JPH0458635A - Data transmitter - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Object of the Invention] [Industrial Application Field] The present invention relates to a data transmission device that cyclically transmits data between transmission stations connected on a LAN (Local Area Network). In particular, the present invention relates to a data transmission device including a redundant transmission station.

[Conventional technology]

Conventionally, multiple transmission stations, each connected to a specific connected device, are connected on a LAN, and the transmission data from each connected device is output from its own transmission station onto the LAN.
BACKGROUND ART A data transmission device is being considered that allows access to transmitted data from other connected devices by accessing an AN.

A conventional example of the data transmission device shown in FIG. 1 is shown.

Reference numeral 1 shown in the figure is a transmission station, and each transmission station is connected to a transmission line 2 on the LAN, and is also connected to a corresponding connected device 4 via an external bus 3.

In the transmission station 1, the CPU 1 connects the transmission circuit 13 . Buffer 7 memory 14 for temporarily storing transmitted and received data. A transmission information memory 15 and a transmission memory 16 are respectively connected to store block information to be transmitted from the own station. The transmission circuit 13 has the function of transmitting the transmission data of its own station onto the transmission line 2, and also accessing the transmission line 2 to take in the transmission data of other stations. As shown in FIG. 6, the transmission memory 16 stores (n+1) professional
The network is divided into blocks, and each transmission station on the LAN is assigned to each block 0 to n. This allocation is determined by the system that applies cyclic transmission, but
Only one transmission station can be assigned to one block.

Each block has a common memory (or dual port memory) configuration that can be accessed from both the CPU II side of its own station and the connected device 4 side. Furthermore, each block has a structure of (m+1) words that can be accessed by the CPUI 1 in association with the access memory.

In the transmission device configured in this way, transmission data is written into the transmission information memory 15 by the connected device 4 via the external bus 3 and the gate 18.

Furthermore, the connected device 3 reads words from each block of the transmission memory 16, reads transmission data from each control device of another station, and executes application processing. Each transmission device on the LAN uses the LAN's broadcast transmission function to cyclically transmit its own block information in the transmission format shown in, for example, FIG. 7. WN indicates the number of words in one block, and BADR indicates the block number. Note that FIG. 7 shows the format within the service data unit provided in the LLC sublayer of the second layer of the 0817 layer model, and the signal that actually flows on the LAN further includes an LLC header, a MAC header, and A trailer will be added. Each transmission device that receives the frame shown in FIG. 7 selects the block indicated by BADH in the frame and
The DATA is written to the storage area of the number of words indicated by N.

This operation is performed by all transmission devices on the LAN, and as a result, the same data is held in the transmission memories 16 of all transmission devices that receive this frame.

Therefore, from the perspective of the connected device 4 that accesses the transmission device, it is possible to easily access data held by each connected AI device on the LAN by simply accessing the transmission memory 16 without having to bother with complicated communication protocols. The advantage is
be.

By the way, when such a transmission device is required to have such high reliability that it is not allowed to stop the transmission process due to a failure, etc., a redundant configuration is adopted in which a spare transmission station 1S with the same function is arranged. ing.

A pair of redundant transmission stations are treated as one station, and the same block is allocated in the transmission memory of each transmission station. One side is set as an online side and the other side is set as a standby side, and when an abnormality occurs on the online side, the switch is switched to the standby side.

However, since the data of the standby redundant transmission station is on the online side (the operating side, not the standby side), in order to access the block of the redundant transmission station, it is necessary to It was necessary to determine whether the station was online before accessing it. Therefore, a separate technical means was required to notify other transmission stations that the accessed transmission station is a redundant transmission station and which side is online.

[Problem to be solved by the invention]

Therefore, as mentioned above, in the conventional data transmission equipment having redundant transmission stations, when accessing the redundant transmission stations, it is not known which station is online, so each time a separate There is an inconvenience in that the operating state must be confirmed by means provided.

The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide a data transmission device in which each transmission station can reliably access the online side of redundant transmission stations.

[Structure of the Invention] [Means for Solving the Three Problems] In order to solve the above problems, the present invention provides a system in which a plurality of transmission stations, each of which is accessed from a corresponding connected device to each transmission memory, can share common data. The plurality of transmission stations may include a pair of redundant transmission stations that are connected to a transmission line and have redundancy such that one is in an online state and the other is in a standby state, and each transmission station is connected to its own connected equipment. In a data transmission device that sends transmission data onto the data transmission path and stores received transmission data in the transmission memory, the data transmission device is provided at each of a pair of redundant transmission stations and connected to the pair of transmission stations. Operation mode data indicating the operating status of each transmission station is written from the same connected device, and an abnormality occurs in the transmission station that was online.1. In such a case, an operation mode storage means is provided in each of the pair of redundant transmission stations, in which operation mode data for switching the standby transmission station to the online state is written, and the operation mode storage means is provided in each of the pair of redundant transmission stations. The operation mode data written in the mode storage means is added to the transmission data of the own station. When transmission data is received, its operation mode is checked, and if operation mode data indicating that it is in standby mode is attached, that transmission data is canceled, and operation mode data indicating that it is in online mode is attached. If the transmission data is transmitted, the transmitter is configured to include receiving means for writing the transmission data into the transmission memory.

[Operation] By taking the above measures, the present invention allows operation mode data indicating the operation status of each transmission station to be connected to each operation mode storage means of a pair of redundant transmission stations. Transmission data written from the same connected device and having an operation mode added thereto by the transmission means is sent onto the transmission path. In addition, when the receiving means of each transmission station receives transmission data with an operation mode attached, it checks the operation mode and cancels the data if the operation mode data indicating standby status is attached. However, if operation mode data indicating an online state is attached, that data is stored in the transmission memory as online data. When the connected device detects that an abnormality has occurred in the online transmission station, operation mode data indicating that the transmission station in the standby state is to be switched to the online state is written in the operation mode storage means.

Therefore, the transmission station that is currently on the standby side is switched to the online side, and the transmission data of this transmission station is stored in each transmission station.

〔Example〕

Examples of the present invention will be described below.

The data transmission device according to this embodiment has the same basic hardware configuration as the transmission device shown in FIG. 1, and therefore will be explained with reference to the same figure.

The transmission memory 20 used in this embodiment consists of a data section made up of a plurality of blocks shown in FIG. 6, and an operation mode section in which the operation mode of the own station given from the connected device 4 is stored. The operation mode section has a minimum memory configuration, for example, one word, and is defined as standby operation when it is "0" and online operation when it is other than "0".

Further, as shown in FIG. 2, the LLC service data unit is provided with a MODE area for adding the operation mode of the transmission station to the unit shown in FIG. 7.

This MODE content corresponds to the data content of the operation mode section of the transmission memory 20.

Next, the operation of this embodiment will be explained with reference to FIGS. 3 to 5.

Connecting equipment 4 connected to a pair of redundant transmission stations
A transmission request is issued at a fixed period, and when this transmission request is issued (step S1), the operating state of each redundant transmission station is checked by the abnormality detection means (step S2), and an abnormality is detected. It is determined whether or not it has occurred (step S3).

If there is no abnormality, the transmission data to be transmitted is created (step S4), and is written into the transmission information memory 15 by controlling the gate 18 (step S5).

Further, in step S3, if an abnormality is found in the online transmission station, the data in the operation mode section of the transmission memory 20 of both transfer stations is rewritten (step S6). That is, the online operation is started by writing a number other than 0° indicating that the online side is in the operation mode section of the transmission memory 20 that is currently on the standby side, and the transmission memory 20 of the transmission station that is currently on the online side is written. In the operation mode section,
Either write “0” indicating that it is on the standby side, or stop the operation.

Then, the connected device 4 transmits the transmission data written in the transmission information memory 15 to both transfer stations 1 in a cyclic manner.
A start command is issued to (step S7).

When the transmission station 1 receives the start command from the connected device 4 (step T1), the transmission station 1 receives the operation mode data written in the operation mode section of the transmission memory 20.

Then, read out the transmission data of the local station written in the transmission information memory 15 (step T2), and assemble the LLC service data unit with the operating mode of the local station as shown in FIG. 2 (step T3). . And transmission circuit 1
3, the service unit having the configuration shown in FIG. 2 is transmitted to the cycle controller (step T4).

On the other hand, each transmission station 1 accesses the transmission path 2 and takes in the service UNI SOTO shown in FIG. Next, the operation mode of the received service unit is checked (step P2), and it is determined whether the received data is from an online transmission station or a staffed transmission station (step P3). When the operation mode is a value other than “0”,
It is determined that the message is from the online side and is written to the corresponding block in the transmission memory 20 (step P4).

If the operation mode is "0", it is determined that the data is from the standby side, and the data is canceled and not captured (step P5). Therefore, only data from the online side is written into each block of the transmission memory 20 of each transmission station.

As described above, according to the present embodiment, an operation mode section is provided in the transmission memory 20 of both redundant transfer stations, and operation mode data indicating the operation state of the transmission station is written into this operation mode section from the connected device. When transmitting data, this operation mode is attached to the transmitted data, and the transmitting station on the receiving side cancels the transmitted data from the standby state and only receives the transmitted data from the online transmitting station. Online data can always be written to the transmission memory 20 of the transmission station 1, and even when accessing a redundant transmission station, the data can be written to the transmission memory 20 without having to judge its operating status each time. Data on the online side can always be obtained simply by accessing it, and data transmission processing at redundant transmission stations can be simplified.

In addition, since the standby transmission station receives and stores online data in its transmission memory 20, even when the standby side operates as the online side by switching the redundancy mode, the online side transmission Data transmission processing can be continued without special operations such as tracking data in memory.

C. Effects of the Invention As detailed above, according to the present invention, even when accessing a redundant transmission station, the system can always be accessed simply by accessing the transmission memory without having to judge its operating state each time. It is possible to provide a data transmission device that can obtain data on the online side and simplify data transmission processing that includes redundant transmission stations.

[Brief explanation of the drawing]

Figure 1 shows the basic configuration of the data transmission device, Figure 2 shows the basic configuration of the data transmission device.
The figure shows the configuration of the data unit used in the embodiment, Figure 3 shows the operation mode switching process by the connected equipment, Figure 4 shows the transmission process of the transmission station, and Figure 5 shows the transmission process of the transmission station. FIG. 6 is a diagram showing the configuration of a transmission memory used in a conventional transmission device, and FIG. 7 is a diagram showing the configuration of a data unit used in conventional data transmission. 1... Transmission station, 2... Transmission line, 3... External bus,
4... Connected device, 11... CPU, 12... Internal bus, 13... Transmission circuit,] 4... Buffer memory,
15... Transmission information memory, 16.20... Transmission memory. Applicant's agent Patent attorney Takehiko Suzue

Claims (1)

[Claims] A plurality of transmission stations whose respective transmission memories are accessed from corresponding connected devices are connected to a common data transmission path, and one of the plurality of transmission stations is in an online state. The other one includes a pair of redundant transmission stations in a standby state, and each transmission station sends out the transmission data of its own connected equipment onto the data transmission path, and stores the received transmission data in the transmission memory. In a data transmission device that stores data in a redundant pair of transmission stations, operation mode data indicating the operating status of each transmission station is transmitted from the same connected device that is installed in each of a pair of redundant transmission stations and connected to the pair of transmission stations. an operation mode storage means in which operation mode data is written indicating that if an abnormality occurs in a transmission station that has been written and is in an online state, the transmission station that has been in a standby state will be switched to an online state; transmitting means provided in each of the pair of transmission stations configured to add operation mode data written in the operation mode storage means of the own station to the transmission data of the own station, and transmitting the data onto the data transmission path; When the transmitting station is equipped with a transmission station and receives transmission data to which the operation mode data has been added, the operation mode is checked and if the operation mode data indicating that it is in a standby state is attached, the transmission data is Cancel and
1. A data transmission device comprising: receiving means for writing transmission data into a transmission memory when operation mode data indicating an online state is attached.