JPS59234A - Signal monitoring controlling system - Google Patents

Abstract

PURPOSE:To obtain a device which inexpensive and has high reliability, by detecting a collision by use of a timer and a detecting circuit of a receiving signal, and also giving a redundant bit to the head part of a transmitting signal. CONSTITUTION:As for a transmitting data inputted to a transmission controlling circuit 34, a redundant bit of fixed length is given to its head part by a redundant bit generator 35, and thereafter, said data is sent to a transmitter 2. As a result, a transition detecting circuit 31b outputs a significant output signal 37 to an AND circuit 30b by the time set by a timer 32. As for the timer 32, the time being equal to a propagation delay time extending from the transmitter 2 of the own station to an output of a waveform shaping circuit 9 through a star coupler 4 is set. When an optical signal of other station is received before receiving an optical signal of the own station, an output signal 10c of the circuit 9 is inputted to an integration circuit 26. A comparator 28 outputs a significant signal to the AND circuit 30b. The circuit 30b applies AND to outputs of the circuit 31b and the comparator 28, and outputs a collision detecting signal 33. The transmission controlling circuit 34 stops immediately transmission of a signal of the own station.

Description

[Detailed description of the invention] A conventional system of this type is shown in FIG.

In the figure, (1) is the transmission signal line, (2) is the transmitter, and (3
) is a light emitting element, (4) is a star coupler, (5a),
(5b), (5c), (6a), (6
b), (6c) are the optical fibers connected to the star coupler, (7) is the light receiving element, (8) is the amplifier, (9) is the waveform shaping circuit, (II is the receiving signal line, (
lυ is a delay circuit, (13 is an exclusive OR circuit, (1
3 is an integration circuit, I is a comparator, (t9 is a threshold setting terminal,
ttn is a collision signal line. FIG. 2 is a waveform diagram showing temporal changes in signals of various parts of the transmission system.

(1a) is the transmitted signal, (II is the delayed transmitted signal,
°(lOa) is the received signal of the transmitting signal of the above aD received by the amplifier (8) via the star coupler, A is the exclusive OR circuit output signal, Qυ is the judgment threshold, (tab)
is a received signal in which a signal sent from another station is received by the amplifier (8), @ is an exclusive OR circuit output signal, @ is an integration circuit output signal, and (c) is a collision detection time.

Next, the operation will be explained. A transmission signal is input from a transmission signal line (1) to a transmitter (2), and the transmitter (2) drives a light emitting element (3) in response to the transmission signal. The output of the light emitting element (3) is input to the first optical fiber (5a) connected to the input side of the star coupler (4), and propagates through the optical fiber (5a) to the star coupler (4). ) connected to the output side. The first optical fiber (6
a), the second optical fiber (6b), and the n-th optical fiber (6c) are inputted with K uniformly distributed optical signal power. Signals from the second optical fiber (5b) and the n-th optical fiber (5c) on the input side are similarly distributed. The optical signal propagated through the optical fiber (6a) is sent to the transmitter (2)
It is input to the light receiving element (71) of the same station as the light receiving element (71).
) converts the optical signal into an electrical signal and then inputs it to the amplifier (8).

The amplifier (8) amplifies the signal and outputs it to the waveform shaping circuit (9), which shapes the input signal into a rectangular wave and outputs it to the receiving signal line q. The delay circuit I is connected to the transmitter (
The transmission signal line (1) has a delay time equal to the propagation delay time from the input point of the waveform shaping circuit (9) to the output point of the waveform shaping circuit (9).
By delaying the above signal, exclusive OR circuit titllc
Output. Exclusive OR (13 is the output of the delay circuit I,
It inputs the signal on the reception signal line aQ and outputs the exclusive OR operation result. Integrating circuit 0 integrates the output of exclusive OR circuit α and outputs it to comparator H. The comparator +14 compares it with the judgment threshold given from the threshold setting terminal (I!9), and outputs a significant signal to the collision display line αQ when the integrated value exceeds the judgment threshold.

Here, the transmission path is optical fiber (5a), (5b)
, (5c), (6a), (6b),
(6c) and Star Kabra (4). Further, the transmission signal length is assumed to be longer than the maximum propagation delay time of the transmission path.

If there is no collision between local station signals and other station signals on the transmission path,
The transmission signal (1a) is delayed by the delay circuit aD to obtain the transmission signal (II) and the reception signal (10a) of the own station output from the waveform shaping circuit (9).At this time, the exclusive OR circuit Q3 outputs the exclusive OR circuit output signal (1) and 9
Since the judgment threshold t2υ is not exceeded, no significant signal is output to the collision signal line αe. On the transmission path, the local station signal and the other station signal collide, and the received signal (10
b) is output, this signal and the delayed transmission signal are processed by an exclusive OR circuit (Ia outputs an exclusive OR circuit output signal (to) and an integral circuit 01 which receives this as input).
outputs the integrator circuit output signal (goods). Since the integrating circuit output signal exceeds the judgment threshold Qυ at the time (to) in the comparator I, a significant signal is output on the collision signal line (IQ). Before receiving, we explained the case of receiving another station's signal light, but even if the other station's signal light is received while receiving the own station's signal, the other station's signal light level is equal to or higher than the own station's signal light level. If the level.

The output signal of the waveform shaping circuit (9) differs from the output signal of the delay circuit aυ, so that collision detection can be performed.

Since the conventional device is configured as described above, the transmission path consists of the star coupler (4), the optical fiber (5a), (
6a) When the propagation delay time is large, the delay circuit I is required to have a large and accurate amount of delay, and the delay circuit 09 is required to have characteristics that transmit the signal without waveform distortion. There were drawbacks such as:

This invention was made in order to eliminate the drawbacks of the conventional ones as described above. After the local station starts transmitting, the first few bits reach all connected stations and each station can detect the carrier wave. Until the device operates, it continues to send out redundant pits that do not contain information signals, and if a received signal is detected between the transmission start time of the own station and the propagation delay time of the own station signal on the transmission path, it is considered a collision. The purpose of the present invention is to provide a signal monitoring control method that immediately stops transmission from its own station after making a determination.

An embodiment of the present invention will be described below with reference to the drawings. 8th
In the figure, (3t)a), (30b) are AND circuits, (81a) (81b> are transition detection circuits,
r82) is a timer, (34) is a transmission control circuit,
(85) is a redundant pit generator. In FIG. 4, (87) is the transition detection circuit output signal, (29
a), (29b) are the integration circuit output signals, ((9
1 is the collision detection time, and (aa) is the collision detection signal.

Transmission control circuit (84) K: The input transmission data is
After a redundant pit generator (to) gives redundant pits of a certain length to the beginning, the signal is sent to the transmitter.

At the same time as the transmission starts, the transmission control circuit G4) sends a significant signal to the transition detection circuit (aia), and the transition detection circuit ("
111) r, t This transition is detected and a significant signal is input to the AND circuit (30a). When the AND circuit (for) receives the significant signal from the transition detection circuit (31a), it inputs the transmission signal +11 to the transition detection circuit (81b). The transition detection circuit (81b) detects the transition and outputs a significant output signal Gη to the AND circuit (30b) for the time set in the timer C33. The timer is set to a time equal to the propagation delay time from the transmitter (2) of the local station via the star coupler (4) to the output of the waveform shaping circuit (9).

Now, when an optical signal from another station is received before receiving the own optical signal, the output signal (10c) of the waveform shaping circuit (9) is input to the integrating circuit. The integrating circuit (a) outputs an integrating circuit output signal (29a) in response to this input. The integration circuit output signal (29b) exceeds the determination threshold @ at the time (to), and the comparator (2) outputs a significant signal to the AND circuit (30b). The AND circuit (30b) is connected to the transition detection circuit (81b).
) and the output of the comparator - to obtain the collision detection signal (to)
Output. Upon detecting the rising edge of the collision detection signal (to), the transmission control circuit (b) immediately stops the signal transmission of its own station so as not to interfere with the transmission of the station that started transmission first.

Signals sent out until a signal collision is detected and transmission is stopped interfere with the signals of other stations, but there is also a propagation delay at the beginning of the signals of other stations from that station to the farthest station. Since redundant bits are provided that are slightly longer than the length corresponding to the time, the signal lost due to interference does not contain true information, so information transmission can be achieved by continuing transmission.

If no other station's signal arrives before the own station's signal is received, the received signal (10a) output from the waveform shaping circuit (9) is input to the integrating circuit (4),
outputs the integrating circuit output signal (29b). The integration circuit output signal (29b) reaches the judgment threshold (value) at the time (to).
is exceeded, a significant signal is output from the comparator (to), but
This is because the output of the transition detection circuit (81b) is reset by the timer and is not significant.

No collision detection signal is output from the AND circuit (30b) and it is assumed that the receiving state is normal.

If the other station's optical signal is also received after receiving the local station's optical signal, collision cannot be detected, but the collision should be detected by the other station, so even if the local station continues transmitting, the collision cannot be detected.
The signal from the colliding partner station is immediately stopped. As described above, the signals during the collision are redundant bits, so the information to be transmitted is not lost.

The time setting of the timer (to) can be easily performed because it does not transmit a transmission signal unlike the conventional delay circuit 6υ. In addition, in the conventional example, the delay time 4 precision of the delay circuit aυ had to be less than the bit period of the signal in order to perform exclusive OR, but in the signal monitoring control system according to the present invention, There is no need to perform logical operations, and the setting accuracy is not strict, so the time can be easily set.

In the above embodiment, the integrating circuit (to) is shown as an analog integrating circuit, but it may also detect transitions in the received signal. Also, a transition detection circuit (81a), (81b> and an AND circuit (
:30a) The logic circuit including (30b) is.

Similar functions can be achieved by replacing this with program control using software.

As described above, according to the present invention, a collision is detected using a timer whose delay time can be easily set and a detection circuit for a received signal, and a collision is detected by providing a redundant bit at the beginning of a transmitted signal. Even if a collision is detected, the transmission can be performed without loss of information, which has the effect of providing an inexpensive and highly reliable device.

[Brief explanation of the drawing]

Fig. 1 is a block diagram for explaining a conventional signal monitoring system, Fig. 2 is a signal waveform diagram in a conventional signal monitoring circuit,
FIG. 8 is a block diagram for explaining the signal monitoring control system according to the invention, and FIG. 4 is a waveform diagram of the signal monitoring circuit according to the invention. (to) is an integrator circuit, @ is a comparator, (30a), (
30b) G3 is a timer, (b) is a transmission control circuit, and 09 is a redundant bit generation circuit. In FIG. 1, the same or corresponding parts are designated by the same reference numerals. Agent Makoto Kuzuno - Figure 1 Figure 2 Figure 4

Claims (1)

[Claims] In the signal monitoring control method, the own station receives the own station's transmitted signal and the other station's transmitted signal, detects that the own station has collided with the other station's transmitted signal while transmitting on the transmission path, and avoids this collision.The own station starts transmitting. After that, until the beginning of the transmitted signal reaches all connected stations, redundant bits that do not include information signals are sent, and from the time the local station starts transmitting until the local station receives the transmitted signal. During this time, the receiver detects the presence or absence of a received signal, and if a received signal is detected, it is determined that there is a collision and the station immediately stops transmitting, and if no received signal is detected, it continues transmitting. A signal monitoring control system with special characteristics.