JPH02288635A - Communication system - Google Patents

Abstract

PURPOSE:To realize a large scale network system with high realization by placing high priority on an emergent data to be transferred by acquiring a channel with priority instead of other emergent data even if they are under transferring. CONSTITUTION:An emergent data flag detection/comparison section 51 and an emergent data flag/data generating section 52 are added to a conventional connection control section. For example, an emergent data with high priority such as an emergent data relating maintenance of network system and its management acquires a channel with priority and is transferred quickly even when other emergent data is being transferred and an idle/busy state flag and an emergent data flag are respectively set. Thus, the large scale network system with high realization is built up.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to a communication method in a loop communication system applicable to a large-scale loop network.

(Conventional technology) With the development of the information society, network systems that connect multiple information systems (stations) to each other via data transmission paths and realize more advanced information processing are becoming popular, such as process control network systems and Various types of network systems have been developed, including OA network systems and factory automation network systems.

However, recent trends call for the development of large-scale, sophisticated network systems that integrate or combine various independently existing network systems to enable even more advanced information processing. The basic requirements for such a large-scale network are: [1] A high-speed, long-distance network; [2]
It must be a multimedia network that can support various media such as audio, still images, videos, and coded data; [3] It must be able to integrate circuit switching and packet switching; [4] It must be able to accommodate a wide variety of terminals. It is possible to connect various types of networks as branch lines.

In order to meet these demands, we have developed a new technology that has excellent compatibility with circuit switching and packet switching, is easy to use optical communication technology, and is easy to construct large-scale network systems, for example, as shown in Figure 4. A loop communication system in which a plurality of stations 2 are connected in a loop via a transmission line 1 is attracting attention.

For example, as shown in FIG. 5, the frame format is such that a frame with a constant period is divided into a synchronization area 3, a connection control area 4, a circuit switching area 5, and a packet switching area 6. 6, depending on the traffic characteristics of the terminal and branch line.

Furthermore, as shown in FIG. 6, it is naturally possible to use the format shown in FIG. 5 without the packet exchange area.

Note that circuit switching is performed by providing a large number of slots in the circuit switching area 5, and allocating the slots according to requests from terminals.
This is achieved by communication using slots assigned to terminals. Control data for allocating slots is communicated using, for example, the connection control area 4 set by dividing the frame.

Figure 7 shows such a connection control area in detail.
In the figure, A shows an example of the format when circuit switching and packet switching are integrated, and B shows an example of the format when only circuit switching is used.

Format A consists of a synchronization area 7, an n-channel connection control area 8, a circuit switching area 9, and a packet switching area 10. Format B consists of a synchronization area 11, an n-channel connection control area 12, and a circuit switching area 13.

Connection control area 8.1 for formats A and B above
Each of the two channels is set to a different band, and these channels are used individually to communicate connection control packets between the control station and each station, and between each station.

Note that the number of channels and bandwidth of the connection control area 8.12 that are divided and set are optimally set according to the system scale such as the number of terminals accommodated in the network, the length of the connection control packet, etc. . The settings may be made, for example, by setting the number of channels and the band at the time of system configuration.

In this example, the connection control area 8.12 is composed of a plurality of channels, but it goes without saying that the number of channels may be just one.

The format of the channel in the connection control area 8.12 is, for example, as shown in C in FIG.
6. It consists of a transmitting station address 17, a transmitting terminal number 18, one command, a data length 20, data 21, and its check code 22.

Using such a channel, connection control data is communicated as shown in FIG. 8, and outgoing calls and the like are controlled.

Connection control data is generally short data, and a large amount of this data is generated in a large-scale network. Therefore, in order to prevent one station from continuing to occupy a channel, an access method is used in which the size of the data part of the channel is set larger than the connection control data, and the channel is released after one communication.

That is, each station acquires a transmission spatio-temporal channel and transmits, and when the used channel returns, it releases the channel.

Therefore, one station does not continue to occupy the channel and use it, and each station is provided with a fair opportunity to access the channel.

FIG. 9 shows an example of the configuration of a station that communicates connection control data via such a channel.

The IllS configuration of this station and its effects will be explained below.

The l frame data received by the receiver 23 is
The signal is taken into the serial/parallel conversion circuit 24 and supplied to the connection control section 25, line switching section 26, and packet switching section 27, respectively. These connection control unit 25, line switching unit 26, and packet switching unit 27 perform their respective functions by transmitting and receiving data to and from the CPU 29 and memory 30 via the CPU bus 28.

The frame synchronization detection circuit 31 detects the beginning of the frame from the synchronization signal inserted into the synchronization area, and at this detection timing, the reception timing generation circuit 32 is activated and the slot counter 33 is initialized. This slot counter 33 counts the word clock generated by the reception timing generation circuit 32 and detects the timing of each slot.

According to the slot timing signal generated by the slot counter 33, the aforementioned connection control section 25, line switching section 26, and packet switching section 27 know the input timing of the corresponding received data and input the data.

Further, transmission data from this station is selectively transmitted from the connection control section 25, line switching section 26, and packet switching section 27 via the selector 35 under the control of the transmission timing generation circuit 34, that is, in the format described above. The timing is controlled, the signal is applied to the parallel-to-serial conversion circuit 36, and then transmitted from the transmitter 37.

Note that when there is no transmission data from the station, the selector 35 selects
The signal received through the serial/parallel conversion circuit 24 is selected and applied to the parallel/serial conversion circuit 36.

This selector 35 allows communication data to bypass the station.

Further, the connection control section 25 is configured as shown in FIG. 10, for example.

That is, the connection control area detection unit 38 detects the connection control area of the received frame from the slot number detected and output by the slot counter 33.

By detecting this connection control area, the data in the connection control area in the received data is taken into the reception latch circuit 39.

The data taken into this reception latch circuit 39 is used in an empty channel horizontal circuit 40 to detect an empty channel, and a DA monitoring circuit 41 checks whether the data is addressed to the own station. Detected. If the data is addressed to the own station, the reception control section 42 is activated, and the reception data stored in the three reception latch circuits is transferred to the reception buffer 43 and taken into the CPU 29.

In this way, the connection control data communicated from the control station or another station is taken into the station and used for data communication control of the station.

When one station transmits, the transmission control section 44 is activated under the control of the CPU 29. When the transmission control section 44 receives a transmission command from the CPU 29, it waits for a detection signal from the empty channel detection section 40. Upon receiving the detection signal, the transmission control section 44
generates a transmission request and applies it to the transmission timing generation circuit 34, and also applies a transmission timing signal to the empty state flag generation section 45, the transmission buffer circuit 46, and the transmission latch circuit 47. As a result, the connection control data previously set in the transmission buffer 46 in accordance with the busy state flag indicating that the channel is in use and the calling request from the station are transferred to the transmission latch circuit 47, and from this transmission latch circuit 47 The connection control unit data will be sent via the .

After completion of such transmission, when the transmission control section 44 detects the return of the channel based on the signal from the connection control area detection section 38, it activates the empty state flag generation section 45 to release the channel.

Incidentally, in addition to the connection control data described above, the data communicated using the channel includes emergency data for maintaining and managing the network system. This emergency data includes system configuration change notifications, fault notifications from each station to the control station, responses to these notifications, and the like.

These emergency data must be transferred as soon as possible to maintain and manage the system, so unlike connection control data, a channel is acquired regardless of the empty status of the channel indicated by the empty status flag. It is considered possible.

In this case, if another station acquires a channel to transmit emergency data while transmitting emergency data, the previous emergency data will be lost, so a flag indicating this is set while transmitting emergency data. While this flag is set, transmission of emergency data from other stations is prohibited.

However, in such a system, emergency data for maintaining and managing the network system has a priority; for example, between a system configuration change notification and a failure notification from each station to the control station, the latter has a higher priority. However, if there is a station that is already transmitting a system configuration change notification, there is a problem in that the communication process for the failure notification will be passed to that station.

(Problem to be Solved by the Invention) As described above, in the access method in the conventional loop communication system, when access to a channel is in progress, a flag indicating that emergency data is being transmitted is set; During this time, transmission of emergency data from other stations is prohibited, so even if the latter notification has a higher priority, the system configuration change notification and the failure notification from each station to the control station will be sent first. If there is a station currently transmitting system configuration change notifications, there is a problem in that communication processing of high-priority failure notifications is delayed.

The present invention was made in response to this situation, and allows emergency data with a high priority to acquire a channel with priority in place of other emergency data even if it is already being transmitted. The purpose of the present invention is to provide a communication method that can transfer data, thereby realizing a highly practical large-scale network system.

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above objectives, the communication system of the present invention has the following features:
A plurality of stations including a control station are connected in a loop through a transmission path, and a frame has one or more channels for communication between each station and includes an idle status flag indicating an idle status of the channel. In the loop communication system, the frame is transmitted from the control station to the transmission path to surround the transmission path, and the station detects an empty/busy status flag of the frame to acquire an empty channel. , the station includes an emergency data flag that the station sets when transmitting emergency data, and data indicating the priority of the emergency data, and the station that sets the emergency data in white has a priority of the emergency data in the frame. If it is lower than the station, the channel is acquired regardless of the set state of the busy status flag and the emergency data flag.

(Function) In the communication system of the present invention, for example, high-priority emergency data such as emergency data related to maintenance and management of a network system is transmitted when other emergency data is already being transferred and the empty status flag and emergency data flag are flagged. Even if they are set, a channel can be acquired preferentially and data can be transferred quickly, making it possible to construct a highly practical large-scale network system.

(Example) Hereinafter, an example of the present invention will be described in detail based on the drawings.

FIG. 1 is a block diagram showing the configuration of a connection control section of a station in a loop communication system according to an embodiment of the present invention.
It is constructed by adding an emergency data flag detection/comparison section 51 and an emergency data flag/data generation section 52 to the conventional connection control section 25 shown in FIG. It is the same as shown in the figure.

FIG. 2 is a diagram showing the format of the channel in this embodiment, in which the emergency data flag 5 is added to the conventional channel format shown in FIG.
3 and priority data 54 is added.

The reception operation of the connection control section in this embodiment is exactly the same as that shown in the conventional example.

That is, the connection control area detection unit 38 detects the connection control area of the received frame from the slot number detected and output by the slot counter 33. By detecting this connection control area, the data in the connection control area in the received data is taken into the reception latch circuit 39.

The data taken into this reception latch circuit 39 is used to detect an empty channel by an empty channel detection circuit 40, and a DA monitoring circuit 41 detects whether the data is addressed to the own station. be done. If the data is addressed to the own station, the reception control section 42 is activated, and the reception data stored in the reception latch circuit 39 is transferred to the reception buffer 43 and taken into the CPU 29.

In this way, the connection control data communicated from the control station or another station is taken into the station and used for data communication control of the station.

On the other hand, when this station transmits, it is performed as shown in FIG.

First, the CPU 29 activates the transmission control section 44 when there is data to be transmitted. When receiving a transmission request from the CPU 29 (step 301), the transmission control unit 44 next checks whether the transmission data is emergency data (step 302).

As a result, if the data is not urgent, an empty channel is detected (step 303) and the data is transmitted (steps 304 and 305). If it is emergency data, an empty channel is detected in the same way (step 306), and if it is an empty channel, it is transmitted as before (steps 304 and 305).
. If the channel is not empty (if the channel is occupied), then the emergency data flag area of the channel being received is checked (step 307). Here, if the emergency data flag is set, the reception priority of the emergency data and the self-receiving priority are compared (step 308), and if the self-receiving priority is low, the emergency data is waited until the next channel and If the flag is not set, start transmission (step 309.3
05).

Further, if the self-imaging priority is high in step 308, transmission is started as is (steps 309 and 305).

The transmission control unit 44 activates the busy status flag generating unit 45 and the emergency data flag/data generating unit 52, and sets respective flags in the busy status flag area and the emergency data flag area of the channel format (step 309). )
. Next, the transmission data is read from the transmission buffer 46,
Transmission is performed (step 305).

After the transmission is completed, the transmission control unit 44 detects the connection control area detection unit 38
When the return of the channel is detected by the signal from the controller (step 310), the empty status flag generating section 45 is activated to release the channel (step 311).

In this way, according to the communication system of this embodiment, when each station transmits emergency data, even if other emergency data is already loaded on the received channel, the priority of the own station's emergency data is determined by the other station. If the priority of emergency data is higher than that of emergency data, the station can acquire the channel and transmit its own emergency data regardless of whether or not the channel is occupied.

Therefore, it becomes possible to quickly maintain and manage the system.

[Effects of the Invention] As explained above, according to the communication method of the present invention, for example, high-priority emergency data such as emergency data related to maintenance and management of a network system can be transmitted even if other emergency data is already being transferred. Even if the empty status flag and emergency data flag are set, a channel can be acquired preferentially and data can be transferred quickly, making it possible to realize a highly viable large-scale network system. .

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of a connection control section of a station in a loop communication system according to an embodiment of the present invention, and FIG.
3 is a flowchart for explaining the operation of the embodiment, FIG. 4 is a schematic configuration diagram of a conventional loop communication system, and FIGS. Figure 7 is a diagram showing the frame format in the same loop communication system, Figure 8 is a sequence diagram showing the operation of the connection control unit in the same system, and Figure 9 is a block diagram showing the configuration of the station in the same system. 10 are block diagrams showing the configuration of the connection control section in the system. 38... Connection control area detection unit, 39... Reception latch circuit, 40... Empty channel detection circuit, 41... DA
Monitoring circuit, 42... Reception control unit, 43... Reception buffer, 44... Transmission control unit, 45... Vacant status flag generation circuit, 46... Transmission buffer, 47... Transmission latch Circuit, 51... Emergency data flag detection/comparison section, 52... Emergency data flag/data generation section. Applicant Toshiba Corporation Patent Attorney Sasa Suyama - 2nd Wa 7th Nuo 52 8th

Claims (1)

[Claims] (1) A plurality of stations including a control station are connected in a loop through a transmission path, and each station has one or more channels for communication between the stations, and an idle status flag indicating the idle status of the channel is set. In a loop type communication system, the control station transmits a frame including a frame to the transmission path to surround the transmission path, and the station detects an empty/busy state flag of the frame to acquire an empty channel, The frame includes an emergency data flag that the station sets when transmitting emergency data, and data indicating the priority of the emergency data, and the station that has the emergency data determines the priority of the emergency data in the frame. A communication system characterized in that, if the channel is lower than that of the own station, a channel is acquired regardless of the set state of the busy state flag and the emergency data flag.