JPH0748737B2 - Token protection method in token passing transmission - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a token passing transmission in which a token is circulated between a plurality of stations connected to a transmission path to transfer a transmission right. The present invention relates to a token protection method that protects a token so that it does not exist.

[Conventional technology]

In general, the data transmission using the token passing system, for example, as shown in FIG. 3, a plurality of stations ST ₀ ~ST _N is connected to the transmission line TL, each station ST ₀ ~ST _N
Has a preset station number and moves the token (transmission right) from the station ST ₀ having the smallest station number to the station having a sequentially larger station number, and the station ST having the largest station number By moving the token from _N to the station ST ₀ having the smallest station number, the tokens are sequentially circulated to move the transmission right, and only the station receiving the token acquires the transmission right to the desired station. I am trying to do data.

In this transmission procedure, as shown in FIG. 4, for example, the station ST ₀ acquires the transmission right and adds the frame F having the transmission destination station number, the transmission source station number, the transmission information part, and the frame status part to the token T. Assuming that data transmission is performed by sending the recorded data to the transmission path, this station ST ₀ monitors the line for a certain period of time and sends the data to the station ST _0.
The station ₁ further monitors until it starts transmitting data with the next station ST ₂ , and determines whether the station ST ₁ has received the token with data. And
After confirming that the station ST ₁ has started the transmission, the station ST ₀ is in the normal reception state until the transmission data addressed to itself arrives.

[Problems to be Solved by the Invention]

However, in the above-mentioned conventional token passing transmission method, since the monitoring time of each station is set to a constant value, the retry time due to the lapse of the monitoring time due to a defective data transmission is duplicated and the station between both stations is duplicated. Since the token cannot be received, both stations mistakenly judge that the other station has disappeared from the transmission line,
There is an unsolved problem that the tokens are likely to be sent to the same transmission path at both stations.

That is, as shown in FIG. 5, stations ST _A and S
Assuming that transmission is performed between two stations of T _B , first, at a time point t ₁ , the station ST _A performs transmission with data in which a frame is added to a token, and the station ST _B receives this and the station ST _A receives its own data. At time t ₂ after the transmission is completed, the station ST _B enters the reception state for monitoring whether the transmission is started to the next station. On the other hand, the station ST _B starts transmitting the token with data to the next destination (station ST _{A in} FIG. 5) at time t ₃ after receiving the transmission with data.

However, the transmission data for the station ST _B is at time t.
_If it is assumed that the data is destroyed due to noise or the like in step ₄ , station ST _A recognizes the reception error because the data is not received within the monitoring time of the other station, and time t ₅
The monitoring timer is reset with and the state becomes monitoring again. Further, the station ST _B also enters the monitoring state of monitoring the data reception of the partner station at time t ₆ after the completion of the data-attached transmission.

Then, when the monitoring timer of the station ST _A times out at time t ₇ , token transmission for retry is performed at time t ₉ thereafter. At this time, if the monitoring timer of the station ST _B times up at time t ₈ before time t ₉ ,
As a result, the station ST _{B is} also in the transition to the retry transmission mode, and cannot receive the token transmitted from the station ST _A.

On the other hand, the token transmitted from the station ST _B at time t ₁₀ is in the process of transition from the transmission mode in which the station ST _A transmitted the token to the partner station monitoring mode, so that the token cannot be received.

This state is repeated by the number of retries is set in advance, but when neither during which the station ST _A and ST _B can not perform reception of the token, both stations ST _A and ST _B are both other party station Transmission line TL
The link is dropped as if it was lost, and tokens are generated from both stations at the same time.

Therefore, the present invention has been made by paying attention to the unsolved problem of the above conventional example, and it is possible to protect the token by preventing the existence of two or more tokens on the same transmission line. It is intended to provide a token protection method in passing transmission.

[Means for Solving the Problems]

To achieve the above object, according to the present invention, in token passing transmission in which a token is circulated among a plurality of stations connected to a transmission path to transfer a transmission right, a transmitting side station holding a token transfers the token When a token is sent to the receiving station to be handed over, the monitoring until the receiving station sends to the next station is monitored at different monitoring times corresponding to the station numbers assigned to each station, When the transmission to the next station is detected, the communication is in the receiving state until the token addressed to itself arrives, and when the transmission to the next station cannot be detected within the monitoring time, the token is transferred to the receiving station that passes the token to the retry transmission mode. It is characterized by doing.

[Action]

According to the present invention, the plurality of stations connected to the transmission line are monitored for the transmission state of the token passing station at the monitoring time corresponding to the station number assigned to them, so that the noise between the two stations can be reduced. Thus, when the transmission data disappears, the retry state in which the token is retransmitted is prevented from being duplicated and the state becomes unreceivable, and it is protected so that two or more tokens do not exist on the same transmission path.

〔Example〕

 Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the present invention.

In the figure, ST _i is a station connected to the transmission line TL and includes a transmission control unit 2 and a reception control unit 5.

The transmission control unit 2 has a built-in monitoring timer 2a, switches the selection circuit 3 to the transmission control unit 2 side in the transmission mode, and transfers the data in the transmission data memory 3 to the transmission line TL via the line driver 1.
The monitoring timer 2a is set after the data is transmitted, and when the detection signal from the carrier detection unit 8 described later is received, the monitoring timer 2a is reset, and when the monitoring timer 2a times out, Resend the token. Here, the set time of the monitoring timer corresponds to the station number assigned to each station at the time of network construction, and the monitoring time sequentially increases by the predetermined time α every time from the station with the smaller station number to the station with the larger station number. Is set.

On the other hand, the reception control unit 5 receives the data via the line receiver 4, and when the data is for itself, stores it in the data memory 6 for receiving the data.

The data received by the line receiver 4 is also supplied to the carrier detection unit 8. The carrier detection unit 8 receives the data via the line receiver 5, detects whether there is data on the transmission line TL, and when there is data, sends a carrier detection signal to the transmission control unit 2. To do.

Further, a waveform warping unit 9 serving as a regenerative repeater is inserted between the selection circuit 3 and the line receiver 5, and in the reception state, the waveform shaping unit 9 corrects the transmission distortion of the received data and the selection circuit 3 and It is sent to the transmission line TL via the line driver 1.

Next, the operation of the above embodiment will be described with reference to FIG. 2 corresponding to FIG. 5 of the conventional example.

First, in the monitoring timer 2a of the stations ST _A and ST _B , the monitoring time of the station ST _B is previously selected as T + α with respect to the monitoring time T of the station ST _A corresponding to the station number (ST _A <ST _B ). It is assumed that

Then, at time t ₁ , the station ST _A that has acquired the transmission right
The transmission control unit 2 of the above performs transmission with data to the station ST _B by adding a frame having a predetermined destination station number, source station number, information section and frame status section to the token, and then at time t ₂ . The monitoring timer 2a is set and the partner station is in the monitoring state. On the other hand, the station ST _{B that} has received the data-attached transmission similarly performs data-attached transmission at time t ₃ .

Then, at time t ₄ , when the data with transmission of station ST _B is destroyed due to noise or the like, station ST _A recognizes the reception error in the monitoring state of the other station, and at time t 4.
_{At 5} the monitoring timer 2a is reset and a new partner station monitoring is executed again.

The station ST _B also shifts to the partner station monitoring state at time t ₆ after the end of the data-attached transmission.

After that, the monitoring timer 2a of the station ST _A times out at time t ₇ , transitions to a retry state in which the token is retransmitted, and the token is retransmitted at time t ₈ .

At this time, the station ST _B cannot receive the token from the station ST _A because the monitoring timer 2a has timed up at the time t ₉ after the time t ₈ and has similarly transitioned to the retry state. At time t ₁₀ , station ST _B
Although the token is transmitted from the station ST _A , the station ST _A is in the transition to the partner station monitoring state after the token transmission and cannot receive the token from the station ST _B.

However, since the monitoring time set in the monitoring timer 2a of the station ST _A and the station ST _B is deviated by a predetermined time α, while the retry state is repeated for several times, the timing of the token retransmission is deviated. as the t _11, prevents the retry status of the station ST _a and ST _B overlap, so that the larger the station ST token station number is a small station ST _a monitoring state of _B station number is received .

Therefore, both stations ST _A and ST _B do not erroneously determine that the other station has disappeared from the transmission line, and the tokens from both stations ST _A and ST _B are transmitted at the same time.
The token is never transmitted to the TL, and the token can be securely protected.

In the above embodiment, the case of the token bus system in which a plurality of stations are connected to one transmission line has been described, but the token ring system in which a plurality of stations are connected to a ring-shaped transmission line is also described. It goes without saying that the present invention can be applied.

〔The invention's effect〕

As described above, according to the present invention, in the token passing transmission method in which a plurality of stations are connected to the transmission line, the monitoring time in the partner station monitoring state after token transmission is set to the station number assigned to each station. Since the corresponding monitoring time is set differently, it is possible to prevent the retry status where the token is retransmitted from overlapping between the predetermined stations due to data transmission / reception failure, and the other station is connected to the transmission line. However, it is possible to obtain the effect of reliably preventing the existence of two or more tokens on the same transmission line by erroneously determining that they have disappeared.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a time chart used for explaining the operation of the present invention, and FIG.
FIG. 4 is a block diagram showing an example of a network adopting the token passing system, and FIGS. 4 and 5 are time charts for explaining the operation of the conventional example. In the figure, ST _{1 to} ST _N and ST _A and ST _B are stations, 1 is a line driver, 2 is a transmission control unit, 3 is a selection circuit, 4 is a transmission data memory, 5 is a line receiver, 6 is a reception control unit,
Reference numeral 7 is a reception data memory, 8 is a carrier detection unit, and 9 is a waveform shaping unit.

Claims (1)

[Claims] 1. In token passing transmission in which a token is circulated between a plurality of stations connected to a transmission path to transfer a transmission right, a transmitting station holding a token sends a token to a receiving station that delivers the token. When a token is transmitted by the receiving station, the receiving station monitors the transmission to the next station at different monitoring times corresponding to the station numbers assigned to each station, and detects the transmission to the next station. Then, it will be in communication reception state until the token addressed to itself arrives, and when transmission to the next station cannot be detected within the monitoring time, it transits to the retry transmission mode of the token to the receiving side station passing the token Token in passing transmission Protection system.