JPH0989955A - Periodic signal disturbance detecting circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect the disturbance of period of an input periodic signal with a simple structure. SOLUTION: A monostable multivibrator (monomulti) 10 outputs monostable mode with the leading edge and trailing edge of an input periodic signal S1 as trigger. This monostable mode is set shorter than one normal period of the signal S1, and when the period of the signal S1 is shorter than the normal one, the monostable mode outputted by the monomulti 10 is continued. Since a monomulti 20 uses the leading edge and trailing edge of the monostable mode in the output signal S10 of the monomulti 10 as trigger, no trigger is added to the monomulti 20 when the monomulti 10 continues the monostable mode, and the monomulti 20 escapes from the monostable mode and shows an abnormality in a disturbance detection signal S20. When the period of the signal S1 is disturbed in the direction of extending the period, the output signal S10 continues the state escaping from the monostable mode, no trigger is added to the monomulti 20, and the signal S20 shows an abnormality.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a periodic disturbance detecting circuit which detects a disturbance of a periodic signal and notifies the detection result to an electronic circuit or the like which operates in synchronization with the periodic signal.

[0002]

2. Description of the Related Art FIG. 2 is a circuit diagram showing a conventional periodic signal abnormality detection circuit. This abnormality detection circuit has an input terminal In
And a monostable multivibrator (hereinafter simply referred to as monomulti) 1 connected between the output terminal Out and the output terminal Out. An external resistor 2 and a capacitor 3 which are connected to a power source are connected to the mono-multi 1. The mono-multi 1 has a structure which outputs the "L" level in the monostable mode in a predetermined period T1 by using the rising edge of the periodic signal as a trigger. The resistor 2 and the capacitor 3 are a time constant circuit that sets the period T1. By the time constant circuit, the period T1 of the monostable mode in the monomulti 1 is set to be longer than one prescribed period (regulated period) of the periodic signal. If the cycle of the periodic signal is a regular cycle, the cycle of the trigger for the mono-multi 1 is also short, and the output of the mono-multi 1 remains at the “L” level, but if the cycle becomes longer than the period T1, the trigger for the mono-multi 1 is made. Also becomes longer, and the output of the monomulti 1 changes to "H" level. That is, it is detected that the period of the periodic signal is lengthened by the output signal of the monomulti 1 being at the “H” level.
There is another type of periodic signal abnormality detection circuit.
In another example of the abnormality detection circuit, the period of the periodic signal is counted using a fine clock signal, and the frequency abnormality of the periodic signal is detected by the count result.

[0003]

However, the conventional periodic signal abnormality detection circuit has the following problems.
FIG. 3 is a time chart showing the abnormality detection operation of FIG. For example, as shown in FIG. 3, even when noise is added to the periodic signal, the monomulti 1 is triggered and the output signal of the monomulti 1 is at the “L” level in the monostable mode during the period T1 from the noise. To maintain. That is, when the change point of the periodic signal is disturbed in a direction in which the change point exceeds the specified number, it cannot be detected. Further, in the method of detecting the abnormality of the periodic signal by counting the period of the periodic signal, another periodic signal such as a clock is required.

[0004]

According to the present invention, in order to solve the above problems, a periodic signal disturbance detection circuit for detecting a disturbance of an input periodic signal has the following configuration. That is, with the rising or falling of the input period signal as a trigger, the first period shorter than the normal one period of the input period signal.
A first mono-multi that outputs a mono-stable mode during the mono-stable period, and one regular cycle of the input cycle signal triggered by the rising or falling of the mono-stable mode in the output signal of the first mono-multi. A second monostable that outputs a monostable mode in a second monostable period that is longer than
The output signal of the second mono-multi is used as the disturbance detection result.

[0005]

According to the present invention, since the periodic signal disturbance detection circuit is configured as described above, the first mono-multi is triggered by the rising or falling of the input periodic signal as a trigger to make one regular cycle of the input periodic signal. The monostable mode is output in the first monostable period shorter than the above. Here, if the rising or falling of the input periodic signal that serves as a trigger arrives earlier than the end of the first monostable period, that is, if the period of the input signal becomes shorter, or noise or the like enters, the first The mono-multi continues to output monostable mode. On the other hand, the second mono-multi outputs a stable mode triggered by the rising or falling of the mono-stable mode in the output signal of the first mono-multi, so that the second mono-multi starts from the middle of the mono-stable mode. Will not be output. Therefore, even if the change point of the input periodic signal is disturbed in a direction in which the change point exceeds the specified number, the disturbance is detected. Further, when the change point of the input periodic signal is disturbed in a direction in which the change point is smaller than the specified number, the first monostable multimeter stops the output in the monostable mode after the first monostable period. As a result, the second mono-multi is not triggered and the monostable mode is not output midway. Therefore, the above problem can be solved.

[0006]

FIG. 1 is a circuit diagram of a periodic signal disturbance detection circuit showing an embodiment of the present invention. This periodic signal disturbance detection circuit includes a first mono-multi 10 connected to an input terminal In1 of the periodic signal S1 and a second mono-multi 20 connected to the output side of the mono-multi 10. 20
The output side of is connected to the output terminal Out1. The mono-multi 10 is an IC, and the resistor 11 and the capacitor 12 are externally connected, and the mono-multi 20 is also an IC.
The resistor 21 and the capacitor 22 are externally connected. The resistor 11 and the capacitor 12 are used for the first monostable period T10 in which the monomulti 10 is in the monostable mode.
Is a time constant setting circuit for setting a period shorter than one regular cycle of the periodic signal. The mono-multi 10 has a monostable mode in the period T10 triggered by the rising edge of the periodic signal input from the input terminal In1. "H" level is output. The resistor 21 and the capacitor 22 are
It is a time constant setting circuit that sets the second monostable period T20 of the monostable mode output from the monomulti 20 to a period longer than one regular cycle of the periodic signal S1. Mono Multi 20
Is triggered by the rise of the output signal S10 of the mono-multi 10 to output the "L" level in the monostable mode during the period T20.

FIGS. 4A to 4C are time charts for explaining the operation of the periodic signal disturbance detection circuit of FIG. 1. FIG. 4A shows the case of a normal frequency, and FIG. Shows the case where noise is included, and FIG. 7C shows the case where the cycle becomes long. When the level of the input periodic signal S1 from the input terminal In1 rises to “H”, the monomulti 10 is triggered, and as shown in FIG.
Becomes the monostable mode, and outputs the "H" level of the monostable mode during the period T10. That is, the output signal S10 of the mono-multi 10 becomes "H" during the period T10. Period T
10 is set to be shorter than the regular one cycle of the periodic signal S1, so that when the period T10 elapses, the monomulti 1
The level of the output signal S10 of 0 returns from the monostable mode to "L". That is, when the periodic signal S1 is normal, the signal S10 returns to the "L" level in the same period as the period of the periodic signal S1. On the other hand, the mono-multi 20 outputs "L" in the monostable mode as a detection signal, triggered by the rising edge of the output signal S10. The signal S20 becomes a disturbance detection signal indicating whether the cycle of the cycle signal S1 is normal,
The state of "L" indicates normal. The period T20 in which the monomulti 20 is in the monostable mode is set longer than one regular cycle of the periodic signal S1.
If there is a section in which the output signal S10 of 1 is always at the “L” level once during one cycle of the cycle signal S1, the monomulti 20
The monostable mode is continued and the detection signal S20 does not become "H" indicating an abnormality. That is, when the periodic signal S1 is normal, the detection signal S20 does not become "H" indicating abnormality. When the cycle of the periodic signal S1 is shortened from the middle, or when a pulse is input as shown in FIG. 4B, the trigger cycle for the monomulti 10 is also shortened. If the cycle of the cycle signal S1 becomes shorter than the period T10 during the operation, the mono-multi 10 continues the monostable mode. Therefore, the trigger for the mono-multi 20 is not applied.
When the trigger of the monomulti 10, that is, the rising edge of the output signal S10 is not input to the monomulti 20, the detection signal output from the monomulti 20 changes to "H" when the period T20 elapses from the start of the monostable mode. . That is, the detection signal S20 indicates a cycle abnormality.

As shown in FIG. 4 (c), when the period of the periodic signal S1 becomes long during the operation, the monomulti 10 is not triggered, that is, the rising edge of the periodic signal S1 does not enter.
The mono-multi 10 does not enter the monostable mode, and the level of the output signal S10 of the mono-multi 10 remains "L".
Therefore, since the rising edge of the output signal S10 is not input to the monomulti 20, the monomulti 20 outputs "H" as the detection signal S20. That is, the detection signal S20
Indicates an abnormality in the periodic signal S1. As mentioned above,
In this embodiment, the mono-multi 10 triggered by the rising edge of the periodic signal S1 and the mono-multi 2 triggered by the rising edge of the output signal S10 of the mono-multi 10.
0 and a periodic signal disturbance detection circuit
The period T10 in which the monostable mode is in the monostable mode is shorter than one regular cycle of the periodic signal, and the period T20 in which the monomulti 20 is in the monostable mode is longer than one regular cycle of the periodic signal. As a result, both sides of the case where the period signal S1 is disturbed in the longer direction and the case where it is disturbed in the shorter direction can be detected as abnormal.
Since it is composed of two mono-multis 10 and 20, it does not need a periodic signal such as another clock and has a simple structure, and the abnormality detection result becomes a level signal, and other holding circuits etc. Does not need Further, the resistors 11 and 21 and the capacitors 12 and 22 are configured to set the periods T10 and T20, and by adjusting the resistance value or the capacitance value thereof, it is possible to change the detection sensitivity. There is. The present invention is not limited to the above embodiment, and various modifications can be made. For example, the mono-multi 10 may be configured to trigger the falling edge of the periodic signal S1, and the mono-stable mode output of the mono-multi 10 is set to the “L” level, and the mono-multi 20 outputs the output signal S10 of the mono-multi 10.
Even if the falling edge of is triggered, the same effect as in the above embodiment can be obtained.

[0009]

As described above in detail, according to the present invention, the first monostable multi-multifunction device which outputs the monostable mode in the first monostable period by using the rising or falling of the input periodic signal as a trigger, and The second is triggered by the rising or falling of the monostable mode in the output signal of the mono-multi of 1.
Since the periodic signal disturbance detection circuit is composed of the second mono-multi that outputs the monostable mode during the monostable period, the disturbance occurs in the direction in which the period of the input periodic signal becomes longer and in the direction in which it becomes shorter. Both sides of the case can be detected as abnormal. In addition, a periodic signal such as another clock is unnecessary and the configuration is simple, and the abnormality detection result is a level signal, so that a holding circuit or the like is not required.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a periodic signal disturbance detection circuit showing an embodiment of the present invention.

FIG. 2 is a circuit diagram showing a conventional periodic signal abnormality detection circuit.

FIG. 3 is a time chart showing the abnormality detection operation of FIG.

FIG. 4 is a time chart explaining the operation of the periodic signal disturbance detection circuit of FIG.

[Explanation of symbols]

 10 First Mono-Multi 20 Second Mono-Multi S1 Input Periodic Signal S20 Disturbance Detection Signal T10 First Monostable Period T20 Second Monostable Period

Claims (1)

[Claims] 1. A periodic signal disturbance detection circuit for detecting a disturbance of an input periodic signal, wherein a first monostable shorter than a regular one cycle of the input periodic signal is triggered by a rise or a fall of the input periodic signal. A first monostable multivibrator that outputs a monostable mode during a period, and 1 of the input period signal triggered by the rising or falling of the monostable mode in the output signal of the first monostable multivibrator. A second monostable multivibrator that outputs a monostable mode in a second monostable period that is longer than the normal cycle, and an output signal of the second monostable multivibrator is the disturbance detection result. A periodic signal disturbance detection circuit having a configuration.