JPH0458637A - Communication control method - Google Patents

Abstract

PURPOSE:To use a transmission line efficiently by preferentially applying polling to a slave equipment with a long queue and also applying polling even to a slave equipment with a short queue periodically. CONSTITUTION:A polling control circuit 101 reads a terminal number of slave equipments 20a-20n from a head address of a sorting memory 103 and applies polling to the slave equipments 20a-20n according to the terminal number. When the length of the queue of the slave equipment after the end of polling processing is a preset threshold value or over, the polling control circuit 101 writes the terminal number of the slave equipments 20a-20n and the length of the queue as one data to a sorting memory 103 and commands sorting of the sorting memory 103 to the sorting circuit 102. When a coefficient of a 1st counter 104 is less than a preset threshold value, the operation above is repeated, the slave equipment with a long queue is polled preferentially among the slave equipments 20a-20n by repeating the operation.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a communication control method used when a plurality of terminal devices transmit and receive data via a common transmission path.

2. Description of the Related Art An example of a conventional communication system is shown in FIG. 2. In FIG. 2, l indicates a main device and 28 to 2n indicate slave devices.

The main device 1 and the slave devices 2a to 2n are connected via a bus 3, and each of the slave devices 28 to 2n is assigned a predetermined unique terminal number. It is composed of a control circuit 11 and a counter 12. The slave devices 28 to 2n each have the same configuration, and include a buffer 21 that temporarily stores transmission information to be transmitted to other devices via the bus 3, and a register that displays flag information indicating the presence or absence of a transmission request. It is composed of 22.

The polling control circuit 11 reads the value of the counter 12, reads the contents of the register 22 of the slave devices 28 to 2n having the terminal number indicated by the value, and checks whether there is a transmission request.

When there is a transmission request, the main device 1 uses the control line of the bus 3, and the slave devices 28 to 2n transfer the transmission information via the bus 3. The counter 12 is the polling control circuit 1
Each time 1 reads the contents of the register 22 of each slave device 2a to 2n, it is incremented modulo the number of slave devices. By repeating the above operations, the main device 1 sequentially processes the transmission requests from each of the slave devices 2a to 2n (.

Problems to be Solved by the Invention However, in the conventional communication control method described above, when there is a bias in traffic between slave devices or when traffic to each slave device varies over time, it is difficult to send data to a certain slave device. A situation may arise where requests are concentrated. Even in such a situation, the master device polls each slave device cyclically and evenly, regardless of whether there is a transmission request, so a slave device with a long queue will poll at the same frequency as a slave device with a short queue. This caused a problem in that the queue was not easily alleviated.

The present invention solves such conventional problems, and provides excellent communication that allows efficient use of transmission paths by fluidly adjusting polling frequency when traffic is unevenly distributed among some slave devices. The purpose is to provide a control method.

Means for Solving the Problems The communication control method of the present invention is composed of a main device and a plurality of slave devices, and transmits and receives data between each slave device via a common transmission path by central control of the main device. It is something that is done;
In particular, the slave device stores the queue length of transmission requests to the master device, and when the master device communicates with each slave device, it stores the terminal number and transmission request queue length of each slave device, and based on this, the master device stores the terminal number and queue length of transmission requests of each slave device. The system is characterized in that transmission permission is granted in order from the slave device with the longest queue length, and communication permission is periodically granted to each slave device.

Furthermore, when the main device periodically grants cyclical transmission permission to each slave device, it clears the stored transmission request queue length and updates the queue length stored in each slave device. The queue length may also be stored.

Operation The present invention has the following effects due to the above configuration. In other words, by giving transmission permission preferentially to a slave device with a long queue length, even if there is traffic imbalance between slave devices, the system as a whole can exchange and forward each transmission request with equal delay quality. can be provided. By periodically granting normal cyclic transmission permission in addition to the above-mentioned priority transmission permission, polling processing opportunities at a certain frequency or higher are guaranteed even to slave devices with small queues that are not subject to priority processing. I can do it.

Also, when the main device periodically grants cyclical transmission permission to each slave device, it clears the stored transmission request queue length and creates a new queue length stored in each slave device. By storing the length, it is possible to flexibly respond to short-term fluctuations in the traffic of each slave device.

Embodiment FIG. 1 shows an embodiment of a communication control device to which the present invention is applied.

In FIG. 1, IO indicates a main device, and 20a to 20n indicate slave devices.The main device IO and the slave devices 20a to 20n are connected via a bus 30. Each of the slave devices 20a to 20n is assigned a predetermined terminal number. The main device IO includes a polling control circuit 101
, sorting circuit 102 , and sorting memory 1
03, a first counter 104, and a second counter 105. The sorting memory 103 stores the terminal numbers and queue lengths of the slave devices 20a to 20n as one data. The sorting circuit 102 has a function of rearranging the queue lengths in the sorting memory 103 according to their values, and is realized by hardware. The first counter 104 is the sorting memory 103
It is incremented each time it is read, and is cleared to O when it reaches a preset threshold. The second counter 105 holds the terminal numbers of the slave devices 208 to 20n polled by the main device 10 when performing cyclic polling. Second
The counter 105 is incremented every time the slave devices 20a to 20n are polled, and the counter 105 is incremented every time the slave devices 20a to 20n are polled.
After polling 0n once, it is cleared to O. The slave devices 20a to 20n have the same configuration and are composed of a buffer memory 201 that temporarily stores transmission requests and a register 202 that stores the queue length.

Next, the operation of the above embodiment will be explained.

The polling control circuit 101 is a sorting memory 103
The terminal numbers of the slave devices 20a to 20n are read from the first address of the slave devices 20a to 20n according to the terminal numbers.
After the polling process is completed, if the queue length of the slave device is greater than or equal to the preset threshold,
The polling control circuit 101 writes the terminal numbers and queue lengths of the slave devices 20a to 20n as one data in the sorting memory 103, and instructs the sorting circuit 102 to sort the sorting memory 103. At the same time, the first counter 104 is incremented.

The polling control circuit 101 is a sorting memory 103
Wait until the queue lengths in
If the coefficient value of the counter 104 is less than a preset threshold, the above operation is repeated. By repeating this, the slave devices 20a to 20 with the longest queues are polled preferentially.

When the coefficient value of the first counter 104 reaches a preset threshold value, all data in the sorting memo January 03 is erased.

When there is no data in the sorting memory 103 or when the data in the sorting memory 103 is erased, the polling control circuit 101 reads the value of the second counter 105 and performs cyclic polling according to that value. After the polling process is finished, if the queue length of the slave devices 20a to 20n is greater than or equal to a preset threshold, the polling control circuit 101 converts the terminal number and queue length of the slave device into one data as described above. After polling all the slave devices A 20a to 20n to be written to the sorting memory 103, the polling control circuit iot instructs the sorting circuit 102 to sort the queue length in the sorting memory 103, and again starts from the beginning of the sorting memory 103. Read the terminal name and poll according to the read terminal number. Therefore,
Since the data in the sorting memory 103 is periodically refreshed by the normal polling operation by the second counter 105, the slave device 20 with a short queue length
A~2On can also receive polling processing periodically.

On the other hand, even when specific slave devices 20a to 20n receive intensive transmission requests in a short period of time, processing can be performed with little delay.

Effects of the Invention As is clear from the above embodiments, the present invention is configured to preferentially poll slave devices with long queue lengths, and periodically poll slave devices with short queue lengths, thereby reducing traffic. Even in the case where there is a bias, the system as a whole can provide exchange and forwarding with equal delay quality for each transmission request, and has the effect that the transmission path can be used efficiently.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embodiment of a communication control device to which the present invention is applied, and FIG. 2 is a block diagram of a conventional communication control device. 1.10...Main device, 28~2n, 20a~20n・
... Slave device, 3.30 ... Bus, 101 ... Polling control circuit, 102 ... Sorting circuit, 103
Sorting memory, 104 First counter, 105 Second counter, 21.201 Buffer memory, 22°202 Register. Agent Patent Attorney Shigetaka Awano Idiot 1 person i@1 Figure

Claims (2)

[Claims] (1) In a communication control method that consists of a main device and a plurality of slave devices, and in which data is sent and received via a common transmission path between each slave device under the centralized control of the main device, the slave devices communicate with each other through a common transmission path. The queue length of transmission requests is memorized, and when the master device communicates with each slave device, it memorizes the terminal number of each slave device and the queue length of transmission requests, and based on this it stores the queue length of transmission requests. 1. A communication control method, characterized in that transmission permission is granted sequentially starting from the device, and cyclic communication permission is periodically granted to each slave device. (2) When the main device periodically grants cyclical transmission permission to each slave device, it clears the stored transmission request queue length and updates the queue length stored in each slave device. 2. The communication control method according to claim 1, further comprising storing a queue length.