JPH04169429A - Redundancy change-over inhibiting device - Google Patents

Abstract

PURPOSE:To inhibit the erroneous operation of switching by inserting a multivibrator circuit having time constant between a D-type latch and a Schmitt trigger circuit through which a protect signal passes. CONSTITUTION:When a protect signal (b) is input, this is delayed by a Schmitt trigger circuit 3 having a delay circuit. A delayed signal (e) and an inner clock signal (c) are input to an AND circuit 9, and its output is input to a multivibrator circuit 4. The fluctuation of noise and so on of the protect signal that passes the AND circuit 9 is eliminated by the multivibrator circuit 4, and is input to a strobing terminal G of a D-type latch 2 as a signal (f). Since an output (d) of the Schmitt trigger circuit 1 to a change-over signal (a) is input to the D-input of the D-type latch, while the signal (f) of the multivibrator 4 from which noise is removed, is input at the same time, it is output without noise to the signal (g) to a change-over circuit.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention is applied to a device having redundant configuration switching. In particular, it relates to protection means for redundant switching.

〔overview〕

The present invention provides a means for inhibiting the function of a redundant switching means of a device using a protect signal in order to maintain the current switching state of the redundant switching means. It has been made possible.

[Conventional technology]

In the conventional example, as shown in FIG. 3, an external switching signal is input to the switching circuit through a D-type latch 7.

Then, to keep the current state of redundancy switching,
A protect signal from the outside was inputted to the strobe terminal of the D-type latch via the Schmitt trigger circuit 8.

[Problem to be solved by the invention]

In this way, in the conventional example, the protect signal input from the outside is input to the strobe terminal of the D-type latch in the middle of the switching signal manually input from the outside through the Schmitt trigger circuit, so the protect signal is not affected by noise etc. If there is an undesired change, the strobe of the D-type latch is released, resulting in redundant switching malfunction due to inversion of the switching signal.

The present invention eliminates these drawbacks, and even if the protect signal has noise or some degree of fluctuation,
The purpose of the present invention is to provide a redundant switching inhibition device that guarantees normal operation.

[Means to solve the problem]

The present invention provides a first Schmitt trigger circuit through which a switching signal passes, a D-type latch in which the output of this first Schmitt trigger circuit is connected to a nine-power terminal and a Q output is connected to a redundant switching means, and a protect signal passes through a D-type latch. A redundant switching inhibiting device comprising a second Schmitt trigger circuit including a delay means includes an AND circuit that controls the protect signal via the second Schmitt trigger circuit using an internal clock, and a signal output from the AND circuit for a predetermined period of time. and a signal holding means for applying the signal to the strobe terminal of the D-type latch after the signal has been applied to the strobe terminal of the D-type latch.

Here, the signal holding means is a multi-channel multifunction device having an input terminal to which the signal output from the AND circuit is applied, a time constant determining means connected to the time constant terminal, and an output terminal connected to the strobe terminal of the D-type latch. It may also be a vibrator circuit.

[Effect]

The protect signal is delayed from the switching signal, and this signal is gated by the internal clock and input to the multivibrator circuit. If this input signal continues for a given period of time,
The output of this multivibrator circuit is applied to the strobe terminal of the D-type latch. This D type latch is
This is a circuit for fixing the applied switching signal. This can prevent the protection signal from fluctuating due to noise or the like, causing the strobe signal to be canceled and the switching signal to be inverted.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of this embodiment.

As shown in FIG. 1, this embodiment has an input terminal connected to a device having redundant switching means and a Schmitt trigger circuit l through which a switching signal passes, and an output terminal connected to the redundant switching means. It is equipped with a D-type latch 2 having a Q and a Schmitt trigger circuit 3 including a delay means through which the protect signal passes.Furthermore, as a feature of the present invention, the protect signal passed through the Schmitt trigger circuit 3 is clocked by an internal clock. The controlling AND circuit 9 and the signal output from the AND circuit 9 are given to the input terminal, and the multi-by-break time constant determining circuit 5, which is a time constant determining means, is connected to the time constant terminals C and C/H. The multivibrator circuit 4 has an output terminal Q connected to a strobe terminal G of the latch 2.

Next, the operation of this embodiment will be explained based on FIGS. 1 and 2.

When a protect signal is inputted from the outside, the signal is first input to a Schmitt trigger circuit 3 having a delay circuit, where the protect signal is delayed from the switching signal a. Thereafter, the delayed protect signal e and the internal clock C are input to the AND circuit 9, and this output signal is input to the multi-by-break circuit 4. In this multi-bye break circuit 4, the output signal has a density ratio of 100% with respect to the internal clock, and protection is set so that the output will not be inverted even if a predetermined number of clocks are stopped.

The protection signal that has passed through the AND circuit 9 has fluctuations such as noise removed by the multivibrator circuit 4, and is input to the strobe terminal G of the D-type latch 2.

FIG. 2 is an operation time chart of this circuit.

2A to 2G show signal waveforms at points a to g marked with an X in FIG. 1. The switching signal a is at time 1. ~t2, time t
3 to t4 and becomes low level (valid) after time t5. The output d of the Schmitt trigger circuit 1 faithfully reproduces this. On the other hand, the protect signal is at time t. -jl
, it became low level (prohibited) after time t3, and further became low level for a short time after time t1 due to noise. This noise appears in the signal e with a little delay, but it is masked by the time constant τ of the multivibrator circuit 40 and the signal f
It does not appear in Therefore, the influence of this noise has been removed from the output g. A low level (valid) signal is sent to the output g only while the switching signal a is low level and the protect signal b (signal f from which noise has been removed) is high level.

〔Effect of the invention〕

As explained above, the present invention eliminates errors in the redundant switching signal of the device by inserting a multi-noise ibrator circuit having a time constant between the Schmitt trigger circuit through which the protect signal passes and the D-type latch. This has the effect of preventing switching malfunctions.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing the configuration of an embodiment of the present invention. FIG. 2 is a waveform diagram showing the waveforms of signals at each part shown in FIG. FIG. 3 is a circuit diagram showing the configuration of a conventional example. 1.3.6.8... Schmitt trigger circuit, 2.7.
...D type latch, 4...Multi-by break circuit, 5...Multi-by break time constant determining circuit, 9...
・AND circuit.

Claims (1)

[Claims] 1. A first Schmitt trigger circuit through which the switching signal passes;
A D-type latch in which the output of the first Schmitt trigger circuit is connected to the D input and the Q output is connected to the redundant switching means, and a second Schmitt trigger circuit including a delay means through which the protect signal passes, prohibiting redundant switching. The apparatus includes: an AND circuit that controls the protect signal that has passed through the second Schmitt trigger circuit with an internal clock; and after the signal output from the AND circuit is applied for a predetermined period, the signal is applied to the strobe terminal of the D-type latch. A redundant switching inhibiting device comprising: signal holding means. 2. The signal holding means is a multivibrator whose input terminal is supplied with the signal output from the AND circuit, the time constant determining means is connected to the time constant terminal, and the output terminal is connected to the strobe terminal of the D-type latch. 2. The redundant switching inhibiting device according to claim 1, which is a circuit.