JPH05314278A - Microcomputer - Google Patents

Abstract

PURPOSE:To minimize the oscillation stablizing time of an oscillation circuit when recovering the microcomputer from a standby mode to an operating mode. CONSTITUTION:The standby mode and operating mode of the microcomputer are switched by controlling an oscillation circuit 1 through an oscillation control circuit 2 corresponding to an instruction from a CPU 3. In the case of recovery from the standby mode to the operating mode, a voltage control circuit 4 is not functioned by the instruction from the CPU 3 but a booster circuit 5 is functioned and at the time of oscillation start, a double voltage prepared at the booster circuit 5 is supplied to the power source of the oscillation circuit 1. When the oscillation is started and the output of the oscillation circuit 1 is passed through an oscillation stability confirmation circuit 6, the voltage control circuit 4 starts functioning and supplies the output voltage of the voltage control circuit 4 to the power supply voltage of the oscillation circuit 1 or the CPU 3. At such a time, the booster circuit 5 is not functioned by the control from the CPU 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microcomputer.

[0002]

2. Description of the Related Art In recent years, semiconductor integrated circuits and microcomputers have been required to have low voltage and low power consumption. With the decrease in the power supply voltage of the microcomputer, the oscillation stabilization time of the oscillation circuit is getting longer when returning from the standby mode (oscillation stop state) to the operation mode.

Oscillation control in a conventional microcomputer will be described below. FIG. 3 shows an example of a circuit configuration of oscillation control in a conventional microcomputer. Reference numeral 1 is an oscillation circuit, and 2 is an oscillation control circuit, which is connected to the oscillation circuit 1. Reference numeral 3 denotes a central processing circuit (hereinafter referred to as CPU) including a ROM, a RAM and an instruction decoder.
, And is connected to the oscillation circuit 1 and the oscillation control circuit 2.
A voltage control circuit 4 is connected to the oscillation circuit 1 and the CPU 3.

Oscillation control in the microcomputer configured as described above will be described.

First, when not in use, a microcomputer is often placed in a standby mode in which the oscillation circuit 1 is in an oscillation stopped state in order to suppress power consumption. To return to the operating mode of the microcomputer,
The oscillation circuit 1 is made to oscillate through the oscillation control circuit 2 in accordance with a command from the CPU 3. At this time, in order to reduce the power consumption in the operation mode of the microcomputer, the oscillation circuit 1 and the CPU 3 are driven by the voltage created by the voltage control circuit 4.
May be driven.

[0006]

However, in the above-mentioned conventional configuration, when the microcomputer is returned from the standby mode to the operation mode at a low voltage (particularly battery voltage drive of 1.5 V / 3 V), the crystal oscillator is activated. However, since the oscillation frequency becomes slower, the oscillation stabilization time of the oscillation circuit 1 takes more than ten seconds.
When the voltage control circuit 4 is used to reduce power consumption, the potential applied to the oscillation circuit 1 is lower than the normal power supply voltage. Therefore, there is a drawback in that the oscillation stabilization time of the oscillator circuit 1 becomes even longer.

The present invention solves the above-mentioned conventional problems, and an object of the present invention is to provide a microcomputer capable of minimizing the oscillation stabilization time of the oscillation circuit when the microcomputer returns from the standby mode to the operation mode. And

[0008]

In order to achieve this object, a microcomputer of the present invention comprises a booster circuit for generating a voltage obtained by boosting a power supply voltage at the time of starting an oscillation circuit in a return from a standby mode to an operation mode. It has a configuration of an oscillation stabilization confirmation circuit for confirming oscillation start-up and a voltage control circuit for controlling the voltage generated by the booster circuit and supplying the voltage to the oscillation circuit and the CPU.

[0009]

With this configuration, since the power supply voltage of the oscillation circuit can be boosted when the oscillation is started, the crystal oscillator can be easily started and the oscillation stabilization time of the oscillation circuit can be shortened. Further, since the voltage control circuit is operated after the oscillation is stabilized, it is possible to eliminate the difficulty in starting the oscillation of the crystal unit due to the low power consumption.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a circuit diagram of a microcomputer according to the first embodiment of the present invention. In FIG. 1, 1 is an oscillation circuit, 2 is an oscillation control circuit, and 3 is a CPU. CP
The output of U3 is connected to the oscillation control circuit 2, and its output is connected to the oscillation circuit 1. The output of the oscillation circuit 1 is connected to the oscillation stability confirmation circuit 6, and its output is connected to the CPU 3. The oscillator circuit 1 and the CPU 3 are connected to the voltage control circuit 4 and the booster circuit 5. The booster circuit 5 is also connected to the external clock input terminal and the voltage control circuit 4.

The operation of the microcomputer configured as described above will be described below.

First, in order to switch between the standby mode and the operation mode of the microcomputer, the oscillation circuit 1 is controlled through the oscillation control circuit 2 by a command from the CPU 3. When the microcomputer returns from the standby mode to the operation mode, the voltage control circuit 4 for reducing power consumption is disabled by an instruction from the CPU 3 or the like. However, the booster circuit 5 is made to function, and the voltage doubler created by the booster circuit 5 is supplied to the power supply of the oscillator circuit 1 at the time of starting the oscillation. By connecting the booster circuit 5 to the external clock input terminal, not only the control by the CPU 3 but also the external control can be performed. When the oscillation of the crystal unit starts and the output of the oscillation circuit 1 passes through the oscillation stability confirmation circuit 6, the voltage control circuit 4 starts to function and the output voltage of the voltage control circuit 4 becomes the power supply voltage of the oscillation circuit 1 or the CPU 3. Supply. At this time, the booster circuit 5 is prevented from functioning under the control of the CPU 3.

As described above, according to the present embodiment, when the oscillation circuit 1 is started up, the doubled voltage boosted by the booster circuit 5 is provided in the power source of the oscillation circuit 1 to facilitate the start-up of the crystal unit.
The oscillation stabilization time of the oscillator circuit 1 can be minimized.
Further, since the voltage control circuit 4 is operated after the output of the oscillation circuit 1 passes through the oscillation stability confirmation circuit 6, the problems of the voltage control method of the oscillation circuit 1 and the CPU 3 in the conventional low power consumption are solved. You can

A second embodiment of the present invention will be described below with reference to the drawings. FIG. 2 is a circuit diagram of the microcomputer according to the first embodiment of the present invention.
The difference from the configuration of FIG. 1 is that the voltage control circuit 4 is replaced with a current control circuit 7.

This is a reduction of the consumption of the microcomputer by voltage control in the first embodiment, and a current control in the second embodiment.

[0017]

As described above, according to the present invention, by providing the booster circuit, the voltage control circuit, and the oscillation stabilization confirmation circuit in the microcomputer, the oscillator circuit is restored when the microcomputer returns from the standby mode to the operation mode. It is possible to realize an excellent microcomputer that can minimize the oscillation stabilization time.

[Brief description of drawings]

FIG. 1 is a block diagram of a microcomputer according to a first embodiment of the present invention.

FIG. 2 is a block diagram of a microcomputer according to a second embodiment of the present invention.

FIG. 3 is a block diagram of a conventional microcomputer.

[Explanation of symbols]

 1 Oscillation Circuit 2 Oscillation Control Circuit 3 CPU 4 Voltage Control Circuit 5 Booster Circuit 6 Oscillation Stability Confirmation Circuit 7 Current Control Circuit

Claims (1)

[Claims] 1. An oscillation circuit, an oscillation stability confirmation circuit for the oscillation circuit, an oscillation control circuit for controlling an operation mode and a standby mode (oscillation stop state) of the oscillation circuit, and a voltage obtained by boosting a power supply voltage at the time of starting the oscillation. A booster circuit that generates
A microcomputer provided with the oscillation circuit, the booster circuit, and a voltage control circuit for controlling the voltage of the central processing circuit.