JPH07230411A - Flash memory card device - Google Patents

Abstract

PURPOSE:To realize large capacity, and to speed up access from an external system (e.g. computer system) and then improve the performance of the external system. CONSTITUTION:This device is equipped with a flash memory part 3 as a main storage memory, a temporary storage memory part 4 which has capacity as large as or larger than the capacity of one specific write unit of the flash memory part 3, and a control part 5 which controls data transfer among the external memory 2, temporary storage memory part 4, and flash memory part 3; when access for writing data to the flash memory card device 1 from the external system becomes necessary, the control part 5 sends a command for transferring data from the temporary storage memory part 4 to the flash memory part 3 after temporarily writing the data in the temporary storage memory part 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flash memory card device, and more particularly to a flash memory card device adapted for high speed access (writing / reading) to a built-in flash memory. With the increase in capacity of semiconductor memories in recent years, there has been a demand for a small external storage device used in a small computer system such as an electronic notebook or a notebook personal computer. For this reason, although a memory card device is provided, a memory card device using a flash memory is widely used because of its relatively large memory capacity. However, in a memory card device using a flash memory, there is a problem that the time required for external access is relatively long (that is, the access speed is slow), and therefore a device for high-speed access is required. .

[0002]

2. Description of the Related Art In a conventionally known memory card device having a built-in flash memory, it is common to write directly to the flash memory from a computer system that uses the memory card device as an external storage device. It was However, due to the nature of the writing form of the flash memory, even if writing 1 byte of data, for example, a block of a predetermined one writing unit is set in advance for each flash memory used (this block has a capacity of 1 byte above). Since it is necessary to write to all of them, it takes a considerable time to transfer the data from the computer system to the flash memory. Therefore, compared with a memory card device using a volatile memory such as SRAM or DRAM, there is a disadvantage that the performance of the computer system is deteriorated.

[0003]

As described above, the memory card device using the flash memory is advantageous in that it has a larger memory capacity than the memory card device using the volatile memory, but There is a problem in that the access (writing or reading) to the memory card device from the computer system is slow.

Further, while the memory card device is being accessed, the computer system cooperating with the memory card device is restricted by the memory card device, resulting in a decrease in the performance of the computer system. Also occurs. The present invention has been created in view of the above problems in the prior art, and realizes a large capacity, speeds up access from an external system such as a computer system, and eventually contributes to performance improvement of the external system. It is an object of the present invention to provide a flash memory card device capable of performing the above.

[0005]

In order to solve the above-mentioned problems, according to the present invention, rather than directly accessing the flash memory section from an external system cooperating with the flash memory card device, it is possible to access at a relatively high speed. The flash memory unit is accessed through a temporary storage memory (for example, a cache memory).

Therefore, according to the present invention, a flash memory unit as a main memory, a temporary storage memory unit having a capacity equal to or larger than the capacity of a block of a predetermined writing unit in the flash memory unit, and an external storage unit A control unit that controls data transfer between the system and the temporary storage memory unit and the flash memory unit, and when the external system makes a data write access to the flash memory card device, the control unit There is provided a flash memory card device, characterized in that, after temporarily writing data in the temporary storage memory unit, a command to transfer data from the temporary storage memory unit to the flash memory unit is issued.

In a preferred embodiment of the present invention, a data read access from the external system to the flash memory card device occurs during data transfer from the temporary storage memory unit to the flash memory unit. In this case, the control unit interrupts the data transfer and prioritizes the data reading process.

[0008]

According to the above-described configuration of the present invention, when the external system makes a write access to the flash memory card device, the data to be written is:
First, it is written in the temporary storage memory unit via the control unit,
After the data writing is completed, the data is transferred from the temporary storage memory unit to the corresponding block in the flash memory unit.

As described above, when the external system cooperating with the flash memory card device accesses to write data, the data to be written is stored in the flash memory unit via the temporary storage memory unit that can be accessed at high speed. Therefore, the write access from the external system can be performed at a high speed as compared with the flash memory card device in which the flash memory unit is directly written as in the conventional type. This contributes to improving the performance of the external system.

Further, since the flash memory section is used as the storage means for the write data, the capacity of the memory card device can be increased. Further, when a data read access is made from an external system during data transfer from the temporary storage memory unit to the flash memory unit, the control unit interrupts the data transfer and prioritizes the data read process. If you do
As in the case of the above data writing, the read access of the external system to the flash memory card device can be realized at high speed.

Details of other structural features and operations of the present invention will be described with reference to the accompanying drawings with reference to the following embodiments.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the configuration of an embodiment of a flash memory card device according to the present invention. In the figure, 1
Is a flash memory card device of, for example, a business card size according to the present embodiment, 2 is a computer system that uses the flash memory card device 1 as an external storage device,
The computer system can be connected to the card device 1 via the external terminals T1 to T4 of the card device 1 as required. Here, the external terminal T1 is used for input / output of the data DT (internal data DT), and the external terminal T2 is used for the address signal AD (internal address signal A).
D ') is used for input, and the external terminal T3 has a read / write control signal R / W (internal read / write control signal R / W).
W ') is input, and the external terminal T4 is used to output a write permission / prohibition control signal WC for instructing the computer system 2 to permit or prohibit writing.

Further, 3 is a flash memory card device 1
Flash memory unit that functions as the main memory of
Is a volatile memory unit (a cache memory unit in this embodiment) having a capacity equal to or larger than the capacity of a block of a predetermined one writing unit in the flash memory unit 3, and 5 is a flash memory unit 3 and a cache memory unit 4. 2 shows a control unit for controlling writing / reading of data between the computer system 2 and the external terminals T1 to T4.

Next, the operation of the flash memory card device 1 according to this embodiment, that is, the writing / writing performed by the control unit 5 will be described.
The read control process will be described with reference to the flowcharts shown in FIGS. First, in step 11, it is determined whether the computer system 2 has accessed the flash memory card device 1 (YES) or not (NO). If the determination result is YES, the process proceeds to step 12, and if the determination result is NO, this flow is “end”. In step 12, it is determined whether the access indicates write or read. If the determination result indicates “write”, the process proceeds to step 21 and the determination result indicates “read”. If so, go to step 31 (see FIG. 3).

In the case of write access ... See steps 21 to 27 In step 21, internal data transfer (that is, data transfer from the cache memory unit 4 to the flash memory unit 3) is being executed in the flash memory card device 1. It is determined whether (YES) or not (NO). Judgment result is Y
If ES, the process proceeds to step 22, and if the determination result is NO, the process proceeds to step 23. In step 23, first, the control signal WC is sent to the computer system 2 to notify it of the write permission, and then the write target data is written in the designated storage area in the cache memory unit 4. In the next step 24, the data written in the cache memory unit 4 is transferred to the flash memory unit 3 (internal data transfer start). Then, the process returns to step 11 and the above process is repeated.

On the other hand, in step 22, since it is determined in step 21 that the internal data transfer is being executed, there is a free area in the cache memory unit 4 (YE
S) or not (NO). If the determination result is YES, the process proceeds to step 23, and if the determination result is NO, the process proceeds to step 25. In step 25, it is determined whether the designated write area (storage area) has a cache hit (YES) or not (NO). The judgment result is YE
In the case of S, the process proceeds to step 26, and in the case of the determination result being NO, the process proceeds to step 27. In step 26, the internal data transfer from the cache memory unit 4 to the flash memory unit 3 is interrupted. Then, the process proceeds to step 23 and the above process is repeated. On the other hand, in step 27, since data cannot be written, a control signal WC is sent to the computer system 2 to notify that writing is prohibited. Then, the process returns to step 11 and the above process is repeated.

In case of read access ... See steps 31 to 37 In step 31, it is determined whether internal data transfer is being executed in the flash memory card device 1 (YES) or not (NO). If the determination result is YES, the process proceeds to step 32, and if the determination result is NO, the process proceeds to step 33. In step 32, the cache memory unit 4
From the internal data transfer to the flash memory unit 3 is interrupted, and then the process proceeds to step 33.

In step 33, the designated read area (storage area) has a cache hit (YES).
Whether or not (NO) is determined. If the determination result is YES, the process proceeds to step 34, and if the determination result is NO, the process proceeds to step 35. In step 34, the data is output from the corresponding memory area in the cache memory unit 4, and then the process proceeds to step 36. On the other hand, in step 35, the data is output from the corresponding memory area in the flash memory unit 3, and then the process proceeds to step 36.

At step 36, internal data transfer is completed in the flash memory card device 1 (Y
It is determined whether ES) or not (NO). If the determination result is YES, the process returns to step 11 to repeat the above process, and if the determination result is NO, the process proceeds to step 37. In step 37, the internal data transfer from the cache memory unit 4 to the flash memory unit 3 is restarted, and then the step 1
The process returns to 1 and the above process is repeated.

As described above, in this embodiment,
When a data write access is made from the computer system 2, the control unit 5 first writes data to the cache memory unit 4, and after the data write is completed, the cache memory unit 4 to the flash memory unit 3 is concerned. The data is transferred to the block.

When a write access is made from the computer system 2 during the data transfer from the cache memory unit 4 to the flash memory unit 3, the data transfer is interrupted and the data is written in the empty area of the cache memory unit 4. If there is no free area, the computer system 2 is notified that the data writing is prohibited (transmission of the control signal WC).

However, even if there is no free area in the cache memory unit 4, if the write area targeted for data writing has a cache hit, the internal data transfer is interrupted and the update processing of the cache memory unit 4 is prioritized. Let Further, when a read access is made from the computer system 2 during the data transfer from the cache memory unit 4 to the flash memory unit 3, the data transfer is temporarily suspended and the data read process is prioritized.

In this data read, if the read area targeted for the data read has a cache hit (that is, if the data in the read area exists in the cache memory unit 4), the cache memory unit 4 The data inside is read and transferred to the computer system 2 via the control unit 5. On the other hand, if the read area targeted for the data read does not have a cache hit (that is, the data in the read area does not exist in the cache memory unit 4 but exists in the flash memory unit 3), The data in the flash memory unit 3 is transferred to the computer system 2.

Since the flash memory card device 1 according to the present embodiment functions and operates as described above, the flash memory card device 1 from the computer system 2 is different from the conventional memory card device that directly writes data in the flash memory portion. Access (writing / reading) can be performed at high speed. Further, since the flash memory unit 3 is used as a storage unit for the write data, it is possible to increase the capacity of the memory card device.

By realizing this high-speed access and increasing the capacity of the memory card device, it is possible to greatly improve the performance of the computer system 2 that cooperates with the memory card device 1. In the above-described embodiment, the case where the cache memory is used as the volatile memory has been described, but the present invention is not limited to this. As is clear from the gist of the present invention, the point is that a volatile memory that can be accessed at a relatively high speed is sufficient as a memory to intervene when writing data to the flash memory unit 3. It is also possible to configure with SRAM, DRAM or the like, for example.

[0026]

As described above, according to the present invention, by mounting a cache memory in a memory card device having a built-in flash memory, a large capacity can be realized while an access from an external computer system ( (Writing / reading) can be performed at high speed. This greatly contributes to improving the performance of the computer system.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment of a flash memory card device according to the present invention.

FIG. 2 is a flowchart (part 1) showing an example of a write / read control process performed by a control unit in FIG.

FIG. 3 is a flowchart (part 2) showing an example of a write / read control process performed by a control unit in FIG.

[Explanation of symbols]

 1 ... Flash memory card device 2 ... Computer system 3 ... Flash memory unit 4 ... Cache memory unit 5 ... Control unit T1 to T4 ... External terminal of flash memory card device WC ... Write enable / disable control signal

Claims (6)

[Claims] 1. A flash memory unit (3) as a main memory, and a temporary storage memory unit (4) having a capacity equal to or greater than the capacity of a block of a predetermined writing unit in the flash memory unit, An external system (2) is provided with a control unit (5) for controlling data transfer between the temporary storage memory unit and the flash memory unit, and the external system (2) writes data to the flash memory card device (1). When an access occurs, the control unit temporarily writes data in the temporary storage memory unit and then issues a command to transfer data from the temporary storage memory unit to the flash memory unit. apparatus. 2. When a data read access is made to the flash memory card device from the external system while data is being transferred from the temporary storage memory unit to the flash memory unit, the control unit: 2. The flash memory card device according to claim 1, wherein the data transfer is interrupted and the data reading process is prioritized. 3. The flash memory card device according to claim 1, wherein the temporary storage memory unit comprises a cache memory unit. 4. When a data write access from the external system to the flash memory card device occurs during data transfer from the cache memory unit to the flash memory unit, the control unit It is characterized in that it is determined whether or not there is a cache hit in the write area that is the target of data writing, and if there is a cache hit, the data transfer is interrupted and the update processing of the cache memory unit is prioritized. The flash memory card device according to claim 3. 5. The control unit notifies the external system of prohibiting the data write when the write area does not have a cache hit. Flash memory card device. 6. The control unit determines whether or not a read area as a target of the data read has a cache hit, and if there is a cache hit, the data is read from the cache memory unit and a cache hit is performed. 4. The flash memory card device according to claim 3, wherein data is read from the flash memory unit when the flash memory unit is not.