Automatic control function programming manual ladder language

2.1.2.4 Real-Time Tasks
Structure of an Application
Tasks %TH0 to %TH15 allow processing of high priority events that cannot wait for the end of the RTC cycle.
Tasks %TH therefore have higher priority than tasks %TS and %TF.
An activated %TH task cannot interrupt a running %TH task.
The hierarchy of %TH task priorities is determined by their number:
Operation of Tasks %TH
%TH0 priority > %TH1 priority > ... > %TH15 priority.
The programmer associates a task %TH with a hardware interrupt by the following functions:
thiti() probe interrupt.
thtimer() timer interrupt.
When the interrupt occurs, the system starts execution of the associated task %TH.
If several %TH tasks are activated during the same RTC cycle, the total time required for processing each interrupt
routine must not exceed 4 ms. If it does, the machine processor goes into the «computation time overrun» error.
MONITOR %TSn (user programme) %THn
1 RTC cycle (20 ms)
Activation
%THn %THn–1
t > 4ms
%THn–1 %TFn
Computation time overrun
machine processor error
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