Patent Publication Number: US-2022236679-A1

Title: Image forming apparatus, control method for the image forming apparatus, and a storage medium

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to a control method and a storage medium for initializing an image forming apparatus comprising a plurality of components. 
     Description of the Related Art 
     In recent years, image forming apparatuses have advanced functions and high expandability such as a server function for holding data as well as copy functions such as copying, scanning, and printing. Therefore, when the system becomes unstable due to a malfunction of a component of a device used for a copying function, a function such as a watchdog timer (WDT) is used to appropriately terminate and restart the system. 
     Japanese Patent Application Laid-Open No. 2019-164536 shows a method having switching means for receiving an interrupt by the CPU and storing in an external memory that a WDT reset is generated when receiving the interrupt input of the WDT from the own chip or the external chip, and then switching the WDT reset to an output outside of the own chip. However, in the case of Japanese Patent Application Laid-Open No. 2019-164536, since the interrupt can be handled only when the CPU is operating, the interrupt is not handled when the system hangs. 
     SUMMARY OF THE INVENTION 
     The WDT interrupts may be applied in a variety of cases. The cases and solutions are exemplified in the following. 
     (Case 1) In the image forming apparatus equipped with suspending or resuming functions for saving power, in a case where a malfunction occurs in the CPU or peripheral devices of a controller board mounted on the image forming apparatus during resume processing of the image forming apparatus, and the resume processing of the image forming apparatus cannot be restored. 
     (Solution for case 1) Recovery operations such as checking boards and retries are executed by resetting with the WDT interrupts. 
     (Case 2) In the image forming apparatus equipped with a scanner device, in a case where a malfunction occurs in motors or optical components of the scanner device, the optical components do not move to a designated position, and a knocking sound is heard. 
     (Solution for case 2) Based on detecting the failure to move to the designated position and the malfunction of the optical detection, the motor is forcibly stopped by resetting with the WDT interrupts. 
     (Case 3) In the image forming apparatus equipped with a facsimile (FAX) device, in a case where a malfunction occurs in the FAX device and the response of a transmission/reception part is discontinued during communication over a telephone line. 
     (Solution for case 3) In a case where the telephone line is forcibly disconnected by resetting with the WDT interrupt. 
     As described above, even if a malfunction may occur in various devices, the target device can be appropriately terminated by the WDT interrupt processing. 
     In general, the power supply of the target device may be controlled by a certain device, and the target device is reset by the WDT interrupts when a malfunction occurs in the certain device. This configuration ensures the starting order of the power plane controlled by the malfunctioning device when the power is turned on again by resetting with the WDT interrupts. If the WDT interrupts reset not only the device whose power is controlled by the malfunctioning device but also the device whose power is not controlled by the malfunctioning device, the devices may be damaged by generating reverse current or the like due to an incorrect starting order of the power plane. 
     In addition, it may be difficult for the controller to constantly monitor the state of the device whose power is not controlled by the malfunctioning device as well as the state of the device whose power is controlled by the malfunctioning device. 
     For the above reasons, in the conventional high-functional image forming apparatus, the controller has a high function and it is more efficient to centrally control the entire power supply. Hereinafter, the conventional image forming apparatus including a high-functional controller will be described. 
     Conventional Example (Advanced Controller) 
     (Configuration of the Power Supply) 
       FIG. 7  shows a configuration of the controller  103  controlling the power supply in the prior art, the controller  103  having a high function and occupying a large proportion of the entire control. In the image forming apparatus  101 , when a power switch  110  is pressed, a power control part of the controller  103  detects pressing the power switch  110  and supplies power to a CPU  340  of the controller  103 . The CPU  340  controls the power switch P 410  to supply power to a printer  104  and the CPU  320  of the printer  104 . Similarly, the CPU  340  controls the power switch Q 411  to supply power to a scanner device  102 , and controls the power switch R 412  to supply power to a FAX device  107 . There are a hierarchy  1  ( 420 ) and a hierarchy  2  ( 421 ) in the conventional power supply structure of the image forming apparatus  101 . The hierarchy  1  ( 420 ) includes the hierarchy  2  ( 421 ). In the hierarchy  2  ( 421 ), the printer device  104 , the scanner device  102 , and the FAX device  107  can individually reset and control the power supply. Further, in the hierarchy  1  ( 420 ), the controller  103  can reset or control the power supply devices in the hierarchy  2  ( 421 ) included in the hierarchy  1  ( 420 ). 
     (WDT Control Processing) 
       FIG. 8  shows a flowchart illustrating the startup processing of the WDT control with the configuration of the conventional power supply ( FIG. 7 ). This flowchart starts when a malfunction occurs in a device monitored by the CPU  340 . In step S 501 , the CPU  340  sets an activation time which is a set time of the countdown of the WDT. In step S 502 , the WDT is activated. Details of step S 502  will be described later. In step S 503 , the CPU  340  checks whether or not the stop event of the WDT has been received from the module controlling the device, the stop event of the WDT corresponding to that there is no malfunction in the device activating the WDT. In a case where the stop event is not received (No in S 503 ), the process proceeds to S 504 . In a case where the stop event is received (Yes in S 503 ), the process proceeds to S 506 . In step S 504 , the controller waits for a predetermined time shorter than the activation time of the WDT in this step. In step S 505 , the activation time of the WDT is reset to extend the countdown time of the WDT. The process returns to step S 503  to continue monitoring the stop event of the WDT. On the other hand, in a case where the stop event is received in S 503 , the WDT is stopped and the processing is terminated without resetting by the WDT in S 506 . 
     (Reset Processing) 
     On the other hand, in a case where the system stalls or the like while monitoring the stop event of the WDT, the WDT is timed up and a reset processing is executed. The reset processing is executed by the controller  103  to the device in the hierarchy  1  ( 420 ) including the hierarchy  2  ( 421 ). When the CPU  340  of the controller  103  receives the end notification by pressing the power switch  110  or the like, the CPU  340  executes the end processing. First, the controller  103  in the hierarchy  1  ( 420 ) and the printer device  104 , the scanner device  102 , and the FAX device  107  in the hierarchy  2  ( 421 ) are reset or turned off by using the power supply control unit of the controller  103  to terminate the termination processing of the image forming apparatus  101 . As described above, the image forming apparatus including the high-functional controller can execute the WDT reset processing. However, for example, in a case where the image forming apparatus includes the functions selected carefully based on the printer function, the printer device occupies a large proportion in the image forming apparatus and the signal lines are also small between the controller and the printer device. Therefore, it is more efficient to control the power supply by the controller in the printer device. In such a configuration, the device whose power is not controlled by the controller of the printer device cannot detect that the malfunctioning device or the device whose power is controlled by the controller of the printer has been reset. Therefore, the device whose power is not controlled by the controller of the printer device cannot perform as the image forming apparatus. 
     In order to solve the above problems, the purpose of the present invention is that when the malfunctioning device is reset by the WDT interrupt to restart the device whose power is controlled by the malfunctioning device, the device whose power is not controlled by the malfunctioning device is notified of the WDT interrupt to properly initialize the whole system. 
     According to an aspect of the present invention, an information processing apparatus including a plurality of devices comprising: a first control unit controlling a power supply for a first apparatus and watchdog timer; and a second control unit controlling a power supply for a second apparatus different from the first control unit or the first apparatus, wherein the first control unit includes setting means for enabling a flag of non-volatile storage means when the watchdog timer is started, and notification means for notifying the second control unit in a case where the flag of the non-volatile storage means is enabled when the first control unit is activated. 
     Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an overall view illustrating a configuration of an image forming apparatus. 
         FIG. 2  is a block diagram illustrating a controller. 
         FIG. 3  is a diagram illustrating a power supply configuration of the image forming apparatus according to the exemplary embodiment. 
         FIG. 4  is a flowchart illustrating the WDT control of the image forming apparatus according to the exemplary embodiment. 
         FIG. 5  is a flowchart illustrating the WDT reset process. 
         FIG. 6  is a flowchart illustrating the startup processing of the controller according to the exemplary embodiment. 
         FIG. 7  is a power supply configuration of a conventional image forming apparatus. 
         FIG. 8  is a flowchart illustrating the WDT control of the conventional image forming apparatus. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     An embodiment of the present invention will be described below with reference to the drawings. 
     System Configuration 
       FIG. 1  is a block diagram illustrating a configuration of an image forming system according to the present embodiment. This example is a multifunction device (MFP) including a printing function, a scanner function, a data communication function, and the like. In  FIG. 1 , the image forming apparatus  101  is configured to receive jobs from computer  109  via LAN  108 . In  FIG. 1 , although there is only one computer, two or more computers may be connected. 
     1. An Image Forming Apparatus 
     The overall configuration of the image forming apparatus 
     The image forming apparatus  101  includes a scanner device  102 , a controller  103 , a printer device  104 , an operation unit  105 , a hard disk  106 , and a FAX device  107 , and is connected with a finisher device  150 . The scanner device  102  optically reads images from a document and converts the read images into digital images. The printer device  104  outputs the digital images to paper devices called papers. The operation unit  105  includes a touch panel and a hard key for receiving a setting for the image forming apparatus from a user and displaying a processing state. The hard disk  106  stores digital images, control programs, and the like. The hard disk  106  may be a non-volatile storage device such as an SSD, an eMMC, or the like. The FAX device  107  transmits and receives digital images to and from a telephone line or the like. Further, the controller  103  is connected to the scanner device  102 , the printer device  104 , the operation unit  105 , the hard disk  106 , and the FAX device  107  to collectively control each module and execute jobs on the image forming apparatus  101 . The image forming apparatus  101  can also input and output digital images, generate jobs, and instruct devices from the computer  109  via the LAN  108 . 
     The Scanner Device 
     The scanner device  102  comprises a document feeding unit  121  and a scanner unit  122 . the document feeding unit  121  can automatically and sequentially replace a bundle of documents. The scanner unit  122  can optically scan the documents and converting the scanned documents into digital images. The converted image data is transmitted to the controller  103 . 
     The Printer Device 
     The printer  104  comprises a marking unit  141 , a paper feeding unit  142 , and a paper discharge unit  143 . The paper feeding unit  142  can sequentially feed paper from a paper bundle one by one. The marking unit  141  prints image data on the fed paper. The paper discharge unit  143  discharges the paper after printing. 
     The Operation Unit 
     The operation unit  105  comprises an LCD touch panel, a power-saving button, a copy button, a cancel button, a reset button, ten keys, a user-mode key, and the like, to provides a user I/F for operating the image input/output system. These keys include hardware keys, software keys displayed on the LCD, and the like., and the presence of hardware keys is not required. 
     The Finisher Device 
     The finisher device  150  performs processing such as paper discharge, sorting, stapling, punching, and cutting on paper devices outputted from the paper discharge unit  143  of the printer device  104  of the image forming device  101 . 
     Further, the image forming apparatus  101  has a switch for controlling the power supply, and when the power supply switch is turned off, the image forming apparatus waits for the termination processing of the software or the hardware, and stops the power supply except for a portion necessary for detecting the on of the power supply switch. 
     2. Functions of the Image Forming Apparatus 
     Examples of executable job functions of the image forming apparatus  101  will be described below. 
     The Copying Function 
     The image forming apparatus  101  has a copying function of storing images read by the scanner device  102  on the hard disk  106  and simultaneously printing the images by the printer device  104 . 
     The image transmission function 
     The image forming apparatus  101  has an image transmission function of transmitting images read by the scanner device  102  to the computer  109  via LAN  108 . 
     The Image Storage Function 
     The image forming apparatus  101  has an image storage function for storing images read by the scanner device  102  on the hard disk  106  and transmitting or printing the images as required. 
     The Image Printing Function 
     The image forming apparatus  101  has an image printing function for analyzing, for example, a page description language transmitted from the computer  109  and printing the images by the printer device  104 . 
     3. Entire Configuration of the Controlling Unit 
     Next, the block diagram of the controller  103  and the peripheral device will be described with reference to  FIG. 2 . The controller  103  comprises a main-board  200  and a sub-board  220 . 
     The Main-Board 
     The main-board  200  is a so-called general-purpose CPU system and includes a CPU  340  controlling the whole board. The main-board  200  also includes a boot ROM  202  including a boot program, a memory  341  used by the CPU  340  as a work memory, a bus controller  204  having a bridge function with an external bus, and a non-volatile memory  205  that retains its contents even when the power supply is cut off. The CPU  340  controls a watchdog timer (WDT)  230  resetting the controller  103 . 
     The main-board  200  further includes a disk controller  206  controlling the storage device, and a flash disk  207 . The flash disk  207  is a storage device having a relatively small capacity and made up of semiconductor devices such as an SSD, an eMMC, or the like. The main-board  200  also includes a USB controller  208  or the like capable of controlling the USB, a network controller  211  managing network connection, and a real-time clock (RTC)  212 . The main-board  200  is externally connected with a USB memory  209 , the operation unit  105 , the hard disk  106 , and the like. 
     The Sub-Board 
     The sub-board  220  includes a relatively small general-purpose CPU system and image processing hardware. The sub-board  220  also includes a CPU  221  controlling the whole board, a memory  223  used by the CPU as a work memory, a bus controller  224  having a bridge function with an external bus, and a non-volatile memory  225  that retains its contents even when the power supply is cut off. The sub-board  220  further includes an image processing processor  227  executing real-time digital image processing and a plurality of device controllers  226 . A scanner device  102  and a printer device  104  are connected with the outside of a controller  103  and pass digital image data via the device controller  226 . The paper device discharged from the printer device  104  is processed by the finisher device  105 . The FAX device  107  is directly controlled by the CPU  221 . 
     Note that this figure is a simplified block diagram. For example, the CPU  340 , the CPU  221 , and the like include many CPU peripheral hardware such as a chip-set, a bus bridge, a clock generator, and the like. This block diagram is described in a simplified form because it is not necessary for the granularity of the description, and this block configuration does not limit the present invention. 
     Controller Operation 
     The operation of the controller  103  will be described with an example of image copying with a paper device. 
     When a user instructs copying of an image from the operation unit  105 , the CPU  340  sends an instruction of reading the image to the scanner device  102  via the CPU  221 . The scanner device  102  optically scans a paper document, converts the scanned paper document into digital image data, and inputs the digital image data to the image processing processor  227  via the device controller  226 . The image processing processor  227  performs DMA transfer to the memory  223  via the CPU  221  to temporarily store digital image data. When it is confirmed that the memory  223  receives and stores a certain amount or all of the digital image data, the CPU  340  instructs an image output to the printer device  104  via the CPU  221 . The CPU  221  notifies the address of the digital image data in the memory  223  to the image processing processor  227 . The digital image data in the memory  223  is transmitted to the printer device  104  via the image processing processor  227  and the device controller  226  in accordance with a synchronization signal from the printer device  104 . The printer device  104  prints the digital image data on a paper device. 
     When a plurality of copies is printed, the CPU  340  stores the digital image data in the memory  223  in the hard disk  106 . In the second and subsequent parts, the digital image data can be sent from the hard disk  106  or the memory  223  to the printer device  104  without receiving the digital image data from the scanner device  102 . 
     4. A Configuration of the Power Unit 
       FIG. 3  is a block diagram illustrating the power supply configuration of the image forming apparatus  101  according to the embodiment of the present invention shown in  FIG. 1 . The controller  103  of the image forming apparatus  101  includes the functions selected carefully. The printer device  104  controls the power supply and many functions in the entire system. 
     The Power Supply Configuration 
     In the image forming apparatus  101  shown in  FIG. 3 , a power supply  301  and a power supply configuration for each apparatus will be described below. In the image forming apparatus  101 , when the power switch  110  is pressed, the power control part of the printer device  104  detects pressing the power switch  110  and supplies power to the CPU  320  of the printer device  104 . The CPU  320  of the printer device  104  controls the power switch A 460  to supply power to the controller  103  and the CPU  340  of the controller  103 . Further, the CPU  320  may individually control the marking unit  141  of the printer device  104 , the paper feed unit  142 , and the paper discharge unit  143  by the power control. However, the description of this configuration is omitted in order to deviate from the purpose of the present application. 
     Similarly, the CPU  340  of the controller  103  controls the power switch B 461  to supply power to the scanner device  102 , and controls the power switch C 462  to supply power to the FAX device  107 . 
     The configuration of the power supply of the image forming apparatus  101  of the embodiment has a hierarchical structure and includes the hierarchy A 470 , the hierarchy B 471 , and the hierarchy C 472 . The hierarchy A 470  includes the hierarchy B 471  and the hierarchy B 471  includes the hierarchy C 472 . In the hierarchy C 472 , the scanner device  102  and the FAX device  107  can individually reset and control the power supply. Further, in the hierarchy B 471 , the controller  103  can reset and control the power supply of the devices in the hierarchy C 472  included in the hierarchy B 471 . Furthermore, in the hierarchy A 470 , the printer device  104  can reset and control the power supply of the devices in the hierarchy B 471  and the hierarchy C 472  included in the hierarchy A 470 . 
     Reset 
     In the configuration described above, when the controller  103  is reset by the WDT, the various registers controlled by the controller  103  are returned to the initial values. Then, the power switch B 461  controlling the scanner device  102  is turned OFF/ON, and a power switch C 462  controlling the FAX device  107  is turned OFF/ON. In the section in which the power supply falls with time due to the power supply switch OFF/ON, the power OFF section can be guaranteed by H/W (hardware) and S/W (software). However, the description of this configuration is omitted in order to deviate from the purpose of the present application. 
     The Termination Processing 
     In the configuration of  FIG. 3  according to the present embodiment, the CPU  340  of the controller  103  in the hierarchy B 471  notifies the end notification to the CPU  320  of the printer device  104  in the hierarchy A 470  when the CPU  340  receives the end notification by pressing the power switch  110  or the like. The CPU  320  of the printer device  104  executes reset processing and power-off processing of the printer device  104  in the hierarchy A 470 , the controller  103  in the hierarchy B 471 , and the scanner device  102  and the FAX device  107  in the hierarchy C 472 , to end the termination processing of the image forming apparatus  101 . In the case of normal termination, the WDT flag is deleted and the WDT is stopped. 
     5. Watch Dog Timer (WDT) Processing 
     In the WDT control process of the present embodiment, the CPU  340  of the controller  103  activates the WDT flag in the non-volatile storage area  205  when starting the WDT. In a case where the WDT flag is enabled in the non-volatile storage area  205  when the WDT times up and the WDT reset is applied, the CPU  320  of the printer device  104  is notified. This configuration is different from the configuration of the conventional example. Referring now to  FIG. 4 , the flowchart of the activation process of the watchdog timer (WDT) control of this embodiment will be described. The same processing as that of the conventional example shown in  FIG. 8  is denoted by the same reference numerals. 
     This flowchart starts when a malfunction occurs in the device monitored by the CPU  340 . First, in step S 501 , the CPU  340  sets the activation time which is a set time of the countdown of the WDT. In subsequent step S 502 , the WDT is activated. Details will be described later with reference to  FIG. 5 . In step S 710 , the CPU  340  enables the WDT flag of the non-volatile storage area  205 . In step S 503 , the CPU  340  checks whether or not the stop event of the WDT has been received from the module controlling the device, the stop event of the WDT corresponding to that there is no malfunction in the device activating the WDT. In a case where the stop event is not received (No in S 503 ), the process proceeds to S 504 . In a case where the stop event is received (Yes in S 503 ), the process proceeds to S 711 . In step S 504 , the controller waits for a predetermined time shorter than the activation time of the WDT in this step. In step S 505 , the activation time of the WDT is reset to extend the countdown time of the WDT. The process returns to step S 503  to continue monitoring the stop event of the WDT. On the other hand, in a case where in step S 711  (Yes in step S 503 : the stop event is received), the WDT flag of the non-volatile storage area  205  is disabled. The WDT is stopped and the processing is terminated in step S 506 . 
     The Reset Processing of the Watchdog Timer (WDT) 
     Next, the watchdog timer (WDT) reset process in step S 502  of the flowchart in  FIG. 4  will be described with reference to the flowchart in  FIG. 5 . First, in step S 601 , the watchdog timer (WDT) starts counting down from the set value of the WDT activation time based on an input clock or the like. In step S 602 , the watchdog timer (WDT) determines whether or not the WDT has been stopped by the notification from the module controlling the device causing the WDT to be activated. In a case where the WDT is stopped (Yes in S 602 ), the process ends. In a case where the WDT is not stopped (No in S 602 ), the process proceeds to S 603 . In step  603 , if the value is not written into the register setting the activation time of the WDT within a predetermined time, the WDT counts down the value to 0 and determines that the time is up. In a case where the WDT does not determine that the time is up (the activation time is reset to the register (S 505  in  FIG. 4 )) (No in S 603 ), the process returns to S 601  and the WDT continues the countdown. On the other hand, in a case where the WDT determines that time is up (Yes in S 603 ), the process proceeds to S 604 . In step S 604 , the WDT generates a WDT signal. By connecting the WDT signal to the reset signal, each device in the hierarchy B ( 471 ) is reset. 
     The method for resetting the devices by using the WDT signal may include various forms such as a method for resetting controller by changing the register value and connecting the register with the reset, a method for changing the register to check by polling from the CPU, and a method for changing the register value and connecting the register with an interrupt to raise the interrupt to the CPU. 
     The structure of the controller  103  of the image forming apparatus  101  according to the embodiment will be described below. In a case where the non-volatile memory is not included in the main-board  200  as the non-volatile storage area  205  for enabling/disabling the WDT flag, the non-volatile memory can be substituted for the flash disk  207  connected with the disk controller  206  or the HDD  106  outside the controller  103 . However, as the distance from the CPU  340  increases, it becomes more difficult to check the WDT flag at an early stage of a startup. The deeper examination is omitted in order to deviate from the purpose of the present application. 
     The Start Processing 
     With reference to  FIG. 6 , the starting processing of the controller of this embodiment, which is continued from  FIGS. 4 and 5 , will be described. 
     In S 503  to S 505  of  FIG. 4 , in a case where the system cannot be controlled due to a system stall and the like, the activation time of the WDT cannot be reset to extend the activation of the WDT. Then, it is determined that the WDT has timed up in S 603  of  FIG. 8 , to reset the WDT in S 604 . Then, the controller  103  is restarted, and the processing of  FIG. 6  is started. This process is also started when the user presses the power switch  110 . In step S 801 , the CPU  340  checks whether or not a flag is set in the non-volatile storage area  205  at the time of the reset or the activation by the power switch  110 , the flag indicating that the WDT is being executed. In a case where the WDT execution flag is not set, the CPU  340  executes normal startup (No in S 801 ) and continues startup processing. In a case where the WDT execution flag is set, the CPU determines that the WDT reset is applied (Yes in S 801 ), and proceeds to step S 802  to disable the WDT flag. In step S 803 , the register for signal notification between the controller  103  and the printer device  104  is controlled, and the signal indicating that the WDT flag has been set is notified to the printer device  104 . In response to receiving the notification from the CPU  340  of the controller  103 , the CPU  320  of the printer device  104  controls each device in the hierarchy A 470  to execute initialization processing such as reset and power OFF/ON. Further, in response to the initialization processing, the CPU  340  of the controller  103  controls each device in the hierarchy B 471  to execute reset and power OFF/ON. 
     According to the above embodiment, the image forming apparatus  101  can notify the printer device  104 , even if the controller  103  is reset by the WDT, the printer device  104  being the power supply control module in the hierarchy A 471  and the controller  103  being the power supply control module in the hierarchy B 470 . As a result, the printer device  104  can execute control such as resetting and power OFF/ON of each device in the hierarchy A 470 . 
     Other Embodiments 
     Embodiment(s) of the present invention can also be realized by a computer of a system or apparatus that reads out and executes computer executable instructions (e.g., one or more programs) recorded on a storage medium (which may also be referred to more fully as a ‘non-transitory computer-readable storage medium’) to perform the functions of one or more of the above-described embodiment(s) and/or that includes one or more circuits (e.g., application specific integrated circuit (ASIC)) for performing the functions of one or more of the above-described embodiment(s), and by a method performed by the computer of the system or apparatus by, for example, reading out and executing the computer executable instructions from the storage medium to perform the functions of one or more of the above-described embodiment(s) and/or controlling the one or more circuits to perform the functions of one or more of the above-described embodiment(s). The computer may comprise one or more processors (e.g., central processing unit (CPU), micro processing unit (MPU)) and may include a network of separate computers or separate processors to read out and execute the computer executable instructions. The computer executable instructions may be provided to the computer, for example, from a network or the storage medium. The storage medium may include, for example, one or more of a hard disk, a random-access memory (RAM), a read only memory (ROM), a storage of distributed computing systems, an optical disk (such as a compact disc (CD), digital versatile disc (DVD), or Blu-ray Disc (BD)™), a flash memory device, a memory card, and the like. 
     While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions. 
     This application claims the benefit of Japanese Patent Application No. 2021-008623, filed Jan. 22, 2021, which is hereby incorporated by reference herein in its entirety.