JPH11154961A - Communication system and polling control method in the communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a communication system where transmission of a text started earlier is not disturbed in the case of starting transmission of texts from pluralities of terminals connecting with a same channel and succeeding collision is avoided at the time of possible collision of text transmission among the terminals. SOLUTION: Upon receipt of a global polling command sent from a control station, a terminal checks to see whether or not a transmission text is in existence (S1). Then, whether or not other terminal starts text transmission is discriminated (S4). When not started, while the transmission text is sent one by one byte (S5), the transmission end of all texts is checked (S6). When transmission of text by other terminals is detected (S4), the transmission processing is interrupted (S8) and a transmission delay time is set (S9) by a random number table. At reception of a succeeding global polling command, whether or not the transmission delay time is set is confirmed (S2), the transmission of text is started with a delay of the set time. When the transmission of text is finished (S6), the transmission delay time is cleared (S7).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polling control method suitable for use in a communication system in which many terminals operate on the same line.

[0002]

2. Description of the Related Art A polling / selecting method is one of transmission control methods used in a communication system in which many terminals are connected to the same line. In this scheme,
A control station such as a communication processor controls a plurality of terminals operating as subordinate stations, and the control station performs control to allocate the plurality of terminals to a line in a time-division manner. However, the control station does not know at which point each terminal has to hold a message to be transmitted to the line. So the control station
A polling command for inquiring about the presence or absence of a transmission message is transmitted to each terminal connected to the line, thereby inquiring about the presence or absence of the transmission message in each terminal.

Here, in the polling / selecting method, inquiries are made to each terminal in accordance with the order of the terminals connected on the line and the like, whereby the advantage that message transmission does not collide between the terminals is obtained. Have. On the other hand, even if each terminal holds a message to be transmitted, each terminal cannot transmit the message until a polling command addressed to itself is received from the control station, and there is a problem that throughput is deteriorated.

For this reason, as a transmission control method other than the polling / selecting method, a global polling control method is used in which all terminals connected to a line are collectively inquired about the presence or absence of a transmission message. In this method, unlike the polling / selecting control method, each terminal does not need to wait until the turn of the polling schedule addressed to its own terminal comes, and a global polling command for permitting transmission of a message is received from the control station. At this point, any terminal can immediately transmit the message.

[0005]

However, when the above-described global polling control method is adopted, if a plurality of terminals hold a transmission message, a plurality of terminals simultaneously respond to one global polling command. Since transmission starts, the following problems occur.

That is, originally, only one terminal can transmit a message on one line at a time.
However, when a global polling command is received, a plurality of terminals transmit messages at the same time, as described above, so that transmitted messages collide on a line. Therefore, the transmitted messages are mutually disturbed, and a transmission failure (transmission failure) occurs in all terminals that have transmitted the messages at the same time. Moreover,
Even when receiving the next global polling command,
The same processing is repeated. For this reason, when employing the global polling control method, it is necessary to perform interlocked control among these multiple terminals so that multiple terminals do not transmit messages at the same time, resulting in problems such as complicated control. there were.

[0007] The present invention has been made in view of the above points, and an object of the present invention is to provide a communication system in which a plurality of terminals are connected to the same line, and in which a plurality of terminals start transmitting a message. It is an object of the present invention to provide a communication system and a polling control method in the communication system that enable normal operation without disturbing a transmission process of a terminal that has started transmitting a message. Another object of the present invention is to provide a communication system and a polling control method in the communication system which can avoid the next collision in advance when a message transmission collides between a plurality of terminals.

[0008]

In order to solve the above problems, the invention according to claim 1 provides a global polling command for permitting transmission of a message to each terminal connected to the same line by a control station. In a polling control method in a communication system in which each terminal transmits a message in response to the global polling command, when each terminal receives the global polling command and transmits the message, Investigate whether a terminal other than the terminal has started transmitting a message, and when detecting the start of the message transmission by the other terminal, suspend or suspend the transmission of the message in the own terminal, the other terminal If the start of message transmission by the terminal is not detected, the terminal transmits the message and completes the transmission process.

According to a second aspect of the present invention, in the first aspect of the present invention, each of the terminals checks whether or not the other terminal has started transmitting a message before transmitting the message, and determines whether the other terminal has started transmitting the message. When detecting, while suspending the transmission of the message in the own terminal, also checks whether the other terminal has started the transmission of the message even during the transmission of the message, when the start of the transmission of the message is detected, The transmission of the electronic message is interrupted. Claim 3
According to the invention described in claim 1, in the invention according to claim 1 or 2, when the terminal suspends or suspends the transmission of the message and then receives the global polling command again, the transmission delay time determined at random elapses. Then, transmission of the message is started.

The invention according to a fourth aspect is characterized in that the control station and a plurality of terminals are connected to the same line, and a global polling command for permitting transmission of a message is sent from the control station to each terminal, and the global polling is performed. In a communication system in which each of the terminals transmits a message in response to a command, each terminal includes a message transmission processing unit that receives the global polling command and transmits the message, and another terminal other than the terminal itself. Detecting that transmission of the message has started,
And a message collision control unit for suspending or interrupting the transmission of the message by the message transmission processing unit.

According to a fifth aspect of the present invention, in the fourth aspect of the invention, the message collision control means detects a start of the message transmission by the other terminal before the message transmission,
Suspending the transmission of the message to the message transmission processing means, detecting the start of the message transmission by the other terminal during the transmission of the message, and interrupting the transmission of the message to the message transmission processing means. It is characterized by: According to a sixth aspect of the present invention, in the fourth or fifth aspect, each of the terminals transmits the global polling message from the control station after the message transmission processing unit suspends or interrupts the transmission of the message. It is characterized by having a message transmission delay control means for detecting that a command has been sent and causing the message transmission processing means to start transmitting the message after a randomly determined transmission delay time has elapsed. .

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram illustrating an overall configuration of a communication system to which a polling control method according to the present embodiment is applied. As shown in the figure, a plurality of terminals 3-1 to 3-n (n is a natural number of 2 or more) are connected to a line 2 connected to a communication processor 1 as a control station. The line is being used effectively. Here, the communication processor 1 has a global polling control function unit 10, while the terminals 3-1 to 3-n have transmission message collision detection function units 30-1 to 30-n and transmission delay function units 31-1 to 31-n. 31-n, global polling control function unit 32
-1 to 32-n.

Of these, the global polling control function unit 10 and the global polling control function unit 32-1
.About.32-n perform the above-described control based on the global polling control method in the communication processor 1 and the terminals 3-1.about.3-n. The global polling control function units 32-1 to 32-n include transmission message collision detection function units 30-1 to 30-n and transmission delay function units 31-1 to 31-31, respectively.
-n is controlled. The details of the functions of the global polling control function units 32-1 to 32-n will be apparent from the description of the operation described later.

On the other hand, transmission message collision detection function units 30-1 to 30-3
0-n has a function of monitoring whether or not a terminal other than the terminal itself has started transmitting a message at the time of starting or during transmitting the message. Then, when detecting that another terminal is transmitting a message, the transmission message collision detection function units 30-1 to 30-n suspend / interrupt the message transmission in the own terminal, thereby transmitting a useless message. Is stopped, and control is performed so as not to disturb the message transmission of other terminals.

On the other hand, the transmission delay function units 31-1 to 31-n
When a collision of a transmission message with another terminal is detected, the message transmission is performed in order to avoid a collision again when the next global polling command is received from the communication processor 1. Control to randomly delay the start timing is performed. Each of the terminals 3-1 to 3-n
Stores an area for storing the transmission delay time used for the above-described random delay control performed by the transmission delay function units 31-1 to 31-n, and a flag indicating whether the transmission delay time is set. (Not shown) provided with an area for storing.

Next, the procedure for implementing the polling control method using the above configuration will be described below. FIG. 2 is a diagram showing each terminal 3-1 for implementing polling control according to the present embodiment.
3 is a flowchart illustrating processing performed in 3-n.
Here, in the following description, the operation in each terminal is mainly performed by the global polling control function units 32-1 to 32-n
Therefore, regarding the processing performed by these, the description that the global polling control function units 32-1 to 32-n perform the processing is omitted.

First, the terminal that has received the global polling command from the communication processor 1 checks whether or not there is transmission data in the terminal itself (step S1). If there is no transmission message, the process is terminated without doing anything.
On the other hand, if the own terminal has a transmission message, it instructs the transmission delay function units 31-1 to 31-n to refer to the contents of the flag and has previously collided with another terminal's message transmission. It is checked whether the transmission delay time has been set (details will be described later) (step S2). If the transmission delay time has not been set, the process proceeds to step S4 in this case, and the transmission message collision detection function units 30-1 to 30-3
An instruction is given to 0-n, and it is checked whether another terminal has started transmitting a message before transmitting the message.

If the other terminal has not started sending a message, the process proceeds to step S5 to start sending a message from the own terminal. That is, first, after transmitting a transmission message by one byte to the line 2 (step S5), it is determined whether or not transmission of all the messages has been completed (step S5).
6). Then, if there are any bytes of the message that have not been transmitted, the process returns to step S4, and until the transmission of all the bytes of the message has been completed, the processing of steps S4 to S6 described above for each subsequent byte is completed. repeat. Thereafter, if the transmission of all the messages has been completed normally, the process proceeds from step S6 to step S7, and if the transmission delay time has been set (in this case, it has not been set), it is changed. Clear and end the message transmission process.

As described above, when no collision of a transmission message occurs with another terminal, an efficient message transmission process can be performed without delaying transmission. On the other hand, whether the message transmission is started (that is, the time when step S4 is first executed after receiving the global polling command) or
Alternatively, if it is detected by the transmission message collision detection function units 30-1 to 30-n that another terminal has started transmission of a message during execution of the loop processing of steps S4 to S6, the processing is stepped. The process proceeds from step S4 to step S8.

In step S8, in accordance with an instruction from the transmission message collision detection function units 30-1 to 30-n, the transmission processing of the message in the own terminal is interrupted. Accordingly, if another terminal has already started the message transmission process at the time of starting the message transmission, it is possible to prioritize the transmission of the other terminal and avoid unnecessary collision in advance. If a collision occurs with another terminal during the message transmission processing, unnecessary transmission processing can be interrupted at an early stage.

Thereafter, the process proceeds to step S9, where the transmission delay time is determined and set by using a random number, and the flag is updated accordingly. Then, the message transmission process is terminated in order to wait for the next global polling command. Thereafter, as long as no global polling command is received from the communication processor 1, only step S1 is repeatedly executed.

Thereafter, when the next global polling command is received, the process proceeds to step S2, and the transmission delay function units 31-1 to 31-n collide with the message transmission of another terminal in the same manner as described above. Check if the transmission delay time has been set. In this case, since the transmission delay time has been set in the processing of step S9, the process proceeds from step S2 to step S3, and the transmission delay time is set according to the instruction from the transmission delay function units 31-1 to 31-n. The transmission start of the message is delayed by the transmission delay time.

The subsequent processing is the same as when the transmission delay time is not set. That is, the process proceeds from step S3 to step S4, and while constantly monitoring whether or not another terminal has started transmission of a message, the message is transmitted one byte at a time until transmission of all messages is completed. At that time, if the transmission of a message from another terminal is detected,
The transmission process is interrupted to set a transmission delay time at random and wait for the next global polling command.

As described above, in the present embodiment, it is checked whether or not a message transmission has collided with another terminal at the time of starting the message transmission after receiving the global polling command or during the message transmission. . If a collision is detected at the start of transmission of the message, the transmission of the message is suspended while the transmission of the message is suspended if a collision is detected during transmission of the message. The message transmission of the terminal that has started transmission is not prevented.

Further, in the present embodiment, when a collision is detected, the timing of starting transmission of a message at the time of receiving the next global polling command is randomly shifted, so that the transmission of the message at the next reception of the global polling command is performed. Collisions are avoided in advance. As described above, in the present embodiment, collision and avoidance of transmission telegrams are performed by control closed to each terminal without performing interlocked control among a plurality of terminals.

[0026]

As described above, according to the present invention,
When sending a message after receiving a global polling command, check whether another terminal has started sending a message.If the start of sending a message by another terminal is detected, suspend or suspend sending the message. On the other hand, if the start of message transmission by another terminal is not detected, the message transmission processing is completed. Thus, in a normal case where the message transmission does not collide with another terminal, the message is immediately transmitted, so that an efficient message transmission process can be performed without delaying the transmission. On the other hand, when a message transmission collision occurs with another terminal, the terminal that has started the message transmission first has priority, so that the operation of the terminal that has started the message transmission does not disturb the operation. Thus, it is possible to prevent a mutual transmission failure or the like caused by a plurality of terminals simultaneously starting message transmission.

According to the second or fifth aspect of the present invention, when the start of transmission of a message by another terminal is detected before the transmission of the message at the own terminal, the transmission of the message is suspended, and during the transmission of the message at the own terminal. When the start of transmission of a message by another terminal is detected, the transmission of the message is interrupted. This makes it possible to avoid unnecessary collision in advance by prioritizing transmission from another terminal at the start of message transmission, and to interrupt unnecessary transmission processing early during message transmission processing. According to the third or sixth aspect of the present invention, after suspending or suspending transmission of a message,
When the next global polling command is received, transmission of a message is started after a random transmission delay time has elapsed. As a result, it is possible to avoid in advance a collision of message transmission when the next global polling command is received.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating an overall configuration of a communication system to which a polling control method according to an embodiment of the present invention is applied.

FIG. 2 is a flowchart showing processing performed in each terminal to implement polling control according to the embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Communication processor 2 line 3-1 to 3-n terminal 10, 32-1 to 32-n Global polling control function unit 30-1 to 30-n Transmission message collision detection function unit 31-1 to 31-n Transmission delay function Department

Claims (6)

[Claims] 1. For each terminal connected to the same line,
A polling control method in a communication system in which each terminal transmits a message in response to the global polling command, wherein the terminal receives the global polling command. When performing the transmission of the message, it is checked whether another terminal other than the own terminal has started transmitting the message, and when the start of the message transmission by the other terminal is detected, the Suspending or interrupting the transmission of the message, if the start of the message transmission by the other terminal is not detected,
A polling control method, wherein the transmission of the electronic message is performed by the own terminal to complete the transmission processing. 2. Each of the terminals checks whether or not the other terminal has started transmitting a message before transmitting the message, and upon detecting the start of the message transmission, suspends transmission of the message in its own terminal. 2. The method according to claim 1, further comprising: checking whether or not the other terminal has started transmitting the message even during the transmission of the message, and interrupting the transmission of the message at the own terminal when detecting the start of the message transmission. Polling control method. 3. When each terminal suspends or suspends transmission of the message and receives the global polling command again, the terminal starts transmission of the message after a transmission delay time determined at random elapses. 3. The polling control method according to claim 1, wherein: 4. A control station and a plurality of terminals are connected to the same line, and a global polling command for permitting transmission of a message is transmitted from the control station to each of the terminals, and each of the terminals responds to the global polling command. In the communication system for transmitting a message, each of the terminals is configured to receive the global polling command and transmit the message, and a terminal other than the terminal itself starts transmitting the message. And a message collision control unit for suspending or suspending the transmission of the message by the message transmission processing unit. 5. The message collision control unit detects a start of transmission of a message by the another terminal before transmitting the message, and suspends transmission of the message to the message transmission processing unit. 5. The polling control method according to claim 4, wherein the start of transmission of the message by the terminal is detected during the transmission of the message, and the transmission of the message is interrupted by the message transmission processing means. 6. The terminal, after the message transmission processing means suspends or suspends the transmission of the message, detects that the global polling command has been sent from the control station, and the terminal transmits the message. 6. The communication system according to claim 4, further comprising a message transmission delay control unit that starts transmission of the message after a transmission delay time determined at random has elapsed.