JPH0514363A - Transciver for local area network - Google Patents

Abstract

PURPOSE:To obtain a transciever provided with the function which automatically locates trouble in a terminal or a transmission line at the time of the occurrence of trouble in a bus type local area network like an Ethernet. CONSTITUTION:The output signal from a collision detector 5 is received by a counting circuit 14 to count the number of times of collision, and the counted value is compared with a preset value by a comparator 17 to automatically discriminate trouble. When the counted value is matched with the preset value, trouble is judged to output the output signal of the comparator to a switching circuit 15, and this circuit 15 locates trouble in the terminal or the transmission line and sends a signal to a state display circuit 18, and this circuit 18 displays the state (the occurrence of trouble or the like).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transceiver and a fault isolation circuit which automatically removes a fault in a bus type local area network such as Ethernet and enables easy recovery. ..

[0002]

2. Description of the Related Art Generally, in a local area network using a coaxial baseband transmission method, most of the configuration examples are CSMA / CD (Carr) adopting a bus type topology.
ierSense Multiple Access /
Collision Detection) control system is adopted.

In this CSMA / CD control system, each terminal observes the transmission medium without providing a polling station,
If there is no signal waveform and it is in a stationary state, it is determined that the other terminal is not transmitting, and the transmission medium is determined to be in a stationary state by considering the time it takes for the signal to propagate through the transmission start method. At that time, signals may collide because other terminals may be transmitting. FIG. 3 is a diagram showing a collision of signals on a transmission line. In the figure, 11 is a transmission line, 12 is a tap, 19 is a terminal, 20 is a controller, 21 is a transceiver cable, 22 is a transceiver, and 23 is a data line. Flow, 24 is a terminator.

Therefore, it is necessary to detect a signal collision and avoid another collision. Conventionally, a transceiver including a detector as shown in FIG. 2 has been proposed to detect such a signal collision. This Figure 2 is Gran
f, Taff, 1980. Xerox Corp. In the figure, 1 and 2 are transmission data and reception data, respectively, which are connected to the transmission path 11 through 12 taps. The tap is a T connector for connecting / disconnecting the electric signal bidirectionally and connecting the transceiver to the transmission path. The received data from the transmission line via the tap is converted between the voltage level and the logic level by the receiving driver 10 and sent to the controller through the separator 6. The separator 6 is an isolation transformer that separates the 1 transmission data transmitted from the terminal via the controller and the previous reception data.

When transmission is performed from the terminal, the terminal connected to the transmission line always observes the signal waveform so that the transmission is performed immediately after the transmission, and the collision detector 5 receives the transmission data and the reception data. A comparison is made with the data, and if the received data do not match, a collision detection signal 13 is issued and transmitted to the controller. The controller sends a bit sequence called jam to clarify the collision. After the jam was sent, the transmission was stopped and re-sent,
A random latency selection called binary exponential backoff is made.

The power supply 3 is supplied from the terminal via the controller, and the DC-DC inverter 7 supplies 4 power.
Separated to the earth.

[0007]

Conventionally, since the collision detection is performed by the above-described structure and method, when a failure occurs, all the terminals connected to the transmission line during that time until the failure is removed. The transmission is canceled and the network function is no longer fulfilled.

When a failure occurs, a collision is notified to the terminal, so that it is impossible to distinguish whether the channel is overcrowded or due to the failure, and there is a problem that the terminal in which the failure has occurred cannot be easily separated.

The present invention has been made in order to solve the above problems, and obtains a transceiver having a function of determining the occurrence of a failure and automatically separating the terminal from the transmission path. The purpose is to

[0010]

A fault isolation circuit for a transceiver according to the present invention includes a counting circuit for counting the number of times a fault is detected in a transceiver including the conventional collision detector shown in FIG. 2, and the counting circuit. Is a transceiver that includes a comparator that sends out a signal when the value of 1 is compared with a preset value, and a disconnecting circuit that disconnects the transmission line and the terminal by the output signal that is sent out.

[0011]

In the present invention, the signal from the collision detector is received, the number of collisions is counted by the counting circuit, the comparator compares it with the preset value, and if it matches the preset value, it is judged that the channel is not overcrowded and a fault occurs. By doing so, a signal is sent to a disconnecting circuit that separates the transmission path and the terminal, and the terminal and the transmission path are automatically separated for each terminal, and the function as a network is restored. Further, by adding the counting circuit, the comparator and the disconnecting circuit in the transceiver, it becomes possible to surely isolate the fault with simple hardware without being aware of the terminal side.

[0012]

EXAMPLES Example 1. FIG. 1 is an overall configuration diagram of an embodiment of a fault isolation circuit for a transceiver according to the present invention.
In FIG. 1, 1 is transmission data, 2 is reception data, 3 is a power supply, 4 is earth, 5 is a collision detector that makes a judgment based on comparison of transmission data and reception data, 6 is a separator, and 7 is earth. DC-DC inverter, 8 is a transmission driver,
Reference numeral 9 is a protection circuit, 10 is a receiving driver, 11 is a coaxial cable as a transmission line, 12 is a tap, and 13 is a collision detection signal.

Further, 14 is a counting circuit, which is a collision detector 5
The counter 17 counts the collision signal, and the comparator 17 compares the count value of the count circuit with the preset value. When the count value and the preset value match, a signal is sent to the disconnecting circuit 15 to disconnect the signal. The circuit receives 16 disconnection signals, separates the transmission line from the terminal, and sends a signal to 18 status display circuits. The status display circuit receives the signals from the disconnection circuits and determines the status (failure occurrence). Etc.).

In the above method, the preset value for judging whether the channel is overcrowded or due to a failure depends on the number of terminals connected to the transmission path and the throughput at each terminal. It needs to be configured at the terminal and is N times the retransmission interval using the binary exponential backoff algorithm (N>
The method such as 1) shall be used. In addition, the preset value may change due to a failure due to a failure of the terminal itself, so it is given in advance in the transceiver.

As described above, according to the present invention, means for automatically determining whether the channel is overcrowded or due to a failure is provided in the transceiver, and the terminals can be automatically separated. Since it is configured as described above, it is not necessary to duplicate the network itself, the terminal itself does not require any change, and there is an effect that the failure countermeasure can be taken at a low cost.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment of a transceiver according to the present invention.

FIG. 2 is a configuration diagram showing a conventional transceiver.

FIG. 3 is a diagram showing data collision on a transmission path.

[Explanation of symbols]

 11 Transmission Line 14 Counting Circuit 15 Cutting Circuit 17 Comparator 19 Terminal 25 Transceiver 26 Network Drive Unit

Claims (1)

Claim: What is claimed is: 1. A network drive unit for performing transmission / reception between a transmission line and a terminal of a bus type local area network,
A count circuit that counts the number of collision detections, a comparator that outputs a signal when the value specified in advance and the value counted by the count circuit are compared and matches, and this output signal is received. A transceiver for a local area network, comprising a disconnecting circuit for disconnecting a transmission line and a terminal.