Classifications

• • G—PHYSICS
  • G11—INFORMATION STORAGE
  • G11C—STATIC STORES
  • G11C16/00—Erasable programmable read-only memories
  • G11C16/02—Erasable programmable read-only memories electrically programmable
  • G11C16/06—Auxiliary circuits, e.g. for writing into memory
  • G11C16/10—Programming or data input circuits
  • G11C16/14—Circuits for erasing electrically, e.g. erase voltage switching circuits
  • G11C16/16—Circuits for erasing electrically, e.g. erase voltage switching circuits for erasing blocks, e.g. arrays, words, groups

Definitions

• the present invention relates to an information ⁇ processing apparatus and a nonvolatile semiconductor memory drive.
• Jpn. Pat. Appln. KOKAI Publication No. 2006-196135 discloses a data storage device having a scramble/descramble function.
• This data storage device includes transmission/reception means, scrambler means, a hard disk, descrambler means, a memory, and initial value varying means.
• the transmission/reception means receives information from outside and transmits information in the data storage device to the outside.
• the scrambler means scrambles the information which the transmission/reception means receives from the outside..
• An output signal from the scrambler means is recorded on the hard disk.
• the descrambler means descrambles the signal that is read out of the hard disk.
• the memory outputs initial values to the scrambler means and the descrambler means.
• the initial value varying means varies the initial values when the data recorded on the hard disk is erased.
• the initial value varying means In this data storage device, if data erase of the hard disk is instructed via the transmission/reception means, the initial value varying means generates new initial values for the scrambler means and descrambler means. Data, which is newly recorded, is subjected to a scramble process and a descramble process on the basis of the new initial values.
• the data, which has already been recorded on the hard disk before the variation of the initial values is descrambled on the basis of initial values which are different from the initial values before the variation, and is then reproduced. Accordingly, since the data, which has already been recorded on the hard disk before the variation of the initial values, is descrambled on the basis of initial values which are entirely different from the initial values at the time of data recording, data with different values is read out. Consequently, since the data, which is stored before the change of the initial values, cannot normally be read out, the change of initial values is virtual erase of the hard disk. Thus, the data can virtually be erased instantaneously, without erase data being overwritten on the hard disk of the data storage device.
• the work time for re-use or discard of the hard disk can remarkably be reduced.
• the conventional data storage device although decoding of scrambled data is difficult, the take-out of the scrambled data can easily be performed. Thus, it is not possible to deny that the scrambled data may be decoded with the progress of decoding technologies.
• the object of the present invention is to provide an information processing apparatus and a nonvolatile semiconductor memory drive, which can surely execute erase of written information and can prevent leak of information .
• an information processing apparatus comprising: an information processing apparatus main body; and a nonvolatile semiconductor memory drive which is accommodated in the information processing apparatus main body, the nonvolatile semiconductor memory drive including a nonvolatile semiconductor memory having a memory area including a plurality of blocks, and control means, the control means having a first erase mode in which an address management table, which is indicative of a correspondency between logical block addresses and physical addresses of the nonvolatile semiconductor memory, is initialized to set the memory area in a state in which no user data is written, a second erase mode in which the address management table is initialized to set the memory area in a state in which no user data is written, and the blocks, other than a defective block, which are included in the memory area, are erased, and a third erase mode in which the address management table is initialized to set the memory area in a state in which no user data is written, and the blocks, including the defective block, which are included in the memory area, are erased, and the control means selective
• This information processing apparatus can surely execute erase of written information and can prevent leak of information.
• FIG. 1 is a perspective view showing the external appearance of an information processing apparatus according to an embodiment of the present invention
• FIG. 2 is a block diagram which schematically shows the structure of the information processing apparatus according to the embodiment
• FIG. 3 is a block diagram which schematically shows the structure of an SSD that is provided in the information processing apparatus according to the embodiment
• FIG. 4 schematically shows the memory capacities and memory areas of the SSD shown in FIG. 3;
• FIG. 5 schematically shows the structure of a NAND memory which is provided in the SSD shown in FIG. 3;
• FIG. 6 is a diagram for explaining three kinds of erase methods, which are executable by the SSD shown in FIG. 3;
• FIG. 7 is a flow chart illustrating an example of the procedure of pseudo-erase, which is executed by the SSD shown in FIG. 3;
• FIG. 8 is a flow chart illustrating an example of the procedure of normal erase, which is executed by the SSD shown in FIG. 3;
• FIG. 9 is a flow chart illustrating an example of the procedure of expansive erase, which is executed by the SSD shown in FIG. 3.
• FIG. 1 is a perspective view showing the external appearance of an information processing apparatus according to an embodiment of the present invention.
• This information processing apparatus 1 as shown in FIG. 1, is composed of a main body 2 and a display unit 3 which is attached to the main body 2.
• the main body 2 has a box-shaped casing 4.
• the casing 4 includes an upper wall 4a, a peripheral wall 4b and a lower wall 4c.
• the upper wall 4a of the casing 4 includes a front part 40, a central part 41 and a back part 42 in the named order from the side close to a user who operates the information processing apparatus 1.
• the lower wall 4c is opposed to an installation surface on which the information processing apparatus 1 is disposed.
• the peripheral wall 4b includes a front wall 4ba, a rear wall 4bb and left and right side walls 4bc and 4bd.
• the front part 40 includes a touch pad 20 which is a pointing device, a palm rest 21, and a light-emitting diode (LED) 22 which is turned on in association with the operation of respective parts of the information processing apparatus 1.
• the central part 41 includes a keyboard mounting part 23 to which a keyboard 23a, which can input character information, etc., is attached.
• the back part 42 includes a battery pack 24 which is detachably attached.
• a power switch 25 for powering on the information processing apparatus 1 is provided on the right side of the battery pack 24.
• a pair of hinge portions 26a and 26b, which rotatably support the display unit 3, are provided on the left and right sides of the battery pack 24.
• An exhaust port (not shown) for exhausting the wind to the outside from the inside of the casing 4, is provided on the left side wall 4bc of the casing 4.
• an ODD (Optical Disc Drive) 27 which can read and write data on an optical storage medium such as a DVD, and a card slot 28, in/from which various cards can be inserted/taken out, are disposed on the right side wall 4bd.
• the casing 4 is formed of a casing cover including a part of the peripheral wall 4b and the upper wall 4a, and a casing base including a part of the peripheral wall 4b and the lower wall Ac.
• the casing cover is detachably coupled to the casing base, and an accommodation space is formed between the casing cover and the casing base.
• This accommodation space accommodates, for instance, an SSD (Solid State Drive) 10 functioning as a nonvolatile semiconductor memory drive.
• SSD Solid State Drive
• the display unit 3 includes a display housing 30 having an opening portion 30a, and a display device 31 which is composed of, e.g. an LCD which can display an image on a display screen 31a.
• the display device 31 is accommodated in the display housing 30, and the display screen 31a is exposed to the outside of the display housing 30 through the opening portion 30a.
• FIG. 2 is a block diagram which schematically shows the system configuration of the information processing apparatus 1.
• EC embedded Controller
• flash memory 112 which stores a BIOS (Basic Input Output System) 112a, a south bridge 113, a north bridge 114, a CPU (Central Processing Unit) 115, a GPU (Graphic Processing Unit) 116 and a main memory 117, in addition to the above- described SSD 10, expansion module 12, fan 13, touch pad 20, LED 22, keyboard 23a, power switch 25, ODD 27, card slot 28 and display device 31.
• BIOS Basic Input Output System
• CPU Central Processing Unit
• GPU Graphic Processing Unit
• the EC (Embedded Controller) 111 is a built-in system which controls the respective parts.
• the north bridge 114 is an LSI which controls connection between the CPU 115, GPU 116, main memory 117 and various buses.
• the CPU 15 is a processor which performs arithmetic processing of various signals, and executes an operating system and various application programs, which are loaded from the SSD 10 into the main memory 117.
• the GPU 116 is a display controller which executes display control by performing arithmetic processing of a video signal.
• the expansion module 12 includes an expansion circuit board, a card socket which is provided on the expansion circuit board, and an expansion module board which is inserted in the card socket.
• the card socket supports, e.g. the Mini-PCI standard.
• Examples of the expansion module board include a 3G (3rd Generation) module, a TV tuner, a GPS module, and a Wimax (trademark) module.
• the fan 13 is a cooling unit which cools the inside of the casing 4 on the basis of air feeding, and exhausts the air in the casing 4 to the outside as the wind via the exhaust port (not shown) .
• the EC 111, flash memory 112, south bridge 113, north bridge 114, CPU 115, GPU 116 and main memory 117 are electronic components which are mounted on the main circuit board. ⁇ Structure of SSD>
• FIG. 3 is a block diagram which schematically shows the structure of the SDD that is applied to the information processing apparatus according to the embodiment.
• the SSD 10 is a nonvolatile semiconductor memory drive which, in place of a hard disk, is used as an external storage device of the information processing apparatus 1.
• FIG. 3 substantially comprises a connector 102, a control unit 103, NAND memories (NAND flash EEPROMs) 104A to 104H, a DRAM (memory) 105, and a power supply circuit 106.
• the SSD 10 is the external storage device which stores data and programs, and the storage content of which is not lost even if no power is supplied.
• the SSD 10 is a drive which, unlike a hard disk drive, does not have a driving mechanism of a magnetic disk, a head, etc., but the SSD 10 can store programs, such as the OS (Operating System) , and data which is created by the user or created on the basis of software, in memory areas of a NAND memory, which is a nonvolatile semiconductor memory, for a long time in a readable/writable manner, and can operate as a boot drive of the information processing apparatus 1.
• programs such as the OS (Operating System)
• data which is created by the user or created on the basis of software
• the control unit 103 is connected to the connector 102, eight NAND memories 104A to 104H, DRAM 105 and power supply circuit 106. In addition, the control unit 103 is connected to the host apparatus 8 via the connector 102, and is connected, where necessary, to an external apparatus 9.
• a power supply 7 is the battery pack 24 or an AC adapter (not shown) . For example, a power of DC 3.3V is supplied to the power supply circuit 106 via the connector 102. In addition, the power supply 7 supplies power to the entirety of the information processing apparatus 1.
• the host apparatus 8 is the information processing apparatus main body 2 (the main circuit board of the main body 2) .
• the south bridge 113 which is mounted on the main circuit board, is connected to the control unit 103 via the connector 102. Data transmission/reception is executed between the south bridge 113 and control unit 103, for example, on the basis of the serial ATA standard.
• the external apparatus 9 is an information processing apparatus which is different from the information processing apparatus 1.
• the external apparatus 9 is connected to the control unit 103 of the SSD 10 which is removed from the information processing apparatus 1, for example, on the basis of the RS-232C standard, and the external apparatus 9 has a function of reading out data which is stored in the NAND memories 104A to 104H.
• the board, on which the SSD 10 is mounted has the same outside size as an HDD (Hard Disk Drive) of, e.g. 1.8-inch type or 2.5-inch type. In the present embodiment, this board has the same outside size as the 1.8-inch type HDD.
• HDD Hard Disk Drive
• the control unit 103 controls data read/write on the NAND memories 104A to 104H. Specifically, in accordance with a request (read command, write command, etc.) from the information processing apparatus main body 2 that functions as the host apparatus 8, the control unit 103 controls the execution of data read/write on the NAND memories 104A to 104H.
• Each NAND memory has a plurality of sectors.
• the control of execution of data read/write in each sector of the NAND memory, 104A to 104H, is executed in units of a predetermined number of sectors, which are called "cluster".
• the data transfer speed is, for example, 100 MB/Sec at a data read and 40 MB/Sec at a data write .
• Each of the NAND memories 104A to 104H is a nonvolatile semiconductor memory having a memory capacity of, e.g. 16 GB.
• 104A to 104H is composed of, e.g. an MLC (Multi-Level CeIl)-NAND memory (multilevel NAND memory) in which 2 bits can be recorded in one memory cell.
• MLC-NAND memory has such features that the allowable number of rewrites is smaller than an SLC (Single-Level CeIl)- NAND memory, but the memory capacity can be increased more easily than the SLC (Single-Level CeIl)-NAND memory.
• the DRAM 105 is a buffer which temporarily stores data when data read/write is executed on the NAND memory, 104A to 104H, by the control of the control unit 103.
• the DRAM 105 functions as a write cache which temporarily stores write data from the information processing apparatus main body 2 that functions as the host apparatus 8.
• the connector 102 has a shape based on, e.g. the serial ATA standard.
• the control unit 103 and power supply circuit 106 may be connected to the host apparatus 8 and power supply 7 via different connectors.
• the power supply circuit 106 converts DC 3.3V, which is supplied from the power supply 7, to, e.g. DC 1.8V and 1.2V, and supplies these three kinds of voltages to the respective parts in accordance with the driving voltages of the respective parts of the SSD 10.
• FIG. 4 schematically shows the memory capacities and memory areas of the SSD 10.
• the control unit 103 of the SSD 10 manages seven kinds of memory capacities 104a to 104g, which are shown in FIG. 4.
• the memory capacity 104a is NAND Capacity, and is a maximum memory capacity using the memory areas of all NAND memories 104A to 104H. Specifically, the memory capacity 104a is the sum of the physical memory capacities of the NAND memories 104A to 104H. For example, if the memory capacity of each of the NAND memories 104A to 104H is 16 GB, the memory capacity 104a is 128 GB.
• the memory capacity 104a i.e. the NAND Capacity, is given by, e.g. NAND structure information of a manufacture information write command of a UART (Universal Asynchronous Receiver Transmitter) .
• the memory capacity 104b is Max Logical Capacity, and is a maximum memory capacity that is accessible by a logical block address (LBA) .
• LBA logical block address
• the memory capacity 104c is a S. M. A. R. T. log area start LBA, and is provided in order to divide the memory capacity 104b and the memory capacity 104d which will be described below.
• the S. M. A. R. T. log area start LBA indicates a first LBA of the memory area which stores log data.
• the memory capacity 104d is Vender Native Capacity, and is a maximum memory capacity which is given as a user use area.
• the memory capacity 104d is given by, e.g. initial Identify Device data of an ATA specific command.
• the memory capacity 104d is determined by the manufacturer (Vender) at the time of design of the SSD 10 on the basis of the IDEMA (The International Disk Drive Equipment and Materials Association) standard, and is expressed by the following equation:
• the memory capacity 104e is OEM Native Capacity, and is a memory capacity which is determined at the time of manufacture by a request of an OEM (Original Equipment Manufacturer) .
• the memory capacity 104e is given by, e.g. unique information write of an ATA specific command.
• the memory capacity 104e is a value which is returned by a Device Configuration Identify command when Device Configuration Overlay Feature Set is supported.
• the memory capacity 104f is Native Capacity, and its initial value is equal to the memory capacity 104e. This value can be varied by a Device Configuration Set command when Feature Set is supported. In addition, the memory capacity 104f is a value which is returned by a Read Native Max Address (EXT) command.
• EXT Read Native Max Address
• the memory capacity 104g is Current Capacity and is a memory capacity during use by the user, and the initial value is equal to the memory capacity 104f.
• This value can be varied by a SET Max Address command. This value is returned by Word 61:60, and Word 103:100 of an Identify Device command.
• the memory areas of the SSD 10 are present between the memory capacities 104a to 104g.
• the memory area (management area) between the memory capacities 104a and 104b stores management data 107a for operating the SSD 10, and an address conversion table (logical/physical table) 108a.
• the address conversion table (logical/physical table) 108a is an address management table for converting the logical block address LBA to a physical address corresponding to a sector which is a memory unit of the NAND memory, 104A to 104H.
• the address conversion table (logical/physical table) 108a indicates the correspondency between the logical block addresses LBAs and the physical addresses of the NAND memory, 104A to 104H.
• the correspondency between the logical block address LBA and the physical address of the NAND memory, 104A to 104H, is managed in units of a cluster.
• Each cluster is composed of a predetermined number of sectors, as described above.
• Each of the NAND memories 104A to 104H has a plurality of sectors.
• Each of the management data 107a and logical/physical table 108a is data which is recorded in fixed areas in the NAND memories 104A to 104H.
• the LBA is not allocated to each of the management data 107a and logical/physical table 108a.
• each of the management data 107a and logical/physical table 108a cannot be accessed, with the LBA being used as a key.
• the control unit 103 has a fixed access path for accessing each of the management data 107a and logical/physical table 108a, and executes access to each of the management data 107a and logical/physical table 108a via the fixed access path.
• the memory area between the memory capacity 104b and memory capacity 104c stores S. M. A. R. T. (Self- Monitoring Analysis and Reporting Technology) log data 107b.
• the S. M. A. R. T. log data 107b is, for instance, statistical information such as temperature information.
• the LBAs, which are allocated to the S. M. A. R. T. log data 107b, are locally used in order for firmware, which is executed in the control unit 103, to access the S. M. A. R. T. log data 107b.
• the firmware which is executed in the control unit 103, can access the S. M. A. R. T. log data 107b by using the LBA as a key.
• the host apparatus 8 cannot access the S. M. A. R. T. log data 107b by an ordinary read or write command.
• a non-use memory area having a memory capacity of, e.g. 2 MB is set in the memory area between the memory capacities 104c and 104d.
• the reason for this is that the minimum memory unit of the LBA is 8 sectors, which is a memory unit corresponding to 4 KB (a large memory unit is 1 MB) , whereas the actual minimum recording unit of data is 1 sector as a matter of course, and thus the S. M. A. R. T. log data 107b and the data recorded in the memory area equal to or lower than the memory- capacity 104d are independently handled by providing an empty memory area with a memory capacity of 1 MB or more between the memory capacities 104c and 104d.
• the memory area between the memory capacities 104d and 104e is a non-use area, and the memory capacity 104d and 104e have the same value except for a particular case.
• the memory area between the memory capacities 104e and 104f is a memory area which is used by the OEM. As described above, the unique information 107e, which is determined by the request of the OEM, is written in this memory area.
• the memory area between the memory capacities 104f and 104g is a memory area which is used by the OEM or the user. Data write is executed in this memory area by the setting of the OEM or user.
• the memory area of the memory capacity 104g is a memory area which is used by the user, and data write is executed in this memory area by the setting of the user.
• the memory capacities 104a to 104g satisfy a relationship which is expressed by the following formula: memory capacity 104a > memory capacity 104b > memory capacity 104c > memory capacity 104d ⁇ memory capacity 104e ⁇ memory capacity 104f ⁇ memory capacity 104g.
• FIG. 5 schematically shows the structure of the NAND memory which is used in the present embodiment.
• FIG. 6 is a diagram for explaining three kinds of erase methods, which are used in the embodiment. Since the NAND memories 104A to 104H have the same function and structure, a description is given of the NAND memory 104A.
• clusters (memory units) 1041 and sectors 1042 indicate cluster numbers and sector numbers.
• Free 1070 schematically represents a set (first memory area) of data-writable blocks 1040
• Active 1071 schematically represents a set (second memory area) of data-written blocks 1040a in which data write is already executed
• Bad Block 1072 schematically represents a set (third memory area) of defective blocks 1043 in which error correction, which will be described later, fails to be executed.
• the Free 1070, Active 1071 and Bad Block 1072 are stored in the management data 107a as parameters which are indicative of the states of the respective blocks 1040. Hatching in FIG. 6 indicates that data is stored.
• the NAND memory 104A is composed of a plurality of blocks 1040. Each block 1040 is composed of 1024 clusters 1041. Each cluster 1041 is composed of eight sectors 1042.
• the control unit 103 executes read from a predetermined number (e.g. 8) of sectors 1042, which constitute the cluster 1041, on the basis of the management data 107a, and temporarily stores the data of these sectors in the DRAM 105.
• the control unit 103 executes, on the DRAM 105, write of write data in the cluster from which data read has been executed, and writes the cluster, in which the write data has been written, into the corresponding cluster 1041 of the NAND memory from the DRAM 105.
• the defective block 1043 which is indicated by hatching, is a block in which an error occurs at a time of data write or data read.
• the defective block 1043 indicates a block 1040 in the SSD 10, in which erase or an error has occurred.
• the control unit 103 controls data write and data read on memory areas (NAND memory areas) of the NAND memories 104A to 104H by using the logical/physical table 108a.
• the control unit 103 has a security erase function for erasing all user data which are stored in the NAND memory areas.
• the control unit 103 has a pseudo-erase mode, a normal erase mode and an expansive erase mode as erase operation modes for erasing all user data which are stored in the NAND memory areas.
• the control unit 103 selectively uses the pseudo-erase mode, normal erase mode and expansive erase mode, thereby executing an erase operation on the NAND memory areas.
• the pseudo-erase mode is a first erase mode in which the logical/physical table 108a is initialized and the NAND memory area including plural blocks 1040 is set in a state in which user data is not written.
• the process of initializing the logical/physical table 108a is a process of setting the logical/physical table 108a in a state in which the physical address corresponding to each logical block address LBA is not written in the logical/physical table 108a.
• the control unit 103 executes, for example, a process of deleting, from the logical/physical table 108a, the physical address corresponding to each LBA, or a process of setting, with respect to each LBA stored in the logical/physical table 108a, a flag which indicates that the memory area corresponding to the LBA is in a non-written state.
• a process of deleting from the logical/physical table 108a, the physical address corresponding to each LBA, or a process of setting, with respect to each LBA stored in the logical/physical table 108a, a flag which indicates that the memory area corresponding to the LBA is in a non-written state.
• a process of actually erasing each block or a process of writing zero data in each block is not executed. Instead, the logical/physical table 108a is initialized. Thereby, user data can be erased more quickly than in the case of executing, e.g. a process of writing zero data in all blocks.
• control unit 103 When the control unit 103 receives a command (specific command) for designating the pseudo-erase mode from the host apparatus 8, the control unit 1.03 initializes the logical/physical table 108a and sets each block in a state in which user data is not written. However, the physical address corresponding to S. M. A. R. T. log data is not deleted from the logical/physical table 108a.
• the control unit 103 determines whether the memory area designated by the LBA included in the read command is in the non-written state, by referring to the logical/physical table 108a. If the memory area designated by the LBA is in the non-written state, the control unit 103 sends to the host apparatus 8 a predetermined value (e.g.
• the normal erase mode is a second erase mode in which the logical/physical table 108a is initialized to set the NAND memory area including plural blocks 1040 in a state in which no user data is written, and the blocks, other than defective blocks, included in the NAND memory area, are erased.
• the process of erasing free blocks (block erase process) is executed in addition to the process of initializing the logical/physical table 108a so that the blocks, in which user data is written, become free blocks.
• defective blocks are excluded from the objects of the erase process.
• the defective block is a block in which an error occurs at a time of data write or data read.
• control unit 103 Upon receiving a command designating the normal erase mode from the host apparatus 8, the control unit 103 initializes the logical/physical table 108a, and sets each block, which stores data (user data) other than management data (including S. M. A. R. T. log data), in a state (free block) in which no user data is written. Then, the control unit 103 executes the block erase process on all free blocks.
• the expansive erase mode is an erase mode in which each defective block is erased, in addition to the erase operation of the normal erase mode.
• the expansive erase mode is a third erase mode in which the logical/physical table 108a is initialized to set the NAND memory area in the state in which no user data is written, and the blocks including defective blocks, which are included in the NAND memory area, are erased.
• the control unit 103 Upon receiving a command designating the expansive erase mode from the host apparatus 8, the control unit 103 initializes the logical/physical table 108a, and sets each block, which stores data (user data) other than management data (including S. M. A. R. T. log data), in a state (free block) in which no user data is written. Then, the control unit 103 executes the block erase process on all free blocks and defective blocks.
• the EC 111 detects the pressing of the power switch 25 and starts supplying power from the power supply 7 to the respective parts of the information processing apparatus 1.
• the EC 111 boots up the information processing apparatus 1 on the basis of the BIOS 112a.
• the user performs an operation on the information processing apparatus 1 by using the touch pad 20 and keyboard 23a, while viewing the display screen 31a of the display device 31.
• the information processing apparatus 1 Upon accepting the operation by the user, the information processing apparatus 1 performs a predetermined operation according to the operation by the user. For example, in the case where the CPU 15 of the information processing apparatus 1 has accepted the operation for displaying the data, which is stored in the SSD 10, on the display device 31, the CPU 115 sends to the SSD 10 a read command for instructing data readout from the SSD 10. Then, the control unit 103 of the SSD 10 executes data read from the NAND memories 104A to 104H, and sends the read data to the GPU 116 via the south bridge 113 and north bridge 114. The GPU 116 displays the data as an image on the display device 31. ⁇ Pseudo-Erase>
• FIG. 7 is a flow chart illustrating an example of the pseudo-erase mode as the first erase mode which is used in the present embodiment.
• the user executes, through the touch pad 20 and keyboard 23a, an operation on an image which is displayed on the display screen 31a of the display device 31 by, e.g. the operation of an application, and instructs erase of, e.g. a document stored in the SSD 10 by using the touch pad 20 and keyboard 23a (step Sl) .
• the CPU 115 instructs erase of data (predetermined information) of the document, the erase of which has been instructed to the SSD 10.
• control unit 115 Upon receiving the instruction from the CPU 115 via the connector the connector 102, the control unit
• the control unit 103 of the SSD 10 refers to the management data 107a of each NAND memory, 104A to 104H, and searches for the NAND memory in which the data of the document is stored. Based on the management data 107a, the control unit 103 determines, for example, whether the data of the document that is the object of erase is stored in a sector included in a block 1044 (e.g. sector 1042a included in the block 1040 shown in FIG. 5) which is in the state of Active 1071 shown in FIG. 6.
• control unit 103 updates the state of the management data 107a, which corresponds to this block 1044, from Active 1071 to Free 1070 (step S2) . It is assumed that the block 1044 stores only the data of the document that is the object of erase.
• the above-described erase method is called the pseudo-erase 1OA, and the state of the management data 107a of the data of the document, which is the object of erase, is simply updated. Since the data of the document itself is not erased, this erase method can quickly be executed. In this erase method, for example, in the case of discarding the SSD 10 which stores data with a high security level, since the data itself remains in the SSD 10, it is possible that the data may be read out.
• the pseudo-erase 1OA has been applied to the erase of a specified one block.
• the pseudo-erase 1OA is applicable to all blocks in which data (user data) other than the management data is written.
• the control unit 103 receives a command (specific command) designating the pseudo-erase mode from the CPU 115, the control unit 103 initializes the logical/physical table 108a and sets each block (each block in the active state) , in which user data is written, in the state (free block) in which user data is not written.
• FIG. 8 is a flow chart illustrating the normal erase as the second erase according to the present embodiment. Referring to the flow chart of FIG. 8, the method of normal erase 1OB is described. In the description below, the operation common to that of the pseudo-erase 1OA is omitted.
• step S3 when the erase of a document is instructed by the user (step S3) , for example, if data of the document that is the object of erase is stored in a sector (written sector) 1042a of a block 1045 that is in the state of Active 1071, as shown in FIG. 6, the control unit 103, on the basis of the management data 17a, erases the data stored in the block 1045 by executing block erase of the block 1045, and updates the state of the management data 107a corresponding to the block 1045 from Active 1071 to Free 1070 (step S4) . It is assumed that the block 1045 stores only the data of the document that is the object of erase.
• the above-described erase method is called the normal erase 1OB, and erase of the data of the document that is the object of erase is executed, and the management data 107a is updated.
• this normal erase 1OB for example, in the case of discarding the SSD 10 which stores data with a high security level, more exact erase than the pseudo-erase 1OA can be executed.
• complete erase which disables read-out of data with a high security level, is executed.
• the normal erase 1OB has been applied to erase of one specified block.
• the normal erase 1OB is applicable to all blocks in which data (user data) other than the management data is written.
• the control unit 103 receives a command designating the normal erase mode from the CPU 115, the control unit 103 initializes the logical/physical table 108a and sets each block (each block in the active state) , in which user data is written, in the state (free block) in which user data is not written. Thereafter, the control unit 103 erases, by block erase, the blocks, other than defective blocks, which are included in the NAND memory area, that is, all free blocks.
• FIG. 9 is a flow chart illustrating the expansive erase as the third erase.
• the expansive erase 1OC erase of all data (user data) of the SSD 10 is executed. For example, assume the case in which an optical disc, which stores the operating system that is necessary for booting the information processing apparatus 1, is inserted in the ODD 27, the information processing apparatus 1 is booted from the optical disc, and an application which can execute the expansive erase 1OC of the SSD 10 is started.
• the user instructs the expansive erase 1OC by using the touch pad 20 and keyboard 23a, while viewing items of erase which are displayed on the display screen 31a (step S5) , and the CPU 115 instructs the SSD 10 to execute the expansive erase 1OC.
• the control unit 103 executes erase of all data stored in the Free 1070, Active 1071 and Bad Block 1072, and executes update of the management data 107a (step S6) .
• the update of the management data 107a means update of the block 1043 and block 1040 from the states of Active 1071 and Bad Block 1072 to the state of Free 1070.
• the above-described erase method is called the expansive erase 1OC. Since the expansive erase 1OC covers the erase of the Bad Block 1072, more exact data erase can be executed than the other erase methods.
• the expansive erase 1OC is suited, for example, to the case of discarding the SSD 10 which stores data with a high security level.
• the expansive erase 1OC may be executed not by the above-described start of the application stored in the optical disc, but by, e.g. a command operation.
• step S6 for example, the following process is executed. Specifically, upon receiving a command designating the expansive erase mode from the host apparatus 8, the control unit 103 initializes the logical/physical table 108a, and sets each block, which stores data (user data) other than management data (including S. M. A. R. T. log data), in a state (free block) in which no user data is written. The control unit 103 executes the block erase process on all free blocks and defective blocks.
• the pseudo-erase 1OA can quickly set each block in the state in which no data is written.
• the reliability of data erase is higher than the pseudo-erase 1OA.
• the expansive erase 1OC the Bad Block 1072, which is not erased in the normal erase 1OB, is also erased, .and it is possible, therefore, to prevent leak of information from the information processing apparatus 1 or SSD 10, which stores data with a high security level, and to safely discard the information processing apparatus 1 or SSD 10. Therefore, in the present embodiment, the pseudo-erase mode, normal erase mode and expansive erase mode can selectively be used according to the purpose of use.
• the present invention is not limited directly to the above-described embodiment.
• the structural elements can be modified and embodied without departing from the spirit of the invention.
• Various inventions can be made by properly combining the structural elements disclosed in the embodiment. For example, some structural elements may be omitted from all the structural elements disclosed in the embodiment. Furthermore, structural elements in different embodiments may properly be combined.

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• 2008
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