JPH02110722A - Oscillation control system - Google Patents

Abstract

PURPOSE:To advance an oscillation starting time by applying a system reset except an oscillation circuit by the deciding result of a power source voltage deciding circuit. CONSTITUTION:When a power source voltage 11 rises, a system reset signal is generated until it reaches a voltage value set beforehand by a voltage detecting circuit built in a system reset generating circuit 3, and after that, when the voltage rises above it, the system reset is canceled and a controller starts a normal operation. Here, the reset is not inputted to the oscillation circuit and therefore, it starts to oscillate the the voltage lower than a voltage detection level. Thus, the oscillation starting time when the power source rises can be advanced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an oscillation control method, and particularly to a control method at power-on.

[Conventional technology]

Conventionally, LSIs such as controllers that execute data processing (
(large-scale integrated circuits), a system reset signal is temporarily generated when the power is turned on.

A system reset generation circuit can also be built into an LSI, and this is becoming more and more common.

By the way, system reset generation circuits are generally capable of generating a reset even when the voltage drops.

This is because, if a certain voltage is first detected when the power is turned on and the reset is canceled when the voltage exceeds that voltage, the voltage can be determined even if the voltage drops.

[Problem to be solved by the invention]

Incidentally, although a crystal oscillation circuit is used as a basic frequency source for a microcontroller or the like, it is desirable that the oscillation start time when the power is turned on be as early as possible. However, the oscillation circuit is also reset by the system, which causes a delay in the start of oscillation when the power is turned on.If the oscillation circuit is reset when the power is temporarily turned off, it takes time to re-oscillate. There is a drawback that it requires

[Means to solve the problem]

In the oscillation control method of the present invention, in a system equipped with at least an oscillation circuit and a power supply voltage determination circuit, a system reset is applied to the parts other than the oscillation circuit based on the determination result.

That is, in the present invention, the oscillation circuit is not reset.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 shows a first embodiment of the present invention, in which 1 is an oscillation circuit, 2 is a controller, and 3 is a system reset generation circuit. FIG. 2 is a time chart for explaining the present invention, in which 1o represents the power supply voltage, 11 represents the GND, 12 represents the voltage detection level, 13 represents the system reset signal, and 22 represents the oscillation start waveform of the present invention.

In FIG. 2, when the power supply voltage 11 rises, a system reset signal is generated by the voltage detection circuit built in the system reset generation circuit 3 until the voltage reaches a preset voltage value. If the voltage increases further after this, the system reset is canceled and the controller 2 enters normal operation. In the oscillation control method of the present invention, since the oscillation circuit is not reset, oscillation is started at a voltage lower than the voltage detection level.

Furthermore, when the period T voltage decreases during normal operation, if the voltage value is a voltage that allows oscillation, oscillation continues regardless of system reset, and normalization of operation is performed smoothly when the power supply voltage is restored. In a crystal oscillation circuit, the oscillation stop voltage is generally lower than the oscillation start voltage, so not resetting the oscillation circuit is effective for continuing oscillation. On the other hand, conventionally, as shown at 21, oscillation stops during period T, and therefore it takes time to recover.

FIG. 3 is a block diagram showing a second embodiment of the present invention. In the figure, ■ is an oscillation circuit, 2 is a controller,
3 represents a system reset oscillation circuit, 31 represents a first system reset signal, and 32 represents a second system reset signal. The system reset signal 31 has the same function as described in the first embodiment, but when the power supply voltage further decreases, a second system reset signal 32 is generated and the oscillation circuit 1
I am trying to hide the reset by including this. This is necessary to suppress standby current when the oscillation circuit is self-biased. Further, the oscillation circuit 1 may be reset by a command issued from the controller 2.

〔Effect of the invention〕

As described in detail above, in a system equipped with at least an oscillation circuit and a power supply voltage determination circuit, the present invention can speed up the oscillation start time and reduce the voltage drop by resetting the system excluding the oscillation circuit based on the determination result. This has the effect of allowing stable oscillation to continue even for

[Brief explanation of drawings]

FIG. 1 is a diagram showing one embodiment of the present invention, FIG. 2 is a time chart for explaining its operation, and FIG. 3 is a diagram of a second embodiment. In the figure, 1 is an oscillation circuit, 2 is a controller, and 3 is a system reset generation circuit. Agent Patent Attorney Shinichi Uchihara

Claims (1)

[Claims] An oscillation control method comprising at least an oscillation circuit and a power supply voltage determination circuit, and a system reset is applied to a portion other than the oscillation circuit based on a determination result from an erroneous determination circuit.