JPH03204257A - Node station - Google Patents

Abstract

PURPOSE:To easily disconnect a transmission line having an error by checking an error of all packets relayed to node stations in a data communication system in which a packet is sent into a unidirectional loop communication network and storing the error when the error is detected. CONSTITUTION:As to a packet relayed by a relay circuit 12, a frame check circuit 14 uses a frame check sequence(FCS) so as to check a frame and when an error is detected in a frame, it is informed to an error storage circuit 15, where the presence of the error is stored. An error of a frame is detected from a packet relayed to a succeeding stations due to the deterioration in the transmission line 2 between one node station 1 and the succeeding node station 1 and the presence of the error is stored in an error storage circuit 15 of the node stations. Thus, the content of the error storage circuit 15 of all the node stations is read to recognize the transmission line having an error.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a node station, and particularly to a note station of a data communication system that performs communication using packets in a loop-type communication network in a unidirectional signal transmission direction.

[Conventional technology]

Conventionally, in this type of node station, only the packet receiving station performs a frame check using a frame check sequence (hereinafter referred to as FC8) included in the frame constituting the packet.

[Problem to be solved by the invention]

Therefore, the packet received at the packet receiving station is FCS
Although it is possible to detect an error using this method, it has the disadvantage that it is not possible to isolate where on the transmission path the error occurred.

[Means to solve the problem]

The node station of the present invention is a node station of a data communication system that performs communication using frame-structured packets having a frame check sequence in a loop-type communication network in which the signal transmission direction is unidirectional. The present invention includes a frame check means for detecting a frame error in a packet using a frame check sequence, and an error storage means for storing the existence of an error when the frame check means detects an error.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a block diagram of an embodiment of the present invention, and FIG. 2 is a block diagram of an example of a data communication system to which the present invention is applied.
FIG. 2 shows an example consisting of a transmission line 2 forming a loop and transmitting data in the direction of the arrow, and four node stations 1 shown in FIG. 1 each having a data processing device 3 connected thereto. A node station 1 in FIG. 1 includes a receiving circuit 11 that receives an input signal from a transmission line 2. A relay circuit 12 that relays packets other than those transmitted from the own station among packets received by the reception circuit 11. A communication control unit 13 controls received packets and transmitted packets, and a frame check circuit 14 checks packets input to the relay circuit 12 for errors. An error storage circuit 15 that stores the existence of an error packet detected by the frame check circuit 14.
It has a transmitting circuit 16 that transmits packets to the transmission path 2.

FIG. 3 shows the format of an example of a frame constituting a packet transmitted in the embodiment of FIG. 1, starting from the beginning with a start identifier (SD), a destination address (DA), a sender address (SA), and a control section (C). , information part (1), frame check sequence (FCS), end identifier (ED)
The configuration has the following in order:

Next, the operation of the node station shown in FIG. 1 will be explained. Now, when one node station 1 transmits a packet in the format shown in FIG. 3, this packet travels along the transmission path 2 in the direction of the arrow and is input to the next node station 1. When the node station 1 receives this packet, if it is a packet addressed to itself, the communication control unit 13
The information part I is sent to the data processing device 3 via.

Also, if the packet is not transmitted from the own station, the relay circuit 12
If the packet is addressed to the node station 1 downstream, the relay circuit 12 stops relaying the packet. At the same time, for the packets relayed by the relay circuit 12, the frame is checked by the frame check circuit 14 using FCS, and if an error is detected in the frame, it is notified to the error storage circuit 15, where The existence of an error is remembered.

Now, due to the deterioration of the transmission path 2 between one node station 1 and the next node station 1, frame errors are detected in the packets relayed to the next node station and beyond, and those nodes The existence of an error is stored in the error storage circuit 15 of the station. Therefore, by reading the contents of the error storage circuits 15 of all node stations, it is possible to know the transmission path where the error occurred.

〔Effect of the invention〕

As explained above, the present invention enables a node station of a data communication system that transmits packets to a unidirectional loop-shaped communication network to check for errors in all relayed packets, and when an error is detected, to store the error. This has the effect of making it easier to isolate the transmission path where an error has occurred.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention, FIG. 2 is a configuration diagram of an example of a data communication system to which the present invention is applied, and FIG. 3 configures a packet used in the embodiment of FIG. 1. This is an example format of a frame. 1... Node station, 2... Transmission line, 3...
- Data processing equipment, 11... Reception circuit, 12... Relay circuit, 13... Communication control unit, 14... Frame check circuit, 15... Error storage circuit, 16... Transmission circuit.

Claims (1)

[Claims] In a node station of a data communication system that communicates using packets with a frame structure that has a frame check sequence in a loop-type communication network in which the signal transmission direction is unidirectional, a frame check sequence is applied to all packets that are relayed or received. 1. A node station comprising: a frame check means for detecting frame errors; and an error storage means for storing the existence of an error when the frame check means detects an error.