Festo CPX-CEC Series Manual page 10

CPX-CEC-...
Functionality/functions
1)
System events start
stop
before_reset
after_reset
shutdown
excpt_cycletime_overflow
excpt_watchdog
excpt_divide_by_zero
CPX_System_Fault
CAN_error_passive
CAN_bus_off
Task configuration in All functions
online mode
Task processing The task with the valid condition is executed: this means after the
time specified under "Interval" has expired or after a leading
edge from the condition variable specified under Event.
If several tasks have a valid condition, the task with the highest
priority is executed.
If several tasks have a valid condition and the same priority, the
task with the longest waiting time is executed.
In online mode, the program calls for each task are processed in
the sequence in which they appear in the task editor from top to
bottom.
PLC_PRG processed as a cyclic task with 10 ms and watchdog.
2)
Extras-> Set debug task
Extras-> Enable/Disable task
Extras-> Callstack
1) The controller is a pre-emptive multitasking system where high-priority tasks can interrupt and
supersede low-priority tasks. The system events are executed in a context where the task with the
highest priority supersedes all other tasks. A system event should therefore contain only a very short
code.
Tasks with priorities between 0 and 16 run in the real-time context of the operating system so that the
–
execution of these tasks is timed precisely!
On the other hand, this means that these kind of tasks have priority over operating system functions
such as network traffic. This must be taken into consideration when programming loops so as not to
block the system. Infinite loops in real-time tasks must be avoided at all costs.
Tasks with priorities >= 17 are not executed in the real-time context and can therefore be interrupted
–
by network traffic, for example.
The IEC task with the highest priority that is running as an event-triggered task should be used for error
handling. Within the context of the event, the system only calls the event that this task is waiting for
(information that would otherwise be lost such as the exact time stamp is retained if required; this should
only include information assigned to global variables).
2) Some functions (e.g. SysRTCSetTime) may trigger the watchdog.
8
Supported
Yes
Yes
Yes
Yes
Yes
Yes
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Yes