JP2002132454A - Semiconductor disk device having compression/ decompression device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for realizing a large-capacity semiconductor disk device at a lower cost. SOLUTION: This invented semiconductor disk device, as its feature, has, in a same housing, at least one nonvolatile semiconductor memory, an external interface device, a memory controller doubling as a file system controller and a data compression/decompression circuit, and has a means for compressing data during the data writing and a means for decompressing the data during the data reading.

Description

DETAILED DESCRIPTION OF THE INVENTION TECHNICAL FIELD OF THE INVENTION

[0001] The present invention relates to a semiconductor disk device.

[Prior art]

2. Description of the Related Art A semiconductor disk device uses a semiconductor memory as a storage medium without using a magnetic disk or the like to replace a disk storage device such as a hard disk device.

In general, a semiconductor disk device emulates a memory array in which a number of nonvolatile semiconductor memories (such as a flash memory or an SRAM having a backup battery) are connected, an interface circuit for connecting to a higher-level device, and a disk device. Configured by rating software.

[0004] Hard disks have the drawback of being susceptible to vibration and shock, and are worn on a daily basis such as portable information terminals.
As a storage device mounted on a device that may cause an accident such as an accidental accident, a device using a nonvolatile semiconductor memory is desirable, and market needs are high.

[0005] In recent years, the exchange of electronic mail with a portable information terminal and the reading of electronic text downloaded on the Internet have become common. The built-in memory of such a portable information terminal is a limited semiconductor memory. Therefore, most portable information terminals allow additional external storage memory to be inserted, allowing backup of internal data such as e-mails and address books, and storage of large data that cannot be stored in the main unit. Generally done.

As with the hard disk of a personal computer, the need for a large-capacity nonvolatile storage medium is increasing.

[Problems to be solved by the invention]

Since a nonvolatile semiconductor memory is expensive as a nonvolatile storage device, it has not been adopted as a large-capacity disk in terms of cost.

However, there is a disadvantage that if a large-capacity external storage memory is constituted only by a semiconductor disk, it becomes very expensive.

When a similar hard disk drive is to be constructed, it is difficult to reduce the size of the hard disk drive, and the hard disk is susceptible to vibration and impact.

It is therefore an object of the present invention to provide a method for realizing a large-capacity semiconductor disk device at a lower cost by improving the semiconductor disk device.

Means for Solving the Invention

A semiconductor disk device according to the present invention includes at least one nonvolatile semiconductor memory, an external interface device, a memory controller also serving as a file system controller, and a data compression / expansion circuit in the same housing, and compresses data when writing data. And means for expanding the data when reading the data.

Since the data compression / expansion device is provided in the same housing, the external interface device can be easily replaced with a conventional magnetic disk device by matching the external interface device with the standard of the magnetic disk device or the like. The feature is that it can be used as a substitute.

Further, as an applied product based on the present invention, the data expansion / compression circuit provided with a bit error correction function, the nonvolatile semiconductor memory, the memory controller and the data compression / expansion circuit are replaced by one dedicated LSI. And IDE as the external interface device
An interface, a PCMCIA card interface as the external interface device, a compact flash card interface as the external interface device, a smart card interface as the external interface device, A virus check function, a function that supports encryption and decryption, a file system controller and a data compression / decompression circuit that can be replaced at the same time, and a data compression / decompression circuit that can be replaced And so on.

BEST MODE FOR CARRYING OUT THE INVENTION

FIG. 1 is a schematic view showing an embodiment of the present invention.

The inside of the bold line of the outer frame in FIG. 1 is housed in one case, and constitutes one storage device as a whole.

As the nonvolatile memory 10, a flash memory (a type of EEPROM capable of erasing and additional storage) or an SRAM having a backup battery can be used.

One or more nonvolatile memories 10 share an address bus and a data bus, and write, read and addressing of data are controlled by a memory controller 12, so that one memory block is constituted as a whole. Note that a plurality of blocks divided into logical partitions may be configured.

The memory controller emulates a logical file I / O such as a magnetic disk to the external interface device 16 by performing I / O with the file system controller.

The external interface 16 has, for example, an ID
An E interface that performs I / O with a higher-level device (such as a computer).

By using a standard compatible with a conventional magnetic disk or the like as the external interface 16, a conventional magnetic disk or the like can be replaced.

The above-mentioned file system controller comprises:
The data is passed to the data compression / expansion circuit 14 in predetermined units, and the compression / expansion circuit performs data compression when writing to the non-volatile memory 10 from the outside, and performs data expansion when reading from the non-volatile memory 10 to the outside. And return data to the file system controller.

The file system controller passes or receives data to and from the memory controller, and the memory controller maps the data before compression and the data after compression, respectively, and writes or reads data to or from the nonvolatile memory.

The data block passed to the compression / expansion circuit is corrected for errors by a bit error correction circuit according to the setting, is checked for infection with a computer virus by a virus check function, and is supported by an encryption / decryption support function. Encryption or decryption may be performed.

【Example】

Hereinafter, as an embodiment of a semiconductor disk device provided with a data compression / decompression device according to the present invention, a case where an IDE hard disk device type semiconductor disk device as an external storage device for a computer is realized by the present invention will be described. I do.

As one embodiment, the nonvolatile memory 10
Use a flash memory that does not require a backup power supply, and
Assume that an E interface is provided.

An electronic computer is connected as a host device, and an IDE interface, which is an external interface device 16 according to the present invention, is connected to an IDE controller on the electronic computer side.

When an electronic computer writes data on a disk, the following operation is performed.

When the computer attempts to write,
A write request is issued with a data block to be written to the IDE controller.

When a write request is issued, the data block passed to the IDE controller reaches the file system controller as a write command via the IDE interface.

The file system controller once passes the write command to the data compression / expansion circuit 14 as a compression request signal and a data block.

The data compression / expansion circuit 14 that has received the data block and the compression request signal performs a compression process on the data block to obtain compressed data.

The compressed data is transferred to the file system controller, and written to the flash memory, which is the nonvolatile memory device 10, via the memory controller.

When the computer reads data from the disk, the operation is as follows.

When the computer issues a read command, the read command reaches the file system controller via the IDE controller and the IDE interface.

The file system controller requests a memory block corresponding to the read request block from the memory controller, and acquires compressed data.

The file system controller sends the compressed data together with a decompression request signal to the data compression / decompression circuit 1.
Hand over to 4.

The data compression / decompression circuit 14 that has received the decompression request signal performs decompression processing on the compressed data to restore the original data block.

The restored data block is passed to the file system controller and output via the IDE interface, and the computer succeeds in reading the data block.

In another embodiment, a backup power supply and a DRAM or S
One using a RAM is conceivable.

A PC as the external interface device 16
As an example of using the MCIA card interface, a PCMCIA card type non-volatile storage device can be considered.

As an example in which a compact flash card interface is used as the external interface device 16, a compact flash card type nonvolatile storage device can be considered.

As an example in which a smart card interface is used as the external interface device 16, a smart card type nonvolatile storage device can be considered.

【The invention's effect】

The present invention provides an interface in the same housing,
A feature of the present invention is that it is extremely easy to replace a conventional magnetic disk device or the like by providing all of the compression / decompression device and the nonvolatile memory.

According to the present invention, more information can be recorded in the device than when no compression is performed due to the effect of data compression.

According to the present invention, data can be read and written at a higher speed than a hard disk device by using a semiconductor memory as a storage device.

According to the present invention, a large-capacity, high-speed disk can be inexpensively constructed by adding a compression / expansion function to a semiconductor disk device.

In the memory device, bits 0 and 1 may be slightly inverted due to the influence of electric noise and atmospheric radiation. According to the present invention, if data is compressed and compressed in consideration of error recovery information, data decompression and bit error recovery can be performed simultaneously during decompression.

By making the data compression / expansion circuit replaceable, a compression / expansion circuit using a higher-performance compression algorithm can be adopted at any time.

By making the file system controller and the data compression / decompression circuit interchangeable at the same time, a file management method suitable for the compression algorithm can be adopted.

As compared with the case where the data is compressed and decompressed by the host device, the calculation load is not applied to the arithmetic unit of the host device.

[0051]

[Brief description of the drawings]

FIG. 1 is a schematic view showing an embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 Non-volatile memory 12 Memory controller and file system controller 14 Data compression / expansion circuit 14a Bit error correction function 14b Virus check function 14c Encryption / decryption support function 16 External interface device

Claims (11)

[Claims] At least one non-volatile semiconductor memory (including an SRAM having a backup battery, etc.), an external interface device, a memory controller also serving as a file system controller, and a data compression / expansion circuit are provided in the same housing. A semiconductor disk device comprising means for compressing data when writing and means for expanding data when reading data. 2. The apparatus according to claim 1, wherein said data decompression / compression circuit has a bit error correction function. 3. The device according to claim 1, wherein said nonvolatile semiconductor memory, memory controller, and data compression / expansion circuit are replaced by one dedicated LSI. 4. An external interface device as an ID
Apparatus according to any of the preceding claims, comprising an E interface. 5. The personal computer as the external interface device.
2. An MCIA card interface.
The apparatus according to any one of claims 1 to 3. 6. The device according to claim 1, further comprising a CompactFlash (registered trademark) card interface as said external interface device. 7. A smart card interface as the external interface device.
An apparatus according to claim 1. 8. The system according to claim 1, wherein a virus check function is added.
An apparatus according to any one of claims 1 to 7. 9. The apparatus according to claim 1, further comprising a function of supporting encryption and decryption. 10. A file system controller and a data compression / expansion circuit which can be replaced simultaneously.
An apparatus according to any one of claims 1 to 9. 11. The apparatus according to claim 1, wherein said data compression / expansion circuit is replaceable.