JPH0652691A - Semiconductor disk device - Google Patents

Abstract

PURPOSE:To improve the life of a semiconductor disk device using a flash EEPROM. CONSTITUTION:Two kinds of flash EEPROMs (11-1)-(11-m), (12-1)-(12-n) whose writing units differ from each other coexist and the chips of these flash EEPROMs are selectively used according to the data size of writing data. Consequently, the most suitable chip is selected among the plural kinds of flash EEPROMs (11-1)-(11-m), (12-1)-(12-n) having different writing units so as to be written according to the data size of writing data. Consequently, the life of the whole device is lengthened without lowering the operating speed by effectively utilizing flash EEPROMs having the limit of the number of times for erasing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor disk device equipped with a flash EEPROM which is a non-volatile memory capable of electrically erasing all at once.

[0002]

2. Description of the Related Art Many conventional information processing apparatuses such as workstations and personal computers use magnetic disk devices as storage devices. The magnetic disk device has advantages such as high recording reliability and a low bit unit price, but has drawbacks such as a large device size and weak physical shock.

That is, the magnetic disk drive is based on the operating principle of magnetically writing data on the rotating disk or reading them by running a magnetic head on the surface of the rotating disk. Mechanically movable parts such as the rotating disk and the magnetic head may naturally malfunction or fail due to physical impact on the device. Further, the need for such a mechanically movable portion is an obstacle to reducing the size of the entire device.

For this reason, the magnetic disk device does not hinder the use of a desktop type computer fixedly mounted on a desk, but in the case of a portable and small laptop computer or notebook computer, these drawbacks are encountered. Is a big problem.

Therefore, in recent years, attention has been focused on a silicon disk device which is small in size and resistant to physical shock. The silicon disk device is a flash EEPROM that is a non-volatile memory that can be electrically erased all together.
Is used as a secondary storage device such as a personal computer like a conventional magnetic disk device. Since this silicon disk device does not have a mechanically movable part like a magnetic disk device, malfunctions and failures due to physical shocks are unlikely to occur. Further, there is an advantage that the size of the device is reduced.

However, the flash memory which is a constituent element of this silicon disk device has the same cell (bit).
By repeatedly writing and erasing data in the cell, the reliability of recording in the cell deteriorates, and the number of times is limited. Normally, the number of write / erase times of a flash EEPROM is on the order of about 10 5 or less, and this number is not a sufficient value to use a silicon disk device as a storage device of a computer like a magnetic disk device. I can't say.

Further, the minimum unit of data to be handled when writing or erasing the flash EEPROM is defined for each product type, and even if a small amount of data needs to be written or erased, the minimum unit is always required. You have to deal with minute data collectively. As a result, some cells needlessly be written or erased, and the reliability is deteriorated quickly. From these things, flash EEPROM
When writing or erasing data, it is necessary to consider doing within the minimum necessary range.

On the other hand, the flash EEPROM of a type having a small writing or erasing unit generally takes a longer time to rewrite data when compared with the flash memory having a larger unit of the same capacity (though it depends on the product type, In one actual example, the former takes a few seconds, while the latter has a difference of 100 ms, which is 10 ms.)
There is a drawback that. This is because, for example, when writing large-sized data to a flash EEPROM of a type having a small writing or erasing unit, it is necessary to repeatedly perform writing and erasing. Therefore, the silicon disk device is used as a flash EEPR of the former type.
It is not a good idea to use only OM in terms of operating speed.

[0009]

Conventionally, when a flash EEPROM having a large writing unit is used, the reliability of the flash EEPROM is deteriorated because a cell in which writing is performed unnecessarily occurs, and the flash EEPROM having a small writing unit is used.
The use of OM has a drawback that the time required for writing becomes long.

The present invention has been made in view of the above circumstances, and a plurality of types of flash EE having different write units are used.
It is an object of the present invention to provide a semiconductor disk device which enables a PROM to be selectively used according to the data size and type of write data, enables high-speed operation, and extends the life of the entire device.

[0011]

Means and Actions for Solving the Problems
In a semiconductor disk device including a flash EEPROM, a plurality of types of flash EEPROM chips having different write units and the flash EEPROM
A memory access unit for performing read / write access to the M chip and an access destination control unit for controlling an access destination of the memory access unit so that the flash EEPROM chip to be write-accessed can be switched according to the data size of write data. It is characterized by having.

In this semiconductor disk device, a plurality of types of flash EEPRO having different write units are used.
Mixed M chips, flash EEPR
The OM chip is selectively used according to the data size of write data. Therefore, from the data size of the write data, the most suitable chip can be selected from a plurality of types of flash EEPROM chips having different write units and writing can be performed, and the flash EEPROM having a limited erase count can be used effectively. It is possible to extend the life of the entire device without lowering the speed.

[0013]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows the configuration of a semiconductor disk device according to an embodiment of the present invention. The semiconductor disk device 10 is used as a secondary storage device of a personal computer as an alternative to a hard disk device or a floppy disk device.
It has an IA interface or an IDE interface. The semiconductor disk device 10 includes a flash memory group 11 as a data storage element. This flash memory group 11 includes a plurality of flash EEPs.
ROM chips 11-1 to 11-m, 12-1 to 12-n
It consists of

These flash EEPROM chips 11
In -1 to 11-m and 12-1 to 12-n, the minimum unit is set for the amount of data to be handled when writing or erasing, and the data for that unit is handled collectively. Here, as an example, the flash EEPROM 11-1 to
11-m is a type that can be written in 1-byte units,
It is assumed that the flash memories 12-1 to 12-n are of a type in which writing can be performed only in page units of 512 bytes. In this case, as a flash EEPROM of a type capable of writing in 1-byte units, for example, N
It is preferable to use an OR-type flash EEPROM, and it is preferable to use a NAND-type flash EEPROM as a type of flash EEPROM capable of writing in units of 512 bytes.

The semiconductor disk device 10 also includes a controller 13 and a host interface 14. The controller 13 controls access to the flash EEPROM chips 11-1 to 11-m, 12-1 to 12-n in response to a disk access request supplied from the host CPU 1 via the host interface 14. The host interface 13 has, for example, a pin arrangement of 40 pins conforming to the IDE interface like the hard disk device connectable to the host system bus, or 68 pins conforming to the PCMCIA interface like the IC card that can be mounted in the IC card slot. It has a pin arrangement of.

The controller 13 uses the address conversion circuit 1
31, a data buffer 132, and a read / write control circuit 133. Address conversion circuit 1
Reference numeral 31 converts an address for disk access supplied from the host CPU 1 into an address for accessing the flash memory group 11. The address conversion circuit 131 includes information such as a drive number, a head number, a cylinder number, and a sector number to be accessed included in the command sent from the host CPU 1, the flash memory number of the flash memory group 11 and the like. There is provided an address conversion table 131a in which the correspondence relationship with the memory address is defined. The specific configuration of the address conversion table 131a will be described later with reference to FIGS.

The data buffer 132 is the host CPU 1
The write data sent from the flash memory and the read data from the flash memory group 11 are temporarily held. The read / write control circuit 133 includes the flash EEPROMs 11-1 to 11-m, 1 in the flash memory group 11.
2-1 to 12-n are selected, and data read / write control for the selected flash EEPROM is performed. In this case, the read / write control circuit 133
In order to select the flash EEPROM corresponding to the memory number output from the address conversion circuit 131,
Flash EEPROM 11-1 to 11-m, 12-1
The chip enable signal CE in the active state is selectively supplied to .about.12-n. Further, the read / write control circuit 133 generates a memory address output from the address conversion circuit 131 as a head address, and executes a data read / write operation for the data size sent from the host CPU 1. , The start address is sequentially incremented. The switching between the read operation and the write operation is controlled by the read / write instruction information included in the command sent from the host CPU 1.

Further, the read / write control circuit 133
Depending on whether or not the data size of the write data is smaller than 512 bytes, one of two chip groups of the flash EEPROM chips 11-1 to 11-m and the flash EEPROM chips 12-1 to 12-n is selected. select. In this case, the read / write control circuit 133
If the data size of the write data is smaller than 512 bytes, write the write data to the flash EE
Write to one of the PROM chips 11-1 to 11-m,
The write data of 512 bytes or more is written in the flash EEPROM chips 12-1 to 12-n. Next, with reference to FIGS. 2 and 3, the flash EEPROMs 11-1 to 11-m, 12-1 to 12
-N Each write unit / erase unit will be described.

FIG. 2 shows a flash EEPROM 11-.
One write / erase unit is shown. As shown in the figure, the flash EEPROM 11-1 has an erase block size of, for example, 4 Kbytes, and is configured to execute writing in 1-byte units in each erase block of 4 Kbytes. This flash EE
In the PROM 11-1, for example, after erasing the first erase block once, data writing in 1-byte units can be performed up to 4K times without erasing operation.

FIG. 3 shows a flash EEPROM 12-.
One write / erase unit is shown. As shown in the figure, the flash EEPROM 12-1 is configured such that the erase block has a size of, for example, 4 Kbytes, and writing is performed in units of 512 bytes in each erase block of 4 Kbytes. In this flash EEPROM 12-1, for example, after once erasing the first erase block, data writing in units of 512 bytes can be performed up to 8 times without erasing operation. Next, an example of a specific configuration of the address conversion circuit 131 will be described with reference to FIG.

As shown, the conversion table 131a is
First and second conversion tables 131a-1 and 131a
-2 is provided. First conversion table 131a-1
Is a conversion table used when selecting the first chip group consisting of the flash EEPROMs 11-1 to 11-m, and is an address for disk access and a memory number assigned to the flash EEPROMs 11-1 to 11-m. And the correspondence with the memory address is defined. Also, the second conversion table 131a-2 is
It is a conversion table used when selecting the second chip group consisting of the flash EEPROMs 12-1 to 12-n, and is an address for disk access, a memory number assigned to the flash EEPROMs 12-1 to 12-n, and a memory. The correspondence with the address is defined.

These first and second conversion tables 13
Which of 1a-1 and 131a-2 is used is determined by the table selection circuit 132. That is, when the data size is smaller than 512 bytes, the table selection circuit 132 uses the flash EEPROM 11-1.
~ 11-m are used so that the conversion table 131a-
1 is selected, and the conversion table 131a-2 is selected so that the flash EEPROMs 12-1 to 12-n are used when the data size is 512 bytes or more. Next, referring to FIGS. 5 and 6, the conversion table 131a
A specific configuration example of -1, 131a-2 will be described.

FIG. 5 shows an example of correspondences between disk addresses (HD addresses) and flash addresses (Flash addresses) defined in the conversion table 131a-1. As described above, the disk address from the host CPU 1 is composed of the drive number, the head number, the cylinder number, and the sector number. Therefore, the flash address corresponding to the drive number, the head number, the cylinder number, and the sector number. EEPROM 11-1 to
A memory number and an in-chip memory address for designating 11-m are defined.

Here, the memory number # 1-1 indicates the flash EEPROM 11-1, and the memory number # 1-n indicates the flash EEPROM 11-m. For example,
When the memory number corresponding to the disk address from the host CPU 1 is “# 1-1”, the read / write control circuit 1
The chip enable signal CE corresponding to the flash EEPROM 11-1 is set to the active state by 33. As a result, the flash EEPROM 11-1
Becomes accessible and data writing to a position designated by a memory address corresponding to a disk address from the host CPU 1 or data reading from that position is executed. Similarly, the memory number corresponding to the disk address from the host CPU 1 is “# 1-m”.
At this time, the read / write control circuit 133 sets the chip enable signal CE corresponding to the flash EEPROM 11-m to the active state, and the flash E
EPROM 11-m is accessed.

FIG. 6 shows an example of correspondences between disk addresses (HD addresses) and flash addresses (Flash addresses) defined in the conversion table 131a-2. Also in this conversion table 131a-2, the memory number and the in-chip memory address for designating the flash EEPROMs 12-1 to 12-n are associated with the disk address including the drive number, the head number, the cylinder number, and the sector number. It is defined.

Here, the memory number # 2-1 indicates the flash EEPROM 12-1, and the memory number # 2-n indicates the flash EEPROM 12-n. For example,
When the memory number corresponding to the disk address from the host CPU 1 is “# 2-1”, the read / write control circuit 1
The chip enable signal CE corresponding to the flash EEPROM 12-1 is set to the active state by 33. As a result, the flash EEPROM 12-1
Becomes accessible and data writing to a position designated by a memory address corresponding to a disk address from the host CPU 1 or data reading from that position is executed. Similarly, the memory number corresponding to the disk address from the host CPU 1 is “# 2-n”.
At this time, the read / write control circuit 133 sets the chip enable signal CE corresponding to the flash EEPROM 12-n to the active state, and the flash E
EPROM 12-n is accessed. Next, the write access control operation of the flash memory group 11 will be described with reference to the flowchart of FIG.

When a data write request is issued from the host CPU 1, first, the drive number, head number, cylinder number, and the like on the semiconductor disk device 10 to be accessed.
Information indicating the data size is sent from the host CPU 1 to the address conversion circuit 131 together with the disk address information such as the sector number. The address conversion circuit 131 detects whether the data size is smaller than 512 bytes (step S11), and determines the conversion table to be referred to according to the detection result.

For example, when the data size is smaller than 512 bytes, the aforementioned conversion table 131a-1 is used for address conversion, and the conversion table 13a-1 is used.
By referring to 1a-1, the transmitted information such as the drive number is converted into the flash memory number of the flash memory group 11 and the address therein (step S12). Then, the flash EEPROMs 11-1 to 11 corresponding to the converted memory number (here, one of # 1-1, ... # 1-m).
The chip enable signal CE is generated for one of -m, and the flash EEPROM is write-accessed (steps S13 and S14).

On the other hand, when the data size is 512 bytes or more, the conversion table 131a is used for address conversion.
-2 is used and the conversion table 131a-2 is referred to, whereby the information such as the drive number sent is converted into the flash memory number of the flash memory group 11 and the address therein (step S1
5). And the converted memory number (here,
# 2-1, ... # 2-n) corresponding to one of the flash EEPROMs 12-1 to 12-n, a chip enable signal CE is generated, and the flash EEPROM is write-accessed. (Step S
16, S17).

In this way, the write destination for the write data having a data size smaller than 512 bytes is selected to the flash EEPROMs 11-1 to 11-m, and the write destination for the write data having a data size of 512 bytes or more. Is flash EEPRO
Selected as M12-1 to 12-n.

Generally, in a computer system, data written in a secondary storage device such as a hard disk device or a floppy disk device is roughly classified into the following two types. One is user data that the user wants to store, and the other is management information that is created by a file system or the like in addition to the user's direct request, and the contents are information for managing files and directories. Is. The minimum unit of writing / reading of the disk device is 1 sector (512 bytes, or 1
024 bytes), user data write /
The data size at the time of reading is usually at least 512 bytes or more. On the other hand, with regard to management information, because of its nature, such as addresses, flags and some kind of counters are the main components, so the data size for rewriting is usually a few bytes. Is. In addition, such management information requires a data rewriting operation for updating the data more frequently than user data.

Therefore, in actuality, in the semiconductor disk device 10, the flash EEPROMs 11-1 to 11-1 in which the management information which is small in size but needs to be rewritten frequently can be written in 1-byte units.
User data that is written in 1-m and that is larger in size than the management information and that does not require a small amount of rewriting frequently is written in the EEPROMs 12-1 to 12-n.

As described above, according to this embodiment, two types of flash EEPROMs, the writing unit of which is 1 byte and 512 bytes, are selected according to the data size of the write data.
Since the writing destination chip can be selected from among the writing destinations and writing can be performed, the number of unnecessary writing and erasing operations can be reduced, and the flash memory 11 having a limited erasing count can be used effectively. It is possible to extend the life of the entire device without lowering the speed. Next, a second embodiment of the present invention will be described.

FIG. 8 shows the structure of a semiconductor disk device 10A according to the second embodiment. This semiconductor disk device 10A is particularly suitable for FAT (File Alloc).
The present invention has a configuration suitable for use as a substitute for a hard disk device or a floppy disk device of an application table) file system.

That is, in the FAT file system, the above-mentioned management information is collectively recorded at a specific place in the disk device. In other words, the data to write is FAT
The range of writing positions on the disk designated by the host CPU 1 is clearly different between management information such as a directory and user data, and user data, and they do not coexist.

Therefore, as shown in FIG. 8, in the semiconductor disk device 10A of the second embodiment, one flash EEPROM capable of writing with 1 byte is used.
11-1 and a plurality of flash EEPROMs 12-1 to 12-n capable of writing with 512 bytes configure a flash memory group 11A, and the flash EEPROM 11-1 has an address corresponding to a write sector position of management information. The address conversion circuit 131A is configured so that the addresses corresponding to the write sector positions of the user data are allocated to the flash EEPROMs 12-1 to 12-n. FIG. 9 shows an example of the configuration of the conversion table 131b provided in the address conversion circuit 131A.

In the conversion table 131b, a drive number and a head are assigned so that the FAT area on the disk for writing the management information is allocated to the flash EEPROM 11-1 and the user data area is allocated to the flash EEPROMs 12-1 to 12-n. A disk address including a number, a cylinder number, and a sector number, and a flash memory address including a memory number and an in-chip memory address are defined.

Here, the memory number # 1 is the flash EE.
The PROM 11-1 is shown, and the memory number # 2-1 is the flash EEPROM 12-1 and the memory number # 2-n.
Indicates a flash EEPROM 12-n. FA
When accessing the T area, the memory number corresponding to the disk address from the host CPU 1 is always "# 1". As a result, the read / write control circuit 133 sets the chip enable signal CE corresponding to the flash EEPROM 11-1 to the active state, and the read / write of management information is performed by the flash EEPROM 11-.
Executed for 1. Also, when accessing the user data area, the memory number corresponding to the disk address from the host CPU 1 is always a value after "# 2-1". As a result, the read / write control circuit 133 sets the chip enable signal CE corresponding to the flash EEPROM 11-1 to the active state, and the read / write of the user data is performed by the flash EEPROM1.
2-1 to 12-n. Next, the write access control operation of the flash memory group 11A in the second embodiment will be described with reference to the flowchart in FIG.

When a data write request is issued from the host CPU 1, first, a drive number, a head number, a cylinder number to be accessed on the semiconductor disk device 10,
Disk address information such as sector number is stored in the host CPU
1 to the address conversion circuit 131A. The address conversion circuit 131A refers to the conversion table 131b, converts a disk address including a drive number, a head number, a cylinder number, a sector number, etc. into a flash memory address, and determines whether or not the memory number is "# 1". It is detected (steps S21 and S22).

When the memory number is "# 1", that is, when the write destination is the FAT area, the flash EEPROM 11-corresponding to the converted memory number # 1.
A chip enable signal CE is generated for 1 and the flash EEPROM 11-1 is write-accessed (steps S23 and S24).

On the other hand, when the memory number is not "# 1", that is, when the writing destination is the user data area, the converted memory number (here, # 2-1,
... Flash E corresponding to any one of # 2-n)
The chip enable signal CE is generated for one of the EPROMs 12-1 to 12-n, and the flash EEP signal is generated.
The ROM is write-accessed (steps S25 and S2).
6).

As described above, also in the second embodiment, since the optimum chip can be selected and written from the two types of flash EEPROMs in which the write unit is 1 byte and 512 bytes, it is useless. The number of writing and erasing operations can be reduced, and the flash memory 11 having a limited number of erasing operations can be effectively used to extend the life of the entire device without lowering the operating speed.

In the above description, the flash E
Although specific numbers are shown for the minimum unit of data that can be handled by the EPROM, these numbers do not necessarily have to be exactly these numbers. For example, the data writing unit is 25
The 6-byte flash EEPROM and the flash EEPROM of which the data writing unit is 512 bytes are mixed, and the management information of small data size and high rewriting frequency is written in the 256-byte flash EEPROM.
User data may be written in a 512-byte flash EEPROM. Also, the type and number of writing units of the flash EEPROM chip provided in the semiconductor disk device may be any number as long as it is plural.

[0045]

As described above in detail, according to the present invention,
Multiple types of flash EEPROMs with different writing units
Can be selectively used according to the data size and type of write data, high-speed operation is possible, and the life of the semiconductor disk device as a whole can be extended.

[Brief description of drawings]

FIG. 1 is a block diagram showing a semiconductor disk device according to a first embodiment of the present invention.

FIG. 2 is a view for explaining a writing unit / erasing unit of a first flash EEPROM chip provided in the semiconductor disk device of the first embodiment.

FIG. 3 is a diagram for explaining a writing unit / erasing unit of a second flash EEPROM chip provided in the semiconductor disk device of the first embodiment.

FIG. 4 is a block diagram showing an example of a configuration of an address conversion circuit provided in the semiconductor disk device of the first embodiment.

FIG. 5 is a diagram showing the contents of a first conversion table provided in the semiconductor disk device of the first embodiment.

FIG. 6 is a diagram showing the contents of a second conversion table provided in the semiconductor disk device of the first embodiment.

FIG. 7 is a flowchart for explaining the operation of the semiconductor disk device of the first embodiment.

FIG. 8 is a block diagram showing a semiconductor disk device according to a second embodiment of the present invention.

FIG. 9 is a diagram showing the contents of a conversion table provided in the semiconductor disk device of the second embodiment.

FIG. 10 is a flowchart for explaining the operation of the semiconductor disk device according to the second embodiment.

[Explanation of symbols]

10 ... Semiconductor disk device, 11 ... Flash memory,
13 ... Controller, 14 ... Host interface,
131 ... Address conversion circuit, 131a ... Conversion table,
132 ... Data buffer, 133 ... Read / write control circuit.

Claims (4)

[Claims] 1. A semiconductor disk device including a flash EEPROM, wherein a plurality of types of flash EEP having different write units are used.
A ROM chip, a memory access unit for read / write access to these flash EEPROM chips, and an access destination of the memory access unit are controlled so that the flash EEPROM chip to be write-accessed can be switched according to the data size of write data. A semiconductor disk device comprising: an access destination control unit. 2. The plurality of types of flash EEPROM chips include a first flash EEPROM chip having a first write unit and a second flash having a second write unit smaller than the first write unit. 2. The semiconductor disk device according to claim 1, further comprising an EEPROM chip. 3. The access destination control means includes a detection means for detecting whether or not the data size of the write data is smaller than the first write unit, and has a data size smaller than that of the first write unit. Detecting by the detecting means so that small write data is written in the second flash EEPROM chip, and write data having a data size larger than the first write unit is written in the first flash EEPROM chip. 3. The semiconductor disk device according to claim 2, wherein the access destination of said memory access means is controlled according to the result. 4. A semiconductor disk device having a flash EEPROM, wherein a first flash EEPR having a first write unit is provided.
OM chip and second flash EEP having a second write unit smaller than the first write unit
A group of flash EEPROM chips having ROM chips, a memory access means for making read / write access to these flash EEPROM chips, and user data written in the first flash EEPROM chip to manage a storage position of the user data. The management information is the second flash EEPROM.
A semiconductor disk device, comprising means for switching the flash EEPROM chip to be write-accessed by the memory access means according to the type of write data so that the data is written in the chip.