JPH09297714A - Data backup method and device - Google Patents

Abstract

(57) [Abstract] [PROBLEMS] To back up data at low cost without maintenance of a backup power supply. SOLUTION: When the power supply 1 is cut off, it is detected by a power supply cutoff detection circuit 2 and transmitted to a CPU 4, and
The power cut-off delay 3 causes the CPU 4 and the EEPROM to wait for several ms until the data writing to the EEPROM 5 is completed.
Power to 5 is backed up. When the CPU 4 is informed that the power supply is cut off, the backup data is written in the EEPROM 5 while shifting the position of the EEPROM 5 by using the address, the data and the sum as one data package. When the power supply 1 is turned on, the CPU 4 inputs all the data of the EEPROM 5, and selects the latest data as the backup data, judging from the address among the data of the data package whose sum matches the predetermined rule.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data backup method and device for backing up data when power is cut off.

[0002]

2. Description of the Related Art FIG. 3 is a block diagram of a conventional data backup device. When the cutoff of the power supply 1 is detected by the power cutoff detection circuit 2, the power supply selection circuit 7 switches the power supply 1 to the backup power supply 6 such as a battery, and the CPU 8 and RA
Power is supplied to the M9 from the backup power supply 6. The power-off detection is also transmitted to the CPU 8, and the CPU 8 sends RA
The data is backed up in M9.

[0003]

The above-mentioned conventional data backup device uses a backup power source such as a battery, and therefore has a problem that maintenance is required and cost is increased. An object of the present invention is to provide an inexpensive data backup method and device that does not require maintenance of a backup power supply.

[0004]

A data backup method of the present invention writes a data package consisting of data, identification information of the data and a check code to an EEPROM while shifting a writing position each time the power is cut off.
When the power is turned on, all the data in the EEPROM is read out, and the latest data judged from the identification information is selected as the backup data from the data in the data package in which the check code matches a predetermined rule. Further, the data backup device of the present invention is an EEP
The ROM, the power cutoff detecting means for detecting that the power is cut off, the control means, and the E until the data writing to the EEPROM is completed after the power is cut off.
An EPROM and a power shutoff delay for supplying power to the control means are provided, and the control means includes data, identification information of the data, and a check code each time the power shutoff detection means notifies the power shutoff. The EEPRO while shifting the writing position of the data package
Writing to M, when the power is turned on, the EEPROM
Of the data package of which the check code matches a predetermined rule, the most recent data judged from the identification information is selected as backup data.

By using the EEPROM (the power supply is required only for writing), maintenance of the backup power supply is unnecessary, the cost is reduced, and the EEPROM is also used.
By backing up the data while shifting the writing position of, the EEPROM can be used semipermanently.

[0006]

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of a data backup device according to an embodiment of the present invention, and FIG. 2 is an EEPROM.
It is a figure which shows the format of the write data of. As shown in FIG. 1, the data backup device according to the present embodiment includes a power supply 1, a power cutoff detection circuit 2, a power cutoff delay 3 such as a capacitor, a CPU 4, and an EEPROM 5. Next, the operation of this embodiment will be described. When the power supply 1 is cut off, it is detected by the power supply cutoff detection circuit 2 and C
It is transmitted to the PU 4 and the power shutoff delay 3 causes the data writing to the EEPROM 5 to be completed by several meters.
During s, the power supply to the CPU 4 and the EEPROM 5 is backed up.

When the CPU 4 is notified that the power supply has been cut off, as shown in FIG. 2, the EEPROM 5 is arranged while shifting the position of the EEPROM 5 by using the address 10 as the identification information, the data 11 and the sum 12 as the check code as one data package. Write backup data to. Here, the address 10 is for distinguishing one data package from other data packages, for example, 0,
The numbers are given in ascending order of 1, 2, ..., When the maximum value is reached, the numbers are given again from 0, 1, 2 ,. The sum 12 is a check code of the data package, and as an example, a value that gives 0 when the data 11, address 10, and all bytes of the sum 12 are added is given. Thereby, the normality / abnormality of the data 11 can be detected. When the power supply 1 is turned on, the CPU 4 inputs all the data of the EEPROM 5, and judges from the address 10 among the data 11 of the data package in which the thumb 12 matches the predetermined rule, and selects the latest data as the backup data. . For example, if the addresses are consecutive 0, 1, 2, ..., 31, the data having the address “31” becomes the latest data. Also, the addresses are 254, 255, 0, ..., 2
If it is consecutive with 9, the data having the address "29" becomes the latest data.

The EEPROM 5 has, for example, 256 bytes,
In the case of 100,000 times writable, if each package data of address 10, data 11 and sum 12 is 8 bytes, (256/8) × 100,000 times = 3.2 million times can be written, and the EEPROM 5 is almost semipermanently written. Can be used.

[0009]

As described above, the present invention is based on the EEP
By using the ROM, maintenance of the backup power supply is unnecessary, the cost is low, and the EEPR
By backing up the data while shifting the writing position of the OM, the EEPROM can be used semipermanently.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a data backup device according to an embodiment of the present invention.

FIG. 2 is a diagram showing a writing format of an EEPROM 5.

FIG. 3 is a configuration diagram of a conventional example of a data backup device.

[Explanation of symbols]

 1 power supply 2 power cutoff detection circuit 3 power cutoff delay 4 CPU 5 EEPROM 6 backup power supply 7 power supply selection circuit 8 CPU 9 RAM 10 address 11 data 12 sum

Claims (2)

[Claims] 1. Each time the power is turned off, a data package consisting of data, identification information of the data, and a check code is written to the EEPROM while the writing position is shifted, and when the power is turned on, all the data in the EEPROM is read and the check code is written. Among the data of the data package which matches the predetermined rule, the latest data judged from the identification information is selected as the backup data. 2. An EEPROM, a power interruption detection means for detecting that the power is cut off, a control means, and the EEPROM and the EEPROM until the end of data writing to the EEPROM after the power is cut off. A power cutoff delay for supplying power to the control means, and the control means generates a data package including data, identification information of the data, and a check code each time the power cutoff detection means notifies the power cutoff. The data is written in the EEPROM while shifting the writing position, all the data in the EEPROM is read out when the power is turned on, and the latest data judged from the identification information among the data in the data package in which the check code matches a predetermined rule. A data backup device that selects data as backup data.