JPH06268655A - Bus type lan - Google Patents

Abstract

PURPOSE:To lower burden at the time of data transmission by selecting a communication enable station with a transceiver and transferring data through a correspondent object station connecting part. CONSTITUTION:A data input/output part 21 sends and fetches a frame on a segment (transmission line) 1. An address added to the fetched frame is compared with an address managed by an address managing part 22 by a data processing part 23. Inside a connecting system changeover part 24, there is a table for managing the active states of connected CPU 11 and 12, the CPU in the active state are successively selected from the high order, and data are transferred. The processing part 23 of a transceiver 8 extracts the destination address from the input/output part 21 and compares it with the self-address of the managing part 22 and only the processing part 23 of the transceiver 8 provided with the coincident address performs detailed processing with data reception. Thus, a data transmitting station can continue communication without being conscious of the state of the destination and performing address changeover processing, and burden at the time of data transmission is reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to, for example, CSMA / CD.
(Carrier Sence Multiple Access with Collision Dete
ction) bus type LAN.

[0002]

2. Description of the Related Art Ethernet is one of CSMA / CD system bus type LANs conforming to ISO (International Organization for Standardization) 802.3. In recent years, there have been many requests from the users of this Ethernet to increase the number of stations, and it is an urgent task to deal with them.

A conventional Ethernet will be described with reference to FIG.

In the figure, reference numerals 41 to 44 denote Ethernet transmission lines, each of which is composed of one segment (one coaxial cable). Each of the transmission lines 41 to 44 is provided with a plurality of transceivers (Tr) 45, and each Tr 45 is connected to, for example, a ring network 46 and CPUs 47 to 52. Note that A to H are destination addresses, and the CPU 4
Two are set for each of 7, 48, 51 and 52. The CPU 47 and the CPU 48 are tightly coupled, and for example, a standby standby system in which the CPU 47 is an operating system and the CPU 48 is a standby system is configured.

In this Ethernet, for example, the CPU 49
When data is communicated to the CPU 47, the frame to which the address A is added is sent from the CPU 49 onto the transmission path 43. Then, the frame is based on the address A, the ring network 46, the segment 41 and the Tr 45.
It is taken into the CPU 47 via the above. In this way, communication is normally continued to this address A.

On the other hand, the CPU 49 periodically sends out the carrier and confirms the communication state by the response. Therefore, if a line failure X occurs, for example, if the communication cable is broken between the Tr 45 and the CPU 47, the CP
There is no response from U47, and the CPU 49 recognizes the abnormality of the line. At this time, whether the CPU 47 itself has a failure or the communication cable is broken, the CPU 49
The side cannot judge.

Therefore, in this case, the CPU 49 sends out a frame to which the address B is newly added, and the transmission line 42
The data is transmitted to the CPU 47 via the. It should be noted that like the configuration of the transmission line 44, two Trs on one transmission line are
The same applies when 45 is connected to the CPU 51.

When the communication failure continues even with the address B, the CPU 49 recognizes that the CPU 47 itself is abnormal at a certain timing (original judgment), performs address switching processing, and the standby CPU 48. Data is transmitted to (destination address C). That is,
In this Ethernet, it is necessary for the CPU 49, which is the transmission source, to always communicate with the communication partner (CPU 47) based on the address and perform the address switching process when a failure occurs.

Further, the Ethernet protocol limits the number of transceivers (maximum 100) that can be connected to one segment (maximum 500 m) and the interval between transceivers (2.5 m or more). Therefore, each Tr 45 and the CPU 47,
If the standby standby system is configured in a two-to-one relationship with 48, not only the installation efficiency of Tr45 is poor, but also many operating stations that operate normally cannot be provided.

[0010]

As described above, in the above-mentioned conventional bus type LAN, when a standby standby system composed of a plurality of stations is constructed on a transmission line, an address is set for each and an address switching process is performed when a failure occurs. Since it is necessary to do and deal with it, a lot of burden was added to the sender. Further, there is a problem that a large number of stations cannot be provided if the standby standby system is configured while the number of transceivers is limited by the regulations.

The present invention has been made to solve such a problem, and when a failure occurs in a standby standby system consisting of a plurality of stations on a transmission line, communication is continued without performing address switching processing. A bus-type LAN that allows for additional stations while the number of transceivers is limited
Is intended to provide.

[0012]

In order to achieve the above-mentioned object, a bus type LAN of the present invention has a transmission path shared by a plurality of stations via a transceiver, and a data transmission station performs carrier detection to perform the transmission. In a bus-type LAN that confirms the usage state of a path and sends a frame with a destination address added when the transmission path is open to perform data communication with another station, the transceiver constitutes a standby standby system. A plurality of station connecting units that respectively connect a plurality of stations, an address management unit that manages the plurality of stations connected to these station connecting units under one address, and A monitoring unit that regularly monitors the active state of the station and the frame that is taken in from the transmission line, and compares the address of the taken-in frame with the address of the address management unit. When the destination of the frame is determined, and the destination determination result shows that the destination is its own, the destination determination unit that receives and processes the data of the frame, and the reception unit that performs the reception process, the monitoring unit obtains A bus-type LAN, comprising: a communication-enabled station selected based on the active state of each station, and a connection system switching unit that transfers data through the target station connection unit corresponding to the communication-enabled station.

[0013]

In the present invention, the transceiver is provided with a plurality of station connecting portions and a monitoring portion corresponding to a plurality of stations forming the standby standby system, and the monitoring portion monitors the active state of each station through the plurality of station connecting portions. We monitor it regularly. Then, when the frame is received by the destination determination unit, the connection system switching unit of the transceiver selects a communicable station in the standby standby system based on the active state of each station obtained from the monitoring unit, and this communication is possible. Data is transferred through the target station connection unit corresponding to the station.

Therefore, the data transmitting station can continue to send data without being aware of the configuration in the standby backup system and the failure state. In other words, the data transmitting station does not need to perform the address switching process unless all stations in the standby standby system are incapable of communicating.

Further, when the transceiver receives a frame based on one address, the transceiver side selects a communicable station, so that it is not necessary to divide the address into each station, and a plurality of stations can be connected to the transceiver. become.

[0016]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 shows a bus type LA according to an embodiment of the present invention.
It is a figure which shows N.

As shown in FIG. 1, 1 is one segment of Ethernet which is a bus type LAN. A segment is a transmission line composed of one coaxial cable. Other segments 43 and 4 are connected to the segment 1 via, for example, the ring network 2. The ring network 2 is provided with network adapters 5, 6, 7 for connection with the respective segments 1, 43, 4. A conventional transceiver (Tr) 45 is provided in each of the segments 1, 43, 4 connected to the network adapters 5, 6, 7, respectively. The structure of the segment 43 is the same as the conventional one in order to make the operation easy to understand.

On the other hand, the transceivers 8 of the present invention are connected to the segments 1 and 4. A plurality of transceiver cables 9 and 10 are connected to the transceiver 8 of the segment 1, and each of them is individually connected to the CPUs 11 to 14. This CPU11 and CPU12, CPU
13 and the CPU 14 respectively form a standby standby system. Further, a plurality of transceiver cables 9 and 10 are respectively connected to the transceiver 8 of the segment 4 in the same manner as described above, but in this case, the two cables are directly connected to one CPU 15 and one CPU 16, respectively. In this embodiment, two CPUs are connected to each transceiver 8 of the segment 1 for easy understanding of the operation, but the number of connections can be further increased.

Next, the configuration of the transceiver 8 of the present invention will be described with reference to FIG.

Since the configuration of each transceiver 8 is the same, description will be given for the transceiver 8 of segment 1.

In FIG. 1, reference numeral 21 is a data input / output unit, which sends and receives a frame on the segment (transmission path) 1. An address management unit 22 manages its own address A. A data processing unit 23 compares the address added to the fetched frame with the address managed by the address management unit 22. Reference numeral 24 is a connection system switching unit, which is a C connected to itself.
It has a table for managing the active state / inactive state of the PUs 11 and 12, and selects the CPU in the active state in the table in order from the higher order and transfers the data. 25 is C
It is a PU monitoring unit and monitors whether or not the CPU 11 is in the active state at predetermined time intervals. 26 is a CPU monitoring unit, which is the CPU 1
Whether or not 2 is active is monitored every predetermined time. 27 is C
A PU target data input / output unit that exchanges data with the CPU 11. Reference numeral 28 denotes a CPU target data input / output unit, which exchanges data with the CPU 12.

Next, the data communication operation in this bus type LAN will be described with reference to the flow chart of FIG. In the operation description, for example, the CPU 49 uses the CPUs 11 and 12
Only when sending data to.

In this case, first, the CPU 49 adds the destination address A and transmits the frame. Then, the frame has a ring network 2 and each segment 1, 3,
The data is received by the data input / output unit 21 of each transceiver 8 through 4 (step 301). The data processing unit 23 of each transceiver 8 extracts the destination address A from the frame received by the data input / output unit 21 and extracts the destination address A.
It is compared with its own address managed by (step 302). As a result of this comparison, the destination is known, and the transceiver (CP
Only the transceiver 8 to which U11 and U12 are connected interprets the data content of the received frame, that is, the data processing unit 23 of the transceiver 8 performs the detailed processing associated with the data reception (step 303). The transceiver 8 whose address does not match the destination address discards the received frame.

On the other hand, the CPU monitoring units 25 and 26 of the transceiver 8 are respectively connected to the CPU target data input / output unit 2
When a carrier is periodically transmitted to the CPUs 11 and 12 through 7 and 28 and a response comes back, the response information is sent to the connection system switching unit 24 each time. Connection system switching unit 2
4 updates the active / inactive state of each CPU 11, 12 in its own table based on the response information from each CPU 11, 12.

In this way, the connection system switching unit 24 is the CPU
The data processing unit 2 monitors the active states of 11 and 12.
When detailed processing of data is performed in 3, CP that can communicate
U is searched (step 305) and the presence or absence thereof is confirmed.

Here, for example, if the CPU 11 is at least in the active state, the connection system switching unit 24 is a CP located in the higher order of the table even if the CPU 12 is in the active state.
U11 is given priority and the communication path is determined to be the CPU 11 side (step 306), and the data is transferred to the CPU 11 through the CPU target data input / output unit 27 (step 307). Further, for example, when the CPU 11 is inactive and the CPU 12 is active, the connection system switching unit 24 switches the communication path to the CPU.
12 side, and transfers the data to the CPU 12 through the CPU target data input / output unit 28.

Further, only when both the CPUs 11 and 12 are inactive, the data input / output unit 21 notifies the transmission source that communication is impossible (step 308).

As described above, according to the Ethernet of the present embodiment, for example, the CPU 49 (source station) is transmitting data to the standby standby system (destination target stations such as the CPU 11 and the CPU 12) and is in use (the CPU 11 or the line). When a failure occurs in the transceiver cable 9 or the like, the transceiver 8 switches the communication path to the other active station (transceiver cable 10 connected to the CPU 12) side to transfer the data, and therefore the transmission source (CPU 49) transmits the data to the CPU.
The data transmission can be continued without being aware of the configurations of 11, 12 and the failure state.

That is, once the transmission source station sends a frame onto the transmission path 1, data transmission is continued without performing address switching processing unless all destination destination stations connected to the transceiver 8 are in the inactive state. Then you can finish.

Further, as in the conventional case, data communication with a plurality of stations is possible even if the destination address is 1, so that many stations can be connected even if the number of transceivers is limited.

Further, in order to add a new station to one segment, it suffices to change the control system on the transceiver side and add the connection port of the station to the transceiver without changing the destination address. There is no need to change even the control software of the LAN, which makes it easy to add stations.

Further, since the transmission source can communicate with the transmission partner without being aware of the transmission partner, frame exchanges can be reduced and congestion of the transmission path can be relieved.

In the present invention, by connecting the transceiver 8 and the CPU 15 with the two transceiver cables 9 and 10 like the connection configuration of the segment 4, for example, one transceiver cable 9 has a physical failure, For example, if the communication cable is broken, the CPU1
It is possible to prevent the communication failure of the wireless communication terminal 5 by switching the communication path to another transceiver cable 10, so that the safety of the system can be improved.

[0035]

As described above, the bus type LA of the present invention
According to N, since the transceiver selects a communicable station and transfers the data through the corresponding target station connecting unit, the data transmitting station communicates without being aware of the state of the destination and without performing the address switching process. Can be continued and the burden on data transmission can be reduced. Further, it is possible to connect a plurality of stations to the transceiver while the number of transceivers is limited by the protocol.

[Brief description of drawings]

FIG. 1 is a diagram showing a bus LAN according to an embodiment of the present invention.

FIG. 2 is a diagram showing a configuration of a transceiver in the bus type LAN of FIG.

3 is a flowchart showing a data communication operation in the bus type LAN of FIG.

FIG. 4 is a diagram showing a conventional bus type LAN.

[Explanation of symbols]

1, 3, 4 ... Segment, 2 ... Ring network,
5, 6, 7 ... Network adapter, 8 ... Transceiver, 9, 12, 13 ... Transceiver cable, 10, 1
1, 14, 15 ... CPU.

Claims (1)

[Claims] 1. A transmission line is shared by a plurality of stations via a transceiver, and a data transmission station performs carrier detection to check the usage state of the transmission line and adds a destination address when the transmission line is open. In a bus-type LAN that transmits a specified frame to perform data communication with other stations, the transceiver connects to a plurality of station connection units that respectively connect a plurality of stations that form the standby standby system and to these station connection units. An address management unit that manages the plurality of stations under the control of one address, a monitoring unit that periodically monitors the active state of each station through the plurality of station connection units, and the frame from the transmission path. Captured, the address of the captured frame is compared with the address of the address management unit to determine the destination of the frame, the destination determination result,
When the destination is its own, the destination determining unit that receives and processes the data of the frame, and when the receiving process is performed by the destination determining unit, the communicable station is selected based on the active state of each station obtained by the monitoring unit. Then
A bus type LAN comprising: a connection system switching unit that transfers data through the target station connection unit corresponding to the communicable station.