JPH05101206A - Microcomputer - Google Patents

Abstract

PURPOSE:To provide a microcomputer containing a function which automatically switches the oscillations in a reset status. CONSTITUTION:A microcomputer contains a main oscillation circuit 4 and a time counting oscillation circuit 5. The circuits 8, 9 and 10 are added to the microcomputer to selectively actuate the circuit 4 or 5 in a reset status. Thus the microcomputer works with the time counting clock if inputted in the reset status or with the main clock if there is no time counting clock.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microcomputer having an oscillation circuit for a timepiece and a main oscillation circuit, and more particularly to a microcomputer with oscillation switching judgment which automatically switches the oscillation circuit at reset. is there.

[0002]

2. Description of the Related Art Generally, in the prior art, there is no microcomputer having a circuit for automatically selecting oscillation.

[0003]

As described above, the conventional microcomputer does not have a built-in selection circuit for selecting oscillation. By the way, in the mask version, as an option at the time of masking, there is one that can select whether the operation from reset is the main clock or the clock for the clock. However, the EPROM version that does not have options,
The OTP version cannot be selected, and it is fixed at either. In addition, two types of EPROM and OT are required to support both.
There was a problem that P had to be made.

In view of the above points, the present invention has been made in order to solve the above-mentioned problems, and in the mask version, option setting is unnecessary and one type of OTP is used.
It is an object of the present invention to provide a microcomputer with oscillation switching judgment that can be adapted to two types of modes, the version and the EPROM version.

[0005]

In order to achieve the above object, a microcomputer according to the present invention is provided with an oscillation circuit for a timepiece and a main oscillation circuit, and determines which one of the oscillation circuits is operated at reset. The microcomputer is selected and the microcomputer is started up by the output signal of the selected oscillation circuit.

[0006]

In the present invention, if there is a clock clock input at the time of reset, the clock clock operates, and if not, the main clock operates.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the embodiments shown in the drawings. FIG. 1 is a block diagram showing an embodiment of the present invention. Here, a concrete example of an oscillation switching determination circuit for selecting a main clock input and a clock clock input is shown. In FIG. 1, a portion surrounded by a one-dot chain line represents the inside of the microcomputer 1, and the microcomputer 1 is supplied with a main clock input IN ₁ and a clock clock input IN ₂ from the outside.

The main clock input IN ₁
A main clock oscillation buffer 2 and a JK flip-flop 3 for oscillating and stopping the main clock
To a main oscillation circuit 4 and a clock clock oscillation buffer 5 for a clock clock input IN ₂ and a JK type flip-flop 6 that oscillates the clock clock at reset. Has been done.

In this case, each JK type flip-flop 3,
The internal reset signal 23 is supplied to the _RD terminal of 6, the J terminal and the K terminal of one flip-flop 3 are connected to the power supply side and the ground side, respectively, and the T terminal is connected to the input IN ₂ side of the clock clock. The Q terminal is connected to the control input side of the buffer 2. The other flip-flop 6 has a T terminal connected to the ground side and a Q terminal connected to the control input side of the buffer 5.

The clock clock input IN ₂ is supplied to the T terminal, and the internal reset signal 23 is supplied to the R _D terminal.
The type flip-flop 8 is for selecting a clock clock or a main clock.
The outputs of the terminal and the bar Q terminal are respectively sent to the AND circuits 9 and 10 to select a clock clock or a main clock, and the selected clock is sent to the timer 12 via the OR circuit 11. Has been sent out.

The timer 12 is for counting the oscillation stabilization time, and its overflow signal 21 is input to the AND circuit 13. As a result, the AND circuit 13 outputs the clock output from the OR circuit 11 as the internal φ signal 22 by the overflow signal 21 from the timer 12. The JK type flip-flop 8 for switching the clock clock / main clock has its J terminal and K terminal connected to the power supply side and the ground side, respectively.

Next, the operation of this embodiment will be described with reference to FIGS.
Will be described. When the internal reset signal 23 arrives in the microcomputer 1 and an internal reset is applied, the respective JK flip-flops 3, 6 and 8 are reset, and the flip-flops 3 and 6 reset the main clock input IN ₁ and the clock. Clock input IN ₂
Or start oscillating.

If there is no input signal from the input IN ₂ of the clock clock (FIG. 2 (a)), the input IN _{1 of the} main clock shown in FIG. 2 (b) is the AND circuit 9 and the OR circuit 1.
The timer 12 counts through 1. When the timer 12 reaches the overflow (t _{A in} FIG. 2), the AND circuit 13 opens the gate by the overflow signal 22 and supplies the main clock from the OR circuit 11 as the internal φ signal 22 (see FIG. c)), Based on the signal, the microcomputer 1 is started up.

When the timer 12 detects a signal from the input IN _{2 of the} clock clock during counting, the JK type flip-flop 6 oscillates by the clock input IN ₂ (FIG. 3 (a)), and the JK type flip-flop 3 Causes the main clock input IN ₁ to stop oscillating (Fig. 3 (b)
). Therefore, the JK type flip-flop 8 is triggered by its clock input IN ₂ and its Q and Q
Inverts the output of the terminal and switches the signal.

That is, the signal input to the timer 12 by the JK flip-flop 8 is the input I of the clock clock.
The clock is switched to the signal from N ₂ , and the clock for the clock is counted by the timer 12. This timer 8
When it overflows (t _{A in} FIG. 3), the clock for that clock is supplied as an internal φ signal 22 (FIG. 3 (c)),
The microcomputer 1 can be started up by the signal.

[0016]

As described above, according to the present invention, in a microcomputer provided with an oscillation circuit for a timepiece and a main oscillation circuit, by incorporating an oscillation switching determination circuit for automatically switching oscillation at reset, There is no need to make two types of OTP and EPROM as in the conventional case, and there is no mask option.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an oscillation switching determination circuit incorporated in a microcomputer according to an embodiment of the present invention.

FIG. 2 is a timing chart for explaining the operation of the present embodiment when there is no clock for clock.

FIG. 3 is a timing chart for explaining the operation of the present embodiment when there is a clock for a clock.

[Explanation of symbols]

4 Main clock oscillator circuit 7 Watch clock oscillator circuit 8 JK type flip-flop for switching watch clock / main clock 9, 10, 13 AND circuit 11 OR circuit 12 Timer

Claims (1)

[Claims] 1. In a microcomputer having an oscillation circuit for a watch and a main oscillation circuit, it is selected which one of the oscillation circuits is to be operated at the time of reset, and the microcomputer is activated by the output signal of the selected oscillation circuit. A microcomputer having a built-in oscillation switching determination circuit for starting up.