JPS5840767B2 - Microcomputer reset circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a microcomputer reset circuit, and particularly to a microcomputer hang-up (
This relates to a reset circuit that automatically cancels the stoppage.

In a conventional microcomputer reset circuit, as shown in FIG. 1, when a power supply VCC is applied to an integrating circuit 1 which is connected to a resistor R1 and a capacitor C1, the terminal voltage of the capacitor C1 changes with time constants C and R1. Rise in Noah
Reset signal 4 is obtained via gate N0R2 and inverter gate INV3.

Further, a switch S is provided so that a manual reset operation can be performed.

In this way, in most conventional circuits, an OR is taken between a power-on reset signal using an integrating circuit of a resistor and a capacitor and a manually operated switch.

However, products using microcomputers have the disadvantage that if large electrostatic noise or power supply noise is applied, they may malfunction, resulting in program runaway and hang-up.

That is, in order to release this hang-up, a reset input signal with a specified pulse width must be applied once again to the reset input terminal of the microcomputer.

This causes the microcomputer to initialize its internal registers and restart.

Since this hang-up is fatal to the device, conventionally, a switch S shown in Fig. 1 is provided externally as a reset switch, and a hang-up can be prevented by manual operation.
The upload is being canceled.

The purpose of the present invention is to eliminate such conventional drawbacks by: 1. An object of the present invention is to provide a reset circuit for a microcomputer that can automatically release a hang-up caused by malfunction of the microcomputer.

The reset circuit for a microcomputer of the present invention is an apparatus using a microcomputer having a control operation input section. A means is provided to generate a reset signal to the computer, and when there is no operation input to the cutting section, the micro-
Applying a reset signal to the computer periodically,
Always initialize the microcomputer,
The present invention is characterized in that application of a reset signal to the microcomputer is stopped when there is an operation input to the input section.

Hereinafter, the present invention will be explained in detail with reference to the drawings.

In this embodiment, a case will be described in which a keyboard is provided as the microcomputer control operation unit.

FIG. 2 is a block diagram of a reset circuit of a microcomputer according to the present invention, and FIG. 3 is an operational waveform diagram thereof.

In FIG. 2, an oscillator circuit 6, an edge trigger type flip-flop (FFA) 7-.

(FFB) 8, an inverter gate (INV) 9, an integrating circuit 10 consisting of a resistor R2 and a capacitor C2, and a Schmitt gate (SMT) 11.
2 is taken out at the output of flip-flop 8.

Here, the oscillation circuit 6 is a circuit for constantly triggering the flip-flop 7.8 at a constant cycle, and the circuit consisting of an inverter gate 9, an integrating circuit 10, and a Schmitt gate 11 triggers the output of the flip-flop 8. This is to reset it after a certain period of time.

As shown in FIGS. 2 and 3, when there is no key press signal 5 from the keyboard to the input terminal S of the flip-flop 7, the output A of the flip-flop T triggered by the oscillator circuit 6 is always I 'H'1, so that the reset signal 12, which is the output of the flip-flop 8, becomes 'L11' at the moment it is triggered.

This level signal L passes through an inverter gate 9, an integrator circuit 10 consisting of a resistor R2 and a capacitor C2, and a Schmitt gate 11 for waveform shaping, and after a certain time delay, becomes an output B, and is sent to the reset input terminal R of the flip-flop 8. is applied to

When the reset input is applied to the terminal R, the flip-flop 8 is inverted and the reset signal 12 becomes H.

In this manner, when there is no key input, a reset signal (level signal L) is periodically generated, and the microcomputer is always initialized by this signal.

Next, when the key is pressed and the key press signal 5 is input manually, the output A of the flip-flop T will always be L I+, and the reset signal which is the output of the flip-flop 8 regardless of the trigger of the oscillator circuit 6. 12 maintains the H state.

In this manner, when there is a key force, the state of the flip-flop 8 does not change, and the reset signal 12 goes to the H state, and this state continues until the key is reset.

Therefore, no reset signal is generated in response to a key-pressed state, and the microcomputer processes normally.

As explained above, according to the present invention, the trigger means includes an oscillation circuit, the configuration includes a D-flip-flop,
Since we have provided a circuit with an inverter gate, an integrating circuit, and a Schmitt gate, a trigger is applied to the flip-flop at a fixed period, and it is reset after a fixed period of time.
If no key power is available, a reset signal can be sent periodically to the microcomputer.

Therefore, even if the microcomputer hangs up, it can be automatically restored after the key is restored.
In this case, you can definitely cancel the hang-up, and it becomes possible to remove the apparent hang-up.

Therefore, by using the reset circuit of the present invention,
There is no need for a power-on reset circuit as shown in FIG. 1, which generates a reset signal upon power-on to perform initialization.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram of a reset circuit of a conventional microcomputer, and Fig. 2 shows an embodiment of the present invention.
FIG. 3 is a block diagram of a computer reset circuit, and FIG. 3 is an operating waveform diagram of FIG. 2. 1.10: Integrating circuit, 2: Noah gate, 3°9...
...Inverter gate, 4, 12: Reset signal,
5: Key press signal, 6: Oscillator circuit, 7, 8: Flip
Flop, 11: Schmidt gate.

Claims (1)

[Claims] 1. In a reset circuit of a microcomputer, a first means for oscillating a signal with a constant period, a second means for generating a reset signal for the microcomputer using the signal, and a reset signal that can be input to the microcomputer. It has an external device that generates a signal, and when there is no input signal from the external device, a reset signal is periodically applied to the microcomputer by the second means, and the input signal from the external device is applied to the microcomputer periodically. A reset circuit for a microcomputer, characterized in that the reset circuit for a microcomputer is configured to stop applying a reset signal to the microcomputer at certain times.