JPS5850029A - Power failure detector - Google Patents

Abstract

PURPOSE:To prevent the malfunction of a device such as a measuring instrument, by writing prescribed data for power failure detection in a prescribed area of a semiconductor memory to be backed-up and reading out this data by a CPU to detect the power failure when power is turned on. CONSTITUTION:If the user of the device turns off a switch SW2 when he turns off a power source 4, an interlocking switch SW1 is turned off. In this case, contents of a RAM are changed because a back-up power source 1 cannot back up the RAM. Meanwhile, if power is not supplied from a power source AC under the state, where the switch SW2 is turned on, because of power failure, the power of the power source 1 is supplied to the RAM. When the power of the device is restored, contents of the RAM are checked to discriminate whether contents of the RAM are changed or not.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to a power outage detection circuit for detecting a power outage in devices such as meters.

Prior Art In recent years, central processing units such as microprocessors and semiconductor memories (ROM) have been used as devices such as conventional instruments.

Many items use string 1). A backup power supply such as a rechargeable battery is used to protect the memory contents in the event of a power outage.

When the power is turned on, the microprocessor determines the stop, power restoration time, etc., depending on whether the power has been restored from a state where the memory was backed up (by the round-up backup power supply due to a power outage) or whether the device was not backed up due to a power outage. It is necessary to select a mode to perform power outage processing that prints and continues operation, or to reset the memory contents and wait, and it is necessary to detect whether there is a power outage or not.

(3) Purpose of the Invention An object of the present invention is to provide a power outage detection device that can easily detect whether or not there has been a power outage in view of one or more points.

(4) Embodiment of the Invention FIG. 1 is an explanatory diagram showing an embodiment of the invention. In the figure, 1 is a backup power source such as a battery, 8WL
is the power switch 8W of the device power supply 4, which will be described later! 2 is a semiconductor memory which stores a predetermined operating program 2 and is composed of a 9ROM and a RAM for temporary storage; 3 is a semiconductor memory that is connected to a conductor memory 3 and other printing devices not shown; 2. An AC power supply AC is supplied externally to the central processing unit such as a microprocessor that performs the control and the 4Fi switch SW2K, and the AC power supply AC is supplied to the equipment power supply that supplies power to each part of the equipment. When the device is operating, the semiconductor memory 30RAM is backed up.

It is written as follows.

When the device user intentionally disconnects the device power source 4, he or she turns off the switch 8w2. At this time, it must be determined that there is no power outage, but the switch awl is also turned off in conjunction with the switch 8w2, and the backup power supply 1 packs the RAM.

Since it cannot be copied, the contents of RAM will change.

Also, in case of a power outage, switch 8w2 remains on and the AC power is turned off.
If the power is no longer supplied, switch awl is turned on, and the power of backup power supply 1 is immediately turned on by switch 8.
RAM K is supplied via w2.

The contents of RAM are retained.

Then, when the device power source 1 is restored, the contents of the RAM in which the power failure detection data M have been written are sent to the central processing unit 3, and changes in the contents are detected. The central processing unit 3 determines whether the contents of the RAM match the known power failure detection data M, and if they do not match, it is determined that there is no power outage, and if they match, it is determined that there is a power outage. In this way, you can check whether there was a power outage or not.

Incidentally, the more locations the power outage detection data M is stored, the higher the probability will be in terms of reliability, but according to experiments, there was no detection chance when 16 words of 8 bits were used.

・)Summary of the Invention This invention writes predetermined (known) power failure detection data in a predetermined area of a semiconductor memory that is backed up by a backup power supply when the device power is turned on, and when the power is turned on, The central processing unit reads this data and detects whether it is a power outage or not based on changes in its contents.

(6) Effects of the Invention Therefore, it is possible to reliably detect whether there is a power outage or not without requiring a separate device, prevent malfunctions of devices such as meters, and achieve high reliability.

[Brief explanation of drawings]

FIG. 1 is a configuration explanatory diagram showing an embodiment of the present invention. 1...Backup power supply, 2...Semiconductor memory. 3... Central processing unit, 8w... Switch, 4...
・Device power supply. M...Memory for power failure detection patent applicant Chino Seisakusho Co., Ltd.

Claims (1)

[Claims] 1. A backup power source that pulls up when the device power is on, a semiconductor memory that is backed up by this backup power source and has known power failure detection data written in a predetermined area, and a semiconductor memory that is backed up when the device power is turned on. A power outage detection device comprising: a central processing unit that reads data for power outage detection and detects whether a power outage has occurred based on a change in the content;