JP3030878B2 - Long time timer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a long time timer used as one function of a product.

[0002]

2. Description of the Related Art Conventionally, when a long time timer is incorporated as one function of a product, an inexpensive one is a CR oscillation. This is, as shown in FIG.
1, inverters 12 and 13, capacitor 14 and resistor 1
Oscillation is performed using the inverters 12 and 13 based on the CR time constant of the capacitor 14 and the resistor 15, and the counter 11 is counted up by using the inverter 12 and 13 as a basic clock to constitute a long time timer.

[0003]

However, in the above-described conventional configuration, the variation of the CR time constant is about 20%, which directly becomes the variation of the long time timer. In some cases, the microcomputer is constituted only by a microcomputer. However, there are problems that the current consumption increases and an inexpensive microcomputer cannot be used due to its function.

The present invention solves the above-mentioned conventional problem. A microcomputer measures one cycle of a CR oscillation circuit in advance and uses a signal from the CR oscillation circuit to measure one cycle.
One cycle time is added for each cycle time.

Accordingly, it is an object of the present invention to significantly improve the error of the long-time timer, and to provide a long-time timer that can be incorporated as a function of a product with low power consumption and low cost.

[0006]

In order to achieve this object, a long-time timer according to the present invention comprises a microcomputer, a crystal oscillator used as a basic clock of the microcomputer, and a CR oscillator which generates a basic time of the timer. During operation of the microcomputer, the time is counted by the crystal oscillation unit, the time of one cycle of the CR oscillation unit is measured in advance, and the crystal oscillation unit is stopped when the microcomputer is in the sleep state. , The time of the timer is added for each period of one cycle.

[0007]

With this configuration, the period T of one cycle of the CR oscillating unit is measured while the microcomputer is operating, and the crystal oscillating unit is stopped when the microcomputer is in the sleep state, and the operation from the CR oscillating unit is stopped. 1 by signal
It is possible to add the timer time for each time T of the cycle.

[0008]

An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, 1 is a microcomputer, 2 is a crystal or ceramic oscillation unit,
3, 4 are NAND gates, 5 is a capacitor, and 6, 7 are resistors.

The operation of the long timer configured as described above will be described below. First, when the power is turned on, the microcomputer 1 sets Port to Hiz,
The CR oscillating unit based on the CR time constant constituted by the capacitor 5 and the resistor 6 is operated, fetched by an INT interrupt signal, and one cycle of the CR oscillation is measured using the crystal oscillating unit 2 as the original oscillation. Thereafter, while performing other processing, the microcomputer 1 sets the Port to Low and stops the CR oscillation. During that time, the timer is performed by the crystal oscillating unit 2. The Port is set to Hiz again, the CR oscillation is restarted, the crystal oscillation unit 2 is stopped, and a sleep state is entered.
At the rising edge of the final output of the R oscillating unit, the microcomputer receives an INT interrupt signal, returns from the sleep state, adds one cycle of CR oscillation, and enters the sleep state again until a preset time is reached. repeat.

As described above, according to the present embodiment, the microcomputer can be used in a low current consumption state, and a long time timer can be configured without a large error in CR oscillation. FIG. 3 shows the flowchart.

[0011]

As described above, according to the present invention, when a long-time timer function is required as one function, a long-time timer error can be reduced and low power consumption and low cost can be incorporated into a product. Become.

[Brief description of the drawings]

FIG. 1 is an electric circuit diagram according to an embodiment of the present invention.

FIG. 2 is an electric circuit diagram of a conventional example.

FIG. 3 is a flowchart of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Microcomputer 2 Crystal or ceramic oscillation part 3, 4 NAND gate 5 Capacitor 6, 7 Resistance

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-64-84183 (JP, A) JP-A-58-113889 (JP, A) JP-A-62-138781 (JP, A) Jpn. 14535 (JP, U) Hikaru Hei 3-70427 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) H03K 17/00-17/693

Claims (1)

(57) [Claims] 1. A microcomputer comprising: a microcomputer or an active element corresponding to the microcomputer; a crystal oscillator used as a basic clock of the microcomputer; and a CR oscillator configured to generate a basic time of a timer. The time is counted by the crystal oscillation unit, and the time T of one cycle of the CR oscillation unit is measured. When the microcomputer is in the sleep state, the crystal oscillation unit is stopped.
A long time timer that adds the timer time for each period T of the cycle.