WO2016051557A1

WO2016051557A1 - Controller

Info

Publication number: WO2016051557A1
Application number: PCT/JP2014/076277
Authority: WO
Inventors: 尚宏加藤
Original assignee: 富士機械製造株式会社
Priority date: 2014-10-01
Filing date: 2014-10-01
Publication date: 2016-04-07
Also published as: JPWO2016051557A1; JP6386575B2

Abstract

A controller 10 is provided with a control device 14, a non-volatile memory 18, and a volatile memory 16. The control device 10 includes: a process execution means that executes pre-set processing in each processing period; a data compression means that compresses non-compressed data stored in the volatile memory 16 as a result of the execution of the processing by the process execution means in the processing period; and a data saving means that, upon detection of a power supply OFF notice signal input from the outside, stores non-compressed data stored in the volatile memory 16 and not compressed by the data compression means, and the compressed data compressed by the data compression means in the non-volatile memory 18.

Description

controller

The technology disclosed in this specification relates to a controller, and more particularly, to a technology for saving data stored in a volatile memory of a controller to a nonvolatile memory when the power is turned off.

In a controller with volatile memory such as RAM (Random-Access Memory), data stored in the volatile memory while the power is on is written and saved to the non-volatile memory when the power is turned off due to a power failure or abnormality. There is. Since the power supply to the controller is also turned off when the power is turned off, the controller needs to save data to the nonvolatile memory within a limited time. For this reason, a method for saving data in a non-volatile memory in a short time has been proposed (for example, Patent Document 1).

In Patent Document 1, when data stored in a volatile memory is written into a nonvolatile memory, first, the data stored in the volatile memory is converted into compressed data. Thereafter, only the converted compressed data is written in the nonvolatile memory. By compressing the data, the amount of data is reduced and the writing time to the volatile memory is reduced. This shortens the time required to save data.

JP 2000-194607 A

In the technique of Patent Document 1, when the power is turned off, data stored in the volatile memory is converted into compressed data, and the converted compressed data is stored in the nonvolatile memory. Therefore, although the data write time can be reduced by reducing the amount of data saved in the non-volatile memory, a process for converting the data stored in the volatile memory into compressed data is required. As a result, there is a problem that the processing time when the power is turned off is not sufficient.

This specification discloses a controller that can perform processing for saving data stored in a volatile memory in a nonvolatile memory in a short time when the power is turned off.

The controller disclosed in this specification includes a control device, a nonvolatile memory, and a volatile memory. The control device compresses the non-compressed data stored in the volatile memory by executing processing set in advance in the processing cycle and processing execution means that executes a preset process for each processing cycle. Data compression means. In addition, when the control device detects the power-off notice signal input from the outside, the control device stores the uncompressed data stored in the volatile memory and not compressed by the data compression unit, and the compressed data compressed by the data compression unit. Are stored in the nonvolatile memory.

In the above controller, uncompressed data stored in the volatile memory is compressed into compressed data in the processing cycle of the control device. Therefore, the control device does not need to compress the non-compressed data into the compressed data by the data saving unit after detecting the power-off notice signal input from the outside. The data saving means only saves the compressed data not compressed by the data compressing means and the data compressed by the data compressing means, and the time required for data saving can be shortened.

It is a block diagram of the servo controller which concerns on a present Example. It is a conceptual diagram explaining the memory area of RAM of FIG. It is a flowchart explaining the normal process of a servo controller. It is a flowchart explaining the process at the time of power-off notice of a servo controller.

The main features of the embodiment described below are listed. The technical elements described below are independent technical elements and exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. Absent.

(Feature 1) The data compression means may compress the non-compressed data stored in the volatile memory in the idle time in which the process execution means does not execute the processing in the processing cycle. According to such a configuration, it is possible to suppress an increase in the processing cycle (one cycle time interval) only for the data compression processing of uncompressed data.

(Characteristic 2) The process execution means may execute a regular process that is periodically performed and an irregular process that is performed when a specific condition is satisfied in the process cycle. The data compressing means may compress the non-compressed data by using the free time due to the fact that the irregular processing is not executed. The irregular process is executed only when a specific condition is satisfied, and is not a process that is always executed. In the above configuration, the processing cycle (one cycle time) of the control device is set so that the regular processing and the irregular processing can be executed within one cycle. Therefore, when the irregular processing is not executed in a certain processing cycle, the control device can execute the data compression processing instead of the irregular processing in the processing cycle. For this reason, it is suppressed that a processing period becomes long for the data compression process by a data compression means.

(Characteristic 3) The control device calculates a power-off time until the power is turned off when the power-off notice signal is detected, and a data saving unit according to the power-off time calculated by the calculation unit Thus, an adjustment unit that adjusts the data amount of the uncompressed data and the compressed data saved in the nonvolatile memory may be provided. According to the above configuration, the amount of data saved in the non-volatile memory is adjusted according to the time until the power is turned off (estimated time), so that the situation where the power supply is stopped during the data saving process is prevented. Can do.

(Feature 4) The volatile memory stores a plurality of compressed data storage areas for storing the compressed data compressed by the data compression means, and management information for specifying where the compressed data is stored in the plurality of compressed data storage areas The management information storage area may be provided. When storing the non-compressed data stored in the volatile memory, the data compression means stores the compressed data in one of a plurality of data storage areas, and stores the management information of the compressed data in the management information storage area May be. When data compression is performed using the free time in the processing cycle, the capacity of the compressed data generated by the data compression means is not constant. According to the above configuration, even if the capacity of the compressed data changes, the management information is stored accordingly, so that the created compressed data can be processed as continuous data.

(Example) The servo controller 10 according to this example will be described below. The servo controller 10 is provided in a mounting machine that mounts electronic components on a board, and controls a servo motor (not shown) provided in the mounting machine. As shown in FIG. 1, the servo controller 10 is connected to the host controller 2. The servo controller 10 controls the operation of the mounting machine by controlling the servo motor based on an instruction from the host controller 2.

The servo controller 10 includes a power supply monitoring circuit 12, a CPU (Central Processing Unit) 14, a RAM (Random Access Memory) 16, a CF (Compact Flash) 18, and an ICH (I / O Controller Hub) 20. ing.

The power supply monitoring circuit 12 is connected to the CPU 14. The power supply monitoring circuit 12 is a known circuit and monitors the power supply voltage supplied to the servo controller 10. The power monitoring circuit 12 outputs a power OFF notice signal to the CPU 14 when the power voltage supplied to the servo controller 10 falls below a predetermined value. In the present embodiment, the power supply monitoring circuit 12 is provided in the servo controller 10, but the configuration is not limited thereto. For example, a power supply monitoring circuit may be provided in the host controller 2 so that a power OFF notice signal is output from the host controller 2 to the servo controller.

The CPU 14 is a processor that controls the operation of the servo controller 10. The CPU 14 is connected to the RAM 16 and is also connected to the CF 18 via the ICH 20. The CPU 14 executes a program stored in advance and controls the servo motor based on an instruction from the host control device 2. When the CPU 14 executes the program, the CPU 14 functions as a process execution unit, a data compression unit, a data saving unit, a calculation unit, and an adjustment unit. The processing by the CPU 14 will be described in detail later.

The RAM 16 is a volatile memory and is connected to the CPU 14. The RAM 16 stores various data generated by the CPU 14 executing the program. Since the RAM 16 is a volatile memory, the stored data is held only while power is supplied from the outside. For this reason, when the external power supply is stopped, the stored data is lost. The data stored in the RAM 16 includes log information indicating a history of processing executed by the CPU 14, compressed log information obtained by compressing the log information, and management information for managing the compressed log information. It is. Specifically, as shown in FIG. 2, the RAM 16 is provided with a data area 202, a compressed data area 204, and a management information storage area 206.

The data area 202 is configured as a ring buffer, and includes four data storage areas 202a to 202d. Log information (uncompressed data) is stored in each of the data storage areas 202a to 202d. The data storage areas 202a to 202d have the same capacity. Therefore, the capacity of log information stored in each of the data storage areas 202a to 202d is also the same. The log information is stored in order from the data storage area 202a to the data storage area 202d. When log information is stored in the data storage area 202d, the log information is stored again in order from the data storage area 202a.

In the compressed data area 204, a compressed log information file obtained by compressing the log information stored in the data area 202 is stored. As will be described in detail later, the log information stored in the data area 202 is compressed for each of the data storage areas 202a to 202d and stored in the compressed data area 204. That is, the compressed data area 204 stores compressed log information files 204a to 204d corresponding to the four data storage areas 202a to 202d of the data area 202, respectively. Specifically, the compressed log information file 204a is stored in the data storage area 202a, the compressed log information file 204b is stored in the data storage area 202b, the compressed log information file 204c is stored in the data storage area 202c, and the compressed log information file 204d is stored in the data storage area. 202d. The capacity of each compressed log information file 204a to 204d varies depending on the contents of the compressed log information (uncompressed data). Therefore, as shown in FIG. 2, the capacities of the compressed

log information files

204a, 204b, and 204d are different from each other.

The management information storage area 206 stores the current data write destination (log information write destination) of the data area 202 and the write destinations and capacities of the compressed log information files 204a to 204d stored in the compressed data area 204. The That is, log information is sequentially generated by the processing performed by the CPU 14, and the log information is sequentially stored in the data area 202. Therefore, the log information to be generated is stored at the correct address in the data area 202 by storing and updating the writing destination of the generated log information in the management information storage area 206. Further, as described above, the capacity of the compressed log information files 204a to 204d stored in the compressed data area 204 differs depending on the contents of the compressed log information. For this reason, if a plurality of compressed log information files 204a to 204d are stored in the compressed data area 204 without being distinguished as continuous data, the boundaries between the compressed log information files 204a to 204d are not known. If the boundaries of the compressed log information files 204a to 204d are not known, the compressed log information files 204a to 204d cannot be decompressed and the log information cannot be restored. Therefore, by storing the write destination and capacity of each compressed log information file 204a to 204d in the management information storage area 206, the boundary between each compressed log information file 204a to 204d can be specified.

CF 18 is a non-volatile memory, and is connected to the CPU 14 via the ICH 20. As will be described later, the CF 18 stores log information (uncompressed data) stored in the data area 202 of the RAM 16 and compressed log information (compressed data) stored in the compressed data area 204 when the power is shut off. Management information stored in the management information storage area 206 is stored. Since the CF 18 is a non-volatile memory, the stored data can be retained even after the external power supply is shut off. For this reason, an abnormality analysis or the like can be performed after the power is restored by using the log information saved in the CF 18 when the power is shut off.

Next, processing performed by the CPU 14 will be described with reference to FIGS. While the power supply to the servo controller 10 is normally performed, the CPU 14 executes the normal process shown in FIG. 3 at a predetermined processing cycle (for example, 250 μs). On the other hand, when a power OFF notice signal is input from the power monitoring circuit 12, the CPU 14 executes a power OFF notice process (interrupt process triggered by the power OFF notice signal) shown in FIG. Hereinafter, the normal process shown in FIG. 3 will be described.

As shown in FIG. 3, the CPU 14 first performs regular processing (S10). The periodic processing is processing for driving the servo motor (processing for servo control), and is always executed in each processing cycle. In the periodic process, the CPU 14 calculates a torque command value of the servo motor from the deviation between the current value of the servo motor and the target value, and performs a process of outputting the torque command value to the servo motor. The target value (for example, target position) of the servo motor is input from the host controller 2 to the servo controller 10. Further, the CPU 14 stores log information (uncompressed data) generated by performing the regular processing in the data area 202 of the RAM 14. Specifically, the generated log information (uncompressed data) is stored in the current write destination stored in the management information storage area 206. When the log information is stored, the current write destination stored in the management information storage area 206 is updated.

Next, the CPU 14 determines whether or not it is necessary to perform irregular processing (S12). Specifically, the CPU 14 determines whether or not irregular processing is necessary depending on whether or not it is necessary to communicate with the host control device 2. For example, when an instruction (target value or the like) is input from the host controller 2 or when the state (event) of the servo controller 10 is notified to the host controller 2, it is determined that it is necessary to perform irregular processing. To do. If it is not necessary to perform irregular processing (NO in S12), the process proceeds to S16. On the other hand, if it is necessary to perform irregular processing (YES in S12), the CPU 14 proceeds to S14 and performs irregular processing. Therefore, the irregular process of S14 is performed only when the specific condition of S12 is satisfied, and is not a process that is always executed. In the irregular processing, the CPU 14 receives an instruction (target value or the like) from the host controller 2 or transmits an event occurring in the servo controller 10 to the host controller 2. Note that log information generated by performing irregular processing is also stored in the data area 202 of the RAM 14. Further, when the log information is stored in the data area 202, the information (current write destination) stored in the management information storage area 206 is also updated accordingly.

Next, the CPU 14 determines whether or not there is a time for performing processing for compressing log information stored in the data area 202 (processing of S20 to S24 described later) in the processing cycle (S16). . That is, in the servo controller 10 of the present embodiment, the processing cycle is set short in order to increase the accuracy of the servo control, and the CPU 14 is allowed to perform only the regular processing (S10) and the irregular processing (S14). It is said. On the other hand, as described above, the irregular process is a process that is performed only under a specific condition, and is not a process that is always performed every processing cycle. Therefore, in this embodiment, processing for compressing log information stored in the data area 202 (processing of S20 to S24 described later) is performed in a processing cycle in which irregular processing is not performed. For this reason, in S16, the CPU 14 determines whether or not there is time to perform processing for compressing the log information (that is, whether or not irregular processing is being performed). If there is no time for performing processing for compressing the log information (NO in S16), S18 to S24 are skipped, and the processing in the processing cycle ends.

On the other hand, when there is time to perform processing for compressing the log information (YES in S16), the CPU 14 determines whether or not the log information stored in the data area 202 has reached the specified capacity (S18). ). As described above, in this embodiment, the log information stored in the data area 202 is compressed for each of the data storage areas 202a to 202d and stored in the compressed data area 204 as compressed log information files 204a to 204d. That is, when log information is stored in the entire data storage area 202a to 202d, the log information in that area is compressed. Therefore, the CPU 14 determines whether or not log information is stored in the entire data storage area (any one of 202a to 202d) that is currently being written. Specifically, the CPU 14 determines whether or not the log information has reached a specified capacity from the information of “current data write destination” stored in the management information storage area 206. For example, in the state shown in FIG. 2, the CPU 14 has written the log information in the data storage area 202c, and can determine from the current write destination information that the log information is not stored in the entire data storage area 202c. . For this reason, the CPU 14 determines that the log information has not reached the specified capacity. If the log information subject to compression processing has not reached the specified capacity (NO in S18), S20 to S24 are skipped, and the processing in the processing cycle ends.

On the other hand, when the log information to be compressed reaches the specified capacity (YES in S18), the CPU 14 compresses the log information (non-compressed data) to be compressed (S20). As a method for compressing log information, a known data compression method can be used. As a result, the log information (uncompressed data) stored in any of the data storage areas 202a to 202d is compressed into a compressed log information file.

Next, the CPU 14 stores the compressed log information file (any one of 204a to 204d) obtained by the compression process of S20 in the compressed data area 204 of the RAM 16 (S22). Next, the CPU 14 stores the write destination and capacity of the compressed log information file stored in S22 in the management information storage area 206 (S24). When S24 ends, the processing in the processing cycle ends.

Next, the power off notice process will be described with reference to FIG. As described above, the power-off notice process is started with the power-off notice signal from the power monitoring circuit 12 as a trigger. Specifically, when the power OFF notice signal output from the power monitoring circuit 12 is input to the CPU 14, the CPU 14 first stops the normal processing shown in FIG. 3, and then the power OFF shown in FIG. Execute the notice process.

In the power OFF notice process shown in FIG. 4, first, the CPU 14 calculates a power OFF time until the power is turned OFF (S30). The power supply OFF time can be calculated from, for example, a change in the voltage value of the external power supply detected by the power supply monitoring circuit 12. In this embodiment, the CPU 14 calculates the power OFF time. However, the host control device 2 may calculate the power OFF time and input the calculated power OFF time to the servo controller 10.

Next, the CPU 14 uses the power-off time calculated in S30 and the writing speed to the CF 18 to calculate the data capacity in which writing to the CF 18 is completed before the power is turned off (S32). Then, the CPU 14 selects data to be saved from the RAM 16 to the CF 18 so that the calculated data capacity is obtained. Specifically, among the data storage areas 202a to 202d of the data area 202, log information (uncompressed data) of the data storage area into which log information was written when the power-off notice process was started, and the compressed data area The compressed log information files 204a to 204d (compressed data) stored in 204 and the data stored in the management information storage area 206 (information on the write destination and capacity of the compressed log information file) are selected. Here, since the log information in the data area 202 and the data in the management information storage area 206 are always selected, the CPU 14 selects the latest compressed log information file saved in the CF 18 based on the power OFF time and the writing speed to the CF 18. Select in order. If it is determined that there is sufficient time from the power OFF time and the writing speed to the CF 18, the CPU 14 selects all the compressed log information files 204a to 204d stored in the compressed data area 204. For example, when the power off notice process is started in the state shown in FIG. 2, the CPU 14 stores the uncompressed data 3 (hatched portion) stored in the data storage area 202 c and the compressed log of the compressed data area 204.

Information files

204a, 204b, 204d (hatched portions) and data in the management information storage area 206 are selected. As a result, it is possible to prevent the unauthorized process from remaining in the CF 18 by interrupting the power-off notice process during saving of data to the CF 18.

Next, the CPU 14 reads the data selected in S32 among the data stored in the RAM 16 (that is, the data saved in the CF 18) (S34). Then, the CPU 14 saves the data read in S34 to the CF 18 via the ICH 20 (S36). There is a limit to the amount of data that can be read from the RAM 16 and written to the CF 18 at a time. Therefore, the CPU 14 determines whether all of the data selected in S32 (data saved in the CF 18) has been saved in the CF 18 (S38). If all the data selected in S32 has not been saved to the CF 18 (NO in S38), the CPU 14 returns to S34 and executes the processing from S34. On the other hand, if all the data selected in S32 has been saved to the CF 18 (YES in S38), the CPU 14 ends the power-off notice process. As a result, all of the data selected in S32 is saved in the CF18. Since the CF 18 is a non-volatile memory, the data saved in the CF 18 is retained even while the power supply to the servo controller 10 is shut off. For this reason, by analyzing the log information saved in the CF 18, it is possible to analyze the situation when the power is shut off.

As is apparent from the above description, in the servo controller 10 of this embodiment, in the normal process (FIG. 3), the log information stored in the RAM 16 is compressed to store the compressed log information files 204a to 204d. Creating. For this reason, in the power-off notification process, the latest log information (uncompressed data) stored in the data storage area, the compressed log information file stored in the compressed data area 204, and the management information storage area 206 You only need to save the data. Since the volume of data to be saved is reduced, the power-off notification process can be performed in a short time. In addition, since a part of the data saved in the CF 18 is encrypted by compression, the security can be improved.

In addition, since the power off notice process can be performed in a short time, the CF 18 that is a low access speed can be used for the nonvolatile memory for saving data. By using CF18, the manufacturing cost of the servo controller 10 can be reduced. Further, since the data is saved by the CF 18 of the non-volatile memory, a backup power source becomes unnecessary, and the substrate size of the servo controller 10 can be reduced.

Further, in the servo controller 10 of the present embodiment, the amount of data saved in the CF 18 is adjusted according to the predicted time until the power is turned off. If the power to the servo controller 10 is cut off during the power-off notice process, an illegal file is created in the CF 18 and the illegal file remains. On the other hand, in the present embodiment, the amount of data to be saved is adjusted according to the predicted time until the power is turned off, so that it is possible to prevent an illegal file from occurring.

Further, in the servo controller 10 according to the present embodiment, a process of compressing log information stored in the data area 202 of the RAM 16 is performed by using the idle time due to not performing the irregular process (S14 in FIG. 3). . For this reason, even if the process of compressing the log information is executed in a regular processing cycle, the compression process does not affect the control of the servo motor.

As mentioned above, although the Example which concerns on the technique disclosed by this specification was described in detail, these are only illustrations and do not limit a claim. The technology described in the claims includes various modifications and changes of the specific examples illustrated above.

(1) For example, in the above embodiment, there is one combination of the data area and the compressed data area corresponding to the data area, but the combination of the data area and the compressed data area corresponding to the data area It is good also as multiple sets. That is, a plurality of data areas (each data area is configured as a ring buffer having a plurality of data storage areas) and a plurality of compressed data areas corresponding to the plurality of data areas may be provided in the RAM. In compression processing, an appropriate compression rate usually varies depending on the contents of uncompressed data (log information). When there is one combination of the data area and the corresponding compressed data area, all data must be compressed in accordance with the uncompressed data (log information) having the lowest compression rate. On the other hand, if the combination of the data area and the compressed data area is a plurality of sets, a plurality of compression ratios are set, the uncompressed data (log information) is classified for each compression reduction ratio, and the data area and the A combination of compressed data areas can be assigned. Thereby, the compression rate of uncompressed data (log information) can be increased, and the data saving time can be further reduced.

(2) In the above embodiment, the CF 18 is used as the nonvolatile memory for saving the log information. However, the log information may be saved by using an HDD instead of the CF 18. When adopting such a configuration, the HDD may have a data save dedicated area. When data is saved using the HDD, an illegal file may be generated if the power is turned off during the data saving process to the HDD. As a result, an illegal file may remain in the HDD, and the capacity of the HDD may be compressed. Therefore, when data is saved using the HDD, it is preferable to determine whether an illegal file exists in the HDD and to delete the illegal file from the HDD. For example, it is possible to determine the presence of an illegal file by the method described below, and to delete the illegal file if it exists. That is, when the servo controller 10 is started up, the used capacity of the HDD before and after data saving is compared. If the difference in the used capacity of the HDD exceeds the capacity of the data before compression, it is determined that an invalid file is stored in the data saving dedicated area. If it is determined that an illegal file is stored in the data save dedicated area, the HDD data save dedicated area is formatted and the illegal file is deleted from the HDD.

(3) Further, in the above embodiment, only the log information is compressed in the normal processing. However, if there is a margin in the processing time, the log information compressed in the normal processing is stored in the nonvolatile memory. You may perform the process to do.

(4) In the above embodiment, the regular processing, irregular processing, and compression processing are performed by a single program, but may be performed independently by different programs. In that case, the CPU includes a periodic processing program for executing periodic processing, an irregular processing program for executing irregular processing, a compression processing program for executing compression processing, a program manager for assigning processing time to each processing program, Is provided. The priority of the processing time assigned by the program manager is set in the order of the periodic processing program, the irregular processing program, and the compression processing program. With this configuration, the program manager assigns processing time to the periodic processing program with the highest priority. For this reason, the periodic processing program is guaranteed to complete processing every processing cycle. The irregular processing program is executed when a specific condition is satisfied (irregular). When the specific condition is satisfied, the program manager gives priority to the allocation of the processing time to the irregular processing program, and therefore does not allocate the processing time to the compression processing program. On the other hand, when the specific condition is not satisfied, the program manager does not allocate processing time to the irregular processing program. For this reason, there is a vacancy in the processing time of the CPU. Therefore, the program manager assigns a processing time to the compression processing program, and the compression processing program is executed. Even with such a configuration, processing equivalent to that in the above embodiment can be realized.

The technical elements described in the present specification or drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology exemplified in this specification or the drawings can achieve a plurality of objects at the same time, and has technical usefulness by achieving one of the objects.

2. High-level control device 10 Servo controller 12 Power supply monitoring circuit 14 CPU
16. RAM
18. CF
20 ・・ ICH
202 Data area 202a-d Data storage area 204 Compression data area 204a-d Compression data storage area 206 Management information storage area

Claims

A control device;
Non-volatile memory;
Volatile memory, and
The controller is
Processing execution means for executing a preset process for each processing cycle;
Data compression means for compressing uncompressed data stored in the volatile memory by executing processing by the processing execution means in the processing cycle;
When detecting a power OFF notice signal input from the outside, the uncompressed data stored in the volatile memory and not compressed by the data compression means and the compressed data compressed by the data compression means are A controller for storing data in the nonvolatile memory.
The controller according to claim 1, wherein the data compression means compresses the uncompressed data stored in the volatile memory in a free time during which the process execution means does not execute the process in the processing cycle.
The process execution means executes a periodic process periodically performed in the process cycle and an irregular process performed when a specific condition is satisfied,
The controller according to claim 2, wherein the data compression unit compresses uncompressed data by using a free time due to the irregular processing not being executed.
The controller is
A calculation means for calculating a power-off time until the power is turned off when the power-off notice signal is detected;
The adjusting unit according to claim 1, further comprising an adjusting unit that adjusts a data amount of the compressed data saved in the nonvolatile memory by the data saving unit according to a power OFF time calculated by the calculating unit. The controller according to any one of the above.
The volatile memory stores a plurality of compressed data storage areas for storing compressed data compressed by the data compression means, and management information for specifying where in the plurality of compressed data storage areas the compressed data is stored. Management information storage area,
When the non-compressed data stored in the volatile memory is compressed, the data compression means stores the compressed data in any one of the plurality of compressed data storage areas, and manages management information of the compressed data. The controller according to any one of claims 1 to 4, which is stored in an information storage area.