JPH04168829A - Communication control system - Google Patents

Abstract

PURPOSE:To transmit an acknowledge frame without intermission even when an acknowledge frame to be sent is missing due to a fault of a station on the way of a network or the like by setting a destination address of the acknowledge frame to a multiple address communication data frame not to a destination but to an address of a succeeding station. CONSTITUTION:Each of stations A-E of the network system employing a token passing bus access system has three sets of address information as a preceding station address, its own station address and a succeeding station address. A logic ring is formed on the network according to the sets of the address information and a token frame is being taken over in the order of a preceding station, its own station and a succeeding station. Suppose that a station C of the network has the token frame and sends a multiple address data frame. The multiple address data frame is one of immediate acknowledge request data frames. Each of the other stations A,B,D and E receives the multiple address data frame and sets succeeding station address information as a destination address of an acknowledge frame with respect to the multiple address data frame.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a communication control system, and particularly to a communication control system in a token passing bus access system of a local area network (hereinafter referred to as LAN).

[Conventional technology]

LAN protocols include token passing bus,
There is something called an access method.

This method is located in the lower layer of the LAN protocol, receives an information frame on the communication medium, and if it is a data frame addressed to the local station, reports the received information to the upper layer, and accesses the communication medium. The following international standard, established in 1987, is one of the protocols for performing control.

namely, ISO 8804-4 Information Handling Systems, Local Area Networks, Part 4, Token Passing Bus Access Methods and Physical Layer Standards (Info
rmation Processing System
s-Localarea networks-Part
4 Token Passing bus accesses
s method and physical 1ay
er 5 specificat-ions).

FIG. 3 shows a schematic diagram of a network system using the token passing bus access method.

Referring to FIG. 3, the network system connected to the token passing bus access method
- As an example, five stations, stations A to D, stations 1 to 5, and communication medium 6.
It is composed of.

Moreover, FIG. 4 is a diagram showing the format of a communication frame.

Access control to the communication medium 6 is performed using a token system. A token is a control frame that controls communication medium access rights, and a station that holds this token obtains the right to transmit data frames. Communication between each station is performed by receiving and passing this token from station to station.

Further, the physical shape of the communication medium 6 is a bus type, and the stations on the network, stations A to D 1 to 5, always use the communication medium 6.
Receive frames sent above.

Each station has three pieces of address information: a preceding station address, its own station address, and a succeeding station address, thereby logically forming a ring-shaped network as shown in FIG. In this logical ring, each station passes a token frame from the preceding station.

As shown in FIG. 4, the communication frame includes a control field,
It has a destination address field and a source address field. The control field in this field determines whether the frame is a token frame or a data frame.

The destination address field indicates the destination of the frame, and is usually set to the address of one station on the network.

The address of the transmitting station is set in the source address field.

The receiving side uses this information to determine whether the received frame is addressed to its own station.

Typically, data frames are sent to one station on the network. Then, the station that receives the data frame transmits a response frame in response to the data frame. The response frame is transmitted when the receiving station receives the token frame addressed to itself and obtains the right to transmit.

Furthermore, there is an immediate response request data frame, and when a data frame is transmitted in this format, the receiving station can immediately transmit a response frame even if it does not have a token frame. In the case of an immediate response request data frame, the transmitting station side also expects that a response frame will be sent after transmission and receives the frame on the communication medium.

As described above, in the case of one-to-one transmission and reception of data frames, by returning a response frame, it can be confirmed whether the data has been correctly transmitted to the other station.

On the other hand, data frames may be transmitted and received on a one-to-many basis.

The simultaneous broadcast data frame is that.

- A broadcast data frame is a transmission to all stations on the network and is constructed by setting a specific value (usually all bits to 1) in the destination address field.

Normally, the receiving station does not transmit a response frame to this broadcast data frame even if it is received. Therefore, in this case, the transmitting station cannot confirm whether or not the transmitted frame has been correctly received. Therefore, even if the data is not transmitted correctly, the broadcast data frame can only send limited information that has little effect on the receiving station or on network maintenance.

Furthermore, an immediate response request frame that requires a response frame for each frame cannot be transmitted as a broadcast data frame.

Here, as a method for transmitting a response frame to a broadcast data frame, there is a method that utilizes a logical ring configured on the network at that time.

In this system, a station that transmitted a broadcast data frame, for example, station A 1, is used as a base point, and response frames are sequentially transmitted to the transmitting station from eight stations 2 located at subsequent stations.

- Station A 1, which transmitted the broadcast data frame, receives the response frames sent one after another, and selects a station whose address matches the address information of its own preceding station, in this case 0 station 4, i.e. By receiving the response frame transmitted from station D-4, it is determined that the response has ended.

- The station that received the broadcast data frame, for example 0 station 3
Now, if the content of the source address field of the received data frame matches the address information of the preceding station, that is, 8 stations 2, held by the own station, a response frame is immediately transmitted.

In other cases, stations other than the own station, i.e., A stations 1 and 8.
Station 2. When each station, D station B and E station 5, receives a response frame transmitted, and the content of the source address field of that frame matches the address information of the preceding station, that is, station 8 2, it transmits the response frame. It was something to do.

[Problem to be solved by the invention]

In the conventional token passing bus access method described above, - When a broadcast data frame is transmitted, the receiving station uses the logical rings configured at that time and responds in the order of the logical rings. The purpose was to transmit frames.

However, in this method, when a station is transmitting response frames in the order of logical rings, if a station leaves the logical ring due to a failure etc., the station following the departing station will receive the response frame. The drawback was that transmission was impossible.

As a result, there is a drawback that time is wasted until the station with the transmission right confirms that an abnormality such as a failure has occurred on the response ring.

Furthermore, there is a drawback that the transmission of a response frame to a broadcast data frame is also interrupted midway.

[Means to solve the problem]

In the communication control method of the present invention, a communication station on a network formed on a bus-type communication medium has address information consisting of a preceding station address, an own station address, and a succeeding station address,
A logical ring is formed by the address information, and among the communication stations, a token station that owns a token frame indicating a transmission right performs communication by transmitting a data frame, and after the transmission of the data frame is completed, the token frame is Preceding station according to address information.

In a token passing bus access method in which communication is controlled by transferring data in the order of the local station and subsequent stations, the data frame is transmitted to all communication stations other than the bait token station forming the logical ring. The subsequent station address information is set as the destination address of the response frame to the broadcast data frame that is being transmitted.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a diagram showing a processing flow of a first embodiment of the present invention, and shows a procedure for transmitting a response frame to a broadcast data frame.

Referring to FIG. 1, the communication control system of the present invention is comprised of ten nodes from the first node 11 to the tenth node 20.

FIG. 3 is a diagram schematically showing a network system using a token passing bus access method including the communication control method of the present invention, and is also used to explain the conventional example.

Referring to FIG. 3, the network system connected to the token passing bus access method
- As an example, five stations, stations A to D, stations 1 to 5, and communication medium 6.
It is composed of.

As mentioned above, each station in a network system using the token passing bus access method has three pieces of address information: the preceding station address, the own station address, and the succeeding station address. Taking Figure 3 as an example, station A 1 is the address of 0 station 4 as the preceding station address and 8 as the succeeding station address.
It will have the address of station 2. Similarly, other stations have three pieces of address information.

Using these address information, a logical ring is constructed on the network, and token frames are received and delivered in the order shown in FIG.

Next, the communication frame used in this embodiment will be explained.

FIG. 4 is a diagram showing the format of a communication frame.

A communication frame consists of a control field, a destination address field, a source address field, a data field,
and a frame check sequence (Fe2).

The control field defines the type of frame. Broadly speaking, there are two types of frames.

One of them is a control frame for controlling the logical ring, which includes a token frame.

The other one is a data frame used for information communication between each station. This data frame further includes three types of frames.

The first one does not require an immediate response to the data frame transmission, the second one requires an immediate response from the destination station to the data frame transmission, and the third one does not require an immediate response to the data frame transmission. is a response frame to an immediate response request.

Here, an immediate response means that a station that receives a data frame immediately transmits a response frame on the spot.

In this embodiment, it is assumed that data communication is performed using this immediate response request data frame.

The immediate response request data frame has a destination address field and a source address field, where the address of the destination station is set in the former and the address of the transmitting station is set in the latter. At this time, a data frame in which all bits in the destination address field are set to "1" becomes a broadcast data frame, and all stations on the network receive the data frame.

A broadcast data frame is a data frame used when a transmitting station sends data to all other stations.

Next, with reference to FIG. 1, the procedure for transmitting a response frame when a -broadcast data frame is received will be described.

Now, in FIG. 3, it is assumed that station 0 3 on the network holds a token frame and transmits a broadcast data frame. As mentioned above, this broadcast data frame is one of the immediate response request data frames.

The other stations, A station 1, 8 station 2, 0 station 4, and 8 station 5, receive this simultaneous broadcast data frame, but they know from the control field that it is an immediate response request data frame. Further, the destination address field indicates that the frame is a broadcast data frame, and the source address field indicates that the frame was transmitted from station 03.

First, the processing procedure of the 8th station 5 will be explained.

According to the processing flow shown in FIG. 1, when the -broadcast data frame is received, the process proceeds from the first node 11 to the second node 12. Here, the source address of the received -broadcast data frame is the address of station 3. Since station 0 3 is located at the preceding station for station 6 5, the determination of the second node 12 is Yes. As a result, the processing is performed at the ninth node 19.
Proceed to.

When the ninth node 19 receives a response frame, it sets its own subsequent station address information in the destination address field of the response frame and transmits it, instead of the source address of the received broadcast data frame. 0 example 6
In the case of station 5, address information indicating 0 station 4 is set. As a result, the process proceeds to the tenth node 20, and the process of transmitting a response frame to the simultaneous broadcast data frame at the six stations 5 is completed.

Next, the processing procedure for station 0 4 will be explained.

Similarly to station 5, - upon receiving the broadcast data frame, the first node 11 to the second node 1 in the processing flow of FIG.
At the second node 12 , the determination is No because station 0 3 is not the preceding station of station 0 4 , and the process proceeds to the third node 13 .

The third node 13 receives response frames transmitted from other stations in response to the broadcast data frame. Based on the positional relationship on the communication network logical ring, station 0 4 receives the response frame transmitted from the previous 6 stations 5. When the response frame is received, the processing starts at the third node 1
3 to the fourth node 14.

The fourth node 14 determines whether the destination address of the received response frame matches the preceding station address of the fourth node. In this case, since the response frame sent by station 6 is received, the destination address is 0 and station 4.
address, and the determination is No. As a result, the process proceeds to the fifth node 15. The fifth node 15 determines whether the source address of the received response frame matches the preceding station address of its own station. In this case, since station 6 5 is the preceding station of station 0 4, the answer is Yes.

As a result, the process proceeds to the ninth node 19.

As described above, the ninth node 19 sets its own subsequent station address information in the destination address field of the response frame and transmits the response frame. In the case of station 0 4, the address information of station A 1 is set. As a result, the process proceeds to the tenth node 20, and the process of transmitting a response frame to the broadcast data frame at station 0 4 is completed.

Next, the processing procedure of station A 1 will be explained.

For station A 1, the processing proceeds in the same way as for station 0 4 up to the third node 13.

However, the first response frame received is the one sent by the 6th station 5, and its destination address is equal to the address of the 0th station 4. Therefore, the 4th node 14 determines Yes, and the 6th node 16 sends the processing. move on.

At the sixth node 16, a timer for measuring a predetermined time is activated, and the process proceeds to the seventh node 17.

The time measured by this timer is that after the preceding station, in this example 1 is 0 station 4, receives the response frame of the broadcast data frame, it determines whether it is the turn for that station to transmit.
As a result, the time required to complete transmission of the response frame is longer than that required for transmission.

The seventh node 17 determines whether the timer that started operating at the sixth node 16 has timed out.

The eighth node 18 determines whether a response frame has been received.

These determinations are repeated until either the seventh node 17 or the eighth node 18 is established.

In the case of A station 1, after station 6 transmits a response frame, 0
Since station 4 subsequently transmits a response frame, it receives a Yes determination at eighth node 18 before timeout.

Processing then proceeds from the eighth node 18 to the ninth node 19, and a response frame is transmitted. The destination address at this time is the address of the 8th station 2.

Here, it is assumed that the transmission system of the A station 1 has failed and the response frame is actually not transmitted onto the communication medium 6.

The processing procedure of the 8th station 2 in this state will be explained.

The process proceeds in the same way as station A 1 for station 8 2, and when it receives the response frame sent by station 0 4, it sends a message from the fourth node 14 to the sixth node.
Processing continues to node 16.

Then, the timer operates as in the case of A station 1, and A station 1
wait for the response frame to be sent.

However, as described above, since station A 1 does not transmit due to a failure, the timeout condition is met. After the timeout is established, the process proceeds to the ninth node 19 and transmits a response frame. The destination address at this time is 0 station 3
address. As a result, the process advances to the tenth node 20, and the process of transmitting a response frame to the simultaneous broadcast data frame at the eight stations 2 is completed.

Station 03, which is the source of the broadcast data frame, receives response frames from each station and checks the response frame from station 8, which is located in the lead of station 3, to receive responses from all stations. know that it has ended.

Also, from the address information in the response frames transmitted by each station, it is known that station A 1 has left the network.

Next, a second embodiment of the present invention will be described.

FIG. 2 is a diagram showing a processing flow of a second embodiment of the present invention, and shows a procedure for transmitting a response frame to a broadcast data frame.

As with the first embodiment, the following description assumes that the network is implemented in the token passing bus access system shown in FIG. 3, and uses the communication frame format shown in FIG. 4.

The second embodiment basically has the same system configuration as the first embodiment, with the difference being the processing flow and the types of communication frames handled.

In the first embodiment, among the three types of data frames, an immediate response request data frame is used, and an immediate response is also provided to the broadcast data frame.

The second embodiment also deals with simultaneous broadcast data frames that are not immediate response data frames.

The response transmission procedure for the simultaneous broadcast data frame of this embodiment becomes the processing flow shown in FIG. 2, which is obtained by adding the 0th node 10 and the 11th node 21 to the processing flow shown in FIG.

Below, differences from the first embodiment will be explained with emphasis to avoid duplication of explanation.

When each station on the network transmits a broadcast data frame, if a response frame is required, it transmits it as an immediate response data frame as in the first embodiment described above. However, if a response from each station is not required, the data frame is not sent as an immediate response data frame.

The receiving side of each station determines whether the data frame received by the 0th node 10 is an immediate response data frame, according to the processing flow shown in FIG. If Yes, proceed to the first node 11.

In the case of No, the process proceeds to the tenth node 20 and ends the process.

When proceeding to the first node 11, if the received data frame is a simultaneous broadcast data frame, subsequent processing is performed according to the same flow as in the first embodiment; otherwise, the process proceeds to the first node 11. The process proceeds to the node 21, receives a normal response frame, and ends the process, so a description thereof will be omitted here.

Although the present invention has been described in detail above, the present invention is not limited to the above embodiments and can be modified in various ways.

〔Effect of the invention〕

As explained above, according to the present invention, - By setting the destination address of a response frame to a broadcast data frame to the address of a subsequent station instead of the destination, response frames are transmitted due to failure of a station on the way on the network, etc. Even in the case of a dropout, the station following the failed station can send the response frames in a shorter order after a predetermined period of time has elapsed, so that response frames can be transmitted without interruption.

In addition, by checking the destination address, it is possible to know the order in which the response frame of the own station is transmitted before the preceding station of the own station sends one response frame. In this case, there is an effect that an abnormality in the preceding station can be detected.

In addition, if an abnormality such as the one described above occurs during the response to a broadcast data frame, the preceding station and succeeding station address information of each station is updated on the spot to efficiently maintain and regenerate the logical ring. The effect is that it can be done.

Furthermore, since response frames can be received from all stations on the network in the order of the logical rings, it is possible to check which stations are connected to the network at a certain point in time and the order of the logical rings. It has the advantage that it can be used for various purposes.

[Brief explanation of drawings]

FIG. 1 is a process flow diagram showing a first embodiment of the present invention, FIG. 2 is a process flow diagram showing a second embodiment of the present invention, and FIG.
This figure is a diagram showing an outline of a network system using a token passing bus access method, and FIG. 4 is a diagram showing a format of a communication frame. 1 to 5: A to E stations connected to the network,
6... Communication medium, 10-21... 0th-11th nodes.

Claims (1)

[Claims] 1. A communication station on a network formed on a bus-type communication medium has address information consisting of a preceding station address, an own station address, and a succeeding station address, and a logical ring is formed by the address information. Among the communication stations, the token station that owns the token frame indicating the transmission right performs communication by transmitting a data frame, and after the transmission of the data frame is completed, the token frame is sent to the preceding station and the own station according to the address information. In a token passing bus access method in which communication is controlled by transferring data frames in the order of a station and a subsequent station, simultaneous transmission of the data frame to all communication stations other than the token station forming the logical ring; A communication control method characterized in that the following station address information is set as a destination address of a response frame to the information data frame. 2. The reception processing device of the communication station includes address decoding means for determining the preceding station address and the succeeding station address, and when the determined destination address information is equal to the preceding station address, the preceding station responds to the response. The device has a time measuring means that measures a predetermined response confirmation time longer than the time required to transmit a frame, and sets a next processing procedure when the response frame of the preceding station cannot be received even after the response confirmation time has elapsed. The communication control method according to claim 1, characterized in that: