5. Initial Programming
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Furthermore, this profile can include event tasks with higher priority than the basic tasks, which can
interrupt (preempt) these tasks execution at any time.
The task called ExternInterruptTask00 is an event task of the External type which execution is
triggered by some external event, such as the variation of a control signal on a serial port or the
variation of a digital input on the NEXTO bus. This task priority is fixed in 02 (two), being
responsible exclusively for the execution of the ExternInterruptPrg00 program. The task called
TimeInterruptTask00 is an event task of the Cyclic type with a priority fixed as 01 (one), being
responsible for the execution exclusively of TimeInterruptPrg00 program.
In the Normal project model, there are five tasks, and its POUs, already fully defines as shown in
Table 5-5. The developer needs only to implement the programs content, opting, on the wizard, for
any of the languages in IEC 61131-3 standard. The tasks interval and trigger events can be
configured by the developer and the unnecessary tasks can be eliminated.
Table 5-5. Normal Profile Tasks
Expert
The Expert Project Profile includes the same basic tasks, CyclicTask<nn>, ExternInterruptTask00
and TimeInterruptTask00 with the same priorities (13, 02 and 01 respectively), but it’s an expansion
from the previous ones, due to accept multiple events tasks. That is, the application can include
various ExternInterruptTask<nn> or TimeInterruptTask<nn> tasks that execute the
ExternInterruptPrg<nn> and TimeInterruptPrg<nn> programs. The additional event tasks priorities
can be freely selected from 08 to 12. In this profile, besides the standard programs, each task can
execute additional programs.
In this project profile, the application may also include the user task FreeTask of the Freewheeling
type with priority 31, responsible for the FreePrg program execution. As this task is low priority it
can be interrupted by all others so it can execute codes that might be blocked.
There are eight tasks already fully defined, as shown in Table 5-6, as well as their associated
programs in the chosen language. Intervals and trigger events of any task, as well as the priorities of
the event tasks can be configured by the user.
When developing the application using Experienced project's profile, a special care is needed with
the event tasks scaling. If there is information and resource sharing between these tasks or between
them and the basic tasks, it is strongly recommended to adopt strategies to ensure data consistency.
Table 5-6. Expert Profile Tasks
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