JP2001249855A - Method for rewriting data of nonvolatile memory and subscriber circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for rewriting data of a nonvolatile memory capable of preventing loss of the data even in the case of interruption of a processing when the data of the nonvolatile memory is rewritten and a subscriber circuit using the method. SOLUTION: Flag information to indicate uncompletion/completion of writing of the data and flag information to indicate validity/invalidity of the data are written in the nonvolatile memory 4 together with entity of the data. A new piece of data is written in idle sector of the memory 4 when the data is rewritten. After that, the flag information about the sector in which the older piece of data to be rewritten is stored is invalidated. Thus, the loss of the data contents is prevented even when power interruption, etc., is generated in process of rewriting of the data and the data is efficiently rewritten.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for rewriting data in a non-volatile memory and a subscriber circuit, and more particularly to a method for rewriting data in a rewritable non-volatile memory and a non-volatile memory in a digital exchange. It relates to a subscriber circuit.

[0002]

2. Description of the Related Art In recent years, data can be rewritten,
Further, devices equipped with a non-volatile memory such as an EEPROM or a flash memory as a storage device capable of retaining stored data as it is even when power is cut off are increasing. One example is a subscriber circuit that accommodates the subscriber lines of a digital exchange. The subscriber circuit realizes various services for the subscriber by the service control program, stores the program in the non-volatile memory, and rewrites the service control program when adding or changing functions. It is configured to be able to. Subscriber circuits tend to be installed in remote office buildings, etc., away from the central office, in accordance with the adoption of optical fibers for subscriber lines, and write service control programs when adding or changing functions. The replacement is performed by remote download.

In a flash memory storing a service control program, it is necessary to temporarily erase a memory area to be written before writing due to its device characteristics. Erasing is performed in fixed units called sectors.
Writing is performed in byte units, and writing cannot be performed again at the address where writing has been performed once. Therefore, in general, when rewriting data in the non-volatile memory, the data in the memory area to which the data in the non-volatile memory is to be written is erased and then new data is written in that area, or The data in the relevant memory area where the data of the memory is to be written is temporarily saved in the volatile buffer memory,
There has been used a method of erasing data in a memory area to which data of a nonvolatile memory is to be written, and then writing new data to the nonvolatile memory.

[0004] However, in the above-mentioned methods, in both cases, if the writing is interrupted due to a power failure or the like between the time when the data in the corresponding memory area is erased and the time when the writing of new data is completed normally, the data is lost. It falls into the situation of doing. In particular, if the data writing is interrupted during the remote download by the above-described subscriber circuit or the like, a long time is required for recovery.

[0005] As a conventional technique relating to rewriting of data in a nonvolatile memory which can solve such a problem, for example, a technique described in Japanese Patent Application Laid-Open No. Hei 8-272698 is known. This conventional technique secures a specific address area in a non-volatile memory as a backup area, and writes data to a certain area.
Copying the data in the address area to the backup area, erasing the corresponding address area, writing new data to the address area, and erasing the data in the backup area after the writing of the new data to the relevant address area is completed. Things.

[0006]

The prior art described in the above-mentioned publication does not lose data when writing is interrupted due to a power supply interruption or the like during writing of new data. Since a specific address area is used as a backup area, the frequency of erasing and writing data in the backup area increases. Due to the characteristics of the non-volatile memory, the backup area deteriorates significantly more than other areas. There is a problem that it is.

In addition, in this prior art, when data is rewritten once, data is erased and written in two areas, that is, an address area and a backup area, so that the data rewriting time is long. A large amount of processing must be performed for rewriting, resulting in poor processing efficiency.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art, to prevent data loss even when processing for rewriting data is interrupted, and to enable efficient data rewriting. An object of the present invention is to provide a method for rewriting data in a nonvolatile memory and a subscriber circuit using the method.

[0009]

According to the present invention, the object is to rewrite data in a non-volatile memory in which data can be rewritten by writing new data after a predetermined memory area is collectively erased. In the method, flag information indicating incomplete / completion of data writing and flag information indicating validity / invalidity of data are written together with the substance of the data in units of the memory area.
This is achieved by writing new data in a free memory area and then invalidating the flag information of the memory area storing the old data to be rewritten.

The object is that the empty memory area is an area where the flag information indicating the validity / invalidity of the data is invalid, or the flag information indicating the validity / invalidity of the data is valid, and An area in which flag information indicating data write incomplete / completion is an area in which write has not been completed. By blanket erasing the free memory area before writing the data of the new data, This is achieved by setting the flag information indicating data incomplete / completion of data writing to uncompleted and setting the flag information indicating validity / invalidity of data to be valid.

Further, the object is to provide a subscriber circuit which implements various services for a subscriber of a digital exchange by a service control program stored in a nonvolatile memory. This is achieved by performing the rewriting method described above.

[0012]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of a data rewriting method for a nonvolatile memory according to the present invention and a subscriber circuit using the method.

FIG. 1 is a block diagram showing a configuration of a subscriber circuit according to an embodiment of the present invention. FIG. 2 is a flowchart for explaining data rewriting processing of a nonvolatile memory. FIG. 3 is a diagram for explaining a memory rewriting sequence. FIG. FIG.
1, 1 is a subscriber line interface unit, 2 is a control unit, 3 is a volatile memory (RAM), 4 is a nonvolatile memory, and 5 is a higher-level device interface unit.

A subscriber circuit according to an embodiment of the present invention shown in FIG. 1 includes a subscriber interface unit 1 connected to a terminal such as a telephone, a control unit 2 for controlling execution of a service control program and rewriting control of memory data. A volatile memory 3 for developing various control programs, a nonvolatile memory 4 such as an EEPROM / flash memory for storing various service control programs and data downloaded from a higher-level device, a higher-level device interface unit connected to the higher-level device 5 is provided.

The illustrated subscriber circuit communicates between a terminal connected via the subscriber line interface unit 1 and another terminal connected via an upper interface unit 5 and a communication network (not shown). And various services such as relaying communication.

Next, a method of rewriting the memory data in the nonvolatile memory 4 will be described with reference to the flow shown in FIG. 2 and the sequence diagram shown in FIG.

As shown in FIG. 3, the non-volatile memory 4 is composed of a plurality of sectors.
A write incomplete / complete flag and a valid / invalid flag are assigned to data in the sector. It is assumed that at least one empty sector always exists in the nonvolatile memory 4. This empty sector is defined as “a sector in which the write incomplete / completion flag indicates an incomplete value, or in which even if this flag is a complete value, the valid / invalid flag indicates an invalid value”. The incomplete value of the write incomplete / completion flag and the valid value of the valid / invalid flag are defined as values immediately after erasing the nonvolatile memory (for example, 0xFF). Conversely, the completion value of the write incomplete / completion flag and the invalid value of the valid / invalid flag are values other than immediately after erasing the nonvolatile memory (for example, 0x
00). In the example shown in FIG. 3, the upper part shows the state before data rewriting, and it is assumed that sector 1 is a free sector and sector 2 is a sector storing data to be rewritten.

(1) A non-volatile memory 4 is mounted on the subscriber circuit shown in the figure, and data or a program on the non-volatile memory 4 is transmitted from the higher-level device through an upper-level interface unit 5 in accordance with an instruction from the higher-level device. It can be updated by downloading. When receiving the download instruction from the host device, the control unit 2 expands the memory rewrite control program from the nonvolatile memory 4 to the work memory area of the volatile memory 3 and starts the rewrite control.

(2) When starting the rewriting control of the memory, the control unit 2 first searches for a free sector in the nonvolatile memory 4 (step S1). The search for an empty sector can be performed by checking a flag in each sector according to the above-described definition. The search for a free sector is not performed after receiving a rewrite instruction, but is performed at the time of startup, and the free (invalid) sector information and the valid sector information (or either of them) are stored in the volatile memory or in the volatile memory. The search result (table information) is stored in a nonvolatile memory, and the table information is read at the time of rewriting, and the table information is updated every time the rewriting is performed. In this search, as shown in the upper part of FIG. 3, it is searched that the sector 1 is a free sector.

(3) After searching for a free sector in the nonvolatile memory 4 in step S1, the free sector is erased (step S2). By erasing the empty sector, as shown in the middle part of FIG. 3, the write incomplete / complete flag of the empty sector is set to an incomplete value, and the valid / invalid flag is set to a valid value.

(4) After erasing the empty sector, new data is prepared in the buffer memory area of the volatile memory 3 (step S3), and the new data in the buffer memory area is stored in the data entity area of the erased empty sector. Write (Step S
4). When the new data is sequentially downloaded from the host device, the processes of steps S3 and S4 are repeated. At this point, the sector 2 having the data to be rewritten still retains the old data.

(5) It is determined whether or not the writing of the new data has all been completed normally (step S5). If the writing has been completed normally, the completion value is set in the write incomplete / completion flag of the sector storing the new data. Is written (step S6), and an invalid value is written to the valid / invalid flag of the sector storing the old data (step S7). As a result, as shown in the lower part of FIG. 3, the state of the nonvolatile memory 4 is such that the sector 2 is invalid, that is, becomes empty, and the sector 2 is replaced by the sector 2 instead of the sector 2 storing the old data. The sector storing the new data obtained by updating the old data becomes valid.

(6) If it is determined in step S5 that the writing of new data has not all been completed normally,
The processing here ends. In this case, the old data to be rewritten is still stored in the sector 2 of the non-volatile memory 4, and the sector 1 in which the new data has been written has the data write incomplete / completion flag incomplete. Since it is a value, it is regarded as a free sector and is not used.
Therefore, the subscriber circuit can continue to operate with the old data.

Normally, when a certain sector is invalidated, the sector is erased. However, when the sector is erased for invalidating the sector, two erasures are performed for one data rewrite. It is necessary to erase the sector. Generally, erasing a non-volatile memory takes a longer time than writing, and the device is degraded each time erasing is performed. Therefore, erasing a sector to invalidate a sector cannot be performed. Very inefficient.

According to the embodiment of the present invention, as described above, instead of erasing the sector to invalidate the sector,
An invalid value is written to the valid / invalid flag, which normally requires two erasures at one rewrite.
By replacing this with one erasure and two writings of the flag information, it is possible to shorten the rewriting time and extend the life of the device.

After the state shown in the lower part of FIG.
When the next download instruction is received, since the valid / invalid flag of the sector 2 is invalidated, the sector 2 becomes an empty sector.

Then, in the above-mentioned flow, sector 1
In the case where the writing to the memory 2 is not completed normally, for example, when the rewriting process is interrupted due to the power-off between the processes from the middle stage to the lower stage in FIG. Since it remains valid and the write incomplete / completion flag of sector 1 indicates incomplete, the next time sector 1 becomes an empty sector again. That is, when the writing to the sector 1 is not completed normally, the state shown in the upper part of FIG. 3 is maintained, and even if the rewriting process is interrupted, no data is lost.

However, the writing of the write completion flag into the sector 1 shown in the lower part of FIG. 3 (step S6 in FIG. 2) and the writing of the invalid flag into the sector 2 (step S6 in FIG. 2)
If the rewriting process is interrupted between 7) and 7), a state where both sector 1 and sector 2 are valid theoretically exists. However, if the processes of step S6 and step S7 are performed continuously, there is no problem because the time between these steps is a short time required for writing one byte to the nonvolatile memory.

As described above, according to the data rewriting method of the non-volatile memory according to the embodiment of the present invention, the old data is retained until the rewriting of the new data is normally completed. Data can be prevented from being lost due to power interruption or the like. Also, for example, a flash memory requires much more time for erasing than for writing, but the embodiment of the present invention does not erase the old data storage sector at the time of rewriting. Since the sector data is regarded as invalid, it is possible to shorten the rewriting time and prevent the device from deteriorating. In addition, since an empty sector moves an address instead of a fixed address, deterioration of only a specific sector can be prevented, and the life of the device can be extended.

The subscriber circuit of the present invention to which the data rewriting method of the non-volatile memory as described above is applied,
High reliability can be achieved.

[0031]

As described above, according to the present invention, loss of data can be prevented even when the process of rewriting data in the nonvolatile memory is interrupted, and efficient data rewriting can be performed. It can be carried out. By using such a method of rewriting data in the nonvolatile memory, the reliability of the subscriber circuit can be improved.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a subscriber circuit according to an embodiment of the present invention.

FIG. 2 is a flowchart illustrating a process of rewriting data in a nonvolatile memory.

FIG. 3 is a diagram illustrating a memory rewriting sequence.

[Explanation of symbols]

Reference Signs List 1 subscriber line interface unit 2 control unit 3 volatile memory (RAM) 4 nonvolatile memory (EEPROM, flash memory) 5 host device interface unit

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Toshiyuki Saito 216 Totsuka-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture Inside the Hitachi, Ltd.Communications Division (72) Inventor Tatsuhiro Fukunari 216 Totsuka-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture Hitachi, Ltd.Communications Division (72) Inventor Yoshinobu Morita 216 Totsuka-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture Co., Ltd.Communications Division, Hitachi Ltd. (72) Inventor Ritsumu Sudo 180-Totsukacho, Totsuka-ku, Yokohama, Kanagawa Prefecture Sun (72) Inventor Kazuhiko Akiyama 2-3-1, Otemachi, Chiyoda-ku, Tokyo Nippon Telegraph and Telephone Corporation F-term (reference) 5B018 GA04 HA35 KA01 KA30 NA06 QA05 RA11 5K051 DD07 HH01

Claims (5)

[Claims] 1. A data rewriting method for a non-volatile memory in which data can be rewritten by writing new data after a predetermined memory area is collectively erased. Flag information indicating incomplete / completion of data writing and flag information indicating validity / invalidity of data are written, and when data is rewritten, new data is written in a free memory area, and then old data to be rewritten is stored. A method of rewriting data in a non-volatile memory, wherein the flag information of the memory area being set is invalidated. 2. The free memory area, wherein an area in which flag information indicating validity / invalidity of the data is invalid, or flag information indicating validity / invalidity of data is valid, and the data has not been written. 2. The data in the non-volatile memory according to claim 1, wherein the flag information indicating completion / completion is an area where writing is not completed, and the free memory area is collectively erased before writing the data of the new data. Rewriting method. 3. A memory area immediately after erasing a memory, wherein flag information indicating incomplete / completed data writing is set to incomplete writing, and flag information indicating valid / invalid of data is enabled. 3. The method for rewriting data in a nonvolatile memory according to claim 2. 4. A search for a free memory area at the time of memory rewriting is performed based on the flag information indicating data incompletion / completion and the flag information indicating data validity / invalidity. 4. The method for rewriting data in a nonvolatile memory according to item 2 or 3. 5. The service control program rewriting in a subscriber circuit which realizes various services for a subscriber of the digital exchange by a service control program stored in a non-volatile memory.
A subscriber circuit, which is performed by the method for rewriting a nonvolatile memory according to any one of the above.