JP3444719B2 - Network system using synchronous data link control procedure - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a synchronous data link control procedure (SDL) for connecting a plurality of control devices at long distances via a communication line.
The present invention relates to a network control device of a system that performs communication using C), and more particularly to a network control device that enables N: M communication by minimizing the influence of a failure on one part on the operation of the entire system.

[0002]

2. Description of the Related Art A loop method based on a communication control procedure of SDLC is known as a method in which a plurality of long-distance stations communicate via a communication line. In this system, a plurality of stations are connected in a single loop through a communication line, a frame is sent from the primary station to the loop communication line, and a plurality of secondary stations are sequentially connected in a certain transmission direction. 1 frame that has been visited
Perform 1: N communication by returning to the next station. The primary station transmits the frame to all secondary stations in the loop or a specific secondary station, and the secondary station receiving the frame confirms the destination address of the received frame and if it is addressed to itself. The secondary station that receives the frame, sends it to another secondary station in the loop without receiving it if it is not addressed to itself, and receives the frame,
Communication is performed by the method of returning the received response frame to the primary station.

As a document related to SDLC, published by Nikkei BP: Nikkei DataPro Data Communication Standard 199.
There is a 2.5 overview report "SDLC" IBM (industry standard and manufacturer standard DS8-321-051-058).

[0004]

DISCLOSURE OF THE INVENTION The conventional SDL described above
In C, a secondary station is sequentially connected from the primary station in a fixed transmission direction on a unidirectional unidirectional loop, and a loop is made to return to the primary station. It is a 1: N communication that communicates with all secondary stations. Therefore, between the secondary stations, data can be sent from the upstream secondary station in the loop to the downstream secondary station, but data cannot be sent from the downstream secondary station to the upstream secondary station. .

Further, since it is a unidirectional single loop,
When a failure occurs in a station or a transmission line on the loop, the frame from the primary station goes around the loop and does not return to the primary station, which causes a problem that communication in the loop cannot be performed.

An object of the present invention is to realize N: M communication by enabling data transmission and reception between secondary stations in a loop in a communication system adopting SDLC, and also to cause a failure on the loop. However, another object of the present invention is to provide a network control device that separates only the faulty part from the loop and enables continuous communication in the loop.

[0007]

The above-mentioned object is to provide a primary station device.
And a plurality of secondary station devices subordinate to the primary station device,
A loop that connects the primary station device and each secondary station device in sequence
Communicate with a synchronous data link control procedure that has a communication line
In the network system for performing the loop communication
Lines are duplicated so that the transmission direction of transmission information is reversed.
It Then, if 1: N transmission control is executed in each loop,
In both cases, the primary station device transmits the same transmission information at the same time to each rule.
Realizes N: M transmission by sending out to loop communication line
This is achieved by (claim 1).

The above-mentioned object is also the above synchronous data link system.
In the network system using the control procedure,
A failure has occurred in the loop communication line or each station device.
When each of the loop communication lines is next to the fault location,
Transmission method of the loop communication line that is a station device in contact
The station device on the downstream side becomes the primary station device and
A station device other than the station device that became the station device becomes the secondary station device.
By doing so, N: M transmission with the fault location isolated
Also it is, achieved (Claim 2).

[0009]

[0010]

In the present invention, the primary station device and each secondary station device
Sending information through a loop communication line that connects
Are provided so that they are reversed, and 1: N transmission is controlled in each loop.
Control, and the primary station device sends the same transmission information.
By sending to each of the loop communication lines at the same time, N: M
Since the transmission is realized, it is possible to perform communication between all the station devices in the loop in one round of the double loop.

Further, when a failure occurs in the station device or the communication line, the downstream station adjacent to the failure point will not be able to circulate the frame, so that the control frame for reporting the failure is sent to all stations in the loop. To the primary station by sending a frame to the primary station.
The next station can switch to the secondary station and continue communication in the loop.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is an overall configuration diagram of a communication system according to an embodiment of the present invention. This communication system is a controller that manages the communication in the loop 1
Next station 5a and three secondary stations 6 subordinate to this first station 5a
a, 6b, 6c are connected by a duplicated loop communication line 3, 4 with opposite transmission directions, and each station 5a, 6a,
6b and 6c are two modems 2a and 2b, 2c and 2 respectively.
d, 2e and 2f, 2g and 2h, one of which is connected to the line 3 and the other of which is connected to the line 4. When transmitting, the primary station sends the same frame to both communication lines 3 and 4 at the same time, and each loop communication line 3 and 4
The frame that has made a round is returned to the primary station.

In the communication system shown in FIG. 1, the loop 3
Is a primary station 5a → secondary station 6a → secondary station 6b → secondary station 6c
→ One loop with the primary station 5a, loop 4 goes through the primary station 5a → secondary station 6c → secondary station 6b → secondary station 6a → primary station 5a, and the loops are transmitted in opposite directions. . Therefore, a station downstream from a certain station on Loop 3 becomes an upstream station on Loop 4. Therefore, in the loop 3, the secondary station, which cannot send a frame to the partner station upstream from its own station, can send the frame because the partner station becomes the downstream station in the loop 4.

FIG. 2 is a diagram showing a time chart in which frames flow in loops 3 and 4. The same frame circulates in the opposite direction from the primary station 5a to the loop 3 and the loop 4 at the same time and returns to the primary station 5a. In this way, using the two loops, the frames transmitted by the primary station 5a are used as a trigger, and at the same time, the transmission directions are opposite to each other, and the same frame makes one round, so that communication between all the stations in the loop is possible. And N: M communication can be realized.

Here, each station, when no trouble has occurred in the communication system, loops 3 and 4
From this, the frame having the same content is received, but in this case, the frame received later is discarded by the processing described later.

FIG. 3 is a functional block diagram of each station. The communication control device 100 in the station has a transmission control unit 101 and a reception control unit 102 inside, and when transmitting the data of the control device 200 to another station, the data is converted into a frame and the transmission control unit. It is simultaneously transmitted to the same loop 3 and loop 4 via 101.

The reception control unit 102 includes a loop 3 and a loop 4
Is constantly monitored, and if the destination address in the frame on Loop 3 and Loop 4 is the same as the address set for the local station, the receiving process for that frame is started, and the receiving process for this frame ends normally. The received data is later passed to the control device 200.

FIG. 4 is a detailed block diagram of each station. The communication control device 100 includes an MPU 104, a ROM 105, and an R
AM 106, interface unit 107, transmission control unit 101, reception control unit 102, transmission number monitoring unit 103
And a counter 11 and an internal bus 109, which are connected to the control device 200 via the interface unit 107 and the common bus 110, and are connected to the two modems 2i and 2j.
(Indicated by 2a to 2h in FIG. 1) are connected to the loop 3 and the loop 4, respectively. MPU104 is R
It operates according to the program stored in the OM 105.

FIG. 5 is a flowchart of the transmission operation. When a request for data transmission is issued to the control device, the control device 200 sends an interrupt to the MPU 104. The MPU 104 that has received the interrupt uses the common bus 110
The data of the control device 200 is read out via the interface unit 107 and stored in the RAM 106.
A transmission command is issued to the transmission control unit 101 via 9. The transmission control unit that receives the command is the RAM 106.
After converting the data stored in to the frame format, the loop 3 and the loop 4 are transmitted via the modems 2i and 2j.
Send to.

FIG. 6 is a diagram showing an example of the frame format. The frame includes an "information frame" for sending data and a message, and a "control frame" for monitoring and controlling the configuration in the loop. The frame length has a variable length, and the flag sequence (F) 61, the receiving station address (D
A) 62, transmitting station address (SA) 63, control unit (C) 6
4, data 65, frame check sequence (FC
S) 66.

The data other than the data (Date) 65 has a fixed length. The flag sequence (F) 61 is a fixed pattern indicating the beginning and end of a frame, the receiving station address (DA) 62 is the destination address of the frame, the transmitting station address (SA) 63 is the address of the station that transmitted the frame, and the frame A check sequence (FCS) 66 indicates a bit string for error detection of this frame.

The control section (C) 64 has an "information frame".
In the case of, the transmission number (Ns) 67 of the number indicating the frame transmission order and the reception number (Nr) of the number indicating the reception order of the frames
68 is entered, and in the case of “control frame”, commands and responses for loop monitoring and configuration control are entered.

FIG. 7 is a flowchart of the receiving operation. The reception control unit 102 constantly monitors the loop 3 and the loop 4 via the modems 2i and 2j, and the receiving station address in the frame from the loop 3 and the loop 4 is its own address or a broadcast address common to all stations. If the reception starts, the data (Date) in the frame is RAM
The data is stored in the RAM 106, and the MPU 104 transfers the data stored in the RAM 106 to the control device 200.

FIG. 8 is a flowchart showing the detailed procedure of the receiving process. When the primary station 5a or the upstream secondary station sends a frame through the loop 3 and the loop 4,
The reception control unit 102 determines the receiving station address (D
A) Reception is started when 62 is the own station address or broadcast address. In this case, in parallel with the operation of the reception control unit 102, the transmission number monitoring unit 103
Is the transmission number (Ns) 6 of the control unit (C) 64 in the frame
7 is confirmed, and if the same frame has already been received from either loop 3 or loop 4, the frame received this time is discarded. If the frame received this time is a new frame, data is received from this frame, and the reception number (Ns) obtained by adding “1” to the transmission number (Ns) at the counter 11 (N
r) into the frame. Then, the transmission control unit 101
Sends the frame and a reception response downstream of the loop that received the frame. By this method, when a station receives a frame having the same transmission / reception number from two loops, the frame received later is discarded so that the same data or information is not duplicated.

FIG. 9 is a diagram showing an operation chart of transmission control. The transmission operation in the loop is a go-ahead signal (GA) of seven "1" patterns following the last "0" or "0" of the flag sequence (F) 61 at the end of the frame transmitted by the primary station 5a. The operation is triggered by "0" of 70. When the secondary station 6a having the data to be transmitted receives the go-ahead signal (GA) 70, the secondary station 6a receives the go-ahead signal (G).
A) The last "1" of seven consecutive "1" s in 70 is converted into "0", and a frame is constructed as a flag sequence (F) and transmitted downstream.

At this time, a series of "0" in the last flag sequence (F) 61 of the frame and a continuous "1" representing the standby state from the upstream station is a go-ahead signal (GA) 70.
Therefore, the next downstream secondary station 6b can similarly perform frame transmission operation. Finally, the primary station 5a confirms that the go-ahead signal (GA) 70 has returned, and returns to the first transmission operation.

Next, a description will be given of the configuration control of intra-loop communication when an abnormality such as an abnormality in the communication line in the loop, a fault in a station, or a power failure occurs. According to the conventional example, the frame is
Normally, the primary station goes around the loop and returns to the primary station. However, if a failure occurs in the loop due to a communication line error in the loop, station failure, power failure, etc.
The transmission frame sent from the primary station is interrupted at the faulty point and does not go around the loop, and communication inside the loop becomes impossible.

On the other hand, in the communication system according to the embodiment of the present invention shown in FIG. 1, intra-loop communication is possible even if a failure occurs. This will be described with reference to FIGS.

In FIG. 10, the secondary station 6b on the loop
However, if communication control becomes impossible due to a failure or power failure, the frame or GA signal sent from the primary station 5a to the loop 3 and the loop 4 is interrupted at the secondary station 6b, and the loop 3
Then, after the secondary station 6c on the downstream side, the loop 4 does not flow after the secondary station 6a on the downstream side.

A station adjacent to the faulty station 6b on the downstream side in the transmission direction, a secondary station 6c in loop 3 and a secondary station 6a in loop 4.
Each of the reception control units 102 of 1 detects that the frame or GA signal has stopped flowing. Then, the transmission control unit 101 sends control frames 41 and 42, which report the occurrence of abnormality to all stations in the loop, to the loops 4 and 3, and at the same time, the secondary station 6c becomes a new primary station of the communication line 3. 5c, and the secondary station 6a becomes a new primary station 5b of the communication line 4. On the other hand, the existing primary station 5a that has received the control frames 41 and 42 sets itself as the secondary station 6d.

In the communication line 3 and the communication line 4 separated from the secondary station 6b of the faulty station, the new primary station 5c and the new primary station 5b of the respective communication lines 3 and 4 respectively serve as the primary station and the frame 3
4 and 35 are started to be transmitted, and in the communication line 3, the primary station 5c → 2
A frame flows from the next station 6d to the primary station 5b, and a frame flows from the primary station 5b to the secondary station 6d to the primary station 5c on the communication line 4, and N: M communication can be continued.

As described above, according to this embodiment, when a failure occurs in the loop, the first downstream station adjacent to the failure point of each loop detects that the frame cannot be received. Since a control frame that reports the occurrence of a failure is sent to all stations in the loop, and it becomes a new primary station of the loop (communication line) and starts sending frames downstream in the transmission direction, N: M communication is performed except for the failed station. You can continue.

[0034]

According to the present invention, it is possible to change the 1: N communication by the SDLC loop method to the N: M communication.
Even if a failure occurs on the communication line, the entire system does not become incommunicable, and the reliability of the communication system is improved.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of a communication system according to an embodiment of the present invention.

FIG. 2 is a time chart in which frames of loop 3 and loop 4 shown in FIG. 1 flow.

FIG. 3 is a functional configuration diagram of each station shown in FIG.

FIG. 4 is a detailed block configuration diagram of each station.

FIG. 5 is a flowchart of a transmission operation.

FIG. 6 is a diagram showing an example of a frame format.

FIG. 7 is a flowchart of a receiving operation.

FIG. 8 is a flowchart of a reception process.

FIG. 9 is an operation chart for transmission control.

FIG. 10 is a configuration diagram of a communication system when a failure occurs.

FIG. 11 is a flowchart of configuration control in the event of a failure.

[Explanation of symbols]

1 ... Station, 2 ... Modem, 3,4 ... Loop, 5 ... Primary station, 6
… Secondary station, 11… Counter, 31-34… Frame, 4
1, 42 ... Control frame, 61 ... Flag sequence (F), 62 ... Receiving station address (DA), 63 ... Sending station address (SA), 64 ... Control unit (C), 65 ... Data (Dat
a), 66 ... Frame check sequence (FCS), 67 ... Transmission number (Ns), 68 ... Reception number (Nr), 70 ... Go ahead signal (GA) 100 ... Communication control device, 101 ... Transmission control unit, 102 ... Reception Control unit 103 ... Transmission number monitoring unit,
104 ... MPU, 105 ... ROM, 106 ... RAM, 107 ...
Interface unit, 108 ... Common bus, control device 20
0.

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Sadao Mizokawa 5-2-1 Omika-cho, Hitachi-shi, Ibaraki Hitachi Ltd. Omika plant (72) Inventor Hisayuki Maruyama 5-chome, Omika-cho, Hitachi-shi, Ibaraki 2-1 Hitachi Ltd. Omika Factory (72) Inventor Hideo Ota 52-1 Omikacho, Hitachi City, Ibaraki Prefecture Hitachi Ltd. Omika Factory (72) Inventor Keijiro Hayashi Omikacho, Hitachi City, Ibaraki Prefecture 5-2-1, Hitachi Ltd. Omika Plant (56) References JP-A-54-41602 (JP, A) JP-A-60-10840 (JP, A) JP-A-59-41941 (JP-A) ) JP 8-18586 (JP, A) JP 2-188044 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H04L 12/42

Claims (2)

(57) [Claims] 1. A synchronization with a primary station, and a plurality of secondary stations subordinate to the primary station, and a loop communication line which connects the primary station and the secondary stations in order In a network system for performing communication in a data link control procedure, the loop communication line is provided in double so that transmission directions of transmission information are reversed, and 1: N transmission control is executed in each loop and
A network system using a synchronous data link control procedure, wherein the next station device realizes N: M transmission by sending the same transmission information to each of the loop communication lines at the same time. 2. When a failure occurs in each of the loop communication lines or each of the station devices, each loop communication line is a station device adjacent to the failure point and a transmission direction of the loop communication line. The station device on the downstream side becomes the primary station device, and the station devices other than the station device that has become the primary station device become the secondary station devices, thereby realizing N: M transmission with the fault location isolated. A network system using the synchronous data link control procedure according to claim 1.