JPH01103046A - Communication control system - Google Patents

Abstract

PURPOSE:To minimize the reduction of service by separating the service period of a terminal equipment responding normally to a polling from a terminal equipment not normally responding to and applying communication control to each terminal equipment in the separated service period. CONSTITUTION:When a communication controller 2 applies polling to terminal equipments 4-7 and, for example, when only a terminal equipment 5 has no reply to said polling, other service period is set to the terminal equipment 5 than the service period to the terminal equipments 4, 6, 7. Thus, the terminal equipments 4, 6, 7 are subjected to communication control in the same service period and the terminal equipment 5 is subjected to communication control respectively in the other service period. When the terminal equipment 5 is recovered from the fault and the power is turned on, the communication controller 2 applies normal service to the terminal equipment 5.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a communication control method for controlling data transfer between a host computer and a terminal connected to the host computer, and particularly relates to a basic data transmission control method. Polling procedure/
This invention relates to a communication control method based on the serenoting method.

[Conventional technology]

FIG. 4 is a block diagram showing the configuration of a computer system including a communication control device that employs this type of conventional communication control method. In the figure, 1 is a host computer that performs data processing, 2 is a communication control device that controls terminals connected to the line, 3 is a line with a branch configuration, 4 is a first terminal connected to line 3, 5 is the second terminal connected to line 3; 6
is the n-th terminal connected to the line 3, and 8 is the first terminal control table provided in the communication control device 2.

Next, the operation will be explained. The host computer 1 issues a polling instruction to the communication control device 2 in order to enable data input (reception) from the terminal.

Upon receiving this instruction, the communication control device 2 first polls the first terminal 4. If there is no data to be transmitted in response to this polling, the first terminal 4 returns a response (EOT) indicating that there is no data to the communication control device 2. When the communication control device 2 receives the EOT from the first terminal 4,
Next, the second terminal 5 is polled. Second terminal 5
Similarly to the first terminal 4, if there is no data to be transmitted, the EOT is returned to the communication control device 2. Communication control device 2
When it receives this EOT, it polls the next terminal. In this way, the communication control device 2
Poll until When polling up to the n-th terminal 6 is finished, the communication control device 2 takes a pause for a certain period of time, and then starts polling again from the first terminal 4.

The above is an operation when there is no data to be transmitted from the terminals 4 to 6 to the host computer 1. If there is data to be transmitted to the terminals 4 to 6, the terminals 4 to 6 transmit the data in response to polling by the communication control device 2, and the communication control device 2 receives this data and sends it to the host computer 1. There is an action to send to. If there is data on terminals 4 to 6,
In either case, the communication control device 2 is connected to the first terminal 4.
to the n-th terminal 6 are uniformly polled.

[Problem that the invention seeks to solve]

As mentioned above, in conventional communication control systems, terminals connected to a branch line are always uniformly polled (serviced), so if a terminal becomes unable to respond to polling due to a failure or power off, etc. In this case, a timeout occurs and the overall service deteriorates by this amount of time. In addition, to avoid this, if a device is configured to stop polling (service) when a certain number of timeouts occur on that device, polling (service) will be stopped when the device recovers from a failure or when the power is turned on. ) requires an operation to restart the process.

This invention was made to solve the above problems, and even if a failure occurs in any terminal on the branch line or the power of the terminal is turned off,
Minimize the decline in service for all terminals as much as possible, and
The purpose of this invention is to provide a communication control method that allows the terminal to return to normal service without any operations when it is restored.

[Means for solving problems]

In the communication control method according to the present invention, when the communication control device 2 polls the terminals 4 to 7, the service cycle between the terminals that respond normally to the polling and the terminals that do not respond normally is determined. The communication control for each terminal 4 to 7 is performed in the divided service cycles, and when a terminal that does not respond normally to polling recovers from a failure or when the terminal is turned on, this terminal The feature is that the service for the machine is returned to normal service.

[Effect]

If the communication control device 2 polls the terminals 4 to 7 and, for example, only the terminal 5 does not respond to this polling, the terminal 5 has a service cycle different from the service period for the terminal 4゜6.7. The service period is set as follows. Therefore, terminal 4. 6. 7 is the same service cycle, and the terminal 5 is communication controlled in a different service cycle. When the terminal 5 complains of a failure or is powered on, the communication control device 2 provides normal service to the terminal 5.

[Embodiments of the invention]

An embodiment of the present invention will be described below based on the drawings. FIG. 1 is a block diagram showing the configuration of a computer system including a communication control device that employs the communication control method of this embodiment. In FIG. 1, components corresponding to those shown in FIG. 4 are given the same reference numerals, and their explanations will be omitted. 1st
In the figure, 7 is the third terminal connected to line 3, 9
is a second terminal control table provided in the communication control device 2.

Next, the operation will be explained. In the initial state, the second
As shown in the figure, all control information from the first terminal 4 to the nth terminal 6 is set in the first terminal control table 8. The host computer 1 issues a polling instruction to the communication control device 2 in order to enable data input from the terminals 4 to 7, as in the conventional communication control system. After receiving this polling instruction, the communication control device 2 operates according to the flowchart shown in FIG.

Next, referring to the flowchart in FIG. 3, the communication control device 2
The operation will be explained. Here, the operation will be described below assuming that the second terminal 5 is powered off.

The communication control device 2 has various counters i used in the following processes.
In step S1), upon receiving a polling instruction from the host computer 1, first, for example, the first terminal 4 is initialized according to the contents of the first terminal control table 8.
(i=first terminal) is polled (step S2). If there is no data to be transmitted in response to this polling, the first terminal 4 responds that there is no data (E
OT) is returned to the communication control device 2. Upon receiving this EOT, the communication control device 2 determines that the reception is a normal response (step S3), and sets the counter i indicating the number of the terminal.
The contents of rlJ are added (step S8). Since the contents of the counter i at this time do not indicate the last terminal 6 (step S9), the process returns to step S2 and the next second terminal 5 is polled. This polling times out because the second terminal 5 is powered off. The communication control device 2 has a counter that indicates the number of times of polling. Add the contents of step S4), and this added value is a certain number of times vJ,
until it becomes larger than L (step S5), step 82
By repeating the processes from S5 to S5, polling of the second terminal 5 is retried a certain number of times. However, in this example, since the second terminal 5 is powered off, there is no response even after a certain number of attempts, and therefore the content of the counter l becomes larger than the certain number of attempts (step 3).
5), the communication control device 2 considers that a failure has occurred in the second terminal 5, clears the contents of the counter l (step S6), and stores the control information of the second terminal 5 in the first terminal control table. 8 to the second terminal control table 9 (step S7). Thereafter, the content of the counter i for indicating the i-th information of the first terminal control table 8 is incremented by "1" (step S8), and it is determined whether the content of the counter i indicates the last terminal 6. In step S9), if the last terminal 6 is not indicated, the process returns to step S2 and the same process is performed. That is, the communication control device 2 sequentially polls from the third terminal 7 to the nth terminal 6 according to the contents of the first terminal control table 8.

When polling up to the n-th terminal 6 is finished, in step S9), the content of the counter j that counts the number of services is incremented by "1", and the content of the counter i indicating the first terminal 4 is incremented by "1". ” Step 5I
O) It is determined whether the content of counter j is greater than a constant number of times J (step 511). That is, after the communication control device 2 finishes polling up to the n-th terminal 6, it repeats polling of the terminals 4 to 7 three times according to the contents of the first terminal control table 8. However, from the second time onwards, the first terminal control table 8 will contain the second terminal 5.
Since there is no control information for the second terminal 5, the second terminal 5 is not serviced.

When the service according to the first terminal control table 8 is completed three times (step 5ll), the communication control device 2 clears the contents of the counter j (step 512), and stores the terminal control information in the second terminal control table 9. It is determined whether or not there is (step 513). In this example, since the control information for the second terminal 5 has been set, the terminal 5 is polled according to the contents of the second terminal control table 9 (step 514). Thereafter, it is determined whether the terminal to be polled is the last according to the contents of the second terminal control table 9 (step 515), and if it is the last, the information of the second terminal in the second terminal control table 9 is indicated. counter K
Set "1" to "1" (step 516), and if it is not the last one, add "1-1" to the counter (step 51).
7). In this example, since terminal 5 is the last one to be polled, the process moves from step S15 to step 816 to step 318, and it is determined whether a normal response has been received from terminal 5. That is, the communication control device 2
If the terminal device 5 responds to the polling according to the contents of the second terminal control table 9, it is assumed that the second terminal device 5 has recovered from the failure, and the control information of the terminal device 5 is transferred to the second terminal device 5.
from the terminal control table 5 to the first terminal control table 4 (step 519). Thereafter, the process returns from step S19 to step S2. As a result, the service of the second terminal 5 returns to normal service. Still the second terminal 5
If the terminal does not respond to polling from the communication control device 2, its control information remains set in the second terminal control table 9.

After completing the service (polling) for one terminal among the terminals corresponding to the control information set in the second terminal control table 9, the communication control device 2 performs the service of the first terminal control table 8. (Return to step S2 from step S19).

In this way, the communication control device 2 repeats the service of the first terminal control table 8 and the service of the second terminal control table 9 at a ratio of J:1. That is, the communication control device 2 processes steps 82 to 311 and steps 312 to S19 at a ratio of J:1.

In addition, in the above embodiment, the number of times of service for a terminal that responds normally is three times, and the number of times of service for a terminal that does not respond normally is once, but if a terminal does not respond normally only once every T seconds, The machine may also be serviced.

〔Effect of the invention〕

As described above, according to the present invention, the service cycles are divided between terminals that respond normally to polling and terminals that do not respond normally, and communication control of each terminal is performed using these divided service cycles, and polling When a terminal that does not respond normally recovers from a failure or when the terminal is turned on, the service for this terminal returns to normal service, so any terminal on the branch line Even when a machine failure occurs or the power is turned off, service degradation for the entire terminal is kept to a minimum, and when the terminal recovers from the failure, normal service is restored (automatically) without any operation. This has the effect of being able to return to the same service.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of a computer system including a communication control device that employs a communication control method according to an embodiment of the present invention, and FIG. FIG. 3 is a flowchart showing the operation of this embodiment.
FIG. 4 is a block diagram showing the configuration of a computer system including a communication control device employing a conventional communication control method. 2... Communication control device, 3... Line, 4... First terminal, 5... Second terminal, 6... nth terminal, 7... Third terminal, 9... second terminal control table.

Claims (1)

[Claims] In a communication control device that controls a plurality of terminals connected to a line having a branch configuration, when the communication control device polls the terminal to enable data reception from the terminal, If some terminals respond normally to this polling and others do not, the service cycle for the terminals that respond normally and the terminals that do not respond normally is divided into predetermined cycles. When a terminal that does not respond normally to the above polling recovers from a failure, or when the terminal is turned on, the service for this terminal is returned to normal. A communication control method characterized by returning to service.