JPH05143473A - Data write system - Google Patents

Abstract

PURPOSE:To improve the reliability of data by inverting and storing a calculated check code in the case of coincidence between the calculated check code and a stored check code and reporting the occurrence of write error at the time of read of pertinent data even in the case that check codes coincide with each other at the time of write. CONSTITUTION:The check code of the final storage unit as the present write object is calculated and is compared with a present check code 3. If they do not coincide with each other, the check code 3 is left unrewritten as it is, and the rewrite processing of next data is started; but otherwise, the check code is inverted and stored because the check code 3 stored at present coincides with the check code calculated in accordance with rewritten data 2, and the next processing is started thereafter. It is discriminated whether data write is completed or not, and this processing is terminated when it is completed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to stored information, and more particularly to a data writing method with improved reliability when writing of stored information is interrupted.

[0002]

2. Description of the Related Art The validity of data stored in a memory is stored in each storage unit by adding a check code to each predetermined storage unit and by a control element incorporated when the target data is read. The authenticity of the data is confirmed by comparing the check code stored with the check code calculation result of the storage unit.

As a concrete example, consider the case of FIG. The initial state of the area to be written is as shown in FIG. 3, and even parity is used as the check code. Here, it is assumed that the control code (valid / invalid of the target sector or used for control when the storage unit spans a plurality of storage units) includes 01, 02, 03 (h) and the order of the storage units. To do. Consider writing data again at this location.

When the first received block is written, it is assumed that the state shown in FIG. 4 is reached (the shaded area in the figure is new). Now assume that the transmission is interrupted. Since the data writing has not been completed, the check code of the second storage unit remains the same as the previous 02 (h).

When reading this data, the check code of each storage unit is calculated and compared with the stored check code. In the second storage unit, the content of the data has changed, but the calculation result of the check code is 02 (h), which is the same as before, and the stored check code is also 02 (h). However, the data after the middle of the second storage unit is not reliable, and NG must be notified when this storage unit is checked. However, according to the conventional method, when the calculation result and the stored check code are compared, they are determined to be correct because they match.

That is, the operation for writing data is
The check code of the storage unit for which writing has been completed is calculated and stored from the control code of the data storage unit together with the data. The check code of the storage unit in the middle of writing is unchanged.

Therefore, when reading out data, the check code of the target storage unit is calculated together with the data itself, and the validity of the data is confirmed by comparing with the stored code. The reliability of the stored data is notified to the host device. That is, the reliability of the data is determined only by the check code, and even if the data is incorrect, if the check codes match, the data is recognized as correct data.

FIG. 4 illustrates a general conventional control method. When the record is read in the <intermediate state> in FIG. 4, if the check code of and the calculation result of the check code of the storage unit including the check code match, the target record is determined to be valid. Therefore, the abnormal notification cannot be sent.

As a method of calculating the check code,
There is a method of calculating even parity or odd parity of each data, or a method of using a generator polynomial. If the checking method is complicated, the reliability of data is improved. However, limited resources (ROM and RA, for example, when storing the check method in an IC card).
When M size) has to be used more efficiently, complicated check methods cannot be stored.

On the other hand, in the case of handling an amount of money such as an IC card or requiring security, it is necessary to further enhance the reliability of data.

That is, it is necessary to consider not only a complicated check method but also a method of improving the reliability of data.

[0012]

In the above checking method, the check codes of the storage units may coincide with each other even if the data is abnormal. In particular, if the stored check code matches the calculated check code even though the writing of the data has not ended normally, and it is determined that the data is correct, Data reliability is not satisfied.

Further, when the size of the receiving buffer is limited, there is no choice but to adopt a chaining system in which data is divided and received, the writing is completed, and a response is returned, and then the next block is received. For this reason, in particular,
When writing long data, the exchange of commands and responses increases in order to complete the writing, so it is possible that the writing operation may not complete for some reason.

According to the present invention, even when the check codes match when writing to the storage means, it is possible to notify that there is a write error when reading the corresponding data, and The purpose is to increase the reliability of.

[0015]

In order to achieve the above object, the data writing method of the present invention calculates a check code for each data storage unit when writing data in the storage means, and checks the stored check. It is characterized in that it is compared with a code, and if they match, the check code is inverted (replaced with a complement) and stored.

[0016]

According to the above-mentioned means, when writing data in the storage means, the check code for each data storage unit is calculated and compared with the stored check code. Since the check code is stored by being inverted (replaced by the complement), the reliability of the data will not be affected when the data is read even if the writing of the data is interrupted and the stored check codes match. It becomes possible to notify the higher-level device that there is not.

[0017]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 is a diagram for explaining a data write control system of an embodiment of the present invention, and FIG. 2 is a flow chart of data write of the present embodiment. A data write operation of the present embodiment with improved data reliability will be described in detail with reference to FIGS. 1 and 2.

Data is already stored in the storage unit,
Consider the case where data is rewritten to that location. First, according to an instruction from the control unit, the data is newly rewritten (step 101). Then, for the storage unit for which writing has been completed, the check code of the corresponding storage unit is calculated (step 102), and a correct value is stored as the check code (step 103).

Next, the check code of the final storage unit to be written this time is calculated and compared with the current (previously stored) check code (step 10).
4). If they do not match, the check code remains as it is and is not rewritten, and the process proceeds to rewriting the next data (step 106). If they match, it means that the currently stored check code and the check code calculated by the rewritten data match, so the check code is inverted (0 and 1 bits are exchanged). After storing, move to the next process (step 10
6). In step 106, it is determined whether or not the data writing is completed, and if the data writing is completed, this process ends. If data writing has not been completed, the process returns to step 101.

That is, in this embodiment, the check code 02 of the second storage unit in the <intermediate state> of FIG.
(H) is changed to FD (h) and stored. As a result, when this data is read, it is determined that the second storage unit is inconsistent in the comparison between the calculation result and the stored check code, so that NG can be notified.

When the writing is completed with the corresponding data, the comparison process is not performed and a normal check code is stored.

When this FIG. 1 is compared with FIG. 4, since the check codes do not match, even if the writing is interrupted at the same point, the reading of that record is conventionally provided. An abnormality will be detected by comparing the check codes.

That is, even if the data write operation ends (abnormally ends) at that point, when the storage unit is read, a check code mismatch portion is always found in one place, so the storage unit It is possible to notify the upper device that the data is not reliable.

Although the present invention has been specifically described based on the embodiments, the present invention is not limited to the above embodiments, and it goes without saying that various modifications can be made without departing from the scope of the invention. Absent.

[0026]

As described above, according to the present invention, the reliability of data can be improved even when the writing of data is not normally completed. Also,
Only by comparing some data to the conventional check method, it is possible to increase the reliability of the data without increasing the program size so much.

[Brief description of drawings]

FIG. 1 is a diagram for explaining a data write control system according to an embodiment of the present invention,

FIG. 2 is a flowchart of data writing according to the present embodiment,

FIG. 3 is a diagram for explaining a conventional data write control system,

FIG. 4 is a diagram for explaining a conventional data write control method.

[Explanation of symbols]

1 ... control code, 2 ... data, 3 ... check code, 4
… Check code calculation range, 5… previous data.

Claims (1)

[Claims] 1. When writing data to the storage means, a check code for each data storage unit is calculated and compared with the stored check code. If they match, the check code is inverted ( A data writing method characterized by storing after being replaced by a complement).