JPH03282903A - Task control method in communication system for programmable controller - Google Patents

Abstract

PURPOSE:To prevent the performance of a data link from being dropped by surely and repeatedly executing a data link task independently of the execution request of other tasks, and during the cycle of the repeated execution, executing only the prescribed number of tasks among other execution waiting tasks. CONSTITUTION:When an execution request is generated from another task during the data linking operation of a certain system program stored in a system program ROM 19 included in a communication unit 16, the system program concerned sets up the request to an execution waiting state and writes the set contents in an internal memory 18. In each completion of the data link task of one cycle, the existence of an execution waiting task is detected. When the existence of plural kinds of the data link tasks is detected, all the detected tasks are executed in accordance with previously determined priority order, but in the case of the same kind of tasks, only one of them is restrictedly executed. Thereby, even when the data link and events are simultaneously executed in parallel, the data link can be prevented from being dropped at its performance.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a task control method for a programmable controller, and more particularly to a task control method in a programmable controller communication system in which communication such as data links and events is performed. It is.

(Prior art) In the communication system of a programmable controller,
A plurality of tasks such as data link tasks and event tasks are defined, and each of these tasks is executed based on a task execution command. In this case, a plurality of tasks are given priorities, and when execution instructions for a plurality of tasks overlap, the tasks are executed according to the priorities.

(Problem to be Solved by the Invention) In the task control described above, depending on the usage status of the user, only tasks with a high priority are executed, and tasks with a lower priority are not executed. There is a possibility that a problem may arise that the performance when the functions are activated simultaneously is not guaranteed. As a specific example, event tasks are generally given higher priority than data link tasks, so in this case, only event tasks are executed and data link tasks are not executed properly, resulting in poor data link performance. There is a risk that the required data link may not be performed.

In view of the above-mentioned problems, the present invention provides a communication system for a programmable controller that ensures that the data link task is repeatedly executed and also allows other tasks to be executed at a predetermined frequency. The purpose is to provide a task control method.

(Means for Solving the Problem) According to the present invention, the above object is to provide a task control method in a communication system of a programmable controller in which a plurality of tasks such as data link tasks and event tasks are defined. If an execution request for a task other than a data link task occurs during task execution, this is stored as an execution waiting state, and the presence or absence of a task in an execution waiting state is checked every time a cycle of data link tasks is completed. is detected, and if there are tasks waiting to be executed, only a predetermined number of tasks among the tasks waiting to be executed are executed at this time, and then the data link task of the next cycle is executed. This is accomplished by a task control method in a programmable controller communication system.

(Operation) In the task control method in the communication system for a programmable controller according to the present invention, the data link task is always repeatedly executed regardless of execution requests of other tasks, and Although other tasks are executed even though the number of executions is limited by Guaranteed.

(Example) The present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 shows the basic configuration of a programmable controller used to implement the task control method according to the present invention. The programmable controller includes a CPU 10 configured by a microprocessor, an internal memory 11,
System program RO that stores system programs
M12, a user program RAM 13 that stores a user program, a human output memory 14 that stores human output data, an input interface that receives an external human power signal, and an output interface that sends out an external output signal. In-out crab knit 15
and a communication unit 16 that communicates control data and the like with other programmable controllers.

The communication unit 16 includes a CPU 10, an internal memory 18, a system program ROM 19 storing a communication system program, a timer module 20, and a communication interface circuit 21.

The programmable controller has a programmable controller body interface task that monitors the status of the programmable controller body, a communication control task that performs transmission/reception processing, etc., and a send/receive and tool (
There are send/receive tool tasks that perform tasks such as monitoring communication status, event tasks that perform event-related processing, data link tasks that perform data link execution, and initial tasks that perform hardware initialization, etc. The data link task is defined as an idle task that runs whenever no other task is running.

These matters are determined by the monitor in the communication system program in the system program ROM 19 of the communication unit 16, and this monitor (operation system) monitors data during task execution while the data link is in operation. When a request for execution of a task other than the link task, that is, a factor occurs, it is placed in the execution waiting state and this fact is written in the internal memory 18, and each time the data link task of -cycle is completed, the task in the execution waiting state is The presence or absence of the task is detected, and if there is a task waiting to be executed, the task is executed at this time. If there are multiple types of tasks, all of the tasks in the waiting state will be executed according to a predetermined priority order, but for tasks of the same type, a predetermined number of tasks will be executed. In the embodiment, only one is executed.

Next, the task control procedure during data link operation will be explained using FIG. First, in step 10, it is determined whether or not the data link processing has started, and this step 1 is performed until the data link processing is started.
If 0 is executed repeatedly and data tank processing is started,
Step 12 is then executed.

In step 12, it is determined whether or not the data link processing has been completed, and this step 12 is repeatedly executed until the data link processing is completed.On the other hand, once the data link processing is completed, the next Step 14 is executed.

In step 14, it is determined whether there is a send/receive tool task factor.

That is, in this step, it is determined whether or not a send/receive tool task currently exists in the execution waiting state. If this exists, step 16 is executed next, and if not, step 16 is executed. If so, a jump is made to step 18.

In step 16, only one send/receive tool task waiting to be executed is executed.

After step 16, the process advances to step 18.

In step 18, it is determined whether or not there is an event task factor. That is, it is determined whether or not there is an event task currently waiting to be executed. If there is an event task waiting to be executed, step 2o is executed next, and if not, step 1o is executed. return.

In step 20, only one event task in the execution waiting state is executed.

After step 20, proceed to step 10.

By performing task control according to the flowchart described above, for example, as shown in FIG. 4, event reception 1 and send command occur during the data link processing of the cycle indicated by symbol A. If you do,
- When the data link processing A of the cycle is completed, the tasks waiting to be executed are executed one by one according to a predetermined priority order. In this case, the send command is processed first, and then the event 1 is processed. Even if event reception 2 occurs during the processing of event 1, this is not executed, and the data link processing of the cycle indicated by symbol B is executed next. If a tool occurs during the data link processing B of the - cycle, after the data processing B of the - cycle is completed, the tool processing is executed first in accordance with the priority order, and then the event 2 is executed.

Note that at startup, each task is executed in the order of initial task, programmable controller main body interface task, event task, send/receive tool task, communication control task, and data link task.

While the data link is stopped, each task may be executed sequentially when a request for execution occurs, and the situation in this case is shown in FIG.

(Effects of the Invention) As is clear from the above explanation, in the task control method in the programmable controller communication system according to the present invention, the data link task is always repeatedly executed regardless of execution requests of other tasks. Then, between the cycles of this data link task, other tasks are executed although the number of executions is limited, and since the number of execution of other tasks is limited, the data link task may not be executed at too long an interval. It is guaranteed that the data link will be executed repeatedly without any delay, and the data link performance will not deteriorate even when the data link and event are executed in parallel.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the basic configuration of a programmable controller used to implement the task control method according to the present invention, FIG. 2 is a block diagram showing the basic configuration of a communication unit of the programmable controller, and FIG. FIG. 4 is a flowchart showing an example of the implementation procedure of the task control method for a programmable controller according to the present invention, FIG. 3 is a flowchart illustrating how to perform task control while a data link is stopped. 10...CPU 11...Internal memory 12...System program ROM 13...User program RAM 14...Person count memory 15...Pass count crab unit 16...Communication unit Fig.

Claims (1)

[Claims] 1. In a task control method in a programmable controller communication system in which multiple tasks such as data link tasks and event tasks are defined, if a request for execution of a task other than the data link task occurs during task execution. This is stored in the execution waiting state, and the presence or absence of an execution waiting task is detected every time the data link task of the cycle is completed, and if there is an execution waiting task, it is executed at this time. 1. A task control method in a programmable controller communication system, characterized in that only a predetermined number of tasks are executed among the tasks, and then a data link task of the next cycle is executed.