JPH0771063B2 - Input signal frequency abnormality detection circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Outline] Input from each terminal of a multiplexer that synchronizes the frequency of an input signal from each of a plurality of asynchronous terminals with each stuff circuit and multiplexes with a multiplexing circuit. The present invention relates to an input signal frequency anomaly detection circuit for detecting an anomaly in the frequency of a signal to be input, for the purpose of providing an input signal frequency anomaly detection circuit that is inexpensive and can reduce the mounting area. The first counting means that emits a pulse when counting a number, the second counting means that inputs and counts the sluff bit insertion signal of the stuff circuit, the pulse of the first counting means, and the second counting means When the pulse is input, the alarm signal is output if the count number of the second counting means is out of the predetermined value range. Configure than the determination means.

[Industrial application field]

The present invention is directed to the abnormality of the frequency of the signal input from each terminal of the multiplex conversion device that synchronizes the frequency of the input signal from each of a plurality of asynchronous terminals with each stuff circuit and multiplexes with the multiplexing circuit. The present invention relates to an input signal frequency anomaly detection circuit for detecting.

[Conventional technology]

FIG. 3 is a block diagram of an example stuff synchronization system, and FIG. 4 is a block diagram of an example stuff circuit.

Third about staff synchronization system using multiplex converter
It will be described with reference to the drawings.

In FIG. 3, the frequencies of the input signals from the asynchronous terminals 10 to 1n to the multiplex converter 5 are synchronized to the same frequency in the stuff circuits 30 to 3n and multiplexed in the multiplex circuit 7.
It is sent to the multiplex converter 6.

In the multiplex converter 6, the signals are separated by the separation circuit 8, and the separated signals are destuffed by the destuff circuits 40 to 4n,
The signal has the same frequency as the terminal on the transmitting side and is sent to the terminals 20 to 2n.

Next, the stuff circuit will be described with reference to FIG.

Input data from the terminal is written in the buffer memory 50 by using the clock of the input signal as a write clock.

On the other hand, a clock from a read clock generation circuit 53 that generates a clock faster than the write clock is input to the buffer memory 50 as a read clock of the buffer memory 50 via the stuff control circuit 52 to read the written data.

The write clock and read clock are phase comparators.
The phases are compared at 51, and the phase difference is 1 of the read clock.
When the number of bits is reached, the stuff request signal is output and input to the stuff control circuit 52.

Then, the stuff control circuit 52 outputs the stuff insertion signal for inserting the stuff bit at the predetermined stuff insertion position of the data being read, inserts the stuff bit in the data being read, and outputs the stuff bit as the synchronization signal. It is sent to the multiplexing circuit 7 in the figure.

That is, since the stuffing circuit inserts stuffing according to the difference between the frequency of the input signal and the frequency of the read clock, the stuffing number increases when the frequency of the input signal becomes lower, and the stuffing number increases when the frequency of the input signal becomes higher. Decrease to create sync signal.

Therefore, even if the frequency of the input signal from the terminal 10 to 1n on the transmitting side goes out of the normal range and becomes abnormal, stuff synchronization is performed, so the multiple conversion devices 5 and 6 do not find it, and the abnormality can be detected. Side terminals 20 to 2n.

If the frequency abnormality is found at the receiving terminals 20 to 2n, the part having the frequency abnormality is the terminal on the transmitting side or the multiplexer 5
It is difficult to determine whether or not it is the multiplex converter 6.

Therefore, conventionally, a frequency measuring device is attached to each of the entrances of the signals input from the terminals 10 to 1n of FIG. 3 to the multiplex conversion device 5, the frequencies of the input signals from the terminals 10 to 1n are measured, and the When the frequency abnormality is detected and the frequency abnormality is detected by the terminals 20 to 2n, the portion having the frequency abnormality is easily identified.

[Problems to be Solved by the Invention]

However, in the input signal frequency abnormality detection method using the conventional frequency measuring device, the frequency measuring device is expensive and large, and therefore there is a problem that the frequency measuring device becomes expensive and the mounting area becomes large.

An object of the present invention is to provide an input signal frequency abnormality detection circuit which is inexpensive and can be mounted in a small area.

[Means for Solving the Problems]

 FIG. 1 is a block diagram of the principle of the present invention.

The frequency of the input signal from each of the multiple asynchronous terminals,
In a multiplex converter that synchronizes with each stuff circuit and multiplexes with a multiplex circuit, as shown in FIG. 1, when a signal indicating a frame of the multiplex circuit is input and a predetermined number is counted, a pulse is emitted. Counting means 1, a second counting means 2 for counting by inputting a stuff bit insertion signal of the stuffing circuit, a pulse of the first counting means 1, and a counting by the second counting means 2. When the number of counts is input and the pulse is input, if the number of counts of the second count means 2 is out of a predetermined value range, the determination means 3 outputs an alarm signal.

[Action]

According to the present invention, the number of stuff bits in a predetermined frame is outside the range of the predetermined value in the determination means 3 based on the pulse and the count number input from the first and second counting means 1 and 2. If so, an alarm signal is output to detect frequency anomalies in the input signal from the terminal.
Even if the first and second counting means 1 and 2 and the judging means 3 are combined, the cost is much cheaper and smaller than the frequency measuring device, the input signal frequency abnormality detecting circuit is cheap, and the actual phase area is small.

〔Example〕

FIG. 2 is a block diagram of an input signal frequency abnormality detection circuit according to the embodiment of the present invention.

For example, the number of stuff bits in 10 frames is normally 8, and if the frequency of the input signal from the terminal can be determined to be abnormal if it goes out of the range of 4 to 12, the second
It will be described with reference to the drawings.

The counter 1 inputs and counts the signal indicating the beginning of the frame from the multiplexing circuit 7 in FIG. 3, and when it reaches 10, sends a pulse of the carry-out signal to the judging circuit 3 and the counter 2 to reset the counter 2.

The counter 2 inputs the stuff insertion signal from the stuff control circuit 52 of FIG. 4, counts it, and inputs the count number to the judgment circuit 3.

The determination circuit 3 compares the count number for 10 frames with a preset range of 4 and 12 according to the pulse from the counter 1 and the count number from the counter 2. If the frequency of the input signal becomes abnormal, an alarm signal is output, and if it is within the range of 4 and 12, no alarm signal is output.

That is, the input signal frequency abnormality detection circuit can be configured with a counter 1 that counts about 10 and a counter 2 that counts about 12 and a determination circuit 3 that compares the count number with a range of 4 and 12, so it is inexpensive. The mounting area can be reduced.

If the input signal frequency abnormality detection circuit is provided for each input signal of the terminals 10 to 1n in the multiplex conversion device 5 of FIG.
Can detect anomalies in the frequency of 10-1n input signals,
When the frequency abnormality is detected at 2n, it becomes easy to find the part where the frequency abnormality occurs.

〔The invention's effect〕

As described in detail above, according to the present invention, it is possible to obtain an inexpensive input signal frequency abnormality detection circuit having a small mounting area.

[Brief description of drawings]

1 is a block diagram of the principle of the present invention, FIG. 2 is a block diagram of an input signal frequency abnormality detection circuit according to an embodiment of the present invention, and FIG.
FIG. 4 is a block diagram of an example stuff synchronization system, and FIG. 4 is a block diagram of an example stuff circuit. In the figure, 1 and 2 are counting means, counters, 3 are determination means and determination circuits, 5 and 6 are multiplex converters, 7 is a multiplexing circuit, 8 is a separation circuit, 10 to 1n and 20 to 2n are terminals, 30 ~ 3n is a staff circuit, 40
4n is a destuff circuit, 50 is a buffer memory, 51 is a phase comparator, 52 is a stuff control circuit, and 53 is a read clock generation circuit.

Claims (1)

[Claims] 1. A multiplexing converter for synchronizing the frequencies of input signals from a plurality of asynchronous terminals by respective stuff circuits and multiplexing by a multiplexing circuit, wherein a signal indicating a frame of the multiplexing circuit is provided. First counting means (1) which emits a pulse when input and counts a predetermined number
A second counting means (2) for inputting and counting a stuff bit insertion signal of the stuffing circuit, a pulse of the first counting means (1), and a second counting means (2) When the counted number is counted and the pulse is inputted, if the counted number of the second counting means (2) is out of a predetermined value range, the judging means (3) outputs an alarm signal. Input signal frequency abnormality detection circuit characterized by.