KR20020020104A - Memory card having the increased input/output speed - Google Patents

Abstract

PURPOSE: A memory card having improved data input/output speed is provided to maintain a record without the separate power supply, and to provide the memory card integrating the characteristic of a cheap flash memory and the characteristic of a high speed SRAM. CONSTITUTION: The memory card(10) comprises a flash memory(100) being capable of storing data without the separate power supply, an SRAM(Static Random Access Memory,300) connecting to the flash memory and storing a part of flash memory data, and a memory controller(200) controlling the data transmission between the flash memory or SRAM and the outside, and maintaining the data consistency between the flash memory and SRAM. The SRAM includes a reading cache(310) temporarily storing the data outputted to the outside of the flash memory and a writing cache(320) temporarily storing the data inputted from the outside.

Description

Memory card with increased data input / output speed {MEMORY CARD HAVING THE INCREASED INPUT / OUTPUT SPEED}

The present invention relates to a memory card having an increased data input / output speed, and more particularly, to a memory card having an improved speed of storing and reading a photographed image.

Recently, memory cards using flash memory, which has been in the spotlight for digital camera systems, have been used in place of hard disks because, unlike DRAM or SRAM, recorded contents are not erased even when power is not supplied.

However, such a memory card has a problem in that data input / output speed is slower than that of DRAM or SRAM.

In particular, when creating a file or updating specific file data in a memory card, the FAT and directory access time are increased according to the characteristics of the File Allocation Table (FAT) file system, thereby reducing overall I / O performance.

In addition, frequent access to a particular sector shortens its lifespan compared to other memories.

There are some memory cards using SRAM to solve this problem, but the price according to the capacity is more expensive than flash memory, and power is required to maintain the contents written in SRAM. Therefore, a battery to supply power must be built in the memory card. The problem is that it is heavy and has a limited lifetime.

Accordingly, an object of the present invention is to provide a memory card that combines the characteristics of a low-speed flash memory with the characteristics of a high speed SRAM while maintaining a recording without a separate power supply device.

1 is a block diagram of a memory card according to an embodiment of the present invention.

2 is a flowchart of an operation of reading data from a memory card according to an embodiment of the present invention.

3 is a flowchart of an operation of writing data to a memory card according to an embodiment of the present invention.

4 is a flowchart illustrating an operation of updating data in an SRAM to a flash memory in a memory card according to an exemplary embodiment of the present invention.

The present invention as a means for achieving the above object is a flash memory capable of storing data without a separate power supply; A temporary storage unit connected to the flash memory and storing some data of the flash memory; And a memory controller which controls data transmission between the flash memory and the temporary storage unit and the outside and maintains data consistency between the flash memory and the temporary storage unit.

The temporary storage unit may be divided into a read storage unit for temporarily storing data output from the flash memory and a write storage unit for temporarily storing data input from the outside, but may be used without separate classification.

The temporary storage unit may store a plurality of sector data, and may include a specific storage unit in which the sector related information is stored.

The specific information storage unit may include a status indication bit indicating whether specific sector data stored in the temporary storage unit is the same as data corresponding to the specific sector stored in the flash memory.

The temporary storage unit may be initialized when power is supplied from the outside, and the size of the write storage unit may be optimized according to a specific condition.

In addition, when there is no empty space for storing new data in the temporary storage unit when data is input to the temporary storage unit, it is preferable to prepare an empty space for storing new data using a required algorithm.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a block diagram of a memory card according to an embodiment of the present invention.

As shown in FIG. 1, a memory card 10 according to an exemplary embodiment of the present invention includes a flash memory 100, a memory controller 200, and an SRAM 300.

The flash memory 100 is a primary memory that stores data including a captured image.

The SRAM 300 is a secondary memory that serves as a cache for the flash memory 100, and its size is smaller than that of the flash memory 100.

The memory controller 200 controls the operations of the flash memory 100 and the SRAM 200.

That is, it decodes a command input from the connector 20 of the digital camera system, reads data from the flash memory 100 or the SRAM 300, and transfers the data to the connector 20, and also inputs from the connector 20. The data to be written into the flash memory 100 or the SRAM 300.

SRAM 300 is composed of a read cache 310 and a write cache 320, each cache has a plurality of sectors (sector).

That is, each sector of read cache 310 and write cache 320 is used as a quick copy of the sector read or written by the digital camera system.

In particular, the number of sectors used as the write cache 320 is equal to the number of sectors that can be written to the flash memory 100 while the memory card 10 exits the connector 20.

The SRAM 300 also includes a sector table in which sector information on which data is recorded is stored. Accordingly, the memory controller 200 may search the sector table in the SRAM 300 to determine whether the corresponding sector data is recorded in the SRAM 300.

In addition, in the case of data input from the connector 20 and written to the write cache 320, when the corresponding sector is also present in the flash memory 100, since the data written to the write cache 320 is correct data, this state is indicated. In order to do this, the sector table is provided with a modulation status bit for indicating whether the data of the sector is correct data.

When the modulation status bit is in the on state, since the data recorded in the write cache 320 is correct data, the memory controller 200 writes the data of the sector in the corresponding sector of the flash memory 100 if necessary. Keep data consistent

The memory controller 200 reads or writes only the sectors stored in the SRAM 300 only in the SRAM 300, and writes or writes the flash memory 100 only to a portion exceeding the capacity of the SRAM 300. Read operation from 100 is performed.

In addition, sectors that have already been read by the digital camera system and transferred from the flash memory 100 to the SRAM 300 that have not been used for a long time are discarded when a new sector is read or written. In particular, the old one of the sectors to be written in the SRAM 300 is actually written to the flash memory 100 when a new sector is written.

The memory controller 200 performs a cache management operation on the read cache 310 and the write cache 320 in the SRAM 300. In this case, when an excellent cache management algorithm is used, data input / output speed through the read cache 310 and the write cache 320 is improved.

The SRAM 300 is initialized when the memory card 10 is inserted into the connector 20 of the digital camera system.

In addition, data stored in the write cache 320 of the SRAM 300 is written to the flash memory 100 when the memory card 10 is removed from the connector 20.

When there is no free space in the read cache 310 and the write cache 320 in the SRAM 300, the memory controller 200 may prepare a free space using a specific algorithm, for example, a Least Recently Used (LRU) algorithm. Can be. Algorithms other than the LRU algorithm may be used. The LRU algorithm requires access time management by special hardware. However, when the special hardware is used, the size and weight of the memory card 10 is increased, and thus the present invention uses a simplified algorithm.

The simplified LRU algorithm records separately the time accessed when there is access to a specific sector portion of the SRAM 300, and then prepares the empty sector with the oldest time accessed at the time of applying the LRU algorithm.

Hereinafter, an operation of a memory card having an increased data input / output speed according to an embodiment of the present invention will be described with reference to FIGS. 2 to 4.

2 is a flowchart of an operation of reading data from the memory card 10 according to an embodiment of the present invention.

When the user of the digital camera system executes a command for reading data recorded in the memory card 10, the command is transmitted to the memory controller 200 of the memory card 10 through the connector 20 of the digital camera system. .

When a command for reading data recorded in the memory card 10 is input from the digital camera system, the memory controller 200 determines whether the sector data of the portion to be read is stored in the SRAM 300. The sector table of S is searched (S10).

As a result of the sector table search, when it is determined that the corresponding sector data does not exist in the SRAM 300 (S20), it is determined whether there is an empty space in which a new sector can be inserted in the sector table (S30).

If an empty space exists in the sector table, the corresponding empty space is designated as a place where new sector data is to be stored (S40). On the other hand, when no empty space exists in the sector table, the empty space prepared by applying Least Recently Used (LRU) is designated as a place to store new sector data (S50 and S40).

Next, the memory controller 200 reads the corresponding sector data from the flash memory 100 (S60), stores the data in the designated place of the SRAM 300, and outputs the same to the connector 20 (S70).

On the other hand, if it is determined that the sector data is present in the SRAM 300 as a result of the sector table search in step S20 (S20), the sector data is output to the connector (S80).

As described above, when the digital camera system reads data from the memory card 10 inserted into the connector 20, if the data is already recorded in the SRAM 300, the data can be read at a very high speed.

3 is a flowchart of an operation of writing data to the memory card 10 according to an embodiment of the present invention.

When the digital camera system transfers data to be recorded with a corresponding command to record specific data such as photographing data to the memory card 10, the memory controller 200 writes a cache of the size of the data in the SRAM 300. It is determined whether the size exceeds 320 (S100).

If the size of the input data does not exceed the size of the write cache 320 in the SRAM 300, the memory controller 200 determines whether there is an empty space in the write cache 320 (S110).

If an empty space exists in the write cache 320, the memory controller 200 writes data input from the connector 20 to the corresponding empty space (S130), and then turns on the corresponding modulation status bit in the sector table (S140). .

This modulation status bit means that new data has been written in the sector, and therefore, if there is a sector in the flash memory 100, the data has already been modulated by the new data and must be updated later with new data.

If no empty space exists in the write cache 320, after preparing an empty space by applying an LRU (S120), the input data is written in the corresponding empty space and the corresponding modulation status bits are turned on (S130, S140). Repeat).

On the other hand, when the size of the input data exceeds the size of the write cache 320, the memory controller 200 writes the corresponding input data to the write cache 320 while preparing the empty space by applying the LRU, and then the corresponding modulation state Turn on the bit (S140, S120, S130). At this time, the data of the portion exceeding the write cache 320 is written in the write cache 320, and then immediately written to the flash memory 100, so that the write operation is completed for the input data exceeding the write cache 320. Can be.

As described above, when the digital camera system writes data to the memory card 10 inserted in the connector 20, the data writing speed becomes very fast by recording all input data in the SRAM 300 having a high writing speed.

4 is a flowchart illustrating an operation of updating data in the SRAM 300 to the flash memory 100 in the memory card 10 according to an exemplary embodiment of the present invention.

The above operation is performed when the user pulls out the memory card 10 from the connector 20 of the digital camera system.

In this case, the memory controller 200 transfers the data recorded in the write cache 320 in the SRAM 300 to the flash memory 100 so that the corresponding data is maintained.

First, the memory controller 200 determines whether the corresponding modulation state bit in the sector table is on (S200). If the modulation status bit is on, the data written in the write cache 320 is correct data, so an update to the flash memory 100 is required. If the modulation status bit is off, the data written in the write cache 320 is off. Since the data in the flash memory 100 and the same are the same, there is no need to update the data.

Therefore, when the modulation state bit is in the on state, the memory controller 200 transfers the data to the flash memory 100 and records the data (S210), and discards the modulation state bit when the modulation state bit is in the off state (S220). In this case, the memory controller 200 does not need to execute a separate operation to execute the discard operation.

Meanwhile, the update operation may be performed in a specific condition, for example, a condition in which the digital camera system does not perform another task or a condition performed every specific period.

Although the present invention has been described with reference to the most practical and preferred embodiments, the present invention is not limited to the above disclosed embodiments, but also includes various modifications and equivalents within the scope of the following claims.

According to the present invention, by accessing frequently accessed sectors using cache memory using a relatively simple cache management algorithm, the FAT and directory access time during file creation or update can be greatly shortened to improve overall I / O performance and Frequently accessing sectors can increase the lifetime of flash memory, which has a relatively short lifespan compared to other memories.

Claims (6)

Flash memory capable of storing data without a separate power supply; A temporary storage unit connected to the flash memory and storing some data of the flash memory; And A memory controller which controls data transmission between the flash memory and the temporary storage unit and the outside and maintains data consistency between the flash memory and the temporary storage unit Memory card comprising a. The method of claim 1, The temporary storage unit includes a read storage unit for temporarily storing data output from the flash memory to the outside and a write storage unit for temporarily storing data input from the outside. The method of claim 1, And the temporary storage unit stores a plurality of sector data, and includes a specific information storage unit in which the sector related information is stored. The method of claim 3, And the specific information storage section includes a status indication bit indicating whether or not specific sector data stored in the temporary storage section is the same as data corresponding to the specific sector stored in the flash memory. The method of claim 2, The temporary storage unit is initialized when power is supplied from the outside, The size of the write storage unit corresponds to the size of data that can be transferred from the write storage to the flash memory when the power supply from the outside is stopped. Memory card. The method of claim 1, When there is no empty space for storing new data in the temporary storage unit when data is input to the temporary storage unit, the memory card is prepared by using a least recently used (LRU) algorithm.