JPH05143754A - Microcomputer - Google Patents

Abstract

PURPOSE:To provide a microcomputer that hardly has the danger of being initially reset in a stand-by state. CONSTITUTION:A stand-by signal generating circuit 7 transmits a stand-by signal to a processor 1, and an initial reset circuit 5 transmits an initial reset signal to the processor 1 when the power voltage drops less than a prescribed level. A microcomputer contains these circuit 7 and 5 and produces the stand-by signal under the stand-by conditions and when the stand-by conditions are satisfied to set the processor 1 in a stand-by mode from an operating mode. At the same time, the microcomputer reduces the power voltage in the stand-by mode. Then a preventing circuit is added to the microcomputer to prevent the input of the initial reset signal to the processor 1 in response to the production of the stand-by signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microcomputer, and more particularly, to a battery-operated microcomputer having a standby mode, which can prevent careless initial resetting during standby, thereby reducing power consumption. Such a microcomputer.

[0002]

2. Description of the Related Art One-chip microcomputers are used for control circuits of cameras and household electric appliances, control circuits of other electronic devices, remote controllers, etc. Has been. This type of one-chip microcomputer differs from a general-purpose microprocessor in that a large number of registers, memories, ALUs, etc. are built in one chip in advance and are connected to each other in advance. And the built-in C
A controller such as PU controls circuits such as an I / O buffer, a RAM, a register, and an ALU to exchange data with an external circuit via the I / O buffer.

Many one-chip microcomputers (one-chip microprocessors) of this type operate on a battery. In the case of a battery-powered type, a standby mode is provided in order to suppress consumption of the battery. this is,
Normally, in a standby state, each circuit of the one-chip microcomputer returns from the standby mode to the operation mode in response to a key input operation or an operation of the operation mechanism. The battery-powered one-chip microcomputer stores the data of the operating state immediately before entering the standby state and the data at the time of standby, and the next time the operating mode is entered, the state immediately before standby or a predetermined designation is set. In many cases, control is performed such that the operation is continuously started from this state. For example, in various household electric appliances and electronic appliances that operate by setting a timer, a one-chip microcomputer that has a function of starting predetermined control at a set time and displaying the time at the same time Built in. In the control, the time data and the data for performing the predetermined control are kept held even in the standby mode. Further, the time is continuously counted by the built-in clock, and the time at each time point is displayed. In this type of control, the data of the program counter, various registers, memories, etc. built in the microcomputer is retained as it is during the standby mode, and further, a specific operation is continued if necessary.

Further, in a remote controller or the like, information on a specific key pressed one time before is stored in a program counter, a register or the like, which is held even in a standby state, and the key is then pressed. When the operation mode is set, control is performed such that the control continues to be started from the state before the standby according to the information stored immediately before the standby.

[0005]

The power supply voltage in the operation mode is usually about 5V, but in the standby mode,
Not only is the operation of each circuit stopped, but the power supply voltage itself is lowered to about 3V. This will further reduce power consumption during standby. However, in a microcomputer in which the power supply voltage is lowered to a predetermined level such as 3 V in the standby state, if the battery is replaced during standby, the initial reset voltage will be generated when the power backup during battery replacement is insufficient. The power supply voltage may drop and the initial reset may be applied. In addition, there is a risk that the initial reset is also applied when the power supply voltage drops during standby due to battery exhaustion or the like. This occurs as long as the initial reset circuit that operates by detecting the power supply voltage is used, and the data held in the register or the program counter is lost when the reset is applied.

In order to avoid such a risk of resetting, the drop of the power supply voltage in the standby state is limited to some extent, and the drop of power consumption is also limited. Therefore, an object of the present invention is to solve the above-mentioned problems of the prior art, and to provide a microcomputer having almost no risk of initial reset in the standby state.

[0007]

The microcomputer of the present invention which achieves the above object is characterized by a standby signal generating circuit for sending a standby signal to a processor and a processor when a power supply voltage is below a predetermined value. And an initial reset circuit that sends an initial reset signal to the processor, and generates a standby signal when the standby condition or the standby condition is met to change the processor from the operation mode to the standby mode, and A microcomputer for reducing the power supply voltage in the mode is provided with a blocking circuit for blocking the input of the initial reset signal to the processor when the standby signal is generated.

[0008]

As described above, by blocking the sending of the initial reset signal to the processor by the standby signal, the power supply voltage in the standby state can be sufficiently lowered. As a result, even if the power supply voltage is lowered to enter the initial reset state when the battery is replaced and the initial reset circuit operates, the initial reset signal generated at that time is not sent to the processor. Therefore, the data in the standby state stored in the register or memory inside the processor can be saved. Further, when there is an external circuit to be reset, the data is saved, and then the processor which has returned to the operating state can continue the operation according to the data.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram of a one-chip microcomputer to which the present invention is applied, and FIG.
It is a block diagram of other one Example. In FIG. 1, 10
Is a one-chip microcomputer having a CPU 1 having a register 2 such as a program counter therein.
And a memory 3, a 2-input AND gate 4, an initial reset circuit 5, an inverter 6, a standby signal generation circuit 7, and a power supply circuit 8. This shifts from the operation mode to the standby mode or vice versa according to the generation and stop of the standby signal 11 of the standby signal generation circuit 7.

In the standby mode, the standby signal generation circuit 7 generates a HIGH level (hereinafter "H") standby signal 11 which is inverted by the inverter 6 and supplies the inverted signal to the CPU 1. Further, the standby signal 11 is sent as it is to the power supply circuit 8 and other circuits for setting the standby state. When the CPU 1 receives a signal (“L”) obtained by inverting the standby signal 11 at the standby terminal (SB), when the CPU 1 and the external circuit such as the memory 3 for controlling the operating state and the standby state are present. The external circuit and the register 2 incorporated therein are set to the standby state from the operating state. Further, a signal for putting various circuits of the one-chip microcomputer 10 into a stopped state is externally generated to stop them. When receiving the standby signal 11, the power supply circuit 8 switches the power supply voltage, which is the output thereof, from the output state of DC5V to the output state of DC3V, for example.

When the key 9a on the keyboard 9 is pressed, the standby signal generating circuit 7 receives the pressing signal from the keyboard 9 and outputs the standby signal 11 from "H" to LO.
The generation of the standby signal 11 is stopped by setting it to the W level (hereinafter "L"). As a result, the CPU 1 and various circuits are returned to the operating state. At this time, the power supply circuit 8 switches its output voltage from DC3V to DC5V output state. The power supply voltage switching process of the power supply circuit 8 is performed by an external output generated by the CPU 1 to the outside by the CPU 1 which receives the inverted signal (“H”) of the signal (“L”) in which the standby signal 11 is stopped. May be received by the power supply circuit 8 and performed accordingly.

The initial reset circuit 5 includes a power supply circuit 8
Is monitoring the voltage of the power supply line + Vcc connected to the output of, and, for example, when it is lower than 2V, the initial reset signal 12 is sent to the AND gate 4, and the reset terminal ( R). When the CPU 1 receives the initial reset signal 12, the CPU 1 resets the register 2 incorporated therein and the external circuit such as the memory 3 which is responsible for standby control to the initial state. Therefore, when the voltage of the power supply line + Vcc drops from 3V to 2V due to battery replacement, battery exhaustion, or other reasons after entering the standby state,
The initial reset signal 12 is generated.

The initial reset signal 12 is input to one input of the AND gate 4 and is supplied to the CPU 1 through the input.
It is supposed to be input to. The AND gate 4 and the inverter 8 are a blocking circuit that blocks the initial reset signal during standby. That is, the AND gate 4 receives the inversion signal (“L”) of the “L” standby signal 11 from the standby signal generation circuit 7 via the inverter 6 in the other input in the standby mode. Therefore, at this time, the AND gate 4 is closed. Therefore, even if the initial reset signal 12 is generated during the standby, it is not added to the CPU 1. Therefore, the CPU 1 is not reset even if the power supply line + Vcc becomes 2 V or less and drops to the initial reset operation voltage as described above. Data in the register 2 and the memory 3 are not lost.

By the way, the minimum voltage for holding data in a memory or register is usually about 1.2V.
Therefore, when replacing the battery, a voltage higher than this is generated by a backup capacitor or the like and applied to a register or a memory. Therefore, even when the battery is removed, power is supplied to various circuits such as a register and a memory for some time. Although this capacitor is a part of the power supply circuit 8, it is not shown in the figure because it is a general one. In the circuit of the previous embodiment, the AND gate 4 blocks the initial reset signal 12 generated at this time even if the battery replacement takes time and the power supply line drops to 2 V or less.
Therefore, as long as the power supply line does not drop below 1.2 V, which is the data holding voltage of the memory 3 or the like, each held data is valid, and the battery-driven microcomputer can be used for battery replacement etc. On the other hand, there is a margin.

When the microcomputer 10 is in the operation mode, the power supply line + Vcc does not become 2 V or less in the battery-operated type, so that the initial reset is not performed in the operating state. When an initial reset is required, stop the generation of the power supply voltage itself by turning the reset switch for a normal initial reset “ON” or the power-on switch “OFF”, or if there is no such switch, remove the battery. You can leave it. As a result, the power supply voltage is not generated, so that the circuit can be started from the next power-on state at any time to enter the operating state, and at this time, the initial reset of each circuit is performed.

Immediately after the battery is removed and loaded (hereinafter, this battery replacement is also considered to be included in the power supply "ON"), or if there is a power switch or standby switch, operate the power switch. "ON"
At this time, the standby signal generation circuit 7 is not in the operating state, and therefore the standby signal 11 (“H”) is not generated. At this time, the output of the inverter 6 becomes "H".
Therefore, with the AND gate 4 being opened and the power supply voltage increasing from the time when the power supply is turned “ON”, the initial reset circuit 5 operates to generate the initial reset signal 12, which is applied to the CPU 1. .. As a result, during the initial reset period when the power is turned on,
Each built-in circuit can be reset. In addition, power supply "ON"
At the same time, the standby signal generation circuit 7 operates, unluckily,
In consideration of an exceptional state in which the keys of the keyboard 9 are operated, it is sufficient to prevent the standby signal 11 from being "H" for a certain period while the power is "ON".

FIG. 2 shows the selective connection circuit 13 and the OR gate 1.
4 is an embodiment in which an external / internal reset selection circuit consisting of 4 and 4 is provided. Thereby, it is possible to select whether to supply a reset signal from the outside or to use the built-in initial reset circuit 5. This is because the output of the initial reset circuit 5 is supplied to one input of the 2-input OR gate 14 via the selective connection circuit 13, and the output of the OR gate 14 is AN.
The data is output to the D gate 4. The other input of the OR gate 14 is connected to the reset terminal 15, which is one of the external terminals. Therefore, a reset signal can be received from the outside through this terminal.

If the selective connection circuit 13 is formed in the same layer as the ROM data and the data is written, it is selected whether the terminals are connected or not connected at the same time when the data is written. It is possible to easily select whether to make the selective connection circuit 13 in the connected state or in the cutoff state by selecting the mask when writing the data. Therefore, it is possible to selectively set the one-chip microcomputer using the built-in initial reset circuit 5 or the one-chip microcomputer using the external reset terminal 15 at the time of writing the ROM data. As a result, it is not necessary to manufacture the one-chip microcomputer 10 in each separate process.

In the embodiment, the standby signal 11 is significant when it is "H". Then, this is generated during the standby period. Also,
In the standby mode, the "H" voltage level of the standby signal itself drops. When this voltage drop affects the voltage of the standby signal "H", the rising or falling edge of the standby signal may be entered into the standby mode. As a result, the standby mode can be entered when the standby condition is satisfied. On the other hand, if the standby signal is made "L" significant, the inverter 8 is unnecessary. At this time, the standby signal 11 becomes "L" immediately after the operating state or the battery is removed and the battery is loaded, or when the power switch or the standby switch is operated to turn the power "ON". There is a possibility. Therefore, at this time, a circuit for setting the standby signal 11 to "H" may be provided. Needless to say, the power supply voltage that is reduced in response to the generation of the standby signal is a voltage that is equal to or higher than the voltage at which the data in the register or memory is not lost.

As described above, the initial reset circuit 5 of the embodiment is the one-chip microcomputer 1
It may be externally attached to 0. In the embodiment, depending on whether the key 9a on the keyboard 9 is operated or not, the standby mode is entered when the key 9a is not operated (so-called "OFF"). When using a switch, power switch, etc., it is "ON" or "OF".
When it is set to F ″, the standby signal generation circuit may generate the standby signal.
It is input to the standby terminal of the CPU.
It may be input to the sleeve terminal in which the CPU is stopped. In addition, although the embodiments have been described by taking an example of battery driving, the present invention is not limited to battery driving in the case of a low power consumption type microcomputer in which an initial reset is applied due to a decrease in a power supply line in a standby mode. It can be applied even if it is not a thing.

[0021]

As can be understood from the above description, in the present invention, the standby signal prevents the initial reset signal from being sent to the processor, thereby sufficiently lowering the power supply voltage in the standby state. It is possible to As a result, even if the power supply voltage is lowered to enter the initial reset state when the battery is replaced and the initial reset circuit operates, the initial reset signal generated at that time is not sent to the processor. Therefore, the data in the standby state stored in the register or memory inside the processor can be saved. Further, when there is an external circuit to be reset, the data is saved, and then the processor which has returned to the operating state can continue the operation according to the data. As a result, there is no risk of data loss, and it is possible to enter the standby state with low power consumption.

[Brief description of drawings]

FIG. 1 is a block diagram of a one-chip microcomputer to which the present invention is applied.

FIG. 2 is a block diagram of another example thereof.

[Explanation of symbols]

1 ... CPU, 2 ... Register, 3 ... Memory, 4 ... 2 Input A
ND gate, 5 ... Initial reset circuit, 6 ... Inverter, 7 ... Standby signal generating circuit, 8 ... Power supply circuit, 9
... keyboard, 10 ... one-chip microcomputer.

Claims (1)

[Claims] 1. A processor that receives a standby signal at a predetermined terminal and is set to a standby mode, and a standby signal that sends the standby signal to the processor either under a standby condition or under a standby condition. A generation circuit, an initial reset circuit that sends an initial reset signal to the processor when the power supply voltage becomes equal to or lower than a predetermined value, and a register that stores data to hold the power supply voltage in the standby state according to the standby signal, A memory circuit or the like receives a power supply circuit that lowers the voltage value higher than a sufficient voltage for holding the data, the standby signal and the initial reset signal, and sends the initial reset signal to the processor in response to the standby signal. And a blocking circuit to block the output of A microcomputer equipped with.