ABB DCS 系统 培训课程 系列讲座 Tasks.doc

Course T530Chapter 13 Tasks 13.1 General Information 13.1.1 DescriptionThis chapter describes what a task is and how to set properties for it.13.1.2 ObjectivesOn completion of this chapter you will be able to: Describe what a task is. Set properties for a task.13.1.3 Reference DocumentationUse the online help: Contents tab, Go Online and Execute Execution13.2 Lesson 1 - Tasks in the templates13.2.1 DescriptionThis chapter describes what a task is and how to set properties for it.13.2.2 ObjectivesOn completion of this lesson you will be able to: Describe what a task is. Set properties for a task.13.2.3 GeneralIn the Project explorer of the Control Builder you will find three default programs, labeled Program1 connected to the task Fast, Program2 connected to the task Normal and Program3 connected to the task Slow. The programs, containing the code, are not executed unless a work scheduler - a task - is connected and serves as an engine running the code in the controller.13.2.4 Task properties windowThe settings of the task are changed in the Task Properties window.13.2.4.1 Task properties13.2.4.1.1 Interval TimeThe interval time the program is executed with is set in the Task Overview window or in the Task Properties dialog box. Default values are 50 ms (Fast), 250 ms (Normal) and 1000 ms (Slow). You can change these values at any time. For a priority-0 task, the interval time can be as low as 1 ms. Tasks of priority 1-5 cannot be below 10 ms. The resolution is 1 ms.13.2.4.1.2 OffsetA mechanism used to avoid an unexpected delay of the execution start time. See Offset in the online help for more details.13.2.4.1.3 PriorityThere are six levels of priority: Time Critical, Highest, High, Normal, Low, and Lowest, numbered from 0 to 5. Time Critical has the highest priority. The tasks execute according to priority. A task with higher priority will interrupt any task with lower priority. Precision tasks interrupt of any point of execution but other tasks interrupt at some distinct points. The task priorities can be set through the SetPriority function.13.2.4.1.4 I/O copyBy using the radio buttons is it possible to select if you want to make the I/O copy before the task executes or after the task executes.13.2.4.1.5 DebugYou can set up a task for non-cyclic execution. Use non-cyclic execution to reduce the system load, and to simplify the debugging of a program. After you enable the debug mode, you can halt the cyclic execution of a task. You can command a task that is in halt to execute one scan each time you click the One Scan button.13.2.5 Task ConnectionIt is possible to connect Function Blocks, Control Modules, Programs and Application to tasks.13.2.6 Creating TasksIt is possible to create your own tasks. The tasks are created in a controller in the project tree.13.2.7 Exercise 13.1 Task handling in the templatesPlease do the exercise 13.1Du kan tag bort denna osynliga text men ltnedanstende Page Break ligga kvar !Lt ven den efterfljande sidan ligga kvar !This page is intentionally left blankThis page is intentionally left blankOsynlig text:Nsta sida mste brja p UDDA sidnummerLmna EN eller TV tomma sidor hr OVANFR.Nedanstende Section Break fr INTE tas bort !Komplettera tom sida vid behov med nedanstende textThis page is intentionally left blank 3BSE 022 858/A 2000/12/4 22:39:00 13-5Course T530TABLE OF CONTENTSChapter 13 Tasks113.1 General Information113.1.1 Description113.1.2 Objectives113.1.3 Reference Documentation113.2 Lesson 1 - Tasks in the templates213.2.1 Description213.2.2 Objectives213.2.3 General213.2.4 Task properties window213.2.4.1 Task properties313.2.4.1.1 Interval Time313.2.4.1.2 Offset313.2.4.1.3 Priority313.2.4.1.4 I/O copy313.2.4.1.5 Debug313.2.5 Task Connection313.2.6 Creating Tasks413.2.7 Exercise 13.1 Task handling in th