KR920008043B1 - Pulse period and shift sensing circuit - Google Patents

Abstract

A circuit for monitoring a transition of pulse to be monitored on the transmission path has two monostable multi-vibrators. A first multi-vibrator (U1a) is connected to an input line to extend the first pulse width of the pulse to be monitored, as a pulse width less than the pulse width to be monitored. A second multi-vibrator (U1b) is connected to the first multi-vibrator (U1a) to perform the same function as the first (U1a). Each of the first and second (U1a)(U1b) has a resistor (RX1)(RX2) and a capacitor (CX1)(CX2). The circuit is used as a clock pulse period monitoring device or a data transmission device of async. system.

Description

Pulse period and transition monitoring circuit

1 is a configuration circuit diagram according to the present invention.

2 is a timing diagram for each circuit part of FIG.

* Explanation of symbols for main parts of the drawings

U1a, U1b: monostable multivibrator RX1, RX2: resistor

CX1, CX2: Capacitor

The present invention relates to a circuit for monitoring the period and transition of a pulse by extending the transition of a pulse to be monitored on a transmission path using two monostable multivibrators for a predetermined time interval depending on the RC time constant value of the multivibrator. .

Conventional pulse transition monitoring circuits, which are frequently used in digital switching systems, require that the frequency of the pulse to be monitored is twice the frequency of the reference pulse to detect that at least one transition occurs within the period of the reference pulse. Since it must be abnormal, a complicated logic circuit is needed to construct this. Since the conventional supervisory circuit composed of one monostable multivibrator and other logic elements monitors only the transition of the input pulse, the time interval by the selected RC time constant value If the input pulse period is very long or short, it cannot be monitored and the transition of the input pulse could not be monitored in detail due to the influence of resistors and capacitors sensitive to environmental factors such as temperature.

The present invention has been made to solve the above problems, the recent development of device technology uses a resistor and a capacitor which is hardly influenced by environmental factors such as temperature, and two monostable multivibrators in one chip In order to monitor the period and transition of the input pulse using the configured device, the monitoring circuit is simply configured and the output pulse width of the configured monitoring circuit has a 100% impact coefficient depending on the RC time constant value. It is easy to monitor even if the period is very long or short, so it is widely used in high clock pulse period monitoring device, data transmission device in asynchronous system, etc. It is an object of the present invention.

Accordingly, in order to achieve the object as described above, the present invention provides an input line for inputting a pulse to be monitored, which is connected to the input line to extend the first pulse width of the pulse to be monitored with a pulse width smaller than the period of the pulse to be monitored. The first multi-vibrator for the second multi-vibrator connected to the output of the first multi-vibrator to perform the same function, and the second multi-vibrator, and the output line connected to the second multi-vibrator.

Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

1 is a configuration circuit diagram according to the present invention, and FIG. 2 is a timing diagram for the respective circuit parts of FIG. Denotes a capacitor, respectively.

In the present invention, a period of an input pulse (a pulse to be monitored) is TM, and a first stage stable multivibrator U1a circuit extending such that 1 / 2TM <TM <3 / 2TM is connected to an output terminal of the circuit. It consists of the 2nd single-stable multivibrator U1b and RC time constant determination RC circuit. If the external control conditions B1, B2 and CLR1, CLR2 of the first and second single-stable multivibrators U1a and U1b are opened, the input pulse of the first single-stable multivibrator U1a is set to logic level low ( When the transition from 0) to high (1), the output Q1 of the first single-stable multivibrator U1a becomes a pulse extended by the time interval Tw1 by the RC time constant value of the first single-stable multivibrator U1a. . In addition, when the output Q1 of the first single-stable multivibrator U1a is applied to the input of the second single-stable multivibrator U1b, it transitions from 0 to 1 of the output Q1 of the first single-stable multivibrator U1a. At this time, the extended pulse of the time interval Tw2 by the RC time constant of the second single-stable multivibrator U1b is output to the output terminal Q2, so that the period and transition of the input pulse can be easily monitored.

The width of the pulse detected here can be calculated by the following equation.

Tw = 0.28 Rx Cx (1.0 + 0.7 / Rx)

Where Tw is the pulse width (ns), Rx is the Kohm, and Cx is the PF unit. or

Tw = 0.45RxCx

Where Tw is pulse width (S), Rx is ohms, and Cx is F units.

Hereinafter, the operation of the pulse period and the transition monitoring circuit will be described with reference to FIGS. 1 and 2. Transmit the period of the input pulse to be monitored TM and the period of transition of the input pulse by the Rx1Cx1 time constant value of U1a when the input pulse to be monitored transitions from 0 to 1 is extended by the Rx2Cx2 time constant value of TW1 and U1b If the period is TW2, the period of the input pulse to be monitored in Figure 2a is TM, and when the input pulse to be monitored transitions from 0 to 1, the portion of the output Q1 of U1a is 1 by the time constant value of Rx1Cx2 (1). As the period longer than / 2) TM and the period shorter than (3/2) TM is 1, TW1 is output, and the output Q2 of U1b is output 1 with period TW2 by the time constant value of Rx2Cx2. When the pulse to be input is input periodically, the constant output Q2 of U1b is always 1. Therefore, when the negative output / Q2 of U1b of FIG. 1 is connected to the monitor circuit composed of the differential transmitter, LED (Light Emitting Diode) and resistor, the LED does not emit light, so the period and transition of the input pulse is normally applied to the pulse transition and periodic monitoring circuit. The input can be visually identified.

In FIG. 2B, when one cycle of the input pulse to be monitored is lost and the cycle of the input pulse becomes longer, transition does not occur in the portion of the input pulse with a longer period, so in this portion, TW1 is not output to the output Q1 of U1a and is in a zero state. In the normal input pulse part, TW1 is outputted with the output Q1 of U1a being 1 state.

At this time, output Q2 of U1b also outputs 0 at the portion where TW1 does not appear at output Q1 of U1a, and outputs Q1, which is the output of U1b, at 1 in the normal input pulse portion. Therefore, if the negative output / Q2 of U1b of Figure 1 is connected to the monitor circuit, the LED will emit light when the output Q2 of U1b is 0, and the input pulse to be monitored is abnormally pulsed when the period of the input pulse to be monitored is long. The input to the cycle and transition monitoring circuit can be visually identified.

In FIG. 2C, when a pulse of a period shorter than the period of the input pulse to be monitored is input, the output Q1 of U1a frequently causes a transition in a portion where a pulse of a period shorter than the period of the input pulse to be monitored is inputted, so that the state 0 is output. 0 status is output only at the normal input pulse. Therefore, output Q2 of U1b is outputted at the state where output Q1 of U1a does not occur transition (after the first TW2 of Q2) and is always 0, and is always 1 at the normal input pulse part having period TM and output Q1 of U1a. . Therefore, when U1b's negative output / Q2 is connected to the monitor circuit, the LED will emit light at the part where U1's constant output Q2 is 0, so the period of the input pulse to be monitored becomes faster and it is abnormally input to the pulse period and the transition monitoring circuit. Can be identified.

In conclusion, it is assumed that the input pulse to be monitored for the status of the LED of the monitor circuit is normally input to the pulse period and the transition monitoring circuit, and the input pulse to be monitored for the LED to emit light abnormally monitors the pulse cycle and transition. If it is assumed that the state is input to the circuit, as shown in Figure 2a when the input pulse to be monitored is normally input to the pulse period and the transition monitoring circuit, the LED of the monitor circuit does not emit light, it can be seen that the input pulse to be monitored is normal, If the period of the input pulse to be monitored is longer or shorter than TW1, as shown in Figure c, the output Q1 of U1a alternately detects 0 and 1, so when the period of the input pulse to be monitored by the LED of the monitor circuit is longer or shorter than TW1 When the LED is turned on and emits light and the period of the input pulse is TM (the part where the input pulse to be monitored is normally input), the LED The input pulses to be monitored does not emit light is program (off) is to be inflated to the input pulse period and a transition monitoring circuit can be visually easily identified.

The invention configured as described above has the following effects.

First, unlike the conventional monitoring circuit composed of a monostable multivibrator 1, it is possible to monitor not only the transition of the input pulse but also the period, so that the monitoring is possible even if the period of the pulse to be monitored is very long or short.

Second, since two monostable multivibrators can be configured with one chip (for example, 74 LS123, a general purpose TTL IC), the supervisory circuit is very simple and economical.

Third, it is used to monitor the system clock pulse in the system that receives the clock pulse from the outside and use it as the system clock pulse, and it is widely used for the high clock pulse periodic monitoring device and the data transmission device in the asynchronous system.

Claims (4)

An input line for inputting a pulse to be monitored, a first multivibrator U1a connected to the input line to extend a first pulse width of the pulse to be monitored to a pulse width smaller than a period of the pulse to be monitored; And a second multivibrator (U1b) connected to an output of the multivibrator (U1a) to perform the same function, and an output line connected to the second multivibrator (U1b). 2. The pulse period and transition monitoring circuit according to claim 1, wherein the first multivibrator U1a includes a resistor RX1 and a condenser CX1 to extend the first pulse width of the pulse to be monitored. . 2. The resistor of claim 1, wherein the second multi-vibrator U1b extends the first pulse width of the output pulse of the first multi-vibrator U1a to output an output pulse in a constant logic state. CX2), characterized in that the pulse period and transition monitoring circuit. 3. The value of the resistor RX1 and capacitor CX1 according to claim 2, wherein the first pulse width of the output pulse of the first multi-vibrator U1a is greater than 1/2 and less than 2/3 of the pulse period to be monitored. A pulse period and transition monitoring circuit, characterized in that the setting.

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