supplied to the main body. A power source that supplies power to one timepiece, a voltage monitoring unit that monitors the output voltage of the power supply, and the reliability of the current time that the first timepiece counts when the output voltage of the power supply falls below a threshold value A flag control unit that controls the flag so as to indicate that there is a possibility that the performance is reduced and stores the flag in the storage unit, and the time data received from the external device due to the control of the flag control unit Provided is a programmable logic controller comprising a time correction unit that corrects the current time of a first time measuring unit.

  Furthermore, the present invention is an external device for a programmable logic controller provided with a first timekeeping unit that measures the current time, a second timekeeping unit that measures the current time, and a storage unit of the main body of the programmable logic controller A determination unit that reads the flag held in the first time unit and determines whether the flag indicates that the reliability of the current time measured by the first time measuring unit may be reduced; When the determination unit determines that the flag read from the storage unit indicates that the reliability of the current time measured by the first time measurement unit may be reduced, the second time measurement An external device is provided, comprising: a correction command generation unit that acquires time data indicating a current time measured by the unit, generates a correction command, and transmits the correction command to the main body.

  According to the present invention, when the output voltage of the power source that supplies power to the first time measuring unit provided in the main body of the PLC is lowered while the power source of the PLC is turned off, the power source of the PLC is connected to the main body after the power source is turned on. The current time of the first timekeeping unit is corrected with the time data supplied from the second timekeeping unit of the external device. The second time measuring unit of the external device can measure the current time, and the current time in the second time measuring unit is sent to the PLC, so that the current time of the PLC can be corrected even at a site such as a factory where radio waves do not reach. In addition, the current time of the first timekeeping unit can be corrected with the time data supplied from the second timekeeping unit of the external device without connecting the terminal device to the GPS receiver via the network. Therefore, the time information of the PLC can be corrected by a simpler and more reliable method than before.

It is a perspective view which shows the external appearance of a programmable logic controller (PLC). It is the figure which showed the front side of the programmable display. It is a block diagram of the main body of PLC. It is a block diagram of a programmable display. It is a flowchart which shows the voltage monitoring process which monitors the output voltage of the power supply which supplies electric power to RTC. It is a flowchart which shows the flag monitoring and the preparation process of a time correction command which a programmable display performs. It is a flowchart which shows the process which determines whether a flag is read. It is a flowchart which shows the time correction process which PLC performs. It is the figure which showed an example of the user interface which switches validity and invalidity of a time correction function.

  An embodiment of the present invention is shown below. The individual embodiments described below will help to understand various concepts, such as the superordinate concept, intermediate concept and subordinate concept of the present invention. Further, the technical scope of the present invention is determined by the scope of the claims, and is not limited by the following individual embodiments.

  FIG. 1A is a perspective view showing an appearance of a programmable logic controller (PLC). The PLC is sometimes referred to simply as a programmable controller. In FIG. 1, the PLC 1 is separated into a main body 2 and an operation module 3. The main body 2 has an input terminal group 4 for connection with input devices such as limit switches and sensors, and an output for connection with output devices such as electromagnetic switches, solenoids, motors, actuators, cylinders, relays, and positioning systems. And a terminal group 5. In addition, a housing 6 for housing the operation module 3 in the form of a module cassette is provided outside the main body 2. That is, the operation module 3 can be attached to or detached from the accommodating portion 6 of the main body 2. The housing 6 is provided with a boss 8 for positioning the operation module 3 and a connector 7 for communicating with a control unit and a storage unit inside the operation module 3. A hole (not shown) into which the boss 8 is fitted is provided on the back surface of the operation module 3. Further, a terminal that contacts the contact of the connector 7 is provided on the back surface of the operation module 3.

  In the present embodiment, a PLC of a type in which the main body 2 and the operation module 3 are separated is assumed. However, the present invention has various types such as a type in which these are not separated and a type in which the operation module 3 does not exist. It is applicable to other PLCs.

  A display unit 10 such as a liquid crystal display device or a self-luminous display device is provided on the front surface of the operation module 3. The display unit 10 displays information about the main body 2 when the operation module 3 is attached to the housing unit 6. On the front surface of the operation module 3, an operation unit 11 for an operator to input various instructions is provided. The operation unit 11 is provided with a plurality of buttons (keys) for receiving operator operations.

  FIG. 1B shows a state in which the operation module 3 is attached to the housing portion 6 of the main body 2 of the PLC 1. As shown in FIG. 1B, a display unit 10 is provided on the front surface of the operation module 3, and the display unit 10 is attached to the main body 2 so as to come to the front surface of the main body 2. Thus, since the operation module 3 is connected to the main body 2 via the connector, a communication cable is unnecessary. That is, the operator does not need to prepare and connect a communication cable. If the communication cable is disconnected, the operation module cannot be used until a new communication cable is prepared. However, the operation module 3 can solve such a problem. In particular, when setting the time for a plurality of PLCs 1 of the same type, the operation module 3 of the present invention will be advantageous in terms of workability.

  FIG. 2 is a diagram showing a programmable display 3 ′ connected to the PLC 1 by wire. The operation module 3 shown in FIG. 1 is a built-in type that is accommodated in the accommodating portion 6, but the programmable display 3 ′ is connected to the PLC 1 via a cable 12 such as a serial communication cable, a LAN cable, or a USB cable. Has been. Note that the programmable display 3 'and the PLC 1 may be connected by wire, or may be connected wirelessly by a wireless LAN, Bluetooth, IrDA, or the like. Similar to the operation module 3, the programmable display 3 ′ includes a display unit 10 and an operation unit 11. The operation unit 11 of the programmable display 3 ′ is a capacitive or pressure sensitive touch panel input device. As shown in FIG. 2, the display unit 10 can display device information (eg, product number, temperature, speed, etc.) read from the PLC 1. The display unit 10 reads device information periodically or irregularly and displays the device information. The device information to be read and the device information read timing are basically defined by the program in the programmable display 3 '. However, for example, it may be defined by a ladder program executed by the PLC 1. The display unit 10 is, for example, a liquid crystal display device or a self-luminous display device. The operation unit 11 may be provided with a plurality of buttons (keys) for an operator (operator) to input various instructions.

  The programmable display 3 'will be described in further detail. The programmable display 3 ′ is an input / output device connected to the PLC 1 or a device for monitoring the operation state (state data) of the PLC 1. On the screen of the programmable display 3 ′, various component images such as lamps, meters, and graphs are displayed as screen components. The layout of various component images displayed on the screen of the programmable display 3 'can be freely edited by a user using screen display data creation software such as a drawing editor. In the programmable display 3 ′ to which the created screen display data has been transferred, the status data of the input / output device connected to the PLC 1, for example, is read from the PLC 1, and a component image (not shown) according to the status data. Changes (for example, the lamp turns on or off, or the meter's needle swings from side to side). Thereby, the user can monitor the operation state of the input / output device connected to the PLC 1.

  As described above, the programmable display 3 ′ has a unique program for monitoring the PLC 1, reads device information from the PLC 1 periodically or irregularly based on its own judgment, and displays it on the display unit 10. It has a function to do.

  The device is a name indicating an area on a memory provided for storing device information as described above. In other words, the device is used to monitor input / output devices connected to the PLC 1. It can also be referred to as an element used in a control program for control, and is used to give data used in an instruction and store an execution result of the instruction. For example, a relay, a timer, a counter, a data memory, etc. are mentioned.

  The device includes a bit device (input bit device) that is turned on / off based on an input signal from the input device, a bit device that is turned on / off to control the operation of the output device (output bit device), and on. There are word devices that store numerical data instead of / off.

  The normal operation of the programmable display 3 ′ will be described. (1) The programmable display 3 ′ issues a device read command for reading the device value to the PLC 1 for the device to be monitored on the screen. Next, (2) the PLC 1 acquires the value of the device designated by the received command, creates a response to the programmable display 3 ', and transmits it. Thereafter, (3) the programmable display 3 ′ reads the device value from the received response and updates the display on the screen. In this way, the programmable display 3 'can monitor the operating state of the PLC 1.

  Thus, it is sufficient that the external device for the programmable logic controller can be connected to the PLC 1. Therefore, it may be a built-in type operation module 3 or an external type programmable display 3 '. Therefore, hereinafter, the programmable display 3 'will be described. Further, the external device does not necessarily require the operation unit 11 and the display unit 10, and may be another external device (eg, a communication interface module, an external storage device module, an expansion unit, etc.) not related to the operation. That is, as will be described later, the external device has a communication unit 61 that communicates with the main body 2 of the PLC 1, a control unit 60, and a timing unit (RTC 62, power source 63, etc.) capable of timing without receiving radio waves. It is enough to have it.

  FIG. 3 is a block diagram of the main body 2 of the PLC 1. A controller provided in the main body 2 includes a logic circuit such as a CPU and an ASIC, and a storage device such as a memory.

  The real-time clock (RTC) 37 is an example of a first timer unit that measures the current time. The RTC power supply 40 is a power supply that supplies power to the RTC 37. The RTC 37 includes a voltage monitoring unit 38 that monitors the output voltage of the RTC power supply 40, time data indicating the current time, and a storage unit 39 that stores control information indicating whether the RTC 37 is operating normally. For example, when the power of the PLC 1 is turned off, the voltage monitoring unit 38 compares the output voltage of the RTC power supply 40 with a threshold value, and stores control information indicating whether the output voltage is less than the threshold value in the storage unit 39. Since the RTC 37 is a primary battery, a secondary battery, or a capacitor, power is supplied to the RTC 37 regardless of whether or not power is supplied to the main body 2 from an external power source (commercial AC power source or the like).

  The control unit 20 accesses the storage unit 30 via the storage unit driver 36. That is, the storage unit driver 36 functions as a writing unit for writing information to the storage unit 30 and a reading unit for reading information from the storage unit 30 in accordance with a write command or a read command from the control unit 20. The storage unit 30 functions as a holding unit that holds setting information such as the ladder program 31 and device information 34 received from the program creation support device 50 via the communication unit 35. The device information 34 is stored in the device 33 that is a storage area secured in the storage unit 30. The log data 32 is data indicating the result of execution of the ladder program 31 by the control unit 20. The log data 32 may include time data when an event such as an error occurs. Therefore, if the time data is incorrect, the usefulness of the log data 32 decreases, which is not preferable.

  The control unit 20 functions as a controlled device control unit that controls the controlled device connected to the main body 2 according to setting information held in the storage unit 30. The control unit 20 includes various control units that realize functions specific to the present embodiment in addition to the function of controlling the controlled device. The time data determination unit 21 determines whether or not the current time measured by the real time clock (RTC) 37 is correct. Since the RTC power source 40 is a primary battery, a secondary battery or a capacitor, for example, when the power of the PLC 1 is turned off, the remaining amount of the battery is reduced, that is, when power is not supplied from the outside for a long time, the RTC 37 Sufficient voltage cannot be supplied. Therefore, the voltage monitoring unit 38 compares the output voltage of the RTC power supply 40 with a threshold value so that an abnormality in the battery voltage can be detected. If the output voltage is less than the threshold value, it is determined that the reliability of the time data counted by the RTC 37 has decreased.

  Note that time correction may be executed depending on whether or not the output voltage has dropped regardless of whether or not the actual current time is incorrect. Therefore, the time data determination unit 21 is an optional control unit and may be omitted. Conversely, time correction may be executed depending on whether the actual current time is incorrect, regardless of whether the output voltage has dropped. In this case, a flag to be described later is a flag that is changed according to whether the current time is incorrect.

  The flag control unit 22 reads the control information from the storage unit 39 of the RTC 37, and determines whether or not the control information indicates that the output voltage of the RTC power supply 40 has dropped below the threshold value. When the control information indicates that the output voltage of the RTC power supply 40 has dropped below the threshold value, the flag control unit 22 turns on the voltage error flag of the register 41 (that is, sets the voltage error flag to 1). To do). Here, it is assumed that the voltage error flag is implemented as a bit that changes depending on whether the output voltage of the RTC power supply 40 is less than or greater than the threshold. As described above, when the voltage error flag is 1, the voltage error flag indicates that the reliability of the current time measured by the RTC 37 may be lowered. There is a possibility that the reliability of the current time measured by the RTC 37 has decreased, that the output voltage of the RTC power supply 40 has decreased below the threshold, and that the current time measured by the RTC 37 needs to be corrected. This is substantially synonymous with the fact that the current time measured by the RTC 37 is incorrect.

On the other hand, when the voltage error flag is off (that is, 0), the voltage error flag indicates that the reliability of the current time measured by the RTC 37 is not lowered. The fact that the reliability of the current time measured by the RTC 37 has not decreased is that the output voltage of the RTC power supply 40 is equal to or higher than the threshold, the current time measured by the RTC 37 need not be corrected, and the current time measured by the RTC 37. Is essentially synonymous with being correct. The voltage error flag may be stored in the device 33 as 1-bit device information 34. That is, it may be stored in the bit device described above. Of course, it may be stored in a word device. Since the device information 34 is information intended to be disclosed outside the PLC 1, an external device such as the programmable display 3 ′ and the operation module 3 and the program creation support device 50 can easily set the voltage error flag to the device information 34. Can be obtained as Hereinafter, the device information 34 will be described as a voltage error flag.

  When the time correction unit 23 receives a correction command to correct the current time of the RTC 37 from the programmable display 3 ′ after the voltage error flag is read by the programmable display 3 ′, the time received from the programmable display 3 ′ The current time of the RTC 37 is corrected with the data.

  The communication unit 42 is a unit for communicating with external devices such as the programmable display 3 ′ and the operation module 3. The interpretation unit 43 interprets data and commands received by the communication unit 42 and passes the interpretation result to the control unit 20.

  FIG. 4 is a block diagram of the programmable display 3 '. The control unit 60 is in charge of display control on the display unit 10, reception control of instructions input from the operation unit 11, and communication control with the main body 2 of the PLC 1 by the communication unit 61.

  Another real-time clock (RTC) 62 mounted on the programmable display 3 ′ is an example of a second clock unit that clocks the current time without receiving a radio wave indicating the time. That is, the RTC 62 is not a receiver that receives a standard time signal carried by radio waves such as GPS satellites, AM / FM / short waves, and acquires the current time. That is, the RTC 62 is a simple timepiece similar to the RTC 37 provided in the PLC 1. The power source 63 is a power source such as a primary battery, a secondary battery, or a capacitor that supplies power to the RTC 62.

  The control unit 60 includes a determination unit 64, a correction command creation unit 65, and a valid / invalid control unit 24. The determination unit 64 reads the voltage error flag held in the storage unit 30 or the register 41 of the main body 2 and determines that the reliability of the current time measured by the RTC 37 of the PLC 1 may be lowered. Determine whether or not. The correction command generation unit 65 is notified from the determination unit 64 that the voltage error flag read from the main body 2 indicates that the reliability of the current time measured by the RTC 37 of the PLC 1 may be reduced. Then, time data indicating the current time measured by the RTC 62 of the programmable display 3 ′ is acquired, a correction command (eg, time correction command) is created and transmitted to the main body 2.

  The valid / invalid control unit 24 functions as a switching unit that switches between enabling and disabling the current time correction function of the time correction unit 23 of the PLC 1. The valid / invalid control unit 24 is based on a switching instruction from a screen display data creation support device 51 (PC on which the above-described screen display data creation software is installed, not shown) connected to the programmable display 3 ′. Enable / disable the correction function. The valid / invalid control unit 24 may switch whether the correction function is valid or invalid by monitoring on / off of a dip switch provided in the main body 2 or the programmable display 3 ′ (on ⇒ Enabled, Off ⇒ Disabled). When the operator does not want to correct the current time of the RTC 37 with the current time of the programmable display 3 ', the operator may set the time correction function to OFF. The screen display data creation support device 51 referred to here may be the same device as the program creation support device 50 connected to the PLC 1 or a different device.

<Flag control process>
FIG. 5 is a flowchart showing a flag control process executed by the flag control unit 22 of the main body 2.

  In S <b> 501, the flag control unit 22 reads control information including the voltage monitoring information output from the voltage monitoring unit 38 from the storage unit 39 of the RTC 37.

  In S502, the flag control unit 22 determines whether the output voltage of the RTC power supply 40 has decreased. For example, the flag control unit 22 determines whether or not the voltage monitoring information extracted from the control information indicates that the output voltage of the RTC power supply 40 has decreased below the threshold value. If the output voltage of the RTC power supply 40 has not decreased below the threshold value, it is not necessary to correct the time, and thus this process ends. Alternatively, if the output voltage of the RTC power supply 40 has not decreased below the threshold value, the process proceeds to S505, and the flag control unit 22 keeps the voltage error flag off. On the other hand, if the output voltage of the RTC power supply 40 has decreased below the threshold, the process proceeds to S503.

  In step S503, the flag control unit 22 sets the voltage error flag to ON to indicate that the reliability of the current time measured by the RTC 37 may be reduced. That is, the flag control unit 22 rewrites the device information corresponding to the voltage error flag in the device information 34 to 1.

  In S504, the flag control unit 22 determines whether or not the current time of the RTC 37 has been corrected. When notified from the time correction unit 23 that the time correction unit 23 has corrected the current time of the RTC 37, the flag control unit 22 determines that the current time of the RTC 37 has been corrected, and proceeds to S505. If the current time of the RTC 37 is not corrected, the flag control unit 22 waits for the correction of the current time of the RTC 37 to be completed.

  In S505, the flag control unit 22 sets the voltage error flag to OFF so as to indicate that the reliability of the current time measured by the RTC 37 has not deteriorated. That is, the flag control unit 22 rewrites the device information corresponding to the voltage error flag in the device information 34 to 0.

<Time correction command creation process>
FIG. 6 is a flowchart showing a time correction command creation process executed by the control unit 60 of the programmable display 3 ′.

  In step S601, the determination unit 64 determines whether the voltage error flag read condition is satisfied. Details of the voltage error flag reading condition determination processing will be described with reference to FIG. As a premise, it is assumed that the power of the PLC 1 is turned on.

  In S <b> 701, the determination unit 64 determines whether or not the programmable display 3 ′ has just started after being supplied with power from an external power source. If the programmable display 3 ′ has just been started after being supplied with power from an external power supply, the process proceeds to S <b> 702 to execute time correction.

If the programmable display 3 ′ is not immediately after being activated with power supplied from the main body 2 or an external power supply, the process returns to S <b> 701.

  In S <b> 702, the determination unit 64 determines whether the programmable display 3 ′ is connected to the main body 2. If the programmable display 3 'is connected to the main body 2, the time is corrected at this timing.

  Specifically, for example, it is determined whether or not a communication command can be normally exchanged between the programmable display 3 ′ and the PLC 1. For example, the programmable display 3 ′ determines whether or not an appropriate response command (ACK or the like) has returned from the PLC 1 in response to the communication establishment command to the PLC 1.

  Thus, it is determined whether or not the device information stored in the PLC 1 can be read. If the programmable display 3 ′ is connected to the main body 2 and the device information stored in the PLC 1 can be read, the process proceeds to S <b> 602. Otherwise, it will wait until it becomes such a state.

  Returning to the description of FIG. In S602, the determination unit 64 reads the device information 34 corresponding to the voltage error flag. Since the device information 34 is disclosed to the outside, the programmable display 3 'can easily read it. In the programmable logic controller, control information of the internal RTC is not directly disclosed to the outside. Therefore, in order to be able to acquire the operating state of the RTC 37 from outside the PLC 1, device information 34 corresponding to a voltage error flag is stored in the device 33 which is a storage area disclosed to the outside.

  In S603, the determination unit 64 determines whether the voltage error flag is turned on. That is, the determination unit 64 determines whether or not the voltage error flag held in the main body 2 indicates that the reliability of the current time measured by the RTC 37 may be reduced. If the voltage error flag is not turned on, this process ends. On the other hand, if the voltage error flag is on, the process proceeds to S604. In other words, the determination unit 64 notifies the correction command generation unit 65 that the voltage error flag held in the main body 2 may have reduced reliability of the current time measured by the RTC 37.

  In step S <b> 604, the correction command generation unit 65 reads time data indicating the current time from the RTC 62.

  In step S <b> 605, the correction command generation unit 65 generates a time correction command including the time data acquired from the RTC 62 and transmits the time correction command to the main body 2 via the communication unit 61.

<Time correction processing>
FIG. 8 is a flowchart showing time correction processing executed by the time correction unit 23 of the PLC 1.

  In S801, the time correction unit 23 determines whether a time correction command is received from the programmable display 3 '. When the interpreter 43 interprets the command received by the communication unit 42 and finds the time correction command, the interpreter 43 outputs a time correction command to the time correction unit 23 together with the time data. When receiving the time correction command from the interpretation unit 43, the time correction unit 23 determines that the time correction command has been received from the programmable display 3 ', and proceeds to S802.

  In step S <b> 802, the time correction unit 23 sets the received time data in the RTC 37 to correct the current time counted by the RTC 37.

  In step S803, the time correction unit 23 turns off the voltage error flag. That is, the time correction unit 23 notifies the flag control unit 22 that the time correction has been completed. The flag control unit 22 turns off the voltage error flag according to this notification.

<Switching the time correction function between enabled and disabled>
There are times when other current times that can be acquired by the PLC 1 are more reliable than the current time of the RTC 62 of the programmable display 3 ′. For example, the time data of the current time may be acquired from a time server (such as an NTP server) on which the PLC 1 operates on the network. The operator may wish to manually set the current time through the operation unit 11. In such a case, it is convenient if the time correction function using the programmable display 3 ′ by the time correction unit 23 described above can be invalidated.

  FIG. 9 is an example of a user interface displayed on the display device of the screen display data creation support device 51 connected to the programmable display 3 ′. The user interface 90 includes a check box 91 for determining whether or not to match the current time measured by the RTC 37 of the PLC 1 with the calendar timer included in the screen display data creation support device 51. Also, a check box for selecting whether to correct the current time of the RTC 37 when the output voltage of the RTC power supply 40 of the PLC 1 is lowered, that is, whether to enable or disable the time correction function of the time correction unit 23. 92 is provided. When the screen display data creation support device 51 detects that the check box 92 is checked, it instructs the valid / invalid control unit 24 to validate the time correction function of the time correction unit 23. On the other hand, when the screen display data creation support device 51 detects that the check box 92 is unchecked, it instructs the valid / invalid control unit 24 to invalidate the time correction function of the time correction unit 23. At this time, if it is detected that the check box 91 is checked, the screen display data creation support device 51 acquires time data from the calendar timer, creates a time correction command including this, and sends it to the control unit 20. Send. The control unit 20 adjusts the current time of the RTC 37 to the calendar timer according to the time correction command. The calendar timer is merely an example, and the control unit 20 may directly access the NTP server and execute time synchronization.

  Here, the time correction command is sent to the control unit 20 in conjunction with the operation of adding / deselecting the check box, but another method is also possible. Specifically, the user selects valid / invalid on the display screen of the screen display data creation support apparatus 51, and this is stored as setting information. When the setting information is transferred to the programmable display 3 ', the setting information is stored in a memory in the programmable display 3'. Then, the validity / invalidity control unit 24 switches the validity / invalidity of the time correction function.

  As described above, according to the present invention, when the output voltage of the RTC power supply 40 that supplies power to the RTC 37 provided in the main body 2 of the PLC 1 decreases, the programmable display 3 ′ connected to the main body 2. The current time of the RTC 37 is corrected with the time data supplied from the RTC 62. Since the RTC 62 of the programmable display 3 'can measure the current time without receiving a radio wave indicating the time, the current time of the PLC 1 can be corrected even at a site such as a factory where the radio wave does not reach. Further, the current time of the RTC 37 can be corrected with the time data supplied from the RTC 62 of the programmable display 3 'without connecting the terminal device to the GPS receiver via the network. Therefore, the time information of the PLC 1 can be corrected by a simpler and more reliable method than before.

  The system operation of the time correction system of the PLC 1 and the programmable display 3 ′ is summarized as follows. First, (1) the power of the PLC 1 and the programmable display 3 'is turned on. (2) The PLC 1 reads the time data and control information from the RTC inside the PLC 1, and turns on the “RTC voltage drop error” flag of the device when the reliability of the time data cannot be confirmed. (3) The PLC 1 starts executing the ladder program. (4) The programmable display 3 ′ starts communication with the PLC 1 according to the setting data held in the internal nonvolatile memory. (5) The programmable display 3 'issues a communication command for reading the "RTC voltage drop error" flag to the PLC. (6) The PLC 1 acquires the value of the “RTC voltage drop error” flag according to the received command, and returns a response. (7) The programmable display 3 ′ confirms the received response, and if the “RTC voltage drop error” flag is ON, the time from the RTC inside the programmable display 3 ′ is corrected to correct the time data of the PLC1. Get the data. (8) The programmable display 3 'issues a time setting command to the PLC 1 based on the time data acquired in (7). (9) The PLC 1 acquires time data from the received command and sets the time for the RTC in the PLC 1. At the same time, the “RTC voltage drop error” flag of the device is turned OFF. Of these, (3) and (4) to (9) are executed asynchronously.

  According to the time correction system that operates in this way, the time information of the PLC 1 can be corrected by a simpler and more reliable method than in the past.

  In addition, according to the present invention, the voltage error flag is stored as the device information 34 in the device 33 disclosed outside the PLC 1, so that the voltage error flag can be easily read from the outside of the PLC 1.

  In addition, according to the present invention, when the PLC 1 is activated or when the programmable display 3 ′ is activated, the voltage error flag is analyzed and time correction is performed, so that an incorrect current time affects the control of the PLC 1. The impact can be reduced.

  In addition, according to the present invention, the current time is corrected in cooperation with external devices that are frequently connected to the PLC 1, such as the programmable display 3 ', the operation module 3, and the serial communication module, so that the operator is not particularly conscious. The current time can be automatically corrected.

  According to the present invention, the time correction function using an external device can be switched to invalid. Therefore, if the operator manually corrects the time or obtains and corrects the time from a more accurate time server, it is convenient to disable the time correction function.

  Moreover, the scope of application of the present invention can be expanded by using an RTC for the timekeeping unit provided in the external device. Generally, the RTC is mounted on many modules. Therefore, the present invention can be realized by updating the firmware of an existing external device. For the PLC 1, the present invention can be implemented by firmware update or a ladder program.

Claims (9)

A programmable logic controller time correction system comprising a programmable logic controller body and an external device connected to the body,
The programmable logic controller is
A first timekeeping section that measures the current time;
Regardless of whether power is supplied to the main body, a power supply that supplies power to the first timekeeping unit;
A voltage monitoring unit for monitoring the output voltage of the power supply;
When the output voltage of the power source falls below a threshold value, the flag is controlled and stored in the storage unit so as to indicate that the reliability of the current time measured by the first timer unit may be reduced. A flag controller;
A time correction unit for correcting the current time of the first time measuring unit,
The external device is
A second timekeeping section for measuring the current time;
The flag held in the storage unit of the main body is read, and it is determined whether or not the flag indicates that the reliability of the current time measured by the first timing unit may be lowered A determination unit;
When the determination unit determines that the flag read from the storage unit of the main body indicates that there is a possibility that the reliability of the current time measured by the first time measuring unit is lowered, the second A correction command for acquiring the time data indicating the current time measured by the timer unit, creating a correction command for correcting the current time of the first time measuring unit, and transmitting the correction command to the main body together with the time data And
With
When the main body receives the correction command, the time correction unit corrects the current time of the first timekeeping unit with the time data received together with the correction command. system.   2. The programmable logic controller according to claim 1, wherein the flag control unit stores the flag as device information in a device that is a storage area that is secured in the storage unit and is open to the outside of the main body. Time correction system. The determination unit of the external device is
When the external device is activated when power is supplied to the external device,
When the external device is wired or wirelessly connected to the main body,
When reading the device information different from the flag displayed on the display unit of the external device periodically or irregularly,
When the main body and the external device are activated by supplying power to the main body in a state where the external device is coupled to the main body,
The time correction system for a programmable logic controller according to claim 1, wherein the flag is read from the main body at least at one timing.   The external device is an operation module including a display unit that displays device information read from a device of the main body, and an operation unit that receives an operation for inputting information to the main body. The time correction system of the programmable logic controller according to any one of claims 1 to 3.   5. The switching unit according to claim 1, further comprising a switching unit that switches between enabling and disabling a current time correction function of the first time measuring unit included in the time correction unit. Programmable logic controller time correction system of description.   6. The time correction system for a programmable logic controller according to claim 1, wherein at least one of the first timer unit and the second timer unit is a real-time clock. A programmable logic controller that can be connected to an external device.
A first timekeeping section that measures the current time;
Regardless of whether power is supplied to the main body, a power supply that supplies power to the first timekeeping unit;
A voltage monitoring unit for monitoring the output voltage of the power supply;
When the output voltage of the power source falls below a threshold value, the flag is controlled and stored in the storage unit so as to indicate that the reliability of the current time measured by the first timer unit may be reduced. A flag controller;
A programmable logic controller comprising: a time correction unit that corrects the current time of the first timekeeping unit with time data received from the external device due to control of the flag control unit. An external device for a programmable logic controller having a first timekeeping unit that measures the current time,
A second timekeeping section for measuring the current time;
Whether the flag held in the storage unit of the main body of the programmable logic controller is read, and whether the flag indicates that the reliability of the current time measured by the first timing unit may be reduced A determination unit for determining
If the determination unit determines that the flag read from the storage unit of the main body indicates that there is a possibility that the reliability of the current time measured by the first time measurement unit is reduced, the second An external device comprising: a correction command generation unit that acquires time data indicating a current time measured by the time measurement unit, generates a correction command, and transmits the correction command to the main body. A time correction system for a programmable logic controller,
The body,
An external device wired or wirelessly connected to the main body,
The body is
A first timekeeping section that measures the current time;
Regardless of whether power is supplied to the main body, a power supply that supplies power to the first timekeeping unit;
A voltage monitoring unit for monitoring the output voltage of the power supply;
A storage unit storing bits that change depending on whether the output voltage of the power source is less than a threshold value or more than a threshold value;
When a correction command is received from the external device to correct the current time of the first timekeeping unit after the bit is read from the external device, the time data received together with the correction command from the external device A time correction unit that corrects the current time of the timekeeping unit of 1,
The external device is
A second timekeeping section for measuring the current time;
When the bit stored in the storage unit of the main body is read and the bit indicates that the output voltage of the power source has dropped below a threshold, the time indicating the current time measured by the second clock unit A time correction system for a programmable logic controller, comprising: a correction command generation unit that acquires data, generates the correction command, and transmits the correction command to the main body.

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