JP2858484B2 - Microcomputer - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microcomputer, and more particularly, to a circuit for controlling a system reset and a low current consumption mode at a control input terminal of a system reset. 2. Description of the Related Art A conventional microcomputer has a control input terminal for system reset and a control input terminal for low current consumption mode. By releasing the mode and supplying a control signal to the internal standby control circuit through the control input terminal of the low current consumption mode, the clock to the microcomputer is stopped to realize the low current consumption mode. Further, a system control circuit has a flag which is set only when the power is turned on, in order to distinguish between a system reset when the power is turned on and cancellation of the low current consumption mode. [0004] The above-mentioned conventional microcomputer has the following disadvantages. First, in order to control each of the two control input terminals, an external reset IC or the like is connected to the system reset control input terminal, and when the power supply voltage reaches the operating voltage range, Apply a control signal to release the active level to the control input terminal of the system reset,
At the time of releasing the low current consumption mode, it is necessary to provide an active level control signal to the control input terminal of the system reset. Also, an external reset IC or the like is connected to the control input terminal of the low current consumption mode, so that when the power supply voltage decreases, the system reset control input terminal changes to the active level. A control signal that changes to the active level at a slightly higher voltage is applied to the control input terminal of the low current consumption mode, and a control signal for releasing the active level when the power supply voltage becomes higher than the operating voltage when the power supply voltage rises is provided. It is necessary to give to the control input terminal of the low current consumption mode. As described above, the lower limit of the operating voltage range
Since it is necessary to control the two control input terminals with different voltage values within a narrow voltage range of the operating voltage, there is a disadvantage that the peripheral circuit is complicated and the control becomes difficult. An object of the present invention is to provide a microcomputer which solves the above-mentioned drawbacks and which can be easily controlled using a simple peripheral circuit. A microcomputer according to the present invention includes a system reset at power-on and a standby system.
Power supply to identify the release from the low current consumption mode
There is a flag that is set only at the time of
Responds to the system reset signal when the
Control the system reset, and the flag is set.
Output low-current-consumption mode release signal when not
A system control circuit that, response to the supply of the standby control signal
In response, the mode shifts to the low current consumption mode,
And a standby control circuit for controlling release of the low current consumption mode in response to supply of a mode release signal.
A common control input for input with the standby control signal
And an input control signal supplied to the control input terminal.
It must be a rising control signal that rises from a predetermined level.
And a rising input detecting circuit for outputting the system reset signal and supplying the system reset signal to the system control circuit, and detecting a falling control signal by detecting that the input control signal is a falling control signal falling from a predetermined level. Faith
A falling input detection circuit that outputs a signal ,
It exits the standby control signal by receiving the supply of the output signal Riken
And a noise elimination circuit . FIG. 1 is a block diagram of a microcomputer according to an embodiment of the present invention. As shown in FIG. 1, the microcomputer of this embodiment detects a control input terminal A and a rising input of the control input terminal A, and outputs an output signal to a system reset signal.
A rising input detection circuit 1 to be supplied to the system control circuit 4 as items, system reset and Stan at power
To identify the release from the low current consumption mode corresponding to the bi-state.
This flag is set only when the power is turned on.
When set, supplies the system reset signal
Responds to control system reset and flag set
A system control circuit 4 that outputs a low-current-consumption mode release signal when not performed, a fall input detection circuit 2 that detects a fall input of the control input terminal A and outputs a fall detection signal , Low consumption by inputting fall detection signal
Standby control, which is a control signal for shifting to the current mode
A noise removal circuit 3 for outputting a signal, and a standby control signal.
Control to shift to the low current consumption mode depending on the
The low current consumption mode responds to the supply of the current consumption mode release signal.
And a standby control circuit 5 for canceling the mode. Next, the operation of this embodiment will be described. The control signal input from the control input terminal A
But sometimes a falling input, the falling input is detected by the falling edge input detecting circuit 2, falling
It is supplied to the noise removal circuit 3 as a beam detection signal . No
The noise elimination circuit 3 outputs a standby control signal to the standby control circuit 5 to shift to a low current consumption mode. [0014] The control signal input from the control input terminal A, sometimes a rising input, the rise input detection circuit 1 this the rising input is detected, the system control circuit 4 as a system reset signal
Give to. At this time, the system control circuit 4 checks the internal flag. If the flag is set, the system control circuit 4 performs the system reset control. If the flag is not set, the system control circuit 4 sends the system control signal to the standby control circuit 5.
By giving a low current consumption mode release signal, control for releasing the low current consumption mode is performed, and a program of the microcomputer is started. As described above, the present invention detects a rising input of a control input terminal and detects a system reset signal.
Standing by detecting the rise input detection circuit, the falling edge input of a control input terminal for providing the system control circuit as No.
A fall input detection circuit that outputs a fall detection signal , and switches the fall detection signal through a noise removal circuit .
To the standby control circuit as a standby control signal ,
Since control is performed to shift to the low-current-consumption mode, system reset and low-current-consumption mode control can be performed with one control input terminal. The effect of external control is that the circuit can be simplified. is there.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of a microcomputer according to an embodiment of the present invention. [Description of Signs] A Control input terminal 1 Rising input detection circuit 2 Falling input detection circuit 3 Noise removal circuit 4 System control circuit 5 Standby control circuit

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G06F 1/26-1/32 G06F 1/24 G06F 15/78 510

Claims (1)

(57) [Claims] [Claim 1] System reset and start-up at power-on
For clearing from the low current consumption mode corresponding to the standby state
This flag has a flag that is set only when the power is turned on.
Supply of system reset signal when is set
Controls the reset of the system in response to
When not set, the low power consumption mode release signal is output.
A system control circuit for the power supply of the standby control signal
To the low power consumption mode in response to
And a standby control circuit for controlling release of the low current consumption mode in response to supply of a current mode release signal , wherein the system reset signal and the standby control signal
A common control input terminal for inputting the control input terminal and an input control signal supplied to the control input terminal
A rising input detection circuit that detects a rising control signal rising from a bell and outputs the system reset signal and supplies the system reset signal to the system control circuit; and a falling control signal that falls the input control signal from a predetermined level. That the falling detection signal is detected.
And falling input detection circuit outputs, said stand the falling supplied with Riken detection signal
Microcon Byuta, characterized in that it comprises a noise removing circuit for outputting a control signal.