JP2008217105A - Program runaway prevention device of microcomputer, and electronic equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a program runaway prevention device certainly resetting a program inside a microcomputer during runaway to prevent capacity run-out of a battery, and to provide electronic equipment therewith. <P>SOLUTION: This electronic equipment 1 has a current detection part 12 monitoring current I flowing into the microcomputer 11 as an example of this program runaway prevention device, in addition to the microcomputer 11 and the battery 10; and a timer part 13 counting a certain prescribed period. The current detection part 12 detects the current when an operation mode of the microcomputer 11 is an active state, operates a counter of the timer part 13, and the timer part 13 performs the reset to the microcomputer 22 when a cancellation signal from the microcomputer 11 is absent and when the counter lapses the prescribed time. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a program runaway prevention apparatus and an electronic apparatus, and more particularly to a program runaway prevention apparatus for preventing program runaway of a microcomputer to which power is supplied from a battery, and an electronic apparatus including the program runaway prevention apparatus.

  Conventionally, microcomputers (hereinafter referred to as microcomputers) are used in various electronic devices such as home appliances such as AV (audio visual) devices and cooking appliances, city gas, LP gas, water meters, and centralized monitoring devices. It is mounted and the electronic equipment is controlled by it.

In an electronic device equipped with a microcomputer, a program of the microcomputer may run away due to external factors such as external noise, and conventionally, an apparatus for detecting this program runaway has been proposed. For example, Patent Document 1 discloses a built-in microcomputer runaway detection device for the purpose of improving the reliability of a runaway detection operation by a runaway detection timer such as a watchdog timer.
JP-A-4-151741

  On the other hand, especially in the electronic device 2 whose main power source is driven by the battery 20 alone as illustrated in FIG. 4, the active state continues due to the program runaway of the control unit (microcomputer) 21, and the battery capacity The problem of cutting is becoming serious.

  However, in the conventional techniques including the technique described in Patent Document 1, the program runaway is monitored by the watchdog timer function that is a function of the microcomputer, but although the runaway can be detected, the runaway itself is caused. The function of the microcomputer itself or the electronic device equipped with the microcomputer cannot always be automatically reset.

  Therefore, the user must press the power-off button or reset button of the electronic device or perform a reset operation on the program. However, as described above, even if the battery run is detected and the user is detected and notified to the user, May cause the battery to run out without being noticed.

  The present invention has been made in view of the above circumstances, and a program runaway prevention device capable of reliably resetting a program in a microcomputer that is running out of control and preventing a battery from running out of capacity, and its device and The purpose is to provide an electronic device equipped with a microcomputer.

  In order to solve the above-described problems, a first technical means of the present invention is a program runaway prevention apparatus for preventing a program runaway in a microcomputer supplied with power from a battery, wherein current flowing into the microcomputer Current detecting means for detecting that is equal to or greater than a predetermined value, detection time measuring means for measuring the output time of the detection signal from the current detecting means, and the output time measured by the detection time measuring means reaches a predetermined time. A reset means for outputting a reset signal for requesting resetting of the program to the microcomputer, and the detection time measuring means outputs a cancel signal from the microcomputer before the predetermined time is reached. Characterized by having means for canceling and restarting the measurement when received A.

  The second technical means is an electronic device provided with the program runaway prevention device in the first technical means, comprising the battery and the microcomputer, and controlled by the microcomputer. is there.

  According to a third technical means, in the second technical means, the microcomputer determines whether or not the program completes processing before the program reaches the predetermined time used in the reset means. And a cancellation means for transmitting the cancellation signal to the detection time measuring means before reaching the predetermined time when it is determined that the completion is not completed as a result of the determination, the completion time determination means The determination is executed at the start time of the program and at the predetermined time interval from the start time.

  According to the present invention, it is possible to reliably reset the program in the microcomputer during the runaway and prevent the battery from running out.

  FIG. 1 is a block diagram illustrating a configuration example of an electronic device according to an embodiment of the present invention, where 1 is the electronic device. FIG. 2 is a diagram for explaining the current value for each operation mode flowing into the microcomputer in the electronic apparatus of FIG.

  The electronic device 1 illustrated in FIG. 1 is a device that uses a battery 10 as a single power source and is driven by a microcomputer 11 as a control unit. Electronic devices 1 include mobile phones, personal digital assistants (PDAs), notebook personal computers (notebook PCs), remote controllers, cameras, and control devices in various devices, as well as in the fields of gas, water, and electricity. Also, various devices such as a centralized monitoring device or a meter can be applied.

  The battery 10 can be applied to either a primary battery or a secondary battery. Note that the electronic device 1 only needs to use the battery 10 as a main power source of the microcomputer 11, and can be similarly applied even when other power sources are supplied to other parts (not shown).

  A program is incorporated in the microcomputer 11 so as to be executable. For example, the microcomputer 11 is provided with hardware such as an arithmetic processing unit such as a CPU, a ROM as a program storage area, and a RAM as a work area, and the program to be executed may be stored in the ROM or hard disk. As a result, an execution target program stored in a ROM or the like can be read out and executed on a RAM by an arithmetic processing unit such as a CPU.

  In addition to the microcomputer 11 and the battery 10, the electronic device 1 includes, as an example of a program runaway prevention apparatus according to the present invention, a current detection unit 12 that monitors the current I flowing into the microcomputer 11 and a timer unit that counts a certain period of time. 13.

  By the way, the operation mode of the microcomputer 11 can be divided into an active state in which the program operates at a high speed and a standby state (inactive state) in which the operation or function is stopped at a low speed. As shown in FIG. 2, the current consumed by the microcomputer 11 is, for example, mA order in the active state and μA order in the standby state.

  The current detection unit 12 detects a current when the operation mode of the microcomputer 11 is in an active state, and operates the counter of the timer unit 13. The timer unit 13 has no cancel signal from the microcomputer 11 and the counter is kept for a certain period. When the time has elapsed, the microcomputer 11 is reset.

  As described above, the program runaway prevention apparatus according to the present invention includes current detection means for detecting that the current flowing into the microcomputer 11 is equal to or greater than a predetermined value, as exemplified by the current detection unit 12. As the predetermined value, a value between the current value when the microcomputer 11 is in the active state and the current value when in the standby state may be employed. In other words, what state is the active state can be arbitrarily determined by a predetermined value.

  Further, the program runaway prevention apparatus according to the present invention, as exemplified by the timer unit 13, is a detection time measuring means for measuring the output time of the detection signal from the current detection unit 12, and the output time measured there is a predetermined time. And reset means for outputting a reset signal for requesting the microcomputer 11 to reset the program. Here, the detection time measuring means has means for canceling and restarting the above-described measurement when a cancel signal is received from the microcomputer 11 before the predetermined time is reached. This means refers to means for canceling the count of the timer unit 13, for example.

  Next, a cancel signal generated by the microcomputer 11 will be described. The microcomputer 11 does not complete as a result of the determination, and a completion time determination unit that determines whether or not the program to be executed completes the process before reaching the predetermined time (predetermined time used in the reset unit). If it is determined, the canceling means transmits the cancel signal to the detection time measuring means on the program runaway prevention device side before reaching the predetermined time. Then, the completion time determination means periodically performs determination at predetermined time intervals from the start time of the execution target program and the start time.

  The predetermined time used in the microcomputer 11 may be obtained by referring to a counter of the timer unit 13 or may be obtained by separately providing a counter in the microcomputer 11 and referring to the counter. Completion of processing indicates completion of processing that requires an active current, that is, completion of processing in which a current of a predetermined value or more flows. If the completion time determination cannot be executed due to runaway of the program to be executed, a reset signal is issued on the timer unit 13 side because no cancel signal is issued as in the case where the processing is completed a predetermined time ago. be able to.

  In addition, the microcomputer 11 includes reset execution means for resetting a program to be executed when a reset signal is received during program runaway. For example, the program can be reset by releasing a work area such as a RAM that has read the program being executed when the reset signal is received and ending the program. However, it is preferable that the execution target program is read again and executed by the reset execution here, and in this case, a runaway prevention program (particularly a program related to the reset) described later is also included. Will be executed again. When the reset is executed so that the execution target program cannot be executed again, it is preferable to give some notification to the user.

  Further, the reset execution means described above can be operated by the user operation by allowing the timer unit 13 to transmit a reset signal similar to the reset signal transmitted when the user manually performs the program reset operation. It can also be defined as a means for executing the same processing as that performed when receiving a reset signal based thereon.

  The above-described completion time determination means, cancellation means, and reset execution means in the microcomputer 11 may be incorporated as a program for preventing runaway on the microcomputer 11 side for causing the microcomputer 11 to function as these means. As a method for incorporation into the microcomputer 11, for example, it may be stored so as to be executable separately from a program to be executed (runaway prevention target) or attached to each of the programs that can be executed.

  FIG. 3 is a diagram illustrating a timing example for explaining the program runaway prevention process in the electronic apparatus of FIG. Hereinafter, the program runaway prevention process of the present invention will be described with reference to FIG. 3 by giving an example of timing for resetting the microcomputer 11 when the timer unit 13 counts five times.

  First, when the microcomputer 11 enters an active state, the current detection unit 12 detects a current greater than a predetermined value, notifies the timer unit 13 of the detection signal, and the timer unit 13 starts counting.

  If the microcomputer 11 determines that the active state can be processed within the time counted by the timer unit 13, the microcomputer 11 ends the process and returns to the standby state. When the microcomputer 11 enters the standby state, the detection signal from the current detection unit 12 is turned off, and the timer unit 13 resets the count and stops. FIG. 3 shows an example in which the standby state is entered with a count of 4.

  On the other hand, when the microcomputer 11 processes the active state for a time longer than the count of the timer unit 13, the microcomputer 11 sends a cancel signal to the timer unit 13, and the timer unit 13 resets the count and starts re-counting. The microcomputer 11 cancels the counter of the timer unit 13 at a constant period until the processing is completed. FIG. 3 shows an example in which the microcomputer 11 issues a cancel signal twice and enters a standby state at the second count for the third time.

  When the program of the microcomputer 11 runs away due to external factors such as external noise, the current detection unit 12 detects the active state, notifies the timer unit 13 of the detection signal, and the timer unit 13 starts counting. In the example of FIG. 3, it cannot be determined whether the active state is due to program runaway / non-runaway until the 4th count, but it can be determined at 5th count to be due to program runaway. When the cancel signal from the microcomputer 11 disappears due to the program runaway and the counter reaches a certain period (5 counts), the timer unit 13 performs an external reset to the microcomputer 11. The microcomputer 11 receives the external reset signal, clears the program runaway, and can start operation normally.

  As described above, according to the program runaway prevention apparatus and the electronic apparatus equipped with the same according to the present invention, the program runaway due to external noise or the like is monitored by the current flowing into the microcomputer itself, and when the abnormal time has elapsed, the microcomputer is forcibly Since the program is normally restored by performing an external reset, it is possible to prevent the battery capacity of the electronic device from running out. Such prevention of running out of capacity is most beneficial for a gas meter or a water meter, for example, in which an electronic device is not normally operated by a user.

It is a block diagram which shows the structural example of the electronic device which concerns on one Embodiment of this invention. It is a figure for demonstrating the electric current value according to the operation mode which flows into the microcomputer in the electronic device of FIG. It is a figure which shows the example of a timing for demonstrating the program runaway prevention process in the electronic device of FIG. It is a block diagram which shows the structure of the electronic device by which a microcomputer drives with a battery power supply by a prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Electronic device, 10 ... Battery, 11 ... Control part (microcomputer), 12 ... Current detection part, 13 ... Timer part.

Claims (3)

  A program runaway prevention device for preventing program runaway in a microcomputer to which power is supplied from a battery, the current detection means for detecting that the current flowing into the microcomputer is a predetermined value or more, and the current detection means A detection time measuring means for measuring the output time of the detection signal, and a reset signal for requesting the microcomputer to reset the program when the output time measured by the detection time measuring means reaches a predetermined time. Resetting means for outputting, wherein the detection time measuring means has means for canceling and restarting the measurement when a cancel signal is received from the microcomputer before the predetermined time is reached. Program runaway prevention device.   An electronic apparatus comprising the program runaway prevention device according to claim 1, comprising the battery and the microcomputer, and controlled by the microcomputer.   When the microcomputer determines that the program is not completed as a result of the determination, and a completion time determination means for determining whether or not the program is completed before reaching the predetermined time used in the reset means And a cancel unit that transmits the cancel signal to the detection time measuring unit before the predetermined time is reached, and the completion time determination unit includes the start time of the program and the predetermined time from the start time. The electronic device according to claim 2, wherein the determination is performed at intervals.

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