JPH0683212B2 - Abnormality processing circuit of repeater - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention relates to a repeater for relaying data or a collision state between segments in a common bus type local area network (LAN) such as CSMA / CD type. Related to the abnormality processing circuit.

<Prior Art> The CSMA / CD type LAN is originally capable of bidirectional transmission because it communicates on one common bus at the baseband, but the repeater used for this type of LAN is Two-way relay is realized by switching the relay direction of signals on the common bus on a first-come-first-served basis without collision.

In this type of LAN, signals from multiple stations collide on a common bus. Therefore, the relay device relays the collision state occurring on both sides or one side thereof, like a normal data packet.

<Problems to be solved by the invention> By the way, in the CSMA / CD type LAN, the operation sequence of each station and the processing method are rigorously determined. Can be predicted. Therefore, the design of the repeater is
It should be done so as to cope with the situation in which it is predicted to occur.

However, not all devices connected to the LAN always operate normally according to the required standard, and sometimes abnormal operation occurs due to a failure. In addition, extraneous noise may cause an abnormal situation that could not have been predicted at the design stage of the repeater.

When such an abnormal situation is transmitted to another normal segment by the repeater, communication is hindered in the other normal segment, and reliability of the entire LAN is significantly impaired.

The present invention has been made in view of the above problems, and when an abnormal situation occurs in any of the segments, the relay operation from the segment in which the abnormality has occurred to another segment is stopped, and the abnormal situation occurs. The purpose is to secure the communication in the normal segment and temporarily improve the reliability of the entire LAN by temporarily disconnecting the abnormal segment from the normal segment until it is resolved.

<Means for Solving the Problems> In order to achieve the above object, the present invention provides the above-mentioned idle state in the main control unit which shifts from an idle state to a required operating state in response to a signal input from each segment. Other than the above, a state detection unit that introduces a state signal indicating each operation state to detect the continuation of the operation state, a timer unit that performs a timer operation for a fixed time in response to the state detection by the state detection unit, and the timer unit And a reset generator for returning the main controller to an idle state in response to the time-up signal of (1) to configure the abnormality processing circuit of the repeater.

<Operation> According to the above configuration, when a signal is input from any of the segments through the transceiver, the main control unit in the repeater shifts from an idle state to an operation state according to the signal input, and a data signal is transmitted to another. However, if an abnormal situation occurs such that a station in one of the segments transmits a data signal that exceeds the maximum packet length due to a failure or the like, the main control unit Signals with a length of more than 1 will result in a long stay in the same operating state.

The state detection unit detects that the main control unit remains in the same operating state. If the time during which the same operating state is stopped exceeds a certain time, a time-up signal is output from the timer section, and the reset generation section outputs the reset signal in response to the time-up signal. By this reset signal, the main control unit returns to the idle state, and the operation is interrupted regardless of the operating state of the repeater itself. As a result, the abnormal segment is separated from the normal segment.

<Examples> Hereinafter, the present invention will be described in detail based on Examples shown in the drawings.

FIG. 1 is a block diagram of an embodiment of the present invention, and FIG. 2 is a state diagram showing the operation of the main control circuit.

In FIG. 1, the repeater 1 of this embodiment is provided between a first segment 2 and a second segment 3. A first transceiver 5 is attached to the first coaxial cable 4 forming the first segment 2, and a second transceiver 7 is attached to the second coaxial cable 6 forming the second segment 3. Has been.

The repeater 1 is composed of a main circuit 8 for relaying a data signal and a collision signal, and an abnormality processing circuit 9.

The main body circuit 8 outputs the signals input through the first and second transceivers 5 and 7 through the first and second decoders 10 and 11 and the first and second transceivers 5 and 7, respectively. The first and second encoders 12 and 13, which respectively encode the power signal, and the collision states on the first and second coaxial cables 4 and 6, respectively, are detected through the first and second transceivers 5 and 7, respectively. First and second collision detectors 14, 15
And a FIFO circuit section (first-in / first-out circuit section) 16 for absorbing an error between the clock of the input signal and the clock of the repeater 1, and an output control section 17 for switching the transmission direction of the signal to the FIFO circuit 16. It has a main controller 18 that receives signals from the decoders 10 and 11 and collision detectors 14 and 15 and controls the switching operation in the output controller 17. Main controller 18
Responds to a signal input from each of the segments 2 and 3 to shift from an idle state, which is a signal input waiting state, to a required operation state.

Further, the abnormality processing circuit 9 includes a state detection unit 19 and a timer unit.
20 and a reset generation unit 21. State detector 19
Introduces a state signal indicating each operating state other than the idle state in the main control unit 18 to detect continuation of the operating state.
The timer unit 20 operates as a timer for a certain period of time in response to the state detection by the state detection unit 19. The fixed time period during which the timer unit 20 operates is set in correspondence with the maximum length of a normal data packet. The reset generation unit 21 includes a timer unit 20.
The reset signal is output in response to the time-up signal of. The reset signal output from the reset generator 21 is
The reset signal is supplied to the main control unit 18 of the main body circuit 8 to reset the operation state of the main control unit 18 to an idle state in which the relay operation is not performed.

Next, the operation of the above configuration will be described.

When both stations in each segment 2 and 3 are normal and are transmitting data packets of a predetermined length, the main circuit 8 of the repeater 1 relays the data packets to the other segments 2 and 3. The operation in this case is as shown in the state diagram of FIG.

That is, when each transceiver 5, 7 does not receive any data packet, the main controller 18 is in the idle state Id.

Now, when the data packet is input to the first decoder 10 through the first transceiver 5, the main control unit 18 detects the signal input from the first segment 2 by the signal from the first decoder 10 and detects the signal input from the first segment 2. From the relay state R12 to the second segment 3 is entered. When the relay state R12 is reached, the switching in the output control unit 17 becomes the switching state according to the relay R12. Therefore, the signal input to the first decoder 10 is decoded by the decoder 10 and then the output control unit 17
Once stored in the FIFO circuit section 16 through the output control section
Sent to the second encoder 13 via 17 and encoded,
It is transmitted on the second segment 3 through the second transceiver 17.

When the signal input from the first segment 2 ends, the main control unit 18 returns from the relay state R12 to the idle state Id,
When a collision occurs in the first segment 2 in the relay state R12, the collision state is detected by the first collision detection unit 14. In response to the detection signal from the collision detection unit 14, the main control unit 18 shifts to the collision relay state J2 in which the collision is relayed to the second segment 3. As a result, the collision state of the first segment 2 is relayed to the second segment 3.

Here, when the signal input from the first segment 2 ends, the main control unit 18 shifts to the idle state Id, but if a signal is input from the second segment 3 in the middle of the collision relay state J2, both segments 2 That is, a collision occurred at 3, 3. In this case, the main control unit 18 shifts to the collision notification state J12 which notifies both segments 2 and 3 of the collision state, and outputs a collision signal to both segments 2 and 3.

Further, if a signal is input from the second segment 3 in the middle of the relay state R12, it means that a collision has occurred between the two segments 2 and 3. In this case as well, the main control unit 18 shifts to the collision notification state J12 for both segments 2 and 3, and outputs a collision signal to both segments 2 and 3.

Each of the above operations is performed when the signal is first input to the first transceiver 5, but when the signal is first input to the second transceiver 7, the main control unit 18 causes Repeat in the opposite direction. That is, if a signal is first input to the second transceiver 7, the main control unit 18 enters the relay state R21 to the first segment 2 and if a collision occurs in the second segment 3 in the middle of the relay state R21. , (1) Move to the collision relay state J1 to the first segment 2 and the collision relay state
When a signal is input from the first segment 2 in the middle of J1,
The collision notification state J12 for both segments 2 and 3 is entered. Also, when a signal is input from the first segment 2 in the middle of the relay state R21, the state goes to the collision notification state J12 for both segments 2 and 3.

In this way, when a signal is input from any of the segments 2 and 3, the main control unit 18 determines that the operating state other than the idle state Id
When the signal shifts to R12, R12, J1, J2, J12 and no signal is input from any of the segments 2 and 3, the idle state Id is restored. The length of the data signal input from each segment 2 and 3 is limited to a fixed packet length, and the signal indicating collision is also shorter than the fixed packet length. Therefore, the time when the main control unit 18 stays in a state other than the idle state Id falls within the time corresponding to the maximum length of the data packet.

However, one of the stations connected to each of the segments 2 and 3 may transmit a data signal longer than a fixed packet length due to a failure or the like. Also, a signal longer than a fixed packet length may be input due to external noise.

In such a case, the main control unit 18 stays in the same operating state for a time longer than the maximum packet length. However, according to the present invention, the operation of the abnormality processing circuit 9 causes the main control unit 18 to operate.
Automatically returns to the idle state Id.

That is, signals indicating operating states other than the idle state Id in the main controller 18 are input to the state detector 19. State detector 19
When the status signal is detected at, the timer unit 20 starts operating in response to the detection. The timer unit 20 counts a time that is the same as or slightly longer than the maximum length of the data packet, and when the same status signal is continuously input to the status detection unit 19, the timer operation is performed. continue.

When the signal input to the repeater 1 is a normal signal, the operating state of the main control unit 18 that operates in response to the signal is within a fixed time. Therefore, the timer unit 20 stops its operation and returns to the initial state before the time is up. However, if the input signal exceeds the maximum packet length, the time during which the main control unit 18 remains in one of the operating states exceeds a certain time.

In this way, if the status signal from the main control unit 18 continues for a certain time or more, the status detection by the status detection unit 19 continues for a long time,
Therefore, the timer unit 20 outputs a time-up signal. With this time-up signal, the reset generator 21 generates a reset signal. Since this reset signal is given to the main control unit 18, the main control unit 18 returns to the idle state Id regardless of the operating state at that time. As a result, the relay between the segments 2 and 3 is cut off.
Thus, if one of the stations in one segment 2 (3) has failed, the segment 2 (3) with the failed station will be the other segment 3
Separated from (2). Therefore, other segment 3
(2) is not affected by the failed station, and communication within the other segment 3 (2) is secured.

If a signal exceeding the maximum packet length is input and the relay is interrupted due to a temporary abnormality of the station or external noise, the abnormality is usually recovered automatically within a short time, and each transceiver Normal signals will be input to 5 and 7. When a normal signal is input, the main control unit 18 shifts from the idle state Id to the required operation state and restarts the relay operation.

<Effects of the Invention> As described above, according to the present invention, when a signal exceeding the maximum packet length is input from any of the segments, the main control unit takes a long time to stay in the same operating state other than the idle state. Therefore, the state detection unit and the timer unit that monitor the operating state of this main control unit operate, the reset signal is output from the reset generation unit, and the state of the main control unit is forced to the idle state by the reset signal. Will be returned. Therefore, the abnormal segment is temporarily separated from the normal segment until the relay operation of the repeater is stopped and the abnormal situation is resolved. This ensures communication within normal segments and enhances overall LAN reliability.

Further, since the abnormality processing circuit is provided separately from the main control unit, the load on the main control unit for coping with the abnormal situation is reduced, the configuration of the main control unit is simplified, and the design is facilitated.

Further, even when the main body circuit including the main controller malfunctions, the relay is interrupted, and it is possible to effectively deal with the occurrence of an abnormality in the repeater itself.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention, and FIG. 2 is a state diagram showing the operation of the main controller. 1 ... Repeater, 2 ... First segment, 3 ... Second segment, 8 ... Main circuit, 9 ... Abnormality processing circuit, 18 ...
Main control block, 19 ... Status detection block, 20 ... Timer block, 21 ...
… Reset generator.

Front page continuation (72) Inventor Kiyoshi Einaga 4-3 Ikejiri, Itami City, Hyogo Prefecture Daini Nippon Electric Cable Co., Ltd. Itami Plant (72) Inventor Kazuharu Yuno 5-2-1 Omika-cho, Hitachi City, Ibaraki Prefecture Incorporated company Hitachi Ltd. Omika factory (72) Inventor Takehiko Nishida 5-2-1 Omika-cho, Hitachi city, Ibaraki Prefecture Incorporated company Hitachi Ltd. Omika factory (72) Inventor Tadao Namaten 5-5 Omika-cho, Hitachi city, Ibaraki prefecture 2-1 Hitachi Ltd. Omika factory

Claims (1)

[Claims] 1. An abnormality processing circuit for a repeater having a main control unit that shifts from an idle state to a required operation state in response to a signal input from each segment, wherein each of the main control unit except for the idle state. A state detection unit that introduces a state signal indicating an operation state to detect continuation of the operation state, a timer unit that operates for a certain period of time in response to the state detection by the state detection unit, and a time-up of the timer unit An abnormality processing circuit for a repeater, comprising: a reset generation unit that gives a reset signal to the main control unit in response to a signal to return the main control unit to an idle state.