JPH0922403A - Integrated circuit having reset control function - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely and quickly perform the reset operation of a microcomputer by detecting the oscillation state of the microcomputer and to perform the optimum reset operation. SOLUTION: This integrated circuit includes a power voltage monitoring part 101, a pulse counter part 103, a coincidence detection part 105, a power-on reset part 107, a watchdog timer control part 109 and a watchdog timer part 111. The watchdog input terminal and the reset output terminal of the part 111 are connected to the watchdog output terminal and the reset input terminal of a microcomputer 113 respectively via a Schmitt inverter 115. At the same time, the input terminal of the part 105 is connected to the oscillation pulse output terminal of the microcomputer 113 via the inverter 115. Then the reset operation is started after a prescribed number of oscillation pulses of the microcomputer 113 are counted, and the reset operation is also started right after the power voltage returned to the operating voltage when the operating power voltage of the microcomputer 113 drops.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an integrated circuit with a reset control function for monitoring a power supply voltage and performing a reset operation, and more particularly to a reset control function for performing an optimum reset operation by detecting an oscillation state of a microcomputer. Integrated circuit.

[0002]

2. Description of the Related Art In recent years, with the progress of semiconductor technology, microcomputers (hereinafter simply referred to as "microcomputers") have been widely applied, and various microcomputers have been applied to each application field.

By the way, when the power is turned on to operate the microcomputer, it is not known what state the circuits such as flip-flops, counters and registers for controlling the operation of the microcomputer are set. The method requires the state of these circuits to be set to some defined state. In addition, even when the microcomputer is operating, some unexpected states may occur, or certain prescribed actions may be repeated forever. It is necessary to return to a normal state.

For this reason, the microcomputer is provided with an integrated circuit with a reset control function for preventing the above-mentioned runaway of the microcomputer, and by this circuit, the circuit for controlling the operation of the microcomputer is forced to a predetermined state. , And resetting to the initial state, the operation of the microcomputer is returned to the normal operating state.

In such an integrated circuit with a reset control function, a power supply IC for monitoring a power supply voltage and performing a reset operation
(Hereinafter, referred to as power supply IC with power supply voltage monitoring). The power supply IC supplies a constant voltage that matches the operating voltage of the microcomputer. By adding a power supply voltage monitoring function to this power supply IC, it is automatically reset when the power is turned on or when the power supply voltage drops during microcomputer operation. A power supply IC with a power supply voltage monitor operates to prevent the microcomputer from running away.

A conventional power supply IC with power supply voltage monitoring will be described below. FIG. 12 shows a conventional power supply I with power supply voltage monitoring.
It is a figure which shows an example of a connection of C and a microcomputer. As shown in FIG. 12, the V _DD output terminal of the power supply voltage monitoring power supply IC 1201 is the V _DD input terminal of the microcomputer 1203, and the reset output terminal of the power supply voltage monitoring power supply IC 1201 is the microcomputer 1
Each of them is connected to a reset input terminal of 203.
The microcomputer 1203 has an oscillation stage circuit 1205.

Next, the reset operation of the power supply IC with power supply voltage monitoring will be described with reference to the timing chart of FIG. Note that FIG. 13 shows the state when the power is turned on.

When the power is turned on, the V _CC (supply voltage for application) rises, and the V _DD (supply power for microcomputer and peripheral circuits) starts to rise.

After the power is turned on, at time t ₁₃₁ in FIG. 13, V _DD supplied to the microcomputer 1203 becomes V ₂ (microcomputer oscillation voltage), and the oscillation stage circuit 1205 of the microcomputer 1203 starts oscillation.

On the other hand, the power supply IC 1201 transfers from the reset output terminal to the reset input terminal of the microcomputer 1203 at time t.
By outputting “0” level up to ₁₃₃ , the microcomputer 12
The reset operation continues at 03. Here, this "0"
The period during which the level is output is determined by the watchdog time constant of the capacitor C and the resistor R, and is set to end after the time t ₁₃₁ when the microcomputer starts oscillation.
This period is called a reset pulse width. In FIG. 13, T ₁₃₁ corresponds to the reset pulse width, and V _DD is V
_From time t ₁₃₂ when ₃ (operating voltage) is reached, time t ₁₃₃ described above
Up to Note that V ₃ > V ₂ .

As described above, even if the microcomputer starts oscillating, the power supply IC continues the reset operation until a fixed time elapses. Therefore, when the power is turned on, the microcomputer is automatically reset and can enter a normal operation state.

[0012]

However, the reset operation of the conventional power supply IC with power supply voltage monitoring has the following problems. The reason is that if the oscillation stage circuit of the microcomputer does not immediately oscillate even if V _DD becomes V ₂ , the reset operation ends before the microcomputer oscillates.
In the end, it means that the reset operation of the microcomputer may not be performed. Hereinafter, description will be made with reference to the timing chart of FIG. Note that FIG. 14 shows the state when the power is turned on.

The oscillation stage circuit of the microcomputer has a characteristic that it does not oscillate immediately even if V _DD becomes V ₂ due to the characteristic of the crystal that determines the oscillation frequency, and starts oscillating after a certain period of time. In some cases, T _sta (oscillation start time) shown in FIG. 14 corresponds to the constant time.

At this time, if the reset pulse width T ₁₄₁ for resetting the microcomputer by the power supply IC is not set sufficiently longer than the oscillation start time, the reset pulse width T ₁₄₁ is reset from the time t ₁₄₄ when the microcomputer starts oscillation. The time t _{143 at which} the operation is finished comes earlier. Therefore, the reset operation of the microcomputer is not executed.

Therefore, there is a method of avoiding the above-mentioned situation by setting the reset pulse width by anticipating the above T _sta in advance. In this method, the reset operation is performed when the power supply voltage drops during microcomputer operation. Causes the following new problems.
This will be described below with reference to the timing chart shown in FIG. 15 when the power supply voltage drops during the operation of the microcomputer. In FIG. 15, A is a case where the reset pulse width is set in consideration of T _{st a} , and B is a case where the reset pulse width is set without considering T _sta .

As shown in FIG. 15, while the microcomputer is operating, V
_{Even if DD} drops below V ₃ , if it does not drop below V ₂ , the oscillation of the oscillation stage circuit is not stopped and the microcomputer continues to oscillate. Therefore, it suffices to end the reset operation without considering the state of the microcomputer as when the power is turned on.

Therefore, as shown by B in FIG.
_{If the} reset pulse width T ₁₅₂ is set without considering _sta , the reset operation can be ended at time t ₁₅₃ and the microcomputer can be restored, but T _sta is expected as shown by A in the figure. Therefore, if the reset pulse width T ₁₅₁ is set, the microcomputer will be reset at time t _154, and the delay will be delayed by the amount of T _sta .

The present invention has been made in view of the above circumstances, and an object thereof is to detect the oscillation state of the microcomputer and perform an optimum reset operation to surely and quickly perform the reset operation of the microcomputer. It is to provide an integrated circuit with a reset control function capable of performing

[0019]

In order to achieve the above-mentioned object, the present invention has a reset control function for ending the reset operation after detecting the oscillation state of the microcomputer when the reset operation of the microcomputer is performed. In the integrated circuit, the power supply voltage is monitored, and an operation determination signal is output when an operating voltage is detected, and an oscillation pulse of the microcomputer is input, and a match signal is output after counting a preset count number. The means for outputting, the means for comparing the output of the means for outputting the coincidence signal with the oscillation pulse of the microcomputer, and the means for outputting the coincidence signal when the power supply voltage is equal to or higher than a preset voltage are in an operable state. Means for inputting the operation determination signal and the coincidence signal, and outputting a reset control signal Means for resetting the microcomputer by the reset control signal, and when the microcomputer is powered on, the reset operation is performed after counting a preset number of oscillation pulses of the microcomputer. When the power supply is started and the power supply drops during operation of the microcomputer, the reset operation is started immediately after the power supply voltage returns to the operating voltage.

According to the above configuration, the reset operation can be started after the microcomputer starts oscillating when the power is turned on, and the reset operation can be started immediately after the operating voltage is restored when the power supply voltage drops during the microcomputer operation. The reset operation can be performed reliably and promptly.

[0021]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an internal block diagram showing a configuration of a power supply IC with power supply voltage monitoring according to an embodiment of the present invention.

In FIG. 1, a power supply IC with power supply voltage monitoring (a portion indicated by A in the figure) according to the embodiment of the present invention monitors the power supply voltage and operates when V ₃ (operating voltage) is detected. A power supply voltage monitoring unit 101 that outputs a determination signal and a pulse counter unit 103 that counts clock pulses input to a clock pulse input terminal and outputs a match detection signal after counting a preset count number.
A match detection unit 105 that compares the output from the pulse counter unit 103 with the clock pulse that is input to the pulse counter unit 103; and a power-on reset unit 107 that inputs a reset signal to the reset input terminal of the pulse counter unit 103. , A watchdog timer control unit 109 that inputs the operation determination signal output from the power supply voltage monitoring unit 101 and the coincidence detection signal output from the pulse counter unit 103, and outputs a reset control signal, and outputs a reset signal to the microcomputer 113 A watchdog timer unit 111, and a watchdog input terminal of the watchdog timer unit 111 is a watchdog output terminal of the microcomputer 113.
The reset output terminal of the watchdog timer unit 111 becomes the reset input terminal of the microcomputer 113, and the match detection unit 105
Input terminals are respectively connected to oscillation pulse output terminals of the microcomputer 113 via the Schmitt inverter 115.

The power supply voltage monitoring unit 101 constantly monitors the fluctuation of V _DD (power supply for microcomputer and peripheral circuits),
Its value when the V ₃ below to output the "1" level signal, when the V ₃ or more outputs "0" level of the signal (operation judging signal).

The pulse counter section 103 is preset with how many clock pulses are input to the clock pulse input terminal, and outputs a "0" level signal until the set count number is counted. ,
When the set count number is counted, a "1" level signal (match detection signal) is output.

The coincidence detecting section 105 includes a pulse counter section 1
03 and the clock pulse input from the microcomputer 113 via the Schmitt inverter 115 are compared, and when the output of the pulse counter unit 103 is at "0" level, the clock pulse is directly used as it is.
03, and the output of the pulse counter unit 103 is “1”.
When it is at the level, the "1" level is output to the pulse counter unit 103 regardless of the clock pulse. The oscillation pulse from the microcomputer 113 can be made into a clean square wave by passing through the Schmitt inverter 115.

In the power-on reset unit 107, V _DD is V
_{When the} voltage becomes equal to or higher than ₁ (power-on reset set voltage), the reset of the pulse counter unit 103 is released, and the pulse counter unit 103 is made operable. When V _DD becomes V ₁ or less, the power-on reset unit 107 resets the pulse counter unit 103. Where V
₁ <V ₂ (microcomputer oscillation voltage).

The watchdog timer control section 109 sends a "0" level signal ("0" level) to the watchdog timer section 111 based on the operation determination signal input from the power supply voltage monitoring section 101 and the coincidence detection signal input from the pulse counter section 103. The reset control signal) is output, and in other cases, a "1" level signal is output.

When the watchdog timer control section 109 receives a reset control signal from the watchdog timer control section 109, the watchdog timer section 111 outputs a reset signal having a reset pulse width determined by the watchdog time constant of the resistor 117 and the capacitor 119 to the microcomputer 113.

Next, the reset operation of the power supply IC with power supply voltage monitoring according to the embodiment of the present invention will be described with reference to the timing chart of FIG. Note that FIG. 2 shows the state when the power is turned on.

When the power source is turned on, the rise of V _DD begins with the rise of V _CC . Then, at time t ₂₁ in FIG.
V _DD becomes V ₁ , and the power-on reset unit 107 releases the reset of the pulse counter unit 103.

At time t ₂₂ , V _DD becomes V ₂ and the oscillation stage circuit (not shown) starts oscillation. The oscillation pulse is used as a clock pulse from the oscillation pulse output terminal of the microcomputer 113 via the Schmitt inverter 115, and the coincidence detection unit 1
05, and the coincidence detection unit 105 is directly input to the pulse counter unit 103. Pulse counter unit 103
When a clock pulse is input, it counts the clock pulse up to a preset count number and outputs a "0" level signal during that period.

[0032] At time t _23, the pulse counter 103 finishes counting the set count, and outputs a "1" level signal. Here, the "1" level signal is input to the coincidence detection unit 105, and the coincidence detection unit 105 receives the microcomputer 1 after the "1" level signal is input.
The signal of “1” level is output to the pulse counter unit 103 regardless of the clock pulse from 3. Therefore, the pulse counter unit 103 outputs the signal of “1” level, that is,
The output of the coincidence detection signal is continued.

On the other hand, while the pulse counter unit 103 is counting the set count number, V _DD becomes V ₃ and the power supply voltage monitoring unit 101 outputs a signal of “0” level, that is,
The operation determination signal is output to the watchdog timer control unit 109.

Thus, at time t ₂₃ , the power supply voltage monitoring unit 101 outputs the operation determination signal and the pulse counter unit 103 outputs the coincidence detection signal to the watchdog timer control unit 109.

The watchdog timer control unit 109 outputs a reset control signal to the watchdog timer unit 111 when the operation determination signal is input from the power supply voltage monitoring unit 101 and the coincidence detection signal is input from the pulse counter unit 103.

When the watchdog timer control section 109 inputs a reset control signal from the watchdog timer control section 109, the watchdog timer section 111 performs a reset operation of the reset pulse width T _{21 on} the microcomputer 113 until time t ₂₄ .

As described above, the power supply IC with power supply voltage monitoring according to the embodiment of the present invention detects the oscillation state of the microcomputer by counting the oscillation pulses from the microcomputer when the power is turned on, and then a certain period of time elapses. Since the reset operation is ended later, the reset operation of the microcomputer can be surely performed.

Next, the reset operation when the power supply voltage drops during the microcomputer operation of the power supply IC with power supply voltage monitoring according to the embodiment of the present invention will be described with reference to the timing chart of FIG.

When V _DD starts to drop at time t ₃₁ and becomes V ₃ or less at time t ₃₂ , the power supply monitoring unit 101 outputs a “1” level signal.

On the other hand, the pulse counter section 103 continues to output the "1" level coincidence detection signal.

Therefore, at time t ₃₂ , the power supply voltage monitoring unit 1
01 indicates a signal of “1” level, and the pulse counter unit 103
Outputs a match detection signal of “1” level to the watchdog timer control unit 109.

When the watchdog timer control section 109 inputs a “1” level signal from the power supply voltage monitoring section 101 and a “1” level match detection signal from the pulse counter section 103, it outputs “1” to the watchdog timer section 111. It outputs a "level signal.

The watchdog timer section 111 stops its operation when it receives a "1" level signal from the watchdog timer control section 109.

When V _DD becomes V ₃ again at time t ₃₃ , the power supply voltage monitoring unit 101 outputs an operation determination signal of “0” level to the watchdog timer control unit 109.

On the other hand, the pulse counter section 103 continues to output the "1" level coincidence detection signal.

Therefore, at time t ₃₃ , the power supply voltage monitoring unit 1
01 outputs an operation determination signal, and the pulse counter unit 103 outputs a coincidence detection signal to the watchdog timer control unit 109.

The watchdog timer control unit 109 outputs a reset control signal to the watchdog timer unit 111 when the operation determination signal is input from the power supply voltage monitoring unit 101 and the coincidence detection signal is input from the pulse counter unit 103.

The watchdog timer section 111 becomes operable when a reset control signal is input from the watchdog timer control section 109, and resets the reset pulse width T ₃₁ to the microcomputer 113 from time t ₃₃ to time t _35.
Do up to.

As described above, the power supply IC with power supply voltage monitoring according to the embodiment of the present invention performs the reset operation of the microcomputer as soon as V _DD returns to V ₃ when the power supply voltage drops during the operation of the microcomputer. Therefore, the microcomputer can be quickly restored.

As described above, according to the embodiment of the present invention, when the power is turned on, the oscillation of the microcomputer is detected, and then the reset operation is started. After the power supply voltage drops during the operation of the microcomputer, the power supply voltage is restored. Since the reset operation is started immediately, the reset operation of the microcomputer can be surely and promptly executed.

Here, the circuits of the power supply voltage monitoring unit 101, the pulse counter unit 103, the coincidence detecting unit 105, the power-on reset unit 107, and the watchdog timer control unit 109 can be configured in various ways. 4A shows a circuit diagram of the power-on reset unit 107 without hysteresis, FIG. 4B shows a circuit diagram of the power-on reset unit 107 with hysteresis, and FIG. 5 shows the pulse counter unit 103 and the coincidence detection unit 105. A circuit diagram and FIG. 6 are circuit diagrams of the power supply voltage monitoring unit 101 and the watchdog timer control unit 109. In FIG. 5, the circuit composed of n D flip-flops 501 corresponds to the pulse counter unit 103, and the OR circuit 503 corresponds to the match detection unit 105. In FIG.
01 and the internal constant voltage circuit 609 correspond to the power supply voltage monitoring unit 101, and the logic circuit 603 corresponds to the watchdog timer control unit 109.

7 to 11 show application examples of the present invention. FIG. 7 is a diagram showing a connection example of a power supply voltage monitoring power supply IC and a microcomputer, and FIG. 8 is a power supply voltage monitoring power supply IC.
FIG. 9 is a diagram showing a configuration example of an IC having only a watchdog timer function, FIG. 10 is a diagram showing a configuration example of an IC having only a reset function, and FIG. 11 is a power supply shown in FIG. Power supply IC with voltage monitoring, IC shown in FIG. 9 having only watchdog timer function, I shown in FIG. 10 having only reset function
FIG. 11 is a block diagram showing an example in which any one of Cs is incorporated in a one-chip microcomputer.

[0053]

As described above, according to the present invention, the reset operation is performed by detecting the oscillation state of the microcomputer.
The reset operation of the microcomputer can be performed reliably and promptly.

[Brief description of drawings]

FIG. 1 is an internal block diagram showing the configuration of a power supply IC with power supply voltage monitoring according to an embodiment of the present invention.

FIG. 2 is a timing chart showing a reset operation when the power supply of the power supply IC with power supply voltage monitoring according to the embodiment of the present invention is turned on.

FIG. 3 is a timing chart showing a reset operation when the power supply voltage drops in the power supply IC with power supply voltage monitoring according to the embodiment of the present invention.

4A is a circuit diagram showing a configuration example without hysteresis of the power-on reset unit shown in FIG. 1, and FIG. 4B is a circuit diagram showing a configuration of the power-on reset unit shown in FIG. 1 with hysteresis. .

5 is a circuit diagram showing configurations of a pulse counter section and a match detection section shown in FIG. 1. FIG.

FIG. 6 is a circuit diagram showing a power supply voltage monitoring unit and a watchdog timer control unit shown in FIG.

FIG. 7 is a diagram showing a connection example between a power supply IC with power supply voltage monitoring and a microcomputer.

FIG. 8 is a diagram showing a configuration example of a power supply IC with power supply voltage monitoring.

FIG. 9 is a diagram showing a configuration example of an IC having only a watchdog timer function.

FIG. 10 is a diagram showing a configuration example of an IC having only a reset function.

11 is a block diagram showing an example in which any one of the power supply voltage monitoring power supply IC shown in FIG. 8, the watchdog timer function-only IC shown in FIG. 9, and the reset function-only IC shown in FIG. It is a figure.

FIG. 12 is a diagram showing an example of connection between a conventional power supply voltage monitoring IC and a microcomputer.

FIG. 13 is a timing chart showing a reset operation when the power supply of the conventional power supply IC with power supply voltage monitoring is turned on.

FIG. 14 is a timing chart showing another reset operation when the power supply of the conventional power supply IC with power supply voltage monitoring is turned on.

FIG. 15 is a timing chart showing the reset operation of the conventional power supply IC with power supply voltage monitoring when the power supply voltage drops.

[Explanation of symbols]

Reference numeral 101 power supply voltage monitoring unit 103 pulse counter unit 105 coincidence detection unit 107 par-on reset unit 109 watchdog timer control unit 111 watchdog timer unit 113, 703, 1203 microcomputer (microcomputer) 115 Schmidt inverter 117, 401, 403, 405, 409 411, 4
13, 417, 423, 425, 427 Resistor 119 Capacitor 407, 415, 419, 421, 1003 Transistor 501 D Flip-flop 503 OR circuit 505 Schmidt inverter 601 Comparator 603 Logic circuit 605 Watchdog timer part 607 Pulse counter part 609 Internal constant voltage Power source 701, 801, 1201 Power supply IC with power supply voltage monitoring 901 IC with watchdog function only 903 Separate power supply 1001 IC with reset function only 1205 Oscillation stage circuit

Claims (1)

[Claims] 1. A reset control function integrated circuit for terminating the reset operation after detecting the oscillation state of the microcomputer when performing the reset operation of the microcomputer, monitors the power supply voltage, and detects the operation voltage. Means for outputting an operation determination signal, means for inputting an oscillation pulse of the microcomputer and for outputting a coincidence signal after counting a preset count number, output for the means for outputting the coincidence signal and the A means for comparing the oscillation pulses of the microcomputer, a means for enabling the means for outputting the coincidence signal when the power supply voltage exceeds a preset voltage, and a means for inputting the operation determination signal and the coincidence signal. Means for outputting a reset control signal, and the microphone according to the reset control signal (B) means for performing a reset operation of the microcomputer, and when the microcomputer is powered on, the reset operation is started after counting a preset number of oscillation pulses of the microcomputer, When the power goes down,
An integrated circuit with a reset control function, which starts a reset operation immediately after the power supply voltage returns to the operating voltage.