JPH0210944A - Access system in loop communication system - Google Patents

Abstract

PURPOSE:To attain the communication with high efficiency in response to a load of access request to a channel by devising the system such that a channel is used continuously when new transmission data exists with a few access requests. CONSTITUTION:In the presence of a transmission request to a station, a CPU 7 starts a transmission control section 29 and when an idle state is detected by an idle channel detector 23, the channel is set busy and a channel release request flag 33 is reset. Succeedingly, a transmission data is read and sent from a transmission buffer 30. After the end of transmission, the control section 29 detects the return of the channel used by a connection control area detection section 21. If no new transmission command exists from the CPU 7 before the detection of return and and channel in use is released. On the other hand, in the presence of a new transmission command and a signal from a flag detector 33 remains reset, the control section 29 makes transmission and uses the channel continuously. when the signal from the detection section 33 is set, the control section 29 release the channel.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to an access method for a loop communication system that can be applied to a large-scale 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, such as OA network systems and factory automation network systems.

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

In order to meet these demands, optical communication technology has excellent compatibility with packet switching and circuit switching, and the advantage of optical communication technology is that it is easy to construct large-scale network systems, such as the one shown in Figure 4. , a loop communication system in which each station is connected in a loop via a transmission path is attracting attention.

Also, as the frame format, for example, the 5th
As shown in the figure, a frame with a fixed period is divided into a synchronization area, a connection control area, a circuit switching area, and a packet switching area, and the circuit switching area and packet switching area are used according to the traffic characteristics of the terminal and branch line. is considered. Furthermore, as shown in FIG. 6, it is naturally possible to create a system in which the packet exchange area is eliminated.

Note that circuit switching is transparently realized by providing a large number of slots in the circuit switching area and allocating the slots according to requests from terminals. Connection control data for this slot assignment is communicated using connection control areas set by dividing the frame, for example.

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

Format A consists of a synchronization area, an n-channel connection control area, a circuit switching area, and a packet switching area.

Format B consists of a synchronization area, an n-channel connection control area, and a circuit switching area.

Each channel in the connection control area of format A and format B described above is set to a different band, and each channel is used individually to communicate connection control packets between each station and the control station. ing.

Note that the number of channels and bandwidth of the connection control area to be 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. Specifically, the number of channels and the band may be set, for example, at the time of system configuration.

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

In addition, the format of a channel in the connection control area is, for example, as shown in C in FIG. It consists of length, data and its check code.

Using such a channel, connection control data is communicated as shown in FIG. 8, and control of outgoing and incoming calls, etc. is performed. Connection control data is generally short data,
In large-scale networks, large amounts of these data are generated. Therefore, in order to prevent one station from continuing to monopolize the channel, an access method is adopted in which the size of the data portion 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 monopolize the channel 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.

To explain the configuration and operation of this station, one frame of data received by the receiver 1 is taken into the serial/parallel converter circuit 2 and sent to the connection control section 3, circuit switching section 4, and packet switching section 5, respectively. Supplied. These connection control parts 3
, the line switching section 4, and the bacherato switching section 5 perform their respective functions by transmitting and receiving data between the CPU 7 and the memory 8 via the CPU bus 6.

The frame synchronization detection circuit 9 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 10 is activated and the slot counter 11 is initialized. This slot counter 11 counts word clocks generated by the reception timing generating circuit 10 and detects the timing of each slot.

In accordance with the slot timing signal generated by this slot counter 11, the connection control section 3, line switching section 4,
The packet exchange unit 5 learns the manual timing of the corresponding received data and inputs the data.

Further, transmission data from this station is transmitted to the connection control section 3 and the line switching section 4 under the control of the transmission timing generation circuit 12.
, from the packet exchange unit 5 via the selector 13, that is, timing-controlled in the format described above, is provided to the parallel-to-serial conversion circuit 14, and transmitted from the transmitter 15.

The selector 13 selects the signal received via the serial-to-parallel conversion circuit 2 and supplies it to the parallel-to-serial circuit 14 when there is no transmission data from the station. This selector 13 allows communication data to bypass the station.

By the way, the connection control section 3 is configured as shown in FIG. 10, for example.

That is, the connection control area detection unit 21 detects the connection control area of the received frame from the slot number detected and output by the slot counter 11.

By detecting this connection control area, the data in the connection control area in the received data is taken into the reception latch circuit 22.

The data taken into the reception latch circuit 22 is used to detect an empty channel by the empty channel detection circuit 23, and the DA monitoring circuit 24 detects whether the data is addressed to the own station. has been done. If the data is addressed to the own station, the reception control unit 25 is activated, and the reception data stored in the reception latch circuit 22 is transferred to the reception buffer 26 and taken into the CPU 7.

The connection control data communicated from the control station in this manner is taken into the station and used for data communication control of the station.

On the other hand, when the station transmits, the transmission control unit 29 is activated under the control of the CPU 7. When the two transmission control units receive a transmission command from the CPU 7, they wait for a detection signal from the empty channel detection unit 23. Upon receiving the detection signal, the transmission control unit 29 generates a transmission request, and sends this to the transmission timing generation circuit 1.
2, and also applies a transmission timing signal to the transmission buffer circuit 30 and the transmission latch circuit 31. As a result, the transmission buffer circuit 30
The connection control data set in the transmission latch circuit 3
1, and this transmission latch 31 sends out the connection control data via the aforementioned selector 31.

After completion of such transmission, when the transmission control section 29 detects the return of the channel based on the signal from the connection control area detection section 21, it activates the empty status flag generation section 32 to release the channel.

By the way, in such a system, in order to return the previously used channel to an empty state after transmission is completed,
After detecting the return of the previously used channel, the channel is released.

For this reason, even when there is no transmission request from another station, that is, when there is a low load on access to the channel, new transmission data cannot be transmitted until at the earliest one frame later, resulting in a problem of poor efficiency.

(Problem to be solved by the invention) As described above, with the access method in the conventional loop communication system, even when access to the channel is under low load, new transmission data cannot be transmitted until at the earliest one frame later. , there is a problem of poor efficiency.

The present invention was made based on the above circumstances, and is a loop communication system that can perform efficient communication according to the load of access requests to a channel and realize a highly practical large-scale network. Its purpose is to provide an access method.

[Structure of the Invention] (Means for Solving the Problems) The present invention connects a plurality of stations including a control station in a loop through a transmission path, and has one or more channels for communication, and A frame including a first flag indicating the empty/busy state of the channel is sent from the control station to the transmission path, circulates around the transmission path, and the station acquires the empty channel by detecting the first flag of the frame. In such a system, the frame includes a second flag that is set only when the first flag detected at the time of transmission by the station is in the blocked state, and the station is configured to transmit new transmitted data after the end of transmission. The second flag included in the return frame is in the reset state, and the channel that was being transmitted until then is continued to be used.

(Function) In the access method of the loop communication system of the present invention, when each station has many access requests to a channel, the station that was using the channel releases the channel with one transmission, and If there is new data to transmit, the channel can continue to be used. Therefore, efficient communication can be performed according to the load of access requests to the channel, and a highly practical large-scale network can be realized.

(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.
A channel release request flag detection unit 33 and a channel release request flag generation unit 3 are added to the conventional connection control unit 3 shown in FIG.
The structure of the other stations is the same as that shown in FIGS. 9 and 10.

FIG. 2 is a channel format diagram in this embodiment, which is obtained by adding a channel release request flag area to the conventional format diagram of FIG. 7C.

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 21 detects the connection control area of the received frame from the slot number detected and output by the slot counter 11, and by detecting the connection control area, the data of the connection control area in the received data is detected. is taken into the reception latch circuit 22.

The data taken into this reception latch circuit 22 is used to detect an empty channel in an empty channel detection circuit 23, and the DA monitoring circuit 24 detects whether or not the data is addressed to the own station. has been done. If the data is addressed to the own station, the reception control unit 25 is activated, and the reception data stored in the reception latch circuit 22 is transferred to the reception buffer 26 and taken into the CPU 7.

The connection control data communicated from the control station in this manner 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.

That is, when there is a transmission request (step 301), the CP
The transmission control unit 29 is activated under the control of U7.

When the transmission control section 29 receives the transmission command from the CPU 7, it waits for a signal from the empty channel detection section 23 (step 302).

Here, if the signal from the empty channel detection section 23 indicates an empty state, the transmission control section 29 activates the empty/busy state flag generating section 32 and the channel release request flag generating section 34 to The blocked state flag area is set to the blocked state, and the channel release request flag area is reset (step 303). Subsequently, transmission data is read from the transmission buffer 30 and transmitted (step 304).

On the other hand, if the signal from the empty channel detector 23 indicates a blocked state, the transmission controller 29 then waits for a signal from the channel release request flag detector 34 (step 305).
). If the signal from the channel release request flag detection section 33 remains reset, the transmission control section 29 activates the channel release request flag generation section 34, sets the channel release request flag area, and transmits the signal (step 30B).
).

Also, the area other than the channel release request flag area is passed through as is. If the signal from the channel release request flag detection section 33 is set, the two transmission control sections do nothing and allow the channel to pass through as is.

After the transmission is completed, the transmission control unit 29 detects the return of the channel based on the signal from the connection control area detection unit 21 (step 307).

If there is no new transmission command from the CPU 7 before the used channel is returned (step 30g)
, the vacancy state flag generating section 32 is activated to make the vacancy state flag area an empty state, and the channel is released (step 309).

On the other hand, if there is a new transmission command from the CPU 7 before the used channel is returned (step 308)
, waits for a signal from the channel release request flag detection section 33. If the signal from the channel release request flag detection unit 33 remains in the reset state (step 310)
, the transmission control unit 29 performs the above-described transmission operation to continue using the channel, and the channel release request flag detection unit 3
If the signal from 3 is in the set state (step 310)
Then, the transmission control unit 29 releases the channel (step 309) and enters a waiting state until an empty channel is acquired.

As described above, in this embodiment, each station acquires an empty channel and transmits data, releases the channel after one frame if another station has data to transmit, and transmits a new channel when the other station has no data to transmit. If there is data to be sent, the channel continues to be used, allowing efficient communication.

〔Effect of the invention〕

As explained above, according to the present invention, when there are few access requests and there is new transmission data, the channel can be used continuously, so efficiency is increased according to the load of access requests to the channel. It is possible to perform good communication and realize a highly practical large-scale network.

[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.
The figure is a channel format diagram in the same embodiment.
The figure is a flowchart for explaining the operation in the same embodiment, Figure 4 is a schematic configuration diagram of the loop communication system, Figures 5, 6 and 7 are frame format diagrams, and Figure 8 is connection control. FIG. 9 is a block diagram showing the structure of the station, and FIG. 10 is a block diagram showing the structure of the connection control section of the conventional station. 7... CPU, 21... Connection control area detection unit, 22
... Reception latch circuit, 23 ... Empty channel detection circuit, 25 ... Reception control section, 26 ... Reception buffer,
29... Transmission control unit, 30... Transmission buffer, 31
... Transmission latch circuit, 32... Vacant state flag generation section, 33... Channel release request flag detection section, 34.
...Channel release request flag generator. Applicant Toshiba Corporation Nippon Telegraph and Telephone Corporation Agent Patent Attorney Suyama Sa - Shizu Figure 4 Figure 5 Figure 6

Claims (1)

[Claims] (1) A frame in which a plurality of stations including a control station are connected in a loop through a transmission path, has one or more channels for communication, and includes a first flag indicating the empty state of the channel. In an access method of a loop communication system, the frame is transmitted from the control station to the transmission path, circulates around the transmission path, and the station acquires an empty channel by detecting the first flag of the frame, The frame includes the first frame detected at the time of transmission by the station.
a second flag that is set only when a flag of An access method for a loop communication system characterized by continuing to use a channel that has been transmitting only at certain times.