JP6118045B2 - Semiconductor memory device - Google Patents

Description

  The present invention relates to a semiconductor memory device.

  A memory system including a memory controller and a memory cell array such as a flash memory has been put into practical use. In a NAND flash memory or the like, there are randomly acquired congenital defective blocks that occur at the time of manufacture, and acquired defective blocks that occur due to normal use after shipment. Since it is necessary to avoid these bad blocks and use them, the position of the bad block is managed by predetermined management information.

  If you try to store management information in the memory cell array that is the memory to be controlled, if the storage block is a congenital defective block, or it was not a congenital defective block at the time of storage, it will later become an acquired defective block. In this case, some or all of the management information data may be destroyed or lost. Also, if the power is forcibly shut down due to a user's mistaken operation while writing new management information to update the management information, some or all of the data in the management information is destroyed or lost. There is a possibility of being. If the management information is destroyed or lost, then the normal operation of the memory system is hindered.

  Therefore, in the memory system according to the background art, by preparing a dedicated non-volatile memory different from the control target memory and storing the management information in the non-volatile memory, destruction of the management information is prevented. . As another method, management information is stored in a non-volatile memory area in the memory controller, or management information is given to the memory controller by setting a DIP switch, thereby preventing destruction of the management information.

  Patent Document 1 listed below discloses a memory system including a controller and a flash memory. Management information including a list of defective blocks is divided into a plurality of divided pieces, and each divided piece is individually stored in the flash memory. A management memory using a volatile memory such as a DRAM is mounted in the controller. Management information is stored in the management memory by reading a plurality of divided pieces from the flash memory to the management memory.

JP 2011-59866 A

  As described above, in the memory system according to the background art, management information is stored in a dedicated non-volatile memory different from the control target memory. Therefore, since it is necessary to add a dedicated non-volatile memory in addition to the control target memory, the manufacturing cost increases and the control becomes complicated.

  The present invention has been made to solve such a problem, and management information is controlled while avoiding a situation in which normal operation is hindered due to the presence of a defective block or forced power shutdown. An object is to obtain a semiconductor memory device that can be stored in a memory.

A semiconductor memory device according to a first aspect of the present invention includes a storage unit having a plurality of blocks, each of which is a data erasing unit, and a control unit that controls the storage unit, and all of the storage unit has A first block composed of a first predetermined number of blocks of four or more, which is limitedly assigned as a block for storing management information necessary for the control unit to manage the storage unit. A second predetermined group that includes a block group and a second block group other than the first block group, and that is selected by the control unit from the first block group and that is three or more and less than the first predetermined number Management information having the same content is stored in each of several blocks. The management information includes first management information and second management information having a higher rewrite frequency than the first management information. Management information in the first block group The second management information is stored in the second block group, and the first management information includes first position information indicating a block storing the second management information in the second block group, The control unit identifies a normal block in which normal first management information is stored from the first block group, the first management information stored in a certain normal block, and the first block By making a majority decision using two pieces of first management information specified based on the second position information indicating the other two blocks in the first block group described in the management information, The first management information is identified, and the second management information is acquired from the second block group based on the first position information included in the valid first management information. It is.

According to the semiconductor memory device according to the first aspect, the first block group including the first predetermined number of blocks of four or more is limitedly assigned as a block for storing the management information. Then, the management information having the same content is stored in each of the second predetermined number of blocks, which is selected by the control unit from the first block group and is less than the first predetermined number. Therefore, even if one of the second predetermined number of first management information stored in the second predetermined number of blocks is destroyed or lost, the control unit is not destroyed or lost. The remaining first management information can be acquired from the storage unit. As a result, it is possible to store the management information in the control target memory while avoiding the situation where the normal operation is hindered due to the presence of a defective block or forced power cut-off.
Further, according to the semiconductor memory device according to the first aspect, the management information includes the first management information and the second management information that is rewritten more frequently than the first management information. The first management information is stored in the first block group, and the second management information is stored in the second block group. By dividing the management information into the first management information and the second management information according to the rewrite frequency, and storing the first management information with a low rewrite frequency in the limited first block group, Data rewriting does not occur frequently in the first block group. As a result, since the occurrence of acquired defective blocks in the first block group is suppressed, the reliability of the apparatus can be improved.
Further, according to the semiconductor memory device according to the first aspect, the control unit identifies a normal block in which normal first management information is stored from the first block group. The first management information stored in one specified normal block and the second position information indicating the other two blocks in the first block group described in the first management information By making a majority decision using the two pieces of first management information specified based on the information, one piece of reasonable first management information is specified. Therefore, even when multiple versions of the first management information are stored in the first block group by repeating the update, it is possible to appropriately specify the appropriate first management information. In addition, by limiting the target of majority decision to the three pieces of first management information, the majority decision can be easily made, so that the time required for processing can be shortened. In addition, since the target of the majority decision can be limited to the first management information having the same contents written at the time of the update, it is possible to increase the possibility that the appropriate first management information can be specified by the majority decision.

The semiconductor memory device according to the second aspect of the present invention is characterized in that, in the semiconductor memory device according to the first aspect , the second management information includes position information indicating a defective block. .

According to the semiconductor memory device according to the second aspect , the second management information includes position information indicating a defective block. Therefore, the control unit can acquire the position information indicating the block storing the second management information by reading the first management information from the storage unit, and stores the second management information based on the position information. By reading from the part, it is possible to acquire position information indicating a defective block.

In the semiconductor memory device according to the third aspect of the present invention, particularly in the semiconductor memory device according to the second aspect, the first management information includes position information indicating a defective block in the first block group. The 2 management information includes position information indicating defective blocks in the second block group.

According to the semiconductor memory device of the third aspect, the first management information includes position information indicating a defective block in the first block group, and the second management information includes a defect in the second block group. Position information indicating a block is included. Therefore, when an acquired defective block occurs in the first block group, only the first management information needs to be updated, and the update of the second management information can be omitted. Similarly, when an acquired defective block occurs in the second block group, only the second management information needs to be updated, and the update of the first management information can be omitted.

The semiconductor memory device according to the fourth aspect of the present invention is, in the semiconductor memory device according to any one of the first to third aspects, particularly two or more selected from the second block group. in each of the three predetermined number of blocks, the second management information of the same content are stored, the first management information, first shows a third predetermined number of blocks storing the second management information 1 Position information is included, and the control unit identifies a third predetermined number of blocks based on the first position information included in the appropriate first management information, and the third predetermined number of blocks One second management information is acquired from the third predetermined number of second management information stored in the storage.

According to the semiconductor memory device of the fourth aspect, the second management information having the same contents is stored in each of the third predetermined number of blocks that are two or more selected from the second block group. ing. Then, the control unit, third identifying a predetermined number of blocks based on the first position information included in the valid first management information, third stored in said third predetermined number of blocks One second management information is acquired from a predetermined number of second management information. Therefore, even if one of the third predetermined number of second management information stored in the third predetermined number of blocks is destroyed or lost, the control unit is not destroyed or lost. The remaining second management information can be acquired from the storage unit. As a result, it is possible to store the management information in the control target memory while avoiding the situation where the normal operation is hindered due to the presence of a defective block or forced power cut-off.

The semiconductor memory device according to the fifth aspect of the present invention is, in the semiconductor memory device according to any one of the first to third aspects, particularly two or more selected from the second block group. 3 Predetermined number of blocks stores third predetermined number of second management information having different versions, and the first management information includes third predetermined number of blocks storing second management information the includes a first position information indicating the control unit, third identifying a predetermined number of blocks based on the first position information included in the valid first management information, said third predetermined One second management information is obtained from a third predetermined number of second management information stored in several blocks.

According to the semiconductor memory device according to a fifth aspect, selected from among the second block group, the third predetermined number of blocks is two or more, the second management version several different third predetermined Information is stored. Then, the control unit, third identifying a predetermined number of blocks based on the first position information included in the valid first management information, third stored in said third predetermined number of blocks One second management information is acquired from a predetermined number of second management information. Therefore, even if one of the third predetermined number of second management information stored in the third predetermined number of blocks is destroyed or lost, the control unit is not destroyed or lost. The remaining second management information can be acquired from the storage unit. As a result, it is possible to store the management information in the control target memory while avoiding the situation where the normal operation is hindered due to the presence of a defective block or forced power cut-off.

The semiconductor memory device according to a sixth aspect of the present invention is the semiconductor memory device according to any one of the first to fifth aspects, and in particular, the control unit includes a congenital defective block from the first block group. The normal block is specified by excluding.

According to the semiconductor memory device of the sixth aspect, the control unit specifies a normal block by excluding a congenital defective block from the first block group. Therefore, it is possible to avoid a situation in which a congenital defective block is specified as a normal block, and it is possible to appropriately specify appropriate first management information.

The semiconductor memory device according to a seventh aspect of the present invention is the semiconductor memory device according to any one of the first to sixth aspects, and in particular, the control unit includes a predetermined invalid flag from the first block group. The normal block is specified by excluding the invalid block to which is added.

According to the semiconductor memory device of the seventh aspect, the control unit specifies the normal block by excluding the invalid block from the first block group. Therefore, since it is possible to avoid a situation where an invalid block is specified as a normal block, it is possible to appropriately specify appropriate first management information.

The semiconductor memory device according to an eighth aspect of the present invention is the semiconductor memory device according to any one of the first to seventh aspects, and in particular, the control unit stores the first block group. A normal block is specified by excluding an abnormal block in which a data error has occurred in the first management information.

According to the semiconductor memory device of the eighth aspect, the control unit specifies the normal block by excluding the abnormal block from the first block group. Accordingly, it is possible to avoid a situation in which an abnormal block is specified as a normal block, and it is possible to appropriately specify appropriate first management information.

A semiconductor memory device according to a ninth aspect of the present invention includes a storage unit having a plurality of blocks, each of which is a data erasing unit, and a control unit that controls the storage unit, and all of the storage unit has A first block consisting of a first predetermined number of blocks of four or more, which is assigned to the block in a limited manner as a block for storing management information necessary for the control unit to manage the storage unit and block group, and a second block group other than the first block group, contains, selected by the control unit from the first block group, three or more and the first second predetermined a predetermined less than several Management information having the same content is stored in each of several blocks. The management information includes first management information and second management information having a higher rewrite frequency than the first management information. Management information is the first block group The second management information is stored in the second block group, and the control unit, when it becomes necessary to update the first management information, is a second predetermined number of blocks in the first block group. The first block is reserved, the updated first management information is written in each of the second predetermined number of free blocks, and the first predetermined block is written in one of the second predetermined number of free blocks. The management information is written together with position information indicating other empty blocks among the second predetermined number of empty blocks.

According to the semiconductor memory device of the ninth aspect, the first block group composed of the first predetermined number of blocks of four or more is limitedly assigned as a block for storing management information. Then, selected by the control unit from the first block group, in each of three or more and a second predetermined number of blocks first are given below a few, the management information of the same content is stored. Therefore, even if one of the second predetermined number of first management information stored in the second predetermined number of blocks is destroyed or lost, the control unit is not destroyed or lost. The remaining first management information can be acquired from the storage unit. As a result, it is possible to store the management information in the control target memory while avoiding the situation where the normal operation is hindered due to the presence of a defective block or forced power cut-off.
According to the semiconductor memory device of the ninth aspect, the management information includes the first management information and the second management information that is rewritten more frequently than the first management information. The first management information is stored in the first block group, and the second management information is stored in the second block group. By dividing the management information into the first management information and the second management information according to the rewrite frequency, and storing the first management information with a low rewrite frequency in the limited first block group, Data rewriting does not occur frequently in the first block group. As a result, since the occurrence of acquired defective blocks in the first block group is suppressed, the reliability of the apparatus can be improved.
According to the semiconductor memory device of the ninth aspect, when the control unit needs to update the first management information, the control unit allocates the second predetermined number of empty blocks in the first block group. The updated first management information is written in each of the second predetermined number of empty blocks. Thereby, even after the update, the second predetermined number of first management information having the same contents can be stored in the first block group.
According to the semiconductor memory device of the ninth aspect, the control unit adds the second predetermined number of empty blocks to the first management information to be written in one empty block of the second predetermined number of empty blocks. Is written including position information indicating other empty blocks. Therefore, since the target of majority decision can be limited to the first management information having the same contents written together at the time of update, it is possible to increase the possibility of specifying appropriate first management information by majority decision.
A semiconductor memory device according to a tenth aspect of the present invention is the semiconductor memory device according to the ninth aspect, in which the control unit writes the error detection code of the first management information in the first management information. It is characterized by.
According to the semiconductor memory device of the tenth aspect, the control unit writes the error detection code of the first management information included in the first management information. Therefore, a majority decision can be made using the error detection code, and as a result, it is possible to improve the accuracy of appropriately identifying the appropriate first management information. In addition, it is possible to determine whether or not a data error has occurred using an error detection code. As a result, when a normal block is identified from the first block group, an abnormality in which a data error has occurred Blocks can be excluded.

A semiconductor memory device according to an eleventh aspect of the present invention is the semiconductor memory device according to the ninth or tenth aspect, in which the control unit excludes a congenital defective block from the first block group. Thus, an empty block is secured.

According to the semiconductor memory device of the eleventh aspect, the control unit secures an empty block by excluding the congenital defective block from the first block group. Therefore, it is possible to avoid a situation where a congenital defective block is selected as a block in which the updated first management information is written.

A semiconductor memory device according to a twelfth aspect of the present invention is the semiconductor memory device according to any one of the ninth to eleventh aspects, in particular, the control unit includes an acquired defective block from the first block group. This is characterized in that an empty block is secured by excluding.

According to the semiconductor memory device in the twelfth aspect, the control unit secures an empty block by excluding the acquired defective block from the first block group. Therefore, it is possible to avoid a situation where an acquired defective block is selected as a block in which the updated first management information is written.

The semiconductor memory device according to a thirteenth aspect of the present invention is the semiconductor memory device according to any one of the ninth to twelfth aspects, and in particular, the control unit includes a first block group from the first block group before the update. An empty block is secured by excluding the second predetermined number of blocks in which one management information is stored.

According to the semiconductor memory device of the thirteenth aspect, the control unit excludes, from the first block group, the second predetermined number of blocks in which the first management information before update is stored, Reserve free blocks. Accordingly, even when the power is forcibly shut down due to a user's erroneous operation or the like during the update process of the first management information, and the first management information after the update is thereby deleted, the first management before the update is performed. Since the information remains in the storage unit, it can be restarted using the information.

The semiconductor memory device according to the fourteenth aspect of the present invention is the semiconductor memory device according to any one of the ninth to thirteenth aspects, and in particular, the control unit is configured to select one of the second predetermined number of empty blocks. When the writing of the first management information to the empty blocks is completed, a predetermined invalid flag is set for one block in the second predetermined number of blocks in which the first management information before the update is stored. Is added.

According to the semiconductor memory device of the fourteenth aspect, when the writing of the first management information to one empty block is completed, the control unit stores one block in which the first management information before update is stored. For this, a predetermined invalid flag is added. As a result, at least the second predetermined number of blocks can always be secured as the blocks in which the first management information is stored. Moreover, since an invalid flag is added instead of erasing data, stress on the memory cell due to erasure can be avoided. As a result, since the occurrence of acquired defective blocks in the first block group is suppressed, the reliability of the apparatus can be improved.

A semiconductor memory device according to a fifteenth aspect of the present invention is the semiconductor memory device according to any one of the ninth to thirteenth aspects, and in particular, the control unit is configured to select one of the second predetermined number of empty blocks. When the writing of the first management information to the empty blocks is completed, the data is erased from one of the second predetermined number of blocks in which the first management information before the update is stored. It is characterized by doing.

According to the semiconductor memory device in the fifteenth aspect, when the writing of the first management information to one empty block in the second predetermined number of empty blocks is completed, the control unit completes the first before update. Data is erased from one of the second predetermined number of blocks in which the management information is stored. As a result, at least the second predetermined number of blocks can always be secured as the blocks in which the first management information is stored.

The semiconductor memory device according to the sixteenth aspect of the present invention is the semiconductor memory device according to any one of the first to fifteenth aspects, in particular, the first predetermined number of blocks excluding the congenital defective blocks are It is assigned as one block group.

According to the semiconductor memory device in the sixteenth aspect, the first predetermined number of blocks excluding the congenital defective blocks are assigned as the first block group. Therefore, since the first predetermined number of blocks can be secured as the blocks constituting the first block group, the reliability of the apparatus can be improved.

  According to the present invention, a semiconductor storage device capable of storing management information in a control target memory while avoiding a situation in which normal operation is hindered due to the presence of a defective block or forced power-off Can be obtained.

1 is a diagram showing a simplified configuration of a semiconductor memory device according to a first embodiment of the present invention. It is a figure which extracts and shows a part of memory space of control object memory. It is a figure which shows the kind of control object memory assumed to be used. It is a figure which shows a 1st block group. It is a figure which shows the allocation of the page in a block. It is a figure which shows the acquisition process of management information in order. It is a figure which shows the acquisition process of management information in order. It is a figure which shows the acquisition process of management information in order. It is a figure which shows the acquisition process of management information in order. It is a figure which shows the acquisition process of management information in order. It is a figure which shows the acquisition process of management information in order. It is a figure which shows the update process of 1st management information in order. It is a figure which shows the update process of 1st management information in order. It is a figure which shows the update process of 1st management information in order. It is a figure which shows the update process of 1st management information in order. It is a figure which shows the update process of 1st management information in order. It is a figure which shows the other example of a 1st block group. It is a figure which shows the other example of a 1st block group. It is a figure which shows a 1st block group. It is a figure which shows the acquisition process of management information in order. It is a figure which shows the acquisition process of management information in order. It is a figure which shows the acquisition process of management information in order. It is a figure which shows the acquisition process of management information in order. It is a figure which shows the acquisition process of management information in order. It is a figure which shows the acquisition process of management information in order. It is a figure which shows the update process of 1st management information in order. It is a figure which shows the update process of 1st management information in order. It is a figure which shows the update process of 1st management information in order. It is a figure which shows the update process of 1st management information in order. It is a figure which shows the update process of 1st management information in order. It is a figure which shows the other example of a 1st block group. It is a figure which shows the other example of a 1st block group. FIG. 10 is a diagram showing a simplified configuration of a semiconductor memory device according to Modification 1; It is a figure which shows the 1st example of a 2nd block group. It is a figure which shows the 2nd example of a 2nd block group.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In addition, the element which attached | subjected the same code | symbol in different drawing shall show the same or corresponding element.

<Embodiment 1>
FIG. 1 is a diagram showing a simplified configuration of a semiconductor memory device 1 according to the first embodiment of the present invention. The semiconductor storage device 1 includes a memory controller 2 (control unit) and a control target memory 3 (storage unit) controlled by the memory controller 2. The control target memory 3 is a non-volatile memory, and is composed of, for example, a NAND flash memory.

  FIG. 2 is a diagram illustrating a part of the memory space of the control target memory 3. The memory space is divided into a plurality of blocks B1 to BN. A block is a unit for erasing data. All the blocks B1 to BN included in the control target memory 3 are classified into a first block group R1 and a second block group R2.

  The first block group R1 is a set of blocks for storing first management information to be described later, and a specific plurality of blocks limited among all the blocks B1 to BN are assigned as the first block group R1. It has been. In the example of the present embodiment, a total of 10 blocks B1 to B10 are allocated as the first block group R1.

  The second block group R2 is a set of blocks other than the first block group R1. Arbitrary data used by the user is stored in the second block group R2. The second block group R2 stores second management information to be described later.

  The management information is information necessary for the memory controller 2 to manage the control target memory 3. In the example of the present embodiment, the management information is divided into first management information and second management information.

  The first management information includes position information indicating the location of the block storing the second management information. As the position information, for example, a block address is used.

  The first management information includes an error detection code. The error detection code is used to determine whether or not a data error has occurred in the first management information. Further, the error detection code is used for majority decision (details will be described later) for specifying appropriate first management information. As an error detection code, a checksum, CRC (Cyclic Redundancy Check), message digest, or the like can be used. In the example of the present embodiment, CRC is used as the error detection code.

  The first management information includes unique ID information (referred to as “management information ID” in this specification). The management information ID indicates the version of the first management information, and the value of the management information ID is updated every time the first management information is updated. In the example of the present embodiment, an integer value incremented by “1” each time the first management information is updated is used as the management information ID. The management information ID is used in a majority vote (details will be described later) for specifying appropriate first management information.

  The first management information includes position information indicating the location of the defective block when there is a defective block in the first block group R1. The defective blocks include congenital defective blocks that occur when the control target memory 3 is manufactured and acquired defective blocks that occur due to normal use after shipment.

  When the first management information is updated, the updated first management information is written in a block different from the block storing the first management information before the update in the first block group R1. When the corresponding block becomes an acquired defective block during writing, the updated first management information is written to another block in the first block group R1.

  The second management information includes position information indicating the location of the defective block when there is a defective block in the second block group R2. The second management information includes various information necessary for the memory controller 2 to manage the control target memory 3, such as the location of the general-purpose area and the access speed to the control target memory 3.

  When the second management information is updated, the updated second management information is overwritten on the same block as the block storing the second management information before the update in the second block group R2. When the corresponding block becomes an acquired defective block during writing, the updated second management information is written in another arbitrary block (excluding the defective block) in the second block group R2. Since the first management information includes the position information of the block storing the second management information, it is necessary to update the first management information when the block storing the second management information is changed. There is.

  From the nature of the information included in each management information, it can be said that the second management information has a higher update frequency (rewrite frequency) than the first management information. For example, when an acquired bad block occurs in the user data area in the second block group R2, the second management information needs to be updated, but the first management information does not need to be updated. Since the number of blocks in the second block group R2 is much larger than the number of blocks in the first block group R1, the probability that an acquired defective block will occur in the second block group R2 is acquired in the first block group R1. It is sufficiently higher than the probability that a bad block will occur. Therefore, the situation of updating the second management information without updating the first management information occurs more frequently than the opposite situation.

  FIG. 3 is a diagram illustrating the types of the control target memory 3 that are assumed to be used. In the present embodiment, it is assumed that a plurality of types (four types in this example) of memories having different page sizes, block sizes, total block numbers, read cycles, and innate defect flag positions are assumed. Each memory is given unique ID information (referred to as “memory ID” in this specification) for identifying the type of memory. The memory ID includes page size and block size information.

  Hereinafter, (1) management information storage example, (2) management information acquisition process, and (3) management information update process will be described in order with respect to the semiconductor memory device 1 according to the present embodiment.

(1) Example of storing management information In the semiconductor memory device 1 according to the present embodiment, three blocks selected from the ten blocks B1 to B10 belonging to the first block group R1 have the same contents. 1 management information is stored. However, the values of “10” and “3” are examples, and are not limited to these values.

  FIG. 4 is a diagram illustrating the first block group R1. In this example, blocks B1 and B5 are congenital defective blocks, and blocks B2 and B4 are invalid blocks (details will be described later).

  Blocks B3, B6 to B9 store first management information. The numbers in parentheses attached to the first management information indicate the management information ID value (left side) and the CRC value (right side). For convenience of explanation, it is assumed that the CRC value when the first management information is written takes the same value as the management information ID value. For a normal block in which no data error has occurred, the CRC value and the management information ID value match, while on the other hand, for an abnormal block in which a data error has occurred due to an acquired bad block, etc. The CRC value does not match the management information ID value. In this example, regarding the first management information (2, 1) stored in the block B6, the CRC value does not match the management information ID value. Therefore, the block B6 is an acquired defective block.

  In the example shown in FIG. 4, the latest first management information is the first management information (4, 4). Here, the first management information (4, 4) is stored only in the two blocks B8 and B9. The reason is that after the data in the block B10 is erased, the first management information (4, 4) is stored. This is because it is assumed that the power supply is forcibly cut off by the user before 4) is written. Therefore, the block B10 is an erased block.

  Further, “BAD” written in the block B3 indicates that the block B3 has become an acquired defective block when the first management information is written in the block B3. However, regarding the first management information (1, 1) stored in the block B3, the management information ID value matches the CRC value. Therefore, it cannot be determined that the block B3 is an acquired defective block by comparing the management information ID value and the CRC value.

  When the first management information is written into the block, if the block becomes an acquired defect block, the memory controller holds the management information ID value attached to the first management information, and thereafter When updating the first management information, the management information ID value may not be used. Thereby, when generating the management information ID value using the cyclic counter, the old first management information stored in the acquired defective block and the new first management information updated after that, A situation in which the management information ID values coincide by chance is avoided.

  FIG. 5 is a diagram showing allocation of pages in the blocks with respect to the blocks B1 to B10. One block is divided into a plurality of pages. A page is a unit for writing and reading data. In this example, page P0 is a page to which a congenital defect flag is added, page PN is a page to which an invalid flag is added, and page PM is a page to which first management information is written. The first management information may be stored on a plurality of pages in the block.

  When a certain block is a congenital defective block, a congenital defective flag is added to page P0 of the block. The page to which the congenital defect flag is added differs depending on the type of the control target memory 3 as shown in FIG.

  When data of a certain block is invalid, an invalid flag is added to the page PN of that block. The page to which the invalid flag is added is common regardless of the type of the control target memory 3.

(2) Management Information Acquisition Processing FIGS. 6 to 11 are diagrams sequentially illustrating management information acquisition processing executed by the memory controller 2 when the semiconductor memory device 1 is activated. It is assumed that the first block group R1 is in the state shown in FIG.

  First, the memory controller 2 acquires a memory ID from the control target memory 3 by issuing a read command requesting the memory ID to the control target memory 3. Since the memory ID includes page size and block size information, an arbitrary page in the control target memory 3 can be accessed by acquiring the memory ID.

<Step of searching for congenital defective blocks>
Next, referring to FIG. 6, the memory controller 2 searches for all congenital defective blocks for all the blocks B1 to B10 belonging to the first block group R1. Specifically, regarding each of the blocks B1 to B10, it is determined whether or not each block is a congenital defective block by accessing the storage page of the congenital defective flag.

  At this time, since the type of the control target memory 3 is not known, the storage page of the congenital defect flag cannot be uniquely specified. Therefore, the memory controller 2 sequentially accesses the storage pages of the congenital defect flags for all types of memories that are assumed to be used. In the example shown in FIG. 3, the memory controller 2 sequentially accesses the 0th byte of the 0th page, the 2048th byte of the 0th page, the 0th byte of the 128th page, and the 8192th byte of the 256th page. Thus, it is determined whether or not a congenital defect flag is added to any storage page. In addition, the access speed to the control target memory 3 at that time is set to the slowest speed at which all types of memories assumed to be used can be normally operated. In the example shown in FIG. 3, access is performed in the slowest read cycle of 50 ns among the four types of memories.

  Note that table information that associates the memory ID with the memory type is created in advance and stored in the memory controller 2, and the memory controller 2 obtains the memory ID from the control target memory 3 and then refers to the table information. The memory type may be specified. In this case, it is possible to determine whether or not a congenital defect flag is added by accessing a storage page corresponding to the specified memory type at an access speed corresponding to the specified memory type.

  As a result of the search, if a congenital defective block exists in the blocks B1 to B10, the memory controller 2 excludes the block from the acquisition target block candidates. In the example shown in FIG. 6, blocks B1 and B5, which are congenital defective blocks, are excluded from candidates. The blocks B2 to B4 and B6 to B10 that remain without being excluded in this step are referred to as “good blocks” in this specification.

<Invalid block search step>
Next, referring to FIG. 7, the memory controller 2 searches the invalid blocks B2 to B4 and B6 to B10 for invalid blocks. Specifically, for each good block, it is determined whether or not each good block is an invalid block by accessing an invalid flag storage page (page PN shown in FIG. 5).

  Similarly to the above, the access speed to the control target memory 3 is set to the slowest speed at which all types of memories assumed to be used can be normally operated. However, when the memory type can be specified based on the memory ID, the access may be performed at an appropriate access speed corresponding to the specified memory type.

  If there is an invalid block in the good block as a result of the search, the memory controller 2 excludes the block from the acquisition target block candidates. In the example shown in FIG. 7, blocks B2 and B4 that are invalid blocks are excluded from the candidates. The blocks B3, B6 to B10 that remain without being excluded in this step are referred to as “effective blocks” in this specification.

<Abnormal block search step>
Next, with reference to FIG. 8, the memory controller 2 searches for the blocks in which the data error has occurred in the effective blocks B3, B6 to B10. Specifically, for each valid block, the first management information storage page (page PM shown in FIG. 5) is accessed to read the first management information, and the CRC calculation is performed on the read first management information. . Then, the CRC value obtained by the calculation is compared with the CRC value included in the read first management information. If both CRC values match, the memory controller 2 determines that the block is a block in which no data error has occurred (referred to herein as a “normal block”), while both CRC values are If they do not match, the block is determined to be a block in which a data error has occurred (referred to herein as an “abnormal block”).
・ Acquired bad block at the time of writing or erasing ・ It was not completed normally due to the power being forcibly cut off at the time of writing or erasing ・ Both CRC values because no data was written in the erased state If they do not match, the block is determined to be an abnormal block.

  Similarly to the above, the access speed to the control target memory 3 is set to the slowest speed at which all types of memories assumed to be used can be normally operated. However, when the memory type can be specified based on the memory ID, the access may be performed at an appropriate access speed corresponding to the specified memory type.

  As a result of the search, when an abnormal block exists in the effective block, the memory controller 2 excludes the block from the acquisition target block candidates. In the example shown in FIG. 8, blocks B6 and B10 that are abnormal blocks are excluded from the candidates.

<Appropriate first management information specifying step>
Next, the memory controller 2 arbitrarily selects four normal blocks from the remaining normal blocks. For example, four normal blocks are selected in ascending order of block addresses. In this example, since the remaining normal blocks are the four blocks B3, B7 to B9, all normal blocks are selected. If the number of normal blocks remaining at this time is two or less, it is determined that the control target memory 3 is faulty because the majority decision described later cannot be performed. If there are three normal blocks remaining at this time, a majority decision described later is performed only once.

  Next, referring to FIG. 9, the memory controller 2 arbitrarily selects three normal blocks from the selected four normal blocks B3, B7 to B9. In this example, three normal blocks B3, B7, B8 are selected in ascending order of block address. Then, the first majority decision is performed by comparing the management information ID value and the CRC value included in the first management information stored in each of the normal blocks B3, B7, and B8. When two or more of the three pieces of first management information match the management information ID value and the CRC value, the memory controller 2 determines that the first management information is valid. In this example, the management information ID values and CRC values of the three pieces of first management information are (1, 1), (3, 3), and (4, 4), respectively. It is determined that there is no information.

  Next, referring to FIG. 10, the memory controller 2 arbitrarily selects the other three normal blocks from the selected four normal blocks B3, B7 to B9. In this example, three normal blocks B7 to B9 are selected in descending order of block address. Then, the second majority decision is performed by comparing the management information ID value and the CRC value included in the first management information stored in each of the normal blocks B7 to B9. In this example, the management information ID value and CRC value of the three pieces of first management information are (3, 3), (4, 4), (4, 4), respectively, and (4, 4) is the same when two or more To do. Therefore, it is determined that the first management information stored in the blocks B8 and B9 is appropriate first management information.

  In addition, when the appropriate first management information can be specified by the first majority decision, the second majority decision is omitted. Further, if the appropriate first management information cannot be specified even by the second majority decision, it is determined that the control target memory 3 is out of order. However, when five or more normal blocks remain, the selection of four normal blocks may be performed again and the majority decision may be performed again.

<Second management information acquisition step>
Next, referring to FIG. 11, the memory controller 2 determines any one piece of first management information from among the identified two or more pieces of appropriate first management information. For example, the block B8 having the smallest block address is selected from the blocks B8 and B9, and the first management information (4, 4) stored in the block B8 is determined as appropriate first management information.

  Next, the memory controller 2 determines the second block group R2 based on the position information (position information indicating the location of the block storing the second management information) included in the determined valid first management information. The second management information is acquired by reading the second management information from the list.

(3) Management information update process When the storage block of the second management information becomes an acquired defect block, the storage block of the second management information is changed to another block in the second block group R2. There is a need. Here, since the first management information includes the location information of the storage block of the second management information, when the storage block of the second management information is changed, it is necessary to update the contents of the first management information. There is. In addition, since the first management information includes the position information of the defective block in the first block group R1, when an acquired defective block occurs in the first block group R1, the first management information The content needs to be updated. Hereinafter, a procedure for updating the first management information will be described.

  12 to 16 are diagrams sequentially illustrating the update process of the first management information executed by the memory controller 2.

  Referring to FIG. 12, the first management information that is currently valid (that is, the first management information before update) is the first management information (4, 4) stored in blocks B8 and B9. Further, the first management information that is a candidate for majority decision for specifying the appropriate first management information at the time of activation is the first management information stored in the blocks B7 to B9. Hereinafter, the blocks B7 to B9 are referred to as “majority target blocks”.

  Next, referring to FIG. 13, the memory controller 2 secures an empty block in which the updated first management information is to be stored from the first block group R1. Specifically, from the blocks B1 to B10, congenital bad blocks, acquired bad blocks, and majority-target blocks are excluded, and three empty blocks are secured. Since the first management information includes the position information of the defective block in the first block group R1, by referring to the currently effective first management information (4, 4), the first management information in the first block group R1 Congenital bad blocks and acquired bad blocks can be identified. In this example, blocks B2 and B4 that are invalid blocks and a block B10 that is an erased block are secured as empty blocks. If the number of free blocks that can be secured is two or less, it is determined that the control target memory 3 is faulty.

  Next, referring to FIG. 14, the memory controller 2 erases the data of any one of the three empty blocks, and then updates the first management information (5, 5) after the update. Write to block. In this example, after the data in the block B10 is erased, the first management information (5, 5) is written into the block B10. When erasing empty block data or writing the first management information (5, 5), if the corresponding block becomes an acquired defective block, the memory controller 2 uses the first management information. The position information of the included bad block is updated, and the free block securing process is repeated.

  Next, referring to FIG. 15, the memory controller 2 adds an invalid flag to any one of the three majority target blocks. In this example, an invalid flag is added to the block B7. If the corresponding block becomes an acquired bad block when the invalid flag is added, the memory controller 2 updates the position information of the bad block included in the first management information and Start over from the securing process.

  Next, referring to FIG. 16, the memory controller 2 erases the data of the next empty block B2 among the three empty blocks, and then writes the first management information (5, 5) to the block B2. Thereafter, an invalid flag is added to the next block B8 among the three majority target blocks. Next, the memory controller 2 erases the data of the last empty block B4 among the three empty blocks, and then writes the first management information (5, 5) to the block B4. Thereafter, an invalid flag is added to the last block B9 among the three majority target blocks. As a result, the first management information (5, 5) having the same contents is stored in the three empty blocks B2, B4, B10.

  Note that data may be erased instead of adding an invalid flag to the majority decision target blocks B7 to B9. In this case, the writing of the first management information to one empty block and the erasure of data for one majority target block are alternately repeated three times.

<Specific Example 1 of Embodiment 1>
FIG. 17 is a diagram illustrating another example of the first block group R1. In this example, blocks B5 and B9 are congenital defective blocks, and blocks B1, B2 and B10 are invalid blocks. Blocks B4 and B8 are acquired defective blocks. However, regarding the blocks B4 and B8, the management information ID value matches the CRC value. The blocks B3, B6, and B7 store the first management information (6, 6).

  The management information acquisition process for the first block group R1 shown in FIG. 17 will be briefly described. First, blocks B5 and B9 that are congenital defective blocks are excluded. Next, blocks B1, B2, and B10 that are invalid blocks are excluded. Next, an abnormal block is searched, but since no abnormal block exists in this example, no block is excluded as an abnormal block. Next, blocks B3, B4, B6, and B7 are selected as four normal blocks.

  Next, the first majority decision is performed for the first three normal blocks B3, B4, and B6. As a result, the first management information (6, 6) stored in the blocks B3 and B6 is valid. It is specified as the first management information.

  Next, based on the first management information (6, 6) stored in one of the blocks B3, B6, the second management information is read out from the second block group R2.

<Specific Example 2 of Embodiment 1>
FIG. 18 is a diagram illustrating another example of the first block group R1. In this example, blocks B5 and B9 are congenital defective blocks, and blocks B1, B2 and B10 are invalid blocks. Blocks B4 and B6 are acquired defective blocks. However, regarding the blocks B4 and B6, the management information ID value matches the CRC value. The blocks B3, B7, B8 store the first management information (7, 7).

  The management information acquisition process for the first block group R1 shown in FIG. 18 will be briefly described. First, blocks B5 and B9 that are congenital defective blocks are excluded. Next, blocks B1, B2, and B10 that are invalid blocks are excluded. Next, an abnormal block is searched, but since no abnormal block exists in this example, no block is excluded as an abnormal block. Next, blocks B3, B4, B6, and B7 are selected as four normal blocks.

  Next, the first majority vote for the first three normal blocks B3, B4, and B6 is performed. However, since the majority vote is not established, it is determined that there is no valid first management information.

  Next, a second majority vote is performed for the last three normal blocks B4, B6, and B7. However, since the majority vote is not established, it is determined that there is no valid first management information. As a result, it is determined that the control target memory 3 is faulty.

<Embodiment 2>
Hereinafter, the semiconductor memory device 1 according to the second embodiment of the present invention will be described focusing on differences from the first embodiment.

  Similar to the first embodiment, the first management information includes position information indicating a storage block for the second management information. The first management information includes a management information ID. Further, the first management information includes position information indicating a defective block in the first block group R1.

  Further, in the present embodiment, in addition to the above, the first management information includes position information (in the present specification, “group” indicating the other two blocks storing the first management information having the same content as the first management information). Address).

  Further, the first management information includes an error detection code. In the example of the present embodiment, the CRC value of the entire area including the group address and the CRC value of the part excluding the group address are included in the first management information. The entire CRC value including the group address is used to determine whether or not a data error has occurred in the first management information. The CRC value excluding the group address is used for the majority vote for specifying the appropriate first management information.

  Hereinafter, (1) management information storage example, (2) management information acquisition process, and (3) management information update process will be described in order with respect to the semiconductor memory device 1 according to the present embodiment.

(1) Storage Example of Management Information FIG. 19 is a diagram showing the first block group R1. In this example, blocks B1 and B5 are congenital bad blocks, blocks B2 and B4 are invalid blocks, and block B10 is an erased block.

  Blocks B3, B6 to B9 store first management information. The numbers in parentheses attached to the first management information indicate the management information ID value and the CRC value. Numbers in angle brackets attached to the first management information indicate group addresses. For example, when the first management information (3, 3) is written in the block B7, it means that the first management information (3, 3) having the same contents is written in the blocks B2, B4.

(2) Management Information Acquisition Processing FIGS. 20 to 25 are diagrams sequentially illustrating management information acquisition processing executed by the memory controller 2 when the semiconductor memory device 1 is activated. The first block group R1 is assumed to be in the state shown in FIG.

  First, the memory controller 2 acquires a memory ID from the control target memory 3 by issuing a read command requesting the memory ID to the control target memory 3.

<Step of searching for congenital defective blocks>
Next, referring to FIG. 20, the memory controller 2 searches for all congenital defective blocks for all the blocks B1 to B10 belonging to the first block group R1.

  As a result of the search, if a congenital defective block exists in the blocks B1 to B10, the memory controller 2 excludes the block from the acquisition target block candidates. In the example shown in FIG. 20, blocks B1 and B5 that are congenital defective blocks are excluded from candidates.

<Invalid block search step>
Next, referring to FIG. 21, the memory controller 2 searches the invalid blocks for the good blocks B2 to B4 and B6 to B10.

  If there is an invalid block in the good block as a result of the search, the memory controller 2 excludes the block from the acquisition target block candidates. In the example shown in FIG. 21, blocks B2 and B4 that are invalid blocks are excluded from the candidates.

<Abnormal block search step>
Next, with reference to FIG. 22, the memory controller 2 searches the effective blocks B3, B6 to B10 for a block in which a data error has occurred. Specifically, for each valid block, the first management information storage page is accessed to read the first management information, and a CRC calculation is performed on the entire area of the first management information including the group address. And the CRC value of the whole area calculated | required by the calculation and the CRC value of the whole area contained in the read 1st management information are compared. If both CRC values match, the memory controller 2 determines that the block is a normal block, and if both CRC values do not match, determines that the block is an abnormal block.

  As a result of the search, when an abnormal block exists in the effective block, the memory controller 2 excludes the block from the acquisition target block candidates. In the example shown in FIG. 22, blocks B6 and B10 that are abnormal blocks are excluded from the candidates.

<Appropriate first management information specifying step>
Next, referring to FIG. 23, the memory controller 2 arbitrarily selects one normal block from the remaining normal blocks B3, B7 to B9. For example, the normal block B3 having the smallest block address is selected. Then, by referring to the group address <4, 6> included in the first management information stored in the normal block B3, a majority decision for the blocks B3, B4, B6 is made. Specifically, the management information ID value and the CRC value (the CRC value excluding the group address) included in the first management information stored in each of the blocks B3, B4, and B6 are compared with each other. Thus, the first majority vote is performed. In this example, since the blocks B4 and B6 are not normal blocks and are excluded from the majority candidates, the first majority vote is not established.

  Next, referring to FIG. 24, the memory controller 2 arbitrarily selects the next normal block from the normal blocks B3, B7 to B9. For example, the normal block B7 having the next smallest block address is selected. Then, a majority decision is made for the blocks B2, B4, and B7 by referring to the group address <2, 4> included in the first management information stored in the normal block B7. Specifically, the management information ID value and CRC value (the CRC value of the portion excluding the group address) included in the first management information stored in each block B2, B4, B7 are compared with each other. The second majority vote is performed. In this example, since the blocks B2 and B4 are not normal blocks and are excluded from the majority candidates, the second majority vote is not established.

  Next, referring to FIG. 25, the memory controller 2 arbitrarily selects the next normal block from the normal blocks B3, B7 to B9. For example, the normal block B8 having the next smallest block address is selected. Then, by referring to the group address <9, 10> included in the first management information stored in the normal block B8, a majority decision for the blocks B8 to B10 is performed. Specifically, by comparing the management information ID value and the CRC value (the CRC value of the portion excluding the group address) included in the first management information stored in each of the blocks B8 to B10, Make a third majority vote. In this example, since the block B10 is not a normal block, it is excluded from the majority candidates, but the management information ID value and CRC value of the two first management information stored in the blocks B8 and B9 are both (4 4), and two or more match. Therefore, it is determined that the first management information stored in the blocks B8 and B9 is appropriate first management information.

  In addition, even if all the normal blocks B3, B7 to B9 are selected, if the appropriate first management information cannot be specified, it is determined that the control target memory 3 is faulty.

<Second management information acquisition step>
Next, the memory controller 2 determines one arbitrary first management information from the two or more specified appropriate first management information. For example, the block B8 having the smallest block address is selected from the blocks B8 and B9, and the first management information (4, 4) stored in the block B8 is determined as appropriate first management information.

  Next, the memory controller 2 acquires the second management information by reading the second management information from the second block group R2 based on the position information included in the determined valid first management information. To do.

(3) Management Information Update Processing FIGS. 26 to 30 are diagrams sequentially illustrating the first management information update processing executed by the memory controller 2.

  Referring to FIG. 26, the currently effective first management information is the first management information (4, 4) stored in blocks B8 and B9. Further, the first management information that is a candidate for majority decision for specifying appropriate first management information at the time of activation is the first management information stored in the majority decision target blocks B8 to B10.

  Next, referring to FIG. 27, the memory controller 2 secures an empty block from the first block group R1. Specifically, from the blocks B1 to B10, congenital bad blocks, acquired bad blocks, and majority-target blocks are excluded, and three empty blocks are secured. In this example, blocks B2, B4 and B7 are secured as empty blocks.

  Next, referring to FIG. 28, the memory controller 2 erases the data of any one of the three empty blocks, and then updates the first management information including the group address to that block. Write to. In this example, after the data in the block B2 is erased, the first management information (5, 5) <4, 7> including the group address <4, 7> indicating the blocks B4, B7 is written into the block B2. .

  Next, with reference to FIG. 29, the memory controller 2 adds an invalid flag to any one of the three majority decision blocks. In this example, an invalid flag is added to the block B8.

  Next, referring to FIG. 30, the memory controller 2 erases the data of the next empty block B4 among the three empty blocks, and then first management information (5, 5) including the group address <2, 7>. 5) Write <2,7> in its block B4. Thereafter, an invalid flag is added to the next block B9 among the three majority target blocks. Next, the memory controller 2 erases the data of the last empty block B7 among the three empty blocks, and then first management information (5, 5) <2, 4 including the group address <2, 4>. > Is written in the block B7. Thereafter, an invalid flag is added to the last block B10 among the three majority target blocks. Thereby, the first management information (5, 5) having the same contents is stored in the three empty blocks B2, B4, B7.

<Specific Example 1 of Embodiment 2>
FIG. 31 is a diagram illustrating another example of the first block group R1. In this example, blocks B5 and B9 are congenital defective blocks, and blocks B1, B2 and B10 are invalid blocks. Blocks B4 and B8 are acquired defective blocks. However, regarding the blocks B4 and B8, the management information ID value matches the CRC value. Also, the first management information (6, 6) <6, 7> is stored in the block B3, and the first management information (6, 6) <3, 7> is stored in the block B6. The block B7 stores first management information (6, 6) <3, 6>.

  The management information acquisition process for the first block group R1 shown in FIG. 31 will be briefly described. First, blocks B5 and B9 that are congenital defective blocks are excluded. Next, blocks B1, B2, and B10 that are invalid blocks are excluded. Next, an abnormal block is searched, but since no abnormal block exists in this example, no block is excluded as an abnormal block.

  Next, the first normal block B3 is selected, and a majority vote is performed on the normal block B3 and the normal blocks B6 and B7 indicated by the group address <6, 7>. As a result, the first management information (6, 6) stored in the blocks B3, B6, B7 is specified as valid first management information.

  Next, based on the first management information (6, 6) stored in any of the blocks B3, B6, B7, the second management information is read out from the second block group R2.

<Specific Example 2 of Embodiment 2>
FIG. 32 is a diagram illustrating another example of the first block group R1. In this example, blocks B5 and B9 are congenital defective blocks, and blocks B1, B2 and B10 are invalid blocks. Blocks B4 and B6 are acquired defective blocks. However, regarding the blocks B4 and B6, the management information ID value matches the CRC value. Also, the first management information (7, 7) <7, 8> is stored in the block B3, and the first management information (7, 7) <3, 8> is stored in the block B7. The block B8 stores the first management information (7, 7) <3, 7>.

  The management information acquisition process for the first block group R1 shown in FIG. 32 will be briefly described. First, blocks B5 and B9 that are congenital defective blocks are excluded. Next, blocks B1, B2, and B10 that are invalid blocks are excluded. Next, an abnormal block is searched, but since no abnormal block exists in this example, no block is excluded as an abnormal block.

  Next, the first normal block B3 is selected, and a majority vote is performed on the normal block B3 and the normal blocks B7 and B8 indicated by the group address <7,8>. As a result, the first management information (7, 7) stored in the blocks B3, B7, B8 is specified as valid first management information.

  Next, based on the first management information (7, 7) stored in any of the blocks B3, B7, B8, the second management information is read out from the second block group R2.

  In specific example 2 (FIG. 18) of the first embodiment, which is the same case, the appropriate first management information could not be specified. On the other hand, in the example of FIG. 32, the appropriate first management information is successfully identified by making a majority decision based on the group address.

<Modification 1>
FIG. 33 is a diagram showing a simplified configuration of the semiconductor memory device 1 according to the first modification. The semiconductor memory device 1 includes a memory controller 2 and a plurality of control target memories (four control target memories 3A to 3D in the example of FIG. 33) controlled by the memory controller 2.

  In such a system configuration, the second management information having a large data size may be divided into a plurality of pieces, and each divided piece may be distributed and stored in a plurality of control target memories. In the example shown in FIG. 33, the second management information is divided into three second management information pieces 121-123. The first management information 11 is stored in the control target memory 3A, the second management information piece 121 is stored in the control target memory 3B, the second management information piece 122 is stored in the control target memory 3C, and the second management information piece 123 is stored. Is stored in the control target memory 3D. The first management information 11 includes position information indicating the locations of the second management information pieces 121 to 123. When reading the second management information, the second management information pieces 121 to 123 are read in parallel from the control target memories 3B to 3D.

<Modification 2>
In the first and second embodiments, the example in which the management information is divided into the first management information and the second management information has been described. However, the management information is not divided and the content of the second management information is included in the first management information. May be included. Since the data size of the management information becomes large, this is effective when there is room for allocating a large number of blocks as the first block group R1.

<Modification 3>
In the first and second embodiments, the example in which the management information is divided into the first management information and the second management information has been described. However, the management information may be divided into three or more. For example, when dividing into three, information with low rewriting frequency is included in the first management information, information with medium rewriting frequency is included in the second management information, and information with high rewriting frequency is included in the third management information. Include in. The first management information is stored in a first block group with a small number of allocated blocks, the second management information is stored in a second block group with a large number of allocated blocks, and the third management information is all blocks Are stored in the third block group other than the first block group and the second block group (the number of blocks is the largest).

<Modification 4>
In the first and second embodiments, the blocks allocated as the first block group R1 are limited to the blocks B1 to B10. Therefore, when there is a congenital defective block in the blocks B1 to B10, the number of blocks that can actually be used in the first block group R1 decreases according to the number of congenital defective blocks. Therefore, congenital defective blocks may be excluded when assigning the first block group. For example, when the blocks B5 and B9 are congenital defective blocks, the blocks B1 to B4, B6 to B8, and B10 to B12 are assigned as the first block group.

<Modification 5>
In the first and second embodiments, the example in which one second management information is stored in the second block group R2 has been described. However, a plurality of second management information may be stored in the second block group R2. .

  FIG. 34 is a diagram illustrating a first example of the second block group R2. In this example, the second management information having the same contents is stored in three blocks arbitrarily selected from all the blocks belonging to the second block group R2. However, the value “3” is an example, and is not limited to this value.

  The second management information includes a management information ID in addition to the position information indicating the location of the defective block. The management information ID indicates the version of the second management information, and the value of the management information ID is updated every time the second management information is updated. In this example, an integer value incremented by “1” every time the second management information is updated is used as the management information ID. The second management information includes an error detection code. In this example, CRC is used as the error detection code.

  In the example shown in FIG. 34, the second management information is stored in blocks B100, B200, and B300. The numbers in parentheses attached to the second management information indicate the management information ID value (left side) and CRC value (right side) of the second management information. For convenience of explanation, it is assumed that the CRC value when writing the second management information has the same value as the management information ID value of the second management information. For a normal block in which no data error has occurred, the CRC value and the management information ID value match, while on the other hand, for an abnormal block in which a data error has occurred due to an acquired bad block, etc. The CRC value does not match the management information ID value.

  Although not shown in FIG. 34, the first management information includes three pieces of position information indicating the locations of the three blocks B100, B200, and B300 that store the second management information.

  When the memory controller 2 determines the appropriate first management information, the memory controller 2 selects any one position information from the three position information included in the determined first management information. For example, position information indicating the block B100 having the smallest block address is selected.

  Next, the memory controller 2 reads the second management information from the block B100, and performs a CRC operation on the read second management information. Then, the CRC value obtained by the calculation is compared with the CRC value included in the read second management information. If both CRC values match, the memory controller 2 determines that the block B100 is a normal block, and acquires the second management information read from the block B100 as valid second management information.

  On the other hand, if the CRC values do not match, it is determined that the block B100 is an abnormal block, and the next position information is selected from the three pieces of position information. For example, position information indicating the block B200 having the next smallest block address is selected. Similarly to the above, the second management information is read from the block B200, and it is determined whether the block B200 is a normal block or an abnormal block.

  When the block B200 is a normal block, the memory controller 2 acquires the second management information read from the block B200 as valid second management information. On the other hand, when the block B200 is an abnormal block, the memory controller 2 selects position information indicating the block B300 from the three pieces of position information. Similarly to the above, the second management information is read from the block B300, and it is determined whether the block B300 is a normal block or an abnormal block. When the block B300 is a normal block, the memory controller 2 acquires the second management information read from the block B300 as valid second management information. On the other hand, when the block B300 is an abnormal block, the memory controller 2 determines that the control target memory 3 is faulty.

  FIG. 35 is a diagram illustrating a second example of the second block group R2. In this example, three pieces of second management information having different versions are stored in three blocks arbitrarily selected from all the blocks belonging to the second block group R2. However, the value “3” is an example, and is not limited to this value.

  In the example shown in FIG. 35, the second management information (3, 3) is stored in the block B100, the second management information (4, 4) is stored in the block B200, and the second management information (5, 5) is stored in the block B300. 5) is stored.

  When the memory controller 2 determines the appropriate first management information, the memory controller 2 obtains three pieces of second management information from the blocks B100, B200, and B300 based on the three pieces of position information included in the determined first management information. read out. Then, the management information ID value included in each second management information is compared to select the latest version of the second management information. In this example, the second management information (5, 5) read from the block B300 is selected as the latest version of the second management information.

  Next, the memory controller 2 performs a CRC calculation on the selected second management information. Then, the CRC value obtained by the calculation is compared with the CRC value included in the selected second management information. If both CRC values match, the memory controller 2 determines that the block B300 is a normal block, and acquires the second management information read from the block B300 as valid second management information.

  On the other hand, if the CRC values do not match, it is determined that the block B300 is an abnormal block, and the next new second management information is selected from the three pieces of read second management information. In this example, the second management information (4, 4) read from the block B200 is selected. Then, similarly to the above, it is determined whether the block B200 is a normal block or an abnormal block.

  When the block B200 is a normal block, the memory controller 2 acquires the second management information read from the block B200 as valid second management information. On the other hand, when the block B200 is an abnormal block, the memory controller 2 selects the second management information read from the block B100. Then, similarly to the above, it is determined whether the block B100 is a normal block or an abnormal block. When the block B100 is a normal block, the memory controller 2 acquires the second management information read from the block B100 as valid second management information. On the other hand, when the block B100 is an abnormal block, the memory controller 2 determines that the control target memory 3 is faulty.

  In the above description, the example in which the CRC value is compared after the management information ID value is compared has been described. On the contrary, the management information is compared after the CRC value comparison (abnormal block elimination). Comparison of ID values (selection of latest version) may be performed.

  In the example shown in FIG. 35, when the second management information is updated, the memory controller 2 updates the block B100 in which the oldest second management information (3, 3) among the normal blocks is stored. The second management information (6, 6) is overwritten.

<Summary>
According to the semiconductor memory device 1 according to the first and second embodiments, the first block group R1 including ten (first predetermined number) blocks B1 to B10 is limited as a block for storing management information. Assigned. Then, the management information having the same contents is stored in each of the three (second predetermined number) blocks less than the first predetermined number selected by the memory controller 2 from the first block group R1. . Therefore, even if one of the second predetermined number of pieces of management information stored in the second predetermined number of blocks is destroyed or lost, the memory controller 2 remains undestructed or lost. The management information can be acquired from the control target memory 3. As a result, it is possible to store the management information in the control target memory 3 while avoiding a situation in which the normal operation is hindered due to the presence of a defective block, forced power shutdown, or the like.

  The second management information is stored in the second block group R2 in which normal user data is stored. With respect to the second block group R2, processing for replacing an acquired defective block or a block in which an error has occurred with a replacement block (so-called replacement processing), and correcting the data in which an error has occurred during reading Data reliability is ensured by general error processing such as processing for rewriting data (so-called refresh processing). By storing the second management information in the second block group R2, the reliability of the second management information can be ensured by these error processes.

  Further, the second predetermined number is set to be less than the first predetermined number. In the first and second embodiments, the second predetermined number is set to 3, and the first predetermined number is set to 10. Has been. Accordingly, assuming that the three pieces of the first management information having the same contents are one set, three sets of the first management information can be stored in the first block group R1. In addition, when the first management information is updated, the updated first management information is written in a block different from the block in which the first management information before the update is stored. Therefore, it is possible to avoid a situation where access concentrates on a specific block in the first block group R1. As a result, since the occurrence of acquired defective blocks in the first block group R1 is suppressed, the reliability of the apparatus can be improved.

  Further, according to the semiconductor memory device 1 according to the first and second embodiments, the management information is divided into the first management information and the second management information that is rewritten more frequently than the first management information. The first management information is stored in the first block group R1, and the second management information is stored in the second block group R2. By dividing the management information into the first management information and the second management information according to the rewrite frequency, and storing the first management information with a low rewrite frequency in the limited first block group R1 In the first block group R1, data rewriting does not occur frequently. As a result, since the occurrence of acquired defective blocks in the first block group R1 is suppressed, the reliability of the apparatus can be improved.

  Further, according to the semiconductor memory device 1 according to the first and second embodiments, the first management information includes the position information indicating the block storing the second management information, and the second management information , Position information indicating a defective block is included. Therefore, the memory controller 2 can acquire the position information indicating the block storing the second management information by reading the first management information from the control target memory 3, and the second management based on the position information. By reading the information from the control target memory 3, it is possible to acquire position information indicating a defective block.

  Further, according to the semiconductor memory device 1 according to the first and second embodiments, the first management information includes the position information indicating the defective block in the first block group R1, and the second management information includes Position information indicating a defective block in the second block group R2 is included. Therefore, when an acquired defective block occurs in the first block group R1, only the first management information needs to be updated, and the update of the second management information can be omitted. Similarly, when an acquired defective block occurs in the second block group R2, only the second management information needs to be updated, and the update of the first management information can be omitted.

Further, according to the semiconductor memory device 1 according to the first and second embodiments, the memory controller 2, 3 or more and the normal block number of blocks hereinafter the first block group from among the first block group R1 Identify. Then, among the first management information that is stored in the specified normal block identifies one reasonable first management information by majority vote. Therefore, even when multiple versions of the first management information are stored in the first block group R1 by repeating the update, it is possible to appropriately specify the appropriate first management information.

  Further, according to the semiconductor memory device 1 according to the first and second embodiments, the memory controller 2 specifies a normal block by excluding a congenital defective block from the first block group R1. Therefore, it is possible to avoid a situation in which a congenital defective block is specified as a normal block, and it is possible to appropriately specify appropriate first management information.

  Further, according to the semiconductor memory device 1 according to the first and second embodiments, the memory controller 2 specifies normal blocks by excluding invalid blocks from the first block group R1. Therefore, since it is possible to avoid a situation where an invalid block is specified as a normal block, it is possible to appropriately specify appropriate first management information.

  Further, according to the semiconductor memory device 1 according to the first and second embodiments, the memory controller 2 specifies normal blocks by excluding abnormal blocks from the first block group R1. Accordingly, it is possible to avoid a situation in which an abnormal block is specified as a normal block, and it is possible to appropriately specify appropriate first management information.

Further, according to the semiconductor memory device 1 according to the first and second embodiments, the memory controller 2 identifies three normal blocks, the first management three stored in the three normal block From the information, one appropriate first management information is specified by majority vote. In this way, by limiting the target of the majority decision to the three pieces of first management information, the majority decision can be easily made, and thus the time required for processing can be shortened.

  Further, according to the semiconductor memory device 1 according to the first embodiment, the memory controller 2 stores the first management information stored in one normal block and the other two normal blocks. A majority decision is made using the two pieces of first management information. Therefore, since it is not necessary to include additional information for limiting the target of the majority decision in the first management information, the processing and configuration can be simplified.

  Further, according to the semiconductor memory device 1 according to the second embodiment, the memory controller 2 includes the first management information stored in a certain normal block and the location information described in the first management information. A majority decision is made using two pieces of first management information stored in two specific blocks. Therefore, since the target of majority decision can be limited to the first management information having the same contents written together at the time of update, it is possible to increase the possibility of specifying appropriate first management information by majority decision.

  Further, according to the semiconductor memory device 1 according to the first and second embodiments, the memory controller 2 cannot identify the appropriate first management information by the majority decision for the three specified normal blocks. Then, the other three normal blocks are specified again and a majority decision is made. As a result, it is possible to increase the possibility of specifying appropriate first management information.

  Further, according to the semiconductor memory device 1 according to the first and second embodiments, the memory controller 2 has the second predetermined value in the first block group R1 when the first management information needs to be updated. Several empty blocks are secured, and the updated first management information is written in each of the second predetermined number of empty blocks. Thereby, even after the update, the second predetermined number of first management information having the same contents can be stored in the first block group R1.

  Further, according to the semiconductor memory device 1 according to the first and second embodiments, the memory controller 2 writes the version information having a different value for each update in the first management information. Therefore, a majority decision can be made using the version information, and as a result, it is possible to improve the accuracy of appropriately identifying appropriate first management information.

  Further, according to the semiconductor memory device 1 according to the first and second embodiments, when the memory controller 2 writes the first management information to the empty block and the empty block becomes an acquired defective block, The value of the version information included in the first management information is not used for subsequent updates. Therefore, even when the counter value for generating the version information value goes around, the first management information stored in the acquired defective block is erroneously specified as the appropriate first management information by majority vote. It is possible to avoid this situation.

  Further, according to the semiconductor memory device 1 according to the first and second embodiments, the memory controller 2 writes the error detection code of the first management information in the first management information. Therefore, a majority decision can be made using the error detection code, and as a result, it is possible to improve the accuracy of appropriately identifying the appropriate first management information. In addition, it is possible to determine whether or not a data error has occurred using an error detection code. As a result, when a normal block is identified from the first block group, an abnormality in which a data error has occurred Blocks can be excluded.

  In addition, according to the semiconductor memory device 1 according to the second embodiment, the memory controller 2 stores the second predetermined number of pieces in the first management information to be written in one empty block among the second predetermined number of empty blocks. Including the position information (group address) indicating the other empty blocks in the empty blocks. Therefore, since the target of majority decision can be limited to the first management information having the same contents written together at the time of update, it is possible to increase the possibility of specifying appropriate first management information by majority decision.

  Further, according to the semiconductor memory device 1 according to the first and second embodiments, the memory controller 2 secures an empty block by excluding the congenital defective block from the first block group R1. Therefore, it is possible to avoid a situation where a congenital defective block is selected as a block in which the updated first management information is written.

  Further, according to the semiconductor memory device 1 according to the first and second embodiments, the memory controller 2 secures an empty block by excluding acquired bad blocks from the first block group R1. Therefore, it is possible to avoid a situation where an acquired defective block is selected as a block in which the updated first management information is written.

  Further, according to the semiconductor memory device 1 according to the first and second embodiments, the memory controller 2 includes the second predetermined number of first management information before update stored in the first block group R1. By removing the block (the majority target block), an empty block is secured. Accordingly, even when the power is forcibly shut down due to a user's erroneous operation or the like during the update process of the first management information, and the first management information after the update is thereby deleted, the first management before the update is performed. Since the information remains in the control target memory 3, it can be restarted using the information.

  Further, according to the semiconductor memory device according to the first and second embodiments, when the writing of the first management information to one free block is completed, the memory controller 2 stores the first management information before the update. A predetermined invalid flag is added to one block that has been stored. As a result, at least the second predetermined number of blocks can always be secured as the blocks in which the first management information is stored. Moreover, since an invalid flag is added instead of erasing data, stress on the memory cell due to erasure can be avoided. As a result, since the occurrence of acquired defective blocks in the first block group R1 is suppressed, the reliability of the apparatus can be improved.

  Further, according to the semiconductor memory device 1 according to the first and second embodiments, the memory controller 2 completes the writing of the first management information to one empty block among the second predetermined number of empty blocks. Then, data is erased from one block among the second predetermined number of blocks in which the first management information before update is stored. As a result, at least the second predetermined number of blocks can always be secured as the blocks in which the first management information is stored.

  Further, according to the semiconductor memory device 1 according to the modification example 4, the first predetermined number of blocks excluding the congenital defective blocks are allocated as the first block group R1. Therefore, since the first predetermined number of blocks can be secured as the blocks constituting the first block group, the reliability of the apparatus can be improved.

  Further, according to the semiconductor memory device 1 according to the first modification, the second management information is divided into the plurality of second management information pieces 121 to 123. The first management information 11 is stored in the control target memory 3A, and the second management information pieces 121 to 123 are stored in the control target memories 3B to 3D, respectively. Therefore, the plurality of second management information pieces 121 to 123 can be read simultaneously from the control target memories 3B to 3D, and as a result, the time required for processing can be shortened.

Further, according to the semiconductor memory device 1 according to the fifth modification, as shown in FIG. 34, each of the three ( third predetermined number) blocks selected from the second block group R2 is Second management information having the same content is stored. Then, the memory controller 2 selects the third predetermined number of second management information stored in the third predetermined number of blocks based on the position information included in the appropriate first management information, One piece of second management information is acquired. Therefore, even if one of the third predetermined number of second management information stored in the third predetermined number of blocks is destroyed or lost, the memory controller 2 is destroyed or lost. No remaining second management information can be acquired from the control target memory 3. As a result, it is possible to store the management information in the control target memory 3 while avoiding a situation in which the normal operation is hindered due to the presence of a defective block, forced power shutdown, or the like.

Further, according to the semiconductor memory device 1 according to the modified example 5, as shown in FIG. 35, the version is added to the three ( third predetermined number) blocks selected from the second block group R2. A different third predetermined number of pieces of second management information are stored. Then, the memory controller 2 selects the third predetermined number of second management information stored in the third predetermined number of blocks based on the position information included in the appropriate first management information, One piece of second management information is acquired. Therefore, even if one of the third predetermined number of second management information stored in the third predetermined number of blocks is destroyed or lost, the memory controller 2 is destroyed or lost. No remaining second management information can be acquired from the control target memory 3. As a result, it is possible to store the management information in the control target memory 3 while avoiding a situation in which the normal operation is hindered due to the presence of a defective block, forced power shutdown, or the like.

  Further, according to the semiconductor memory device 1 according to the first and second embodiments, the first block group R1 including the first predetermined number of blocks is limitedly assigned as a block for storing the management information. Yes. The management information includes first management information and second management information that is rewritten more frequently than the first management information. The first management information is stored in the first block group R1, and the second management information is stored in the second block group R2. As described above, the management information is divided into the first management information and the second management information according to the rewrite frequency, and the first management information having a low rewrite frequency is included in the limited first block group R1. By storing the data, rewriting of data does not occur frequently in the first block group R1. As a result, since the occurrence of acquired defective blocks in the first block group R1 is suppressed, the reliability of the apparatus can be improved.

DESCRIPTION OF SYMBOLS 1 Semiconductor memory device 2 Memory controller 3 Memory to be controlled

Claims (16)

A storage unit having a plurality of blocks, each of which is a data erasure unit;
A control unit for controlling the storage unit;
With
In all blocks of the storage unit,
A first block group consisting of a first predetermined number of blocks of four or more, which is assigned in a limited manner as blocks for storing management information necessary for the control unit to manage the storage unit;
A second block group other than the first block group;
Contains
Management information of the same content is stored in each of the second predetermined number of blocks that is three or more and less than the first predetermined number selected by the control unit from the first block group,
Management information
First management information;
Second management information having a higher rewrite frequency than the first management information;
Including
The first management information is stored in the first block group,
The second management information is stored in the second block group,
The first management information includes first position information indicating a block storing the second management information in the second block group,
The controller is
A normal block in which normal first management information is stored is identified from the first block group,
It is specified based on the first management information stored in one normal block and the second position information indicating the other two blocks in the first block group described in the first management information. By identifying a single piece of reasonable first management information by making a majority vote using two pieces of first management information,
A semiconductor memory device that acquires second management information from a second block group based on first position information included in the appropriate first management information.
The semiconductor memory device according to claim 1, wherein the second management information includes position information indicating a defective block. The first management information includes position information indicating a defective block in the first block group,
The semiconductor memory device according to claim 2, wherein the second management information includes position information indicating a defective block in the second block group. Second management information of the same content is stored in each of a third predetermined number of blocks that are two or more selected from the second block group,
The first management information includes first position information indicating a third predetermined number of blocks storing the second management information,
Wherein the control unit, third identifying a predetermined number of blocks based on the first position information included in the valid first management information, the third predetermined stored in said third predetermined number of blocks The semiconductor memory device according to claim 1, wherein one second management information is acquired from several pieces of second management information. A third predetermined number of second management information of different versions are stored in a third predetermined number of blocks that are two or more selected from the second block group,
The first management information includes first position information indicating a third predetermined number of blocks storing the second management information,
Wherein the control unit, third identifying a predetermined number of blocks based on the first position information included in the valid first management information, the third predetermined stored in said third predetermined number of blocks The semiconductor memory device according to claim 1, wherein one second management information is acquired from several pieces of second management information.   The semiconductor memory device according to claim 1, wherein the control unit specifies a normal block by excluding a congenital defective block from the first block group.   The semiconductor memory according to claim 1, wherein the control unit specifies a normal block by excluding an invalid block to which a predetermined invalid flag is added from the first block group. apparatus.   8. The control unit according to claim 1, wherein the control unit identifies a normal block by excluding an abnormal block in which a data error occurs in the stored first management information from the first block group. A semiconductor memory device according to claim 1.   A storage unit having a plurality of blocks, each of which is a data erasure unit;
  A control unit for controlling the storage unit;
With
  In all blocks of the storage unit,
  A first block group consisting of a first predetermined number of blocks of four or more, which is assigned in a limited manner as blocks for storing management information necessary for the control unit to manage the storage unit;
  A second block group other than the first block group;
Contains
  Management information of the same content is stored in each of the second predetermined number of blocks that is three or more and less than the first predetermined number selected by the control unit from the first block group,
  Management information
  First management information;
  Second management information having a higher rewrite frequency than the first management information;
Including
  The first management information is stored in the first block group,
  The second management information is stored in the second block group,
  The controller is
  When it becomes necessary to update the first management information, a second predetermined number of empty blocks are secured in the first block group, and each of the second predetermined number of empty blocks is updated Write first management information,
  A semiconductor memory device that writes the first management information to be written in one empty block of the second predetermined number of empty blocks, including position information indicating other empty blocks in the second predetermined number of empty blocks .   The semiconductor memory device according to claim 9, wherein the control unit writes the error detection code of the first management information so as to be included in the first management information.   11. The semiconductor memory device according to claim 9, wherein the control unit secures an empty block by excluding a congenital defective block from the first block group.   The semiconductor memory device according to claim 9, wherein the control unit secures an empty block by excluding acquired acquired blocks from the first block group.   The control unit secures an empty block by excluding a second predetermined number of blocks storing the first management information before update from the first block group. The semiconductor memory device according to any one of the above.   When the writing of the first management information to one empty block of the second predetermined number of empty blocks is completed, the control unit stores the second predetermined number of the first management information before the update. The semiconductor memory device according to claim 9, wherein a predetermined invalid flag is added to one of the blocks.   When the writing of the first management information to one empty block of the second predetermined number of empty blocks is completed, the control unit stores the second predetermined number of the first management information before the update. 14. The semiconductor memory device according to claim 9, wherein data is erased from one of the blocks.   The semiconductor memory device according to claim 1, wherein a first predetermined number of blocks excluding congenital defective blocks are allocated as a first block group.

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