JPS6019222A - Clock generating circuit - Google Patents

Abstract

PURPOSE:To produce a clock which actuates a microcomputer at a speed approximate to the highest processing speed by providing a circuit which detects the power supply voltage and produces a clock signal slightly lower than the maximum working clock frequency that is decided in response to said detected power supply voltage. CONSTITUTION:The value of voltage applied to an input terminal for power supply voltage is converted into a digital signal 14 by an A/D converter 21. An oscillator 22 delivers a clock 12 of a prescribed frequency, and a divider 23 devides the clock 12 and delivers a clock signal 13 having plural different frequencies. A data selector 24 selects one of the signals 13 in response to the signal 14. This selected signal 13 is applied to a microcomputer 25 in the form of a clock signal 15. In such a way, it is possible to obtain a generating circuit for microcomputer clock which actuates the computer 25 at a speed approximate to the highest processing speed corresponding to the power supply voltage.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a clock generation circuit that supplies a clock signal to a microcomputer.

The maximum operating clock frequency and power supply voltage of a microcomputer generally have a relationship as shown by characteristic line 1 in FIG. For example, in a microcomputer with an operating power supply voltage range of 3 to 6 cm and a standard voltage of 5 V, the standard voltage is 5 V,
When using in a power environment with a minimum value of 3V and a maximum value of 6V (in Figure 1, Vz = 3V, V2 = 5V, 'Va = 6V),
The frequency of input 7J is the lowest value of the power supply voltage used (
Here, the maximum operating clock frequency f1' of the microcomputer at the lowest value of the power supply voltage used is set to be lower than the maximum operating clock frequency f1' so that the microcomputer can operate normally even at 3V. .

The clock frequency set as above is.

As shown by characteristic line 2, it is constant regardless of the power supply voltage, and is a much lower value (about a minus digit) than the maximum operating clock frequency (f2 in Figure 1) under standard usage conditions (5V in this case). . Therefore, the processing speed of the microconbeater becomes a slow value determined by the lowest value of the power supply voltage used (the lowest value that can be obtained in the operating power supply voltage range). in this way,
A clock whose frequency is constant regardless of the microcomputer power supply voltage? If a conventional clock generating circuit is used, the microcomputer is forced to operate at a much lower processing speed than the maximum processing speed determined by its power supply voltage.

SUMMARY OF THE INVENTION An object of the present invention is to provide a clock generation circuit for a microcomputer that fully operates the microcomputer at near its maximum processing speed.

A clock generation circuit according to the present invention includes a first circuit for detecting a power supply voltage applied to a microcomputer, and a clock generating circuit that has a frequency close to the maximum operating clock frequency of the microcomputer that is determined in accordance with the power supply voltage, and A second circuit is constructed in which a tarokk signal of a slightly lower frequency is generated in response to the output of the first circuit.

The present invention will now be described in detail with reference to all the drawings.

FIG. 2 is a block diagram showing one embodiment of the present invention. 1
1 is a power supply voltage input terminal; 21 is an A/V converter that converts the value of the power supply voltage from the power supply voltage input terminal 11 into an all-digital signal 14;
It is a D converter. 22 is an oscillator, which outputs all clocks 12 of a predetermined frequency. 23 is a frequency divider, which divides the clock 12 by seven to generate clock signals 1 with different frequencies.
Outputs 3. 24 is a data selector which selects all one of the clock signals 13 in response to the digital signal 14 and supplies it to the microcomputer 25 as the clock signal 1H 15.

FIG. 3 shows that the power supply voltage in the embodiment of FIG. 2 changes stepwise along a characteristic line 1 (the characteristic line 1 indicates the entire maximum operating clock frequency of the microcomputer 1). Compared to the characteristic line 2 of the conventional clock generation circuit, the characteristic line 3 of this embodiment is on the upper side over most of the power supply voltage range. Therefore, the microcomputer 25 can operate at a value close to the maximum operating clock frequency at the power supply voltage over most of the power supply voltage range, including the entire standard voltage V2, and can operate at extremely high processing speeds. becomes.

As explained above, according to the present invention, when the microphone o core is near the maximum processing speed of the microphone o core
It is possible to provide a clock generation circuit for a microcombiner and a heater operated by a heater.

[Brief explanation of drawings]

Fig. 1 is a diagram showing the characteristics of the clock frequency with respect to the power supply voltage of the microcontroller/computer in a conventional microconvenience store clock generation circuit, Fig. 2 is a block diagram showing an embodiment of the present invention, and Fig. 3 is 2 is a diagram showing the characteristics of the clock frequency with respect to the power supply voltage of the microcomputer in the embodiment of FIG. 2 in comparison with the conventional example of FIG. 1; FIG. Characteristic line showing the maximum operating clock frequency with respect to the power supply voltage of a typical microcontroller, 2
...Characteristic line showing the clock frequency with respect to the power supply voltage of the microcomputer in the conventional clock generation circuit, 3...... Showing the clock frequency with respect to the power supply voltage of the microcomputer in the embodiment of the present invention Characteristic line, 21... A/D converter, 22...
Self-oscillator, 23... group frequency divider, 24... data selector, 25... microcomputer. FfL (V) 1st Figure 4 2 Figures 3 V

Claims (2)

[Claims] (1) A first circuit that detects all power supply voltages applied to the microcomputer, and a clock whose frequency is close to, but slightly lower than, the maximum operating clock frequency of the microcomputer determined in accordance with the power supply voltage. The second value generated in response to the output of the first circuit
A clock generation circuit comprising a circuit. (2) In the clock generation circuit according to claim 1, the first circuit does not include an analog-to-digital converter that converts the magnitude of the power supply voltage into an all-digital 4-digit signal; The circuit is an oscillator that generates No. 1a of a constant frequency. a frequency divider that multiplies the constant frequency by the base metal and generates a plurality of pulse numbers 45 having different frequencies; and a circuit that selects the pulse number 45 having a frequency corresponding to the digital number as the clock signal. Tarock generation circuit consisting of.