JP2000267943A - Data writing management system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent an unusable area from being increased by providing sector write time prescribed values by sectors and deciding no time-out error occurrence sector on condition that the write time of data is shorter than the sector write time prescribed value even if it takes a long time to write bytes to some of sectors. SOLUTION: When a host 1 attains data write access through an interface bus 7 and an interface 3, a CPU 2 gains data write access to a flash memory 5 through a connecting circuit 4. When data begin to be written, the CPU 2 starts measuring the write time by its timer to measure the write time of data of one sector. Here, an external storage device is provided with sector write time prescribed values by sectors and even if it takes a long time to write bytes to some of sectors, no time-out error occurrence sector is decided on condition that the write time of the data is shorter than the sector write time prescribed value, so that no write time-out error will be decided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data writing method for an external storage device using a memory such as a flash memory which takes a long time to write data. Belongs to the technical field to secure.

[0002]

2. Description of the Related Art Recently, flash memories have been attracting attention as electrically rewritable nonvolatile memories, although the number of times of rewriting is limited, and they have been used for portable devices, memory cards, and the like. The flash memory has a high data read access speed, but takes a long time to write data, and has a variation of 8 μS to 2 ms per byte.
Further, the flash memory has a limit on the number of times of erasing, and when the number of times of erasing is increased and the deterioration proceeds, the data writing time is further reduced.

For this reason, a specified value is provided in 1-byte writing, and a time-out error is provided when a longer writing time than the specified value is required.

However, when a flash memory is used as an external storage device, the host accesses the external storage device in sector units and does not access data in byte units. Therefore, if it takes time to write a certain byte in one sector, the other sector becomes a sector that is not used as a defective sector even if it is within the specified write time, and the unusable area as an external storage device is used. Was causing the increase.

[0005]

SUMMARY OF THE INVENTION In an external storage device using a memory having a variable time for data writing, even if the writing time of a part of the sector of the sector which is a unit accessed by the host exceeds the writing time. An object of the present invention is to secure a usable area without determining it as an unusable area by setting a usable area if the sector write time is within a specified value.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems, and in an external storage device using a flash memory, even if it takes a long time to write data in a part of a sector, the entire sector can be used. An object of the present invention is to provide a data write management method that does not determine a defective sector if the write time is within a specified value.

Therefore, the data write management method of the present invention comprises an interface with a host, a flash memory for actually storing data, a CPU, a control circuit for controlling access to the CPU and the flash memory, an interface between the host and the host. , A control data bus connecting the interface and the control circuit, a CPU control bus connecting the control circuit and the CPU, control signals, a data bus connecting the control circuit and the flash memory, and a memory control line.

[0008] The sector write time to the flash memory is measured by a timer in the CPU, and if the data write time in sector units is within the sector write specified value, it is not determined to be a defective sector and is regarded as a usable area.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described with reference to the drawings.

As an example, a description will be given on the assumption that a flash memory is used as the external storage device and the sector size is 512 bytes.

(Embodiment 1) FIG. 1 is a flow chart of sector-based writing.

When a data write access occurs from the host, a timer in the CPU 2 is started to start measuring a write time in sector units. A specified sector write time value is set in the CPU 2, and the specified sector write time value is a specified byte write time value × the number of bytes for one sector.

One sector (51) is stored in the flash memory.
When the data write of (2 bytes) is completed, the timer in the CPU 2 is terminated and the time required for one sector write access is measured. If the time required for the write access for one sector is within the sector write time specified value and no write timeout error occurs, the write access in the sector unit is continuously repeated for the specified sector, and the writing of all data is completed. The process ends at this point.

If the sector write time is equal to or longer than the sector write time prescribed value, an error occurrence report is sent to the host, and
The sector in which the error has occurred is registered as an error, and writing is completed.

FIG. 2 is a configuration diagram of the external storage device.

A write access method for executing FIG. 1 will be described. When a data write access is received from the host 1 via the interface bus 7 and the interface 2, the CPU 1
2 performs data write access to the flash memory 5 via the control circuit 4. CP at the start of data write
U2 is a timer in the CPU 2 which starts measuring the write time and measures the data write time for one sector.

FIG. 3 is a comparison of the timeout error detection between the case where the conventional byte write time prescribed value is provided in the data writing and the case where the sector write time prescribed value is provided by the present method.

When a byte write time stipulated value is provided in the conventionally proposed data write, data is written in byte units. If a byte of a part of the data exceeds the byte write time stipulated value, the sector is used. It is registered as an impossible write timeout error occurrence sector.

In the case where a sector write time prescribed value is provided in the data write according to the present method, even if the byte write time of the sector 1 part takes a long time, it takes one sector (5 bytes).
If the data write time (12 bytes) is short, it is not registered as a write timeout error.

That is, even if it takes time to write one copy of a byte, if it is within the specified write time as a whole, it is not registered as an error, so that it is determined that the write timeout error occurrence area cannot be used in the prior art. The area becomes a usable area.

Even if it takes a byte write time for a part of the data of the sector, it is not registered as an error, so that an unusable area can not be increased.

(Embodiment 2) FIG. 4 is a configuration diagram of an external storage device at the time of speeding up data access.

Each of the flash memories 5a to 5d has a memory data bus 13, and the memory data bus 13 accesses the control circuit via the data bus 11. CPU
The specified sector write time set in the timer 2 is set to a value obtained by dividing the specified byte write time × the number of bytes for one sector by 4 which is the number of simultaneous accesses to the flash memory. This is because, since the parallel access is performed, the sector write time is shortened accordingly.

FIG. 5 shows data writing to the flash memory of one sector.

When the memory data bus is 8 bits, the data bus is a 32-bit data bus, and four bytes of flash memory are accessed simultaneously in parallel with 4 bytes.

FIG. 6 is a comparison between the conventional case where the prescribed value of byte write time is provided and the time out detection in the case where the prescribed value of sector write time is provided by the present method in the data write at the time of speeding up data access.

In the data writing, when the specified byte write time value is provided, even if the data write time falls within the specified byte write time value between the flash memories 5a to 5c, the specified byte write time value is stored in the flash memory 5d. If it exceeds, the area of the flash memories 5a to 5c in which the same sector has been written and the area in which the write timeout error has occurred in 5d are registered as error areas and become unusable areas.

In the data write, when a sector write time prescribed value is provided, even if it takes time for data write access in the flash memory 5d, the flash memory 5a
A data waiting time is provided between .about.5c so that the writing of data into the flash memory 5d is completed, and when the writing into the flash memory 5d is completed, a new data bus is used through the data bus and the memory data bus of the flash memories 5a to 5d. Then, writing of 32-bit data to the flash memory is continued.

There is a variation in the writing time between the flash memories that are simultaneously accessed. For example, even if it takes a writing time in one flash memory, if it is within the sector writing time specified value, it is not registered as a sector in which an error has occurred. The area is not determined to be an impossible write timeout error occurrence area. In addition, the specified value of the sector write time can be set to 、, and data write access can be speeded up by accessing with 32 bits. Further, when an error occurs in data write and data is to be saved in a replacement sector In this case, the evacuation time can be set to ４, so that the access time can be shortened as a whole of the external storage device.

In this method, the flash memory is 8 bits, the host access is 32 bits, and the sector size is 512 bytes. However, even if the flash memory, the data width of the host, and the sector size are changed, the flash memory is accessed in parallel. A similar method can be adopted by changing the number of the symbols.

[0031]

According to the present invention, a sector write time specified value is provided for each sector, and even if it takes time to write a byte in a part of the sector, if the data write time is within the sector write time specified value, the sector is not regarded as a timeout error occurring sector. Thus, it is possible to reduce the increase in defective sectors without determining that a write timeout error has occurred.

[Brief description of the drawings]

FIG. 1 is a flowchart for writing data in a sector unit in an external storage device according to the present invention.

FIG. 2 is a configuration diagram of an external storage device according to the present invention.

FIG. 3 is a diagram showing a comparison between the present invention and a conventional example of timeout detection.

FIG. 4 is a configuration diagram of an external storage device at the time of speeding up data access according to the present invention.

FIG. 5 is a diagram showing data writing to a flash memory for one sector when data access is speeded up in the present invention.

FIG. 6 is a diagram showing a comparison of timeout detection when speeding up data access according to the present invention and a conventional example.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Host, 2 ... CPU, 3 ... Interface, 4 ... Control circuit, 5 ... Flash memory, 6 ... External storage device, 7
... Interface bus, 8 ... Control data bus, 9 ... C
PU bus, 10 ... control signal, 11 ... data bus, 12 ...
Memory control line, 13 ... Memory data bus.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yuji Sugaya 882-Chair, Oaza-shi, Hitachinaka-city, Ibaraki Pref. Inside the Measuring Instruments Division, Hitachi, Ltd. F term in Hitachi Science Systems, Ltd. (reference) 5B018 GA01 GA05 HA31 KA01 NA06 QA15 5B060 CB00

Claims (2)

[Claims] 1. An external storage device using a memory as a medium in which a byte write time of data varies, and when a read or write unit of a host is a sector unit having a fixed number of bytes, a byte write time specified value is set. However, when a write timeout is provided, even when a byte write time is required in one part of the sector and a write timeout error occurs and the sector becomes a bad sector, when the data of the number of bytes of the sector is written, all of the sector is lost. If the sector write time, which is the sum of the byte write times of the data of, is smaller than the sector write time specified value that is the sum of the sector byte number of the specified byte write time when a write error is provided in bytes, By not setting a time-out error, even if it takes time to write data to a part of the sector, it is determined as a bad sector. Have data write management method. 2. The data management method according to claim 1, wherein
Extends the data bus to enable multiple memory accesses in parallel, and divides the sum of the specified byte write time by the number of sector bytes by the number of flash memories that are accessed in parallel to obtain the specified sector write time. When writing data, multiple flash memories are accessed in parallel, data is written to each flash memory, and even if the byte write time for each flash memory varies, it matches the memory with the slowest byte write. A data write management method that enables high-speed access between the host and the memory by repeating byte writing until the writing of sector data is completed.