JPH04157548A - Information storage device - Google Patents

Abstract

PURPOSE:To extend the period of replacement based upon the life of a PROM by transferring information stored in an SRAM to an electric erasable PROM and storing it when the voltage of a backup power source which powers the SRAM stored temporarily with information by a microcomputer drops below a preset reference voltage. CONSTITUTION:The SRAM 12 is stored temporarily with the information by the microcomputer 11. A power source monitor circuit 15 outputs an alarm signal when the voltage of the backup power source 14 which is supplied to the SRAM 12 drops below the preset reference voltage. A control circuit 16 transfers the backup information stored in the SRAM 12 to the E<2>PROM 13 in response to the alarm signal and stores the information. Consequently, even if the frequency of information variation resulting from the processing of the microcomputer 11 increases, such a problem that the replacement period of the E<2>PROM based upon the life becomes short is eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an information storage device, and in particular to an electrically erasable FRO.
The present invention relates to an information storage device using M.

[Conventional technology]

FIG. 2 is a block diagram of an example of a conventional information storage device.

The conventional example is an electrically erasable PROM which stores backup information for the microcomputer 21.
OM) 22 and a backup power supply 24 that is charged by power supplied from an external power supply 23. When the internal information during operation changes, the microcomputer 21 always stores the changed information in the E2PROM 22. When the power supply from the external power supply 23 is temporarily stopped, when the power is supplied again, the microcomputer 21 reads the information before the supply stop from the E2 PROM 22 and resumes processing. Note that the backup power supply 24 is
If the power supply from the external power supply 23 stops while information is being stored from the microcomputer 21 to the E2 PROM 22, this is a rechargeable power supply that backs up the information until all the information has been stored.

[Problem to be solved by the invention]

In the above-mentioned conventional information storage device, information backup by E2FROM is limited by the lifespan of E2PROM as the frequency of information changes due to microcomputer processing increases.
There was a problem that the OM replacement period was shortened.

[Means to solve the problem]

The information storage device of the present invention includes an SRAM that temporarily stores information using a microcomputer, a power supply monitoring circuit that outputs an alarm signal when the voltage of a backup power supply supplied to the SRAM falls below a preset reference voltage. and a control circuit that transfers information stored in the SRAM to an electrically erasable PROM and stores it in response to the alarm signal.

〔Example〕

Next, the present invention will be explained with reference to the drawings. FIG. 1 is a block diagram of one embodiment of the present invention.

This embodiment includes a low power consumption SRAM 12 that stores backup information of a microcomputer, and a power supply monitoring circuit 15 that outputs an alarm signal when the voltage of a backup power supply 14 supplied to the SRAM 12 falls below a preset reference voltage. , and a control circuit 16 that transfers backup information stored in the SRAM 12 to the E2PROM 13 and stores it in response to an alarm signal.

Next, the operation will be described. The backup power supply 14 charges when power is supplied from the external power supply 17, and when the power supply from the external power supply 17 stops, the backup power supply 14 charges the SRAM 12°E2 PROM 13. Power is supplied to the voltage monitoring circuit 15 and the control port Fl@16. The microcomputer 11 updates the storage contents of the SRAM 12 every time information necessary for backup changes during processing.

When the power supply from the external power supply 17 is stopped, the storage contents of the SRAM 12 are retained by the backup power supply 14 for a while.
Although the memory content of the SRAM 12 is retained, if the power supply from the backup power supply 14 is stopped, the memory content of the SRAM 12 will be lost. Therefore, the voltage monitoring circuit 15 monitors the voltage of the backup power supply 14, and if it falls below the reference voltage, the memory content of the SRAM 12 will be lost. The control circuit 16 transfers the memory contents of the SRAM 12 to E2 PR.
Transfer to AMl B.

In this way, the microcomputer 11 can first read out the storage contents of the SRAM 12 at startup, and if the storage contents have disappeared, can read backup information from the E2 PROM 13.

〔Effect of the invention〕

As explained above, the present invention provides an electrical erasing method to erase information stored in the SRAM when the voltage of the backup power supply supplied to the SRAM that temporarily stores information by a microcomputer falls below a preset reference voltage. By transferring and storing the information in FROM, it is possible to extend the replacement period due to the life of FROM.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention, and FIG. 2 is a block diagram of an example of a conventional information storage device. 11.21...Microcomputer, 12...S
RAM, 13.22...E2 PROM, 14°24
...Backup power supply, 15...Voltage monitoring circuit, 1
6...Control circuit, 17.23...External power supply.

Claims (1)

[Claims] SRA that temporarily stores information using a microcomputer
M, a power supply monitoring circuit that outputs an alarm signal when the voltage of the backup power supply supplied to the SRAM falls below a preset reference voltage, and an electrically erasable PROM that outputs information stored in the SRAM according to the alarm signal. 1. An information storage device comprising: a control circuit for transferring information to and storing the information.