JP2000306389A - Storage device using non-volatile semiconductor memory - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a high-speed storage device for a sector read command in a storage device using a non-volatile semiconductor memory such as a flush memory. SOLUTION: Sector data that are not read by a host computer 2 are also stored into a data buffer 13. When the host computer 2 successively reads the sector data, the data transmission time from a flush memory 17 can be reduced since the sector data have already been stored in the data buffer 13, thus achieving a high-speed sector read.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a storage device using a nonvolatile semiconductor memory as a storage medium, and more particularly, to a storage device for reading sector data at high speed.

[0002]

2. Description of the Related Art As a storage device using a nonvolatile semiconductor memory, there is a storage device using a flash memory. As this conventional example, there is "an external storage system using a semiconductor memory and a control method thereof" described in Japanese Patent Application Laid-Open No. 5-27924. In a conventional storage device, based on a command written by the host computer and a sector address written by the host computer along with the command,
It performs writing and reading of sector data.

A host computer such as a personal computer that stores sector data in a storage device includes:
When reading continuous sector data, it is divided into a plurality of sector read commands. For example, when a host computer reading sector data in units of 64 Kbytes (128 sectors) reads sector data of 128 Kbytes (256 sectors), the host computer
The sector read command of the sector is issued twice and 12
Read 8K bytes of sector data.

[0004]

According to the above prior art, when a host computer reads sector data,
No consideration is given to successive sector read commands from the host computer, and there is a problem in increasing the speed of reading sector data.

An object of the present invention is to speed up the reading of sector data when the host computer issues sector read commands continuously.

[0006]

In order to achieve the above object, a storage device of the present invention first determines whether or not sector data read by a host computer is stored in a data buffer. If the data buffer stores the sector data to be read by the host computer, the storage device immediately notifies the host computer that the sector data can be read, and notifies the host computer of the sector stored in the data buffer. The data is read by the host computer.

When the host computer reads out one sector data, the host computer reads out all the blocks in the flash memory including the sector data to be read out to the data buffer.

Further, when the host computer reads a plurality of sector data, the host computer reads all blocks in the flash memory in which the sector data to be read last is stored into a data buffer.

If the last sector data read by the host computer matches the last sector data in the block in the flash memory, the sector data of the next sector address of the sector data read by the host computer is stored. Block from the flash memory to the data buffer.

Accordingly, when the host computer continuously issues a sector read command in order to read continuous sector data, the storage device of the present invention provides a time required for the host computer to prepare sector data to be read first. Can be greatly reduced.

As described above, by preparing the sector data to be read by the host computer in advance, it becomes possible to speed up the reading of the sector data.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a storage device using a nonvolatile semiconductor memory according to the present invention will be described below.

FIG. 1 shows an example of the configuration of a storage device according to an embodiment of the present invention, which is applied to a storage device of a computer.

In FIG. 1, reference numeral 1 denotes a storage device using a nonvolatile semiconductor memory, which is a storage device of a host computer 2. The host computer 2 writes and reads sector data to and from the storage device 1. Examples of the host computer 2 include a personal computer (PC) and a digital still camera.

The storage device 1 is called a flash memory card because a flash memory is used as a nonvolatile semiconductor memory. Hereinafter, the storage device 1 is referred to as a flash memory card 1.

The flash memory card 1 is a PCMCI
It receives commands from the host computer 2 and transfers sector data via the A bus 21. In FIG.
The PCMCIA bus 21 conforming to the PCMCIA interface will be described as an example. In addition to the PCMCIA bus, ID
There is no particular limitation as long as there are various interfaces such as an E (ATA) interface and a SCSI interface, and a protocol agreement with the host computer 2 that requires an external storage device.

In the flash memory card 1, 11
Is a host interface unit for controlling an interface with the host computer 2.

Reference numeral 12 denotes a data buffer control unit for controlling sector data transfer between the host computer 2 and the data buffer 13 and between the data buffer 13 and the flash memory 17.

Reference numeral 13 denotes a data buffer for temporarily storing sector data when exchanging sector data between the flash memory card 1 and the host computer 2.

Reference numeral 15 denotes a flash interface unit for controlling an interface with the flash memory 17.

Reference numeral 16 denotes a microcomputer (hereinafter abbreviated as a microcomputer) which analyzes and controls commands written by the host computer 2, manages sector data written by the host computer 2, and controls the flash memory 1
7 is performed.

Reference numeral 17 denotes a flash memory for storing sector data to be written by the host computer 2. The flash memory 17 is connected to the flash interface unit 15 by a flash bus 106. FIG. 3 shows the internal configuration of the flash memory 17. The flash memory 17 forms one block with four sectors. Here, one block can be simultaneously erased at a time.

In the flash memory 17 shown in FIG. 3, the block data of the block address BA (k) includes sector addresses SA (4n), SA (4n + 1), SA (4n).
4 (n + 2) and SA (4n + 3). The block data of the block address BA (m) includes a sector address SA (4n + 4),
SA (4n + 5), SA (4n + 6), SA (4n +
7) four sector data are stored. The sector address is the address of the sector data addressed by the host computer 2. The block address is
This is an address for accessing block data stored in the flash memory 17. The relationship between the sector address and the block address is controlled by the microcomputer 16.

FIG. 2 shows an outline of an operation flow of the flash memory card 1 shown in FIG. First, in step S201, the flash memory card 1 waits for writing of a command by the host computer 2. Commands written by the host computer 2 are written to the host interface unit 11. The host interface unit 11 notifies the microcomputer 16 via the microcomputer bus 105 when the host computer 2 writes the command.

Next, in step S202, the type of command is determined. The microcomputer 16 reads out and analyzes the command written in the host interface unit 11 through the microcomputer bus 105.

When the host computer 2 writes a "sector write command" which is a command for writing sector data, the flash memory card 1 executes a "sector write process (step S203)". Step S2
In the sector write process 03, the sector data written by the host computer 2 is stored in the flash memory 17 of the flash memory card 1.

When the host computer 2 writes a "sector read command" which is a command for reading sector data, the flash memory card 1 executes "sector read processing (step S204)". Step S2
In the sector read process 04, the sector data stored in the flash memory 17 is output to the host computer 2.

A "non-data transfer command" which is a command by which the host computer 2 does not transfer sector data.
Is written, the flash memory card 1 executes a “non-data transfer process (step S205)”. here,
The command that does not transfer the sector data is a command that reads the state of the flash memory card 1 or instructs the flash memory card 1 to perform power control or the like.

Here, in step S202 in FIG. 2, the type of command is determined. At the same time, the start address and the number of sectors of the sector data accessed by the host computer 2 are also determined.

Next, details of the sector read process in step S204 will be described.

FIG. 13 shows an embodiment of the sector read process (step S204) of FIG. Here, the sector data read by the host computer 2 is referred to as the sector data HR.
Call. The sector data HR always changes and does not indicate the same sector data. For example, when the host computer 2 reads two sector data of the sector address SA (n) and the sector address SA (4n + 1) consecutively (same command), the first sector data HR read by the host computer 2 is the sector address. The second sector data HR read by the host computer 2 is the sector data of SA (4n), which is the sector data of the sector address SA (4n + 1).

First, in step S301, it is determined whether or not the data buffer 13 stores the sector data HR read by the host computer 2. If the sector data HR is not stored in the data buffer 13 (No), the process proceeds to step S302. Sector data HR is stored in data buffer 13 (Y
es) At the time, the process proceeds to step S307.

In step S302, it is confirmed whether or not block data including sector data HR is being transferred from the flash memory 17 to the data buffer 13. If the block data including the sector data HR is not being transferred (No), the process proceeds to step S303. If the data transfer of the block data including the sector data HR is being performed (Yes), the process proceeds to step S306.

In step S303, the sector data HR
Checks whether block data that does not include is being transferred. If the data transfer of the block not including the sector data HR is being executed (Yes), the block data transfer is interrupted (step S304), and then the data transfer of the block including the sector data HR is started (step S305). If the data transfer of the block not including the sector data HR has not been executed (No), the data transfer of the block including the sector data HR is started (step S305).

Next, in step S306, it is confirmed whether or not the data transfer of the sector data HR from the flash memory 17 to the data buffer 13 has been completed.
When the data transfer of the sector data HR is completed, step S
Proceed to 307.

In step S307, the data buffer 1
3, the sector data HR read by the host computer 2.
Is output to the host computer 2 in order to inform the host computer 2 that is stored.

When the flash memory card 1 outputs data ready, the host computer 2 starts reading sector data HR.

Next, in step S308 (FIG. 14), the flash memory card 1 checks whether the sector data read by the host computer 2 is the last sector data read by the host computer 2. If the sector data is read last by the host computer 2 (Yes), the process proceeds to step S310. If the host computer 2 does not read the last sector data (No), the process proceeds to step S309.

In step S310, it is determined whether or not the last sector data read by the host computer 2 is the last data in the block of the flash memory 17. For example, referring to FIG. 3, if the sector data read by the host computer 2 is the sector address SA (4n + 3), the result is Yes, and the process proceeds to step S311. The sector data read by the host computer 2 is composed of sector addresses SA (4n) to SA (4n +
If 2), the result is No, and the sector read process ends.

In step S311, the data transfer of the block storing the next sector data is started. For example, if the sector data read by the host computer 2 is the sector address SA (4n + 3) in FIG. 3, the data of the block address BA (m) is transferred to the data buffer 13.

In step S309, the flash memory card 1 waits for the host computer 2 to finish reading sector data. When the reading of the sector data by the host computer 2 ends (Yes),
Returning to step S301, the same processing is repeated.

Next, the flow of the sector read process described with reference to FIGS. 13 and 14 will be described using a specific example.

FIG. 4 is a timing chart showing the timing when the host computer 2 reads the sector addresses SA (4n + 1) and SA (4n + 2).

At time t001, when the host computer 2 writes the "sector read command 1", the microcomputer 16 detects this and analyzes the type of command.
This corresponds to steps S201 and S202 in FIG.
It corresponds to. “Sector read command 1” is a command by which the host computer 2 reads the sector addresses SA (4n + 1) and SA (4n + 2).

After the type of command is determined, the sector data read by the host computer 2 is transferred to the data buffer 1.
3 is determined (step S301 in FIG. 13).

FIG. 4 shows a case where the data buffer 13 does not store the sector data read by the host computer 2.

Next, at time t002, the microcomputer 1
No. 6 issues a “flash read command 1” to read block data from the flash memory 17 based on the result of the command type determination (step S305 in FIG. 13). "Flash read command 1"
This is a command to the flash memory 17 for reading the sector address SA (4n + 1) and subsequent addresses of the block address BA (k) of the flash memory 17. Commands to the flash memory 17 are transmitted to the flash interface unit 15.
Is issued to the flash memory 17.

At time t003, actual data transfer from flash memory 17 to data buffer 13 is started. The transfer of the sector address SA (4n + 1) is performed at time t0.
When the process ends in step 04, a data ready is output to the host computer 2 (step S30 in FIG. 13).
7). Upon receiving the data ready, the host computer 2 receives the sector address SA (4n) at time t005.
Reading of sector data of (+1) is started.

FIG. 6 shows the state of the data buffer 13 at time t004. The data buffer 13 in the present embodiment has a capacity capable of storing four sector data 131 to 134. However, the capacity of the data buffer may be the same as or larger than the block of the flash memory 17. At time t004, the data buffer 13 stores the sector address SA in 132.
(4n + 1) sector data are stored. 131, 1
33 and 134 are empty.

Since the reading of the sector data of the sector address SA (4n + 1) by the host computer 2 is not the reading of the last sector data by the host computer 2, the flash memory card 1 stores the sector address SA (4n + 1) by the host computer 2. Wait until the reading of the sector data is completed (step S309 in FIG. 14).

After the reading of the sector data at the sector address SA (4n + 1) by the host computer 2 is completed, the sector data at the sector address SA (4n + 2) has been transferred from the flash memory 17 to the data buffer 13, so at time t007 The data ready is output to the host computer 2 (step S307 in FIG. 13). Upon receiving the data ready, the host computer 2 starts reading the sector data of the sector address SA (4n + 2) at time t005. The reading of the sector data at the sector address SA (4n + 2) by the host computer 2 is the reading of the last sector data by the host computer 2, so that the processing for the "sector read command 1" ends.

FIG. 7 shows the contents of the data buffer 13 at time t008 in FIG. 132-
134, the sector addresses SA (4n + 1) to SA (4N
+3) sector data is stored.

FIG. 5 is a timing chart showing the timing when the host computer 2 reads the sector data of the sector address SA (4n + 3). Further, in the timing chart of FIG. 5, following the "sector read command 1" by the host computer 2 shown in FIG. 4, the sector data of the sector address SA (4n + 3) is read.

First, at time t009, when the host computer 2 writes the "sector read command 2", the microcomputer 16 detects this and analyzes the command type (steps S201 and S202 in FIG. 2).
The "sector read command 2"
Is a command for reading the sector address SA (4n + 3).

Since the reading of the sector data by the host computer 2 in FIG. 5 is an operation subsequent to the reading in FIG. 4, the sector data of the sector address SA (4n + 3) is stored in the data buffer 134.
Therefore, the sector data of the sector address SA (4n + 3) is transferred from the flash memory 17 to the data buffer 1
3 does not need to be forwarded.

That is, since the sector data read by the host computer 2 is stored in the data buffer 13 after the command type is determined, data ready is output to the host computer 2 (step S307 in FIG. 13). . The host computer 2 receives the data ready, and at time t010, the sector address S
Reading of sector data of A (4n + 3) is started.

Next, the sector address SA (4n + 3)
Is the last sector data read out by the host computer 2 and is the last sector data in the block BA (k), so the step S311 in FIG.
Is executed. Time t011 corresponds to step S3 in FIG.
Here, the sector data (sector address SA (4n +
A “flash read command 2” for reading a block (in FIG. 3, a block address BA (m)) including the sector data following the (3) sector data) is issued to the flash memory 17.

From time t012 to t016,
The block data at the block address BA (m) in the flash memory 17 is transferred to the data buffer 13.

FIG. 8 shows the contents of the data buffer 13 at time t013, and FIG. 9 shows the contents of the data buffer 13 at time t016. As shown in FIG.
After the sector data of the sector address SA (4n + 3) shown in FIG. 5 is read out, if the host computer 2 newly reads the sector data of the sector address SA (4n + 4), the sector address SA (4
Since the (n + 4) sector data has already been stored in the data buffer 13, the time taken to read data from the flash memory 17 can be apparently reduced to zero.

As described above, by storing the sector data read by the host computer 2 in the data buffer 13 in advance, the transfer time from the flash memory 17 to the data buffer 13 for the sector data read by the host computer 2 is apparently zero. It is possible to speed up the reading of sector data.

Next, another embodiment of the present invention will be described with reference to FIG.

First, at time t101, the host computer 2 writes a “sector read command 1” to the flash memory card 1 using the PCMCIA bus. “Sector read command 1” is the same as that in FIG. 4, and includes sector addresses SA (4n + 1) and SA (4n).
+2) is a command for reading the two sector data. As described with reference to FIG. 4, when the "sector read command 1" is written, the data buffer 1
3 includes the sector address SA (4n + 1) and SA
Description will be made assuming that two sector data of (4n + 2) are not stored.

FIG. 10 is almost the same as the timing chart shown in FIG. However, the timing of outputting data ready to the host computer 2 is immediately after the sector data of the sector address SA (4n + 1) is transferred to the data buffer 13 in FIG. 4, but in FIG. 10, the sector address SA (4n + 1) is output. To SA (4n +
This is immediately after the three sector data of 3) is transferred to the data buffer 13. That is, the block address BA
After the block data of (k) is transferred, the data transfer of the host computer 2 is started.

As a result, the data transfer between the flash memory 17 and the data buffer 13 and the data transfer between the host computer 2 and the data buffer 13 can be executed separately, so that the control can be simplified.

The sector addresses SA (4n + 1) and SA (4n +) shown in the timing chart of FIG.
When the reading of the sector data of the sector address SA (4n + 3) occurs after the reading of the sector data of 1), the timing chart is the same as that of FIG. Therefore, by storing the sector data read by the host computer 2 in the data buffer 13 in advance, the transfer time from the flash memory 17 to the data buffer 13 for the sector data read by the host computer 2 can be made apparently zero. Thus, the speed of reading the sector data is increased.

FIG. 1 shows another embodiment of the present invention.
1 will be described.

First, at time t201, the host computer 2 writes a “sector read command 1” to the flash memory card 1 using the PCMCIA bus. “Sector read command 1” is the same as that in FIG. 4, and includes sector addresses SA (4n + 1) and SA (4n).
+2) is a command for reading the two sector data. As described with reference to FIG. 4, when the "sector read command 1" is written, the data buffer 1
3 includes the sector address SA (4n + 1) and SA
Description will be made assuming that two sector data of (4n + 2) are not stored.

In FIG. 11, "flash read command 3" is issued to flash memory 17 instead of "flash read command 1" in FIG. 4 (time t2).
02). The “flash read command 3” is a command for transferring all block data at the block address BA (k) of the flash memory 17 to the data buffer 13.

At time t204, sector address S
When the sector data of A (4n + 1) is transferred to the data buffer 13, the host computer 2 starts reading the sector data of the sector address SA (4n + 1) from time t205. Thereafter, the same operation as in FIG. 4 is performed.

The sector addresses SA (4n + 1) and SA (4n +) shown in the timing chart of FIG.
When the reading of the sector data of the sector address SA (4n + 3) occurs after the reading of the sector data of 1), the timing chart is the same as that of FIG. Therefore, by storing the sector data read by the host computer 2 in the data buffer 13 in advance, the transfer time from the flash memory 17 to the data buffer 13 for the sector data read by the host computer 2 can be made apparently zero. Thus, the speed of reading the sector data is increased.

Finally, another embodiment of the present invention is shown in FIG.
2 will be described.

First, at time t301, the host computer 2 writes a “sector read command 1” to the flash memory card 1 using the PCMCIA bus. “Sector read command 1” is the same as that in FIG. 4, and includes sector addresses SA (4n + 1) and SA (4n).
+2) is a command for reading the two sector data. As described with reference to FIG. 4, when the "sector read command 1" is written, the data buffer 1
3 includes the sector address SA (4n + 1) and SA
Description will be made assuming that two sector data of (4n + 2) are not stored.

In FIG. 11, "flash read command 3" is issued to the flash memory 17 instead of "flash read command 1" in FIG. 10 (time t3).
02). The “flash read command 3” is a command for transferring all block data at the block address BA (k) of the flash memory 17 to the data buffer 13.

At time t305, sector address S
When the sector data of A (4n) to SA (4n + 3) is transferred to the data buffer 13, the host computer 2
Starts reading the sector data at the sector address SA (4n + 1) from time t306. Thereafter, the same operation as in FIG. 10 is performed.

The sector addresses SA (4n + 1) and SA (4n +) shown in the timing chart of FIG.
When the reading of the sector data of the sector address SA (4n + 3) occurs after the reading of the sector data of 1), the timing chart is the same as that of FIG. Therefore, by storing the sector data read by the host computer 2 in the data buffer 13 in advance, the transfer time from the flash memory 17 to the data buffer 13 for the sector data read by the host computer 2 can be made apparently zero. Thus, the speed of reading the sector data can be increased.

Further, in FIG. 11 and FIG. 12, even when the sector data of the sector address SA (4n) is read after the read of the sector data by the respective host computers 2, the sector address SA
Flash memory 17 for (4n) sector data
From the data buffer 13 to the data buffer 13 can be apparently reduced to zero, and the speed of reading sector data can be increased.

[0077]

As described above, according to the present invention,
In a storage device using a nonvolatile semiconductor memory such as a flash memory, there is an effect that a storage device that realizes high-speed reading of sector data can be provided.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a storage device according to an embodiment of the present invention.

FIG. 2 is a flowchart illustrating a processing procedure of the storage device of the present invention.

FIG. 3 is a diagram showing a configuration example of a flash memory 17;

FIG. 4 is a timing chart showing reading of sector data from a storage device.

FIG. 5 is a timing chart showing reading of sector data from a storage device.

FIG. 6 is a diagram showing an example of the contents of a data buffer 13 at a certain time.

FIG. 7 is a diagram showing an example of the contents of a data buffer 13 at a certain time.

FIG. 8 is a diagram showing an example of the contents of a data buffer 13 at a certain time.

FIG. 9 is a diagram showing an example of the contents of a data buffer 13 at a certain time.

FIG. 10 is a timing chart showing reading of sector data from a storage device.

FIG. 11 is a timing chart showing reading of sector data from a storage device.

FIG. 12 is a timing chart showing reading of sector data from a storage device.

FIG. 13 is a flowchart showing a sector read processing procedure of the storage device of the present invention.

FIG. 14 is a flowchart showing a sector read processing procedure of the storage device of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Flash memory card (storage device), 2 ... Host computer (PC etc.), 11 ... Host interface part, 12 ... Data buffer control part, 13 ... Data buffer, 15 ... Flash interface part, 16 ... Microcomputer (microcomputer) , 17 ... flash memory, 21 ... PCMCIA bus, 105 ... microcomputer bus,
106: Flash bus.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Kunihiro Katayama 1099 Ozenji Temple, Hitachi, Ltd. (72) Inventor Tomohisa Hatano 1099 Ozenji Temple, Aso-ku, Kawasaki City, Kanagawa Prefecture F-term in Hitachi System Development Laboratory (Reference) AC20 CA04 CA06

Claims (8)

[Claims] 1. A storage device connectable to a host computer, the storage device comprising: a nonvolatile semiconductor memory for storing sector data written by the host computer; connection means for connecting to the host computer; Control means for the nonvolatile semiconductor memory; and a data buffer temporarily used in reading and writing of sector data by the host computer. The nonvolatile semiconductor memory includes a large number of nonvolatile memory cells. One block is constituted by a set of memory cells, the block can be collectively erased, and the block can store a plurality of sector data. When the sector data is read by the host computer, the nonvolatile semiconductor memory All sector data stored in the block is always One of the storage device using a nonvolatile semiconductor memory, wherein the reading command. 2. The storage device according to claim 1, wherein, when sector data to be read by said host computer is already stored in said data buffer, said sector data is read by said host computer. A storage device using a nonvolatile semiconductor memory. 3. The storage device according to claim 1, wherein when the last sector data read by said host computer is the last sector data of said block of said flash memory, said host computer reads said last sector data. A storage device using a nonvolatile semiconductor memory, wherein all sector data of a block of the flash memory including sector data of a sector address next to the sector data of the sector data is read out to the data buffer. 4. A storage device connectable to a host computer, the storage device comprising: a nonvolatile semiconductor memory for storing sector data to be written by the host computer; connection means for connecting to the host computer; Control means for the nonvolatile semiconductor memory; and a data buffer temporarily used in reading and writing of sector data by the host computer. The nonvolatile semiconductor memory includes a large number of nonvolatile memory cells. One block is constituted by a set of memory cells, and the block can be collectively erased. The block can store one or more sector data. When the host computer reads one sector data, the host computer The sector storing the sector data read by the computer. Storage device using a nonvolatile semiconductor memory, characterized in that reading out all sector data stored in the blocks of the volatile semiconductor memory to the data buffer. 5. The storage device according to claim 4, wherein when sector data to be read by said host computer is already stored in said data buffer, said sector data is read by said host computer. A storage device using a nonvolatile semiconductor memory. 6. A storage device using a nonvolatile semiconductor memory according to claim 4, wherein the last sector data read by said host computer is the last sector data of said block of said flash memory. A storage device using a nonvolatile semiconductor memory, wherein all sector data of a block of the flash memory including sector data of a sector address next to the last sector data read by the host computer is read into the data buffer. 7. A storage device connectable to a host computer, the storage device comprising: a nonvolatile semiconductor memory for storing sector data written by the host computer; connection means for connecting to the host computer; Control means for the nonvolatile semiconductor memory; and a data buffer temporarily used in reading and writing of sector data by the host computer. The nonvolatile semiconductor memory includes a large number of nonvolatile memory cells. One block is constituted by a set of memory cells, the block can be collectively erased, and the block can store a plurality of sector data. When the sector data is read by the host computer, the nonvolatile semiconductor memory All sector data stored in the block is always One of the storage device using a nonvolatile semiconductor memory, which is a sector data read method from said non volatile semiconductor memories, characterized in that to read the command. 8. A storage device connectable to a host computer, the storage device comprising: a nonvolatile semiconductor memory for storing sector data written by the host computer; connection means for connecting to the host computer; Control means for the nonvolatile semiconductor memory; and a data buffer temporarily used in reading and writing of sector data by the host computer. The nonvolatile semiconductor memory includes a large number of nonvolatile memory cells. One block is constituted by a set of memory cells, and the block can be collectively erased. The block can store one or more sector data. When the host computer reads one sector data, the host computer The sector storing the sector data read by the computer. A storage device using a nonvolatile semiconductor memory, wherein the sector data is read from the nonvolatile semiconductor memory, wherein all sector data stored in a block of the volatile semiconductor memory is read out to a data buffer. .