JPS63103311A - Processing method for microcomputer system at time of service interruption - Google Patents

Abstract

PURPOSE:To improve the reliability of a microcomputer system by restarting automatically the system operation as long as the power supply voltage drops less than a prescribed level owing to an instantaneous service interruption of the power supply, etc., is reset to its original level within a prescribed period of time. CONSTITUTION:The DC power supply voltage VC supplied to a microcomputer system is impressed on a voltage detecting circuit 2. The circuit 2 transmits a signal that is changed to logical L from a logical H to an output terminal 3 when the voltage VC drops less than the voltage V1 and then to an output terminal 4 when the VC drops less than the voltage V2 respectively (V1>V2). The output of the terminal 3 is supplied to a data bus of a CPU and a terminal NMI via a buffer circuit 5 and a flip-flop circuit 6 respectively. While the output of the terminal 4 is supplied to a reset terminal of the CPU via inverter circuits 7 and 8, etc. Thus the operation can be restarted automatically without stopping working of the microcomputer system as long as the dropped voltage VC is reset to its original level within a prescribed period of time.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a processing method when the AC power supply of a microcomputer system momentarily drops below a predetermined value due to a momentary power outage or noise.

(Prior art) N-units and H22s are sometimes controlled by a microcomputer system, but such microcomputer systems cannot be used when the power supply is cut off during operation due to a power outage or noise, or due to a drop in voltage. If programs and data are destroyed, the microcomputer system may not be able to operate normally even if power is supplied and the microcomputer system starts operating again.

Therefore, in many cases, there are microcomputer systems that have the ability to automatically terminate a program normally and retain data using a backup battery when the power supply is cut off.

Normally, a microcomputer system that serves as such a backup battery assumes that a power outage will occur when the power supply voltage drops, and after executing the process for normal termination in the event of a power outage (power outage processing). , the microcomputer system stops operating or is forced to reset and terminate.

(Problem to be Solved by the Invention) The conventional microcomputer system's processing method in the event of a power outage is that even though the detection circuit has started processing the power outage as a power outage due to a momentary power outage in the AC power supply, There was a problem in that even if the voltage of the AC power supply recovered to a normal value immediately after that, the microcombinator system would stop operating.

Furthermore, static electricity or external noise can cause an instantaneous drop in the power supply voltage, which is detected by the detection circuit as a power outage, and the power outage is handled and the operation is stopped. This leaves little margin for noise, resulting in high reliability. There is a problem in that such conventional microcomputer system processing methods during power outages cannot be used in systems that require the following.

(Means for Solving the Problems) In order to solve the above problems, the present invention detects that the power supply voltage has dropped below a predetermined value when a power outage occurs during the operation of a microcomputer system, and In a microcomputer system that handles a power outage by stopping operation before the voltage is cut off or by issuing an interrupt such as a reset, the power supply voltage is supplied to the microcomputer system, and the first voltage and this first voltage are lower second
a voltage detection circuit having first and second output terminals, each of which changes the state of a sending signal when detecting a voltage of a flip-flop circuit that sends information to the CPU that the power supply voltage has changed from a state higher than a first voltage to a state lower than the first voltage; and a first resistor to which an output signal from a second output terminal is supplied. a second resistor whose other end to which the other end of the first resistor is connected is grounded, and a capacitor whose other end is supplied with the power supply voltage;
of the resistor Il! ! The output signal from the end causes the CPU to
and a circuit to obtain a reset signal to the above? 11i When the power supply voltage becomes lower than the first voltage, the CPU is interrupted to perform power outage processing, and when the power supply voltage is restored within a predetermined time, the power outage processing recovery processing is performed and the power supply A method for processing a power outage in a microcomputer system is provided, in which the CPU is reset when the voltage becomes lower than a second voltage.

(Implementation VA> FIG. 1 is a block system diagram for explaining the processing method at the time of power outage in the microcomputer system of the present invention, FIG. 2 is a flowchart of the same, and FIG. 3 is a time chart of the same waveforms.

In FIG. 1, reference numeral 1 denotes an input terminal to which a DC power supply voltage Vc is supplied to the micro combi coater system.
supplied to

This voltage detection circuit 2 uses a well-known circuit using, for example, a constant voltage diode, to output a signal to an output terminal 3 when the power supply voltage Vc is below the voltage V1, and when the power supply voltage Vc is below the voltage 2.
This is a circuit that sends a signal whose state changes from a logic H signal @ (hereinafter simply referred to as 1) to a logic high signal (hereinafter simply referred to as L) to the output terminal 4, and here the voltage is 1.
It is assumed that the voltage is larger than the voltage ■2.

The output signal of the output terminal 3 is supplied to the buffer circuit 5 and the flip-flop circuit 6, respectively, and the output signals of the buffer circuit 5 and the flip-flop circuit 6 are connected to a CPU data bus (not shown).
and the NMI terminal.

At the bottom, the output signal of the output terminal 4 is supplied to one end of a resistor R1, and the other end of this resistor R1 is connected to one end J3 and the other end of a resistor R2, the other end of which is supplied with the power supply voltage VC. are connected to one end of a capacitor C which is grounded.

Furthermore, the output signal at the other end of the resistor R1 is sent to the inverter circuit 7.
．． 8 are each serially supplied to a reset terminal of a CPU (not shown).

Next, the operation of the processing method for a microcomputer system during a power outage according to the present invention will be explained with reference to FIGS. 1 to 3.

AC for an instant (time T) as shown at P in Figure 3 (A).
Suppose that the line voltage becomes zero. However, this AC
The line voltage is converted to a predetermined DC power supply voltage VC by a transformer, rectifier circuit, constant voltage circuit, etc. (not shown), but these circuits have large capacitors and resistors, so they have a large time constant. It is common to have one.

Therefore, the power supply voltage Vc decreases with a certain time constant as shown in FIG. 3(B), and when it becomes less than the voltage v1, the output signal of the output terminal 3 of the voltage detection circuit 2 changes as shown in FIG. 3(C). As shown in FIG. 2, the state changes from G1 to L, and the CPU enters an interrupt operation for the program that has been running so far (step 1 in FIG. 2).

Next, the flip-flop circuit 6 performs power outage processing by supplying the output signal inverted at the edge to H to the NM[end f] of the CPU.
PtJ is a buffer circuit 5 obtained via a data bus (not shown) after performing power outage processing.
Determine whether or not the power supply voltage Vc is higher than the voltage v1 based on the signal from the power supply. If the power supply voltage VC is higher than the voltage v1 (Yes in step 3 in Figure 2), the CPU performs a recovery process that returns the power failure process to oil. (Step 4 in FIG. 2) is carried out, and the process returns to the normal operation at the beginning of the interrupt (Step 5 in FIG. 2). Directly, the CPU sends a signal to the flip-flop circuit 6,
The output signal of the flip-flop circuit 6 is returned from L to H as shown in FIG. 3(D).

Here, even if the voltage of the AC line becomes zero for a time T,
In order to prevent the power supply voltage Vc from falling below V2, the time T can be arbitrarily set by selecting the time constants of the rectifier circuit, constant voltage circuit, etc.

Next, when the voltage of the AC line is zero for a period of time 1 or more, the power supply voltage Vc becomes the voltage v as shown in the Q series of FIG. 3(B).
2 or less (step 6 in Figure 2), the voltage detection circuit 2 detects this and the output signal at the output terminal 4 changes state to H, and until then the capacitor C is connected to the resistor R.
2 to the power supply voltage Vc, but the resistor R
Since one end of 1 becomes low, the voltage of capacitor C will be discharged through resistor R1, and when it becomes below the threshold level of inverter circuit 7, the output signal of inverter circuit 7 will become H, so the voltage of capacitor C will be discharged through resistor R1. The output signal of the circuit 8 reaches the level shown in FIG. 3(E), and the microcomputer system is reset, that is, the operation is terminated.

(Effects of the Invention) According to the present invention, in a microcomputer system having a backup battery, N8. Even if the power supply voltage drops to zero or below a predetermined voltage due to an instantaneous power outage, static electricity, noise, etc., if the power supply voltage is restored within the predetermined time, the microcomputer system will continue to operate automatically without stopping. It has the advantage of being able to be re-operated at any time and also having a large margin against noise.

[Brief explanation of the drawing]

FIG. 1 shows P of the microcomputer system of the present invention;
! FIG. 2 is a block system diagram for explaining the method of processing electric power, FIG. 2 is a flowchart of the same, and FIG. 3 is a time chart of the same waveforms. DESCRIPTION OF SYMBOLS 1... Input terminal, 2... Voltage detection circuit, 3... First output terminal, 4... Second output terminal I, 5... Buffer circuit, 6... Flip-flop circuit , 7.8...
・Inverter circuit, C... capacitor, R1... first resistor, R2... second resistor, T... time,
■1...First voltage, ■2...Second voltage, Vc.
...DC power supply voltage.

Claims (1)

[Claims] When a power outage occurs while the microcomputer system is operating, it detects that the power supply voltage has dropped below a predetermined value.
In a microcomputer system that handles a power outage by stopping the operation or by interrupting such as a reset before this power supply voltage is cut off, the power supply voltage is supplied to the microcomputer system, and the first voltage and this first voltage are
A voltage detection circuit has first and second output terminals that each change the state of a sending signal when detecting a second voltage lower than the voltage of C;
A buffer circuit that supplies the PU, a flip-flop circuit that sends to the CPU that the power supply voltage has transitioned from a state higher than the first voltage to a lower state, and an output signal of a second output terminal is supplied to one end. a second resistor whose other end is grounded to which the other end of the first resistor is connected; and a capacitor whose other end is supplied with the power supply voltage; a circuit that obtains a reset signal to the CPU based on an output signal from the other end of the resistor, and interrupts the CPU to perform power outage processing when the power supply voltage becomes lower than a first voltage, and When the power supply voltage is restored within a time, a recovery process of the power failure process is performed, and when the power supply voltage becomes equal to or lower than a second voltage, the CPU is reset. Method.