JP2513421B2 - Storage device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a storage device used in a computer system, and more particularly to a storage device for backing up data sent from an external device.

[0002]

2. Description of the Related Art In a computer system, a CPU (ce
ntral processing unit)
Some are equipped with a readable storage device. In this type of conventional storage device, an EEPROM (electrically erasable progr.
A method of directly writing and reading from a CPU at a predetermined timing by using an ammable read only memory) is widely adopted.

[0003]

However, the above-mentioned E
EPROM has the advantage that it does not require power for storage to retain written data,
It has the disadvantage that the write operation is slower than volatile RAM. Therefore, in the method of directly writing and reading data to and from the EEPROM by the CPU, processing of an external device is stopped until the writing operation is completed, resulting in a reduction in the overall processing speed. Furthermore, EEP
The upper limit of the number of times of writing in the ROM is about 10,000 times, and if data is sequentially written from an external device, the writing operation is frequently repeated, which has a drawback of shortening the life of the EEPROM. On the other hand, if a volatile RAM is used as a memory, the data write operation can be performed faster, but there is a disadvantage that the stored data is lost when the power from the outside is stopped. For this reason, it is necessary to provide a power source for holding the stored data.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a storage device which can quickly perform a data write operation, prolong the life of a nonvolatile memory, and hold data without providing a power supply for holding the memory. To do.

[0005]

SUMMARY OF THE INVENTION A storage device of the present invention writes data between a volatile first memory capable of writing and reading data sent from an external device and the first memory. And a readable non-volatile second memory, an address range of an unused storage area of the first memory before writing the data sent from the external device to the first memory, and an external device. The full range detecting means for comparing the address range of the data sent from the first memory to detect whether or not the storage area of the data in the first memory is full;
Writing means for writing all data stored in the second memory into the second memory. An EEPROM may be used as the second memory. In addition, a search unit may be provided that searches for data stored in the first memory and then searches for data stored in the second memory in response to a data read request from an external device.

[0006]

The operation of the storage device according to claim 1 or 2 is as follows.
It is as follows. When data is sent from an external device,
The fullness detecting means compares the address range of the unused storage area of the first memory with the address range of the data sent from the external device before writing the data in the first memory, It is detected whether or not the data storage area of the first memory is full. When it is detected that the data storage area of the first memory is full, the writing unit writes all the data stored in the first memory to the second memory. In the storage device according to claim 3, when a data read request is issued from an external device, the read means searches the data stored in the first memory and then retrieves the data stored in the second memory. Search for.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a schematic electrical configuration of a computer system incorporating a storage device as an embodiment. The computer system shown is a CPU (not shown)
(Central processing unit), an I / O circuit, and the like as an external control unit 10, and the external control unit 10
And a storage device 20 for transmitting and receiving data to and from.

The storage device 20 stores data between the first memory 21 and a first memory 21 composed of a volatile RAM or the like for transmitting and receiving data to and from the external control section 10. Second memory 22 composed of EEPROM as a non-volatile memory for writing and reading
A memory controller 23 provided between the first memory 21 and the second memory 22, and the first memory 21.
And a backup power supply 24 connected to. The second memory 22 has the same or larger storage capacity as the first memory 21.

The memory control section 23 has the following functions. (1) Before writing the data sent from the external device in the first memory 21, the address range of the unused storage area of the first memory and the address range of the data sent from the external device are set. Comparing, the full detection means for detecting whether or not the data storage area of the first memory 21 is full.

(2) By the full detection by the full detection means,
A writing unit that writes all data stored in the first memory into the second memory 22. (3) In response to a data read request from the external device 10,
Retrieval means for retrieving the data stored in the second memory 22 after retrieving the data stored in the first memory 21.

The backup power supply 24 temporarily supplies electric power for holding the data stored in the first memory 21 for a predetermined time when the electric power supplied from the outside is stopped.

Next, the operation of the storage device having the above configuration will be described. <Write Operation> The data sent from the external control unit 10 is the memory control unit 2
3, the memory control unit 23 controls the writing of the received data and the address information corresponding to each data in the data storage area of the first memory 21. Then, the above write operation is repeated until the data storage area of the first memory 21 is full.

More specifically, the memory control unit 23 compares the address range of the unused storage area of the first memory 21 with the address range of the data to be written immediately before the write operation of each data and address information. To do. When it is determined by this comparison that the amount of data to be written does not exceed the capacity of the unused storage area, the write operation is repeatedly executed.

On the other hand, when the amount of data to be written exceeds the capacity of the unused storage area, all the data stored in the first memory 21 is written in the second memory 22.
Write in. After that, the data stored in the storage area of the first memory 21 is erased, and subsequent data and address information are sequentially written and controlled.

When a data write request is issued from the external control unit 10 to the same address in the first memory 21 in which the data has already been written, the address corresponding to the address in the first memory 21 is dealt with. The new data is overwritten only in the storage area to be used. Therefore, even in such a case, the write operation to the second memory 22 is not performed.

Further, even when the power supplied from the outside is stopped in the middle of writing, the data stored in the first memory 21 is written in the second memory 22 and stored in the first memory 21. The data that is stored may be protected.

<Read Operation> When a data read request is issued from the external control unit 10 after the write operation is completed, the memory control unit 23
First, the address of the first memory 21 is referred to, and the data corresponding to this address is searched in the first memory 21.
Then, when the corresponding data is stored, the corresponding data is read from the first memory 21 and sent to the external control unit 10. On the other hand, when there is no corresponding data in the first memory 21, the data is read from the second memory 22 and sent to the external control unit 10.

In the storage device 20 described above, when the storage area of the first memory 21 is full, all the data stored in the first memory 21 is transferred to the second memory 2.
Since the data is written into the second memory 22, the number of times of writing data into the second memory 22 can be suppressed to the necessary minimum. As a result, EEPRO is used as the second memory 22.
Even when M is used, the life of the EEPROM is not shortened.

Further, the first memory 21 for transmitting and receiving data to and from the external device 10 is a volatile R that can perform writing and reading operations at a relatively high speed.
Since the AM is used, the processing speed of the write operation is not reduced. Furthermore, in this embodiment, since the non-volatile memory is used as the second memory, it is not necessary to provide a battery for holding the memory. Thereby, it is possible to reduce the power consumption and the manufacturing cost.

By the way, in this embodiment, when the external device 10 issues a data read request to the memory controller 23, the memory controller 23 first reads the data from the first memory 21 in which the latest data is written. I try to search. Therefore, if the data to be read is stored in the first memory 21, it is not necessary to search the second memory 22, so that the time required for data search can be shortened. It should be noted that the present invention is not limited to the illustrated or described embodiment, and that various modifications can be made within the scope of the invention.

[0021]

According to the storage device of the first or second aspect, before writing the data sent from the external device to the volatile first memory, an unused storage area of the first memory is stored. Of the first memory is compared with the address range of the data sent from the external device to detect whether or not the data storage area of the first memory is full. Only when it is detected that the memory is full, all the data stored in the first memory is written to the nonvolatile second memory.

As a result, the data write operation can be performed quickly, the number of data writes to the second memory can be suppressed to the necessary minimum, and the life of the nonvolatile memory can be extended. Further, since the non-volatile memory is used as the second memory, it is not necessary to provide a power source for holding the memory.

According to the storage device of the third aspect, in addition to the effect obtained by the first or second aspect, the data retrieval is performed from the first memory in which the latest data is written, and the first memory is used. If the data to be read is stored in the second memory, the second memory does not need to be searched, so that the time required for the data search can be shortened.

[Brief description of drawings]

FIG. 1 is a block diagram showing a schematic electrical configuration of a computer system incorporating a storage device as an embodiment of the present invention.

[Explanation of symbols]

 10 External Control Unit 20 Storage Device 21 First Memory 22 Second Memory 23 Memory Control Unit 24 Backup Power Supply

Claims (3)

(57) [Claims] 1. A volatile first memory capable of writing and reading data sent from an external device, and a nonvolatile second memory capable of writing and reading data between the first memory and the volatile first memory. Before writing the memory and the data sent from the external device to the first memory,
Compare the address range of the unused storage area of the memory with the address range of the data sent from the external device,
Full detection means for detecting whether or not the data storage area of the first memory is full, and all data stored in the first memory is detected by the full detection means by the full detection means. A storage device comprising: a writing unit that writes data to the storage device. 2. The storage device according to claim 1, wherein the second memory is an EEPROM. 3. A search means for searching the data stored in the first memory and then searching the data stored in the second memory in response to a data read request from an external device. The storage device according to 1 or 2.