Lenze DDS v2.3 Manual de usuario descargar pdf (Pagina 221)

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8-31

l DDS EN 2.3

8.8.4 If a task overflow leads to a system error

If, for instance, a continuous loop or too much program content has been programmed for a task

and the task cannot process the program within the specified interval time, a system error will occur

in the automation system.

System errors can also occur when a running task is interrupted so frequently by other tasks that

the program cannot be processed within the specified task runtime.

A system error trips the automation system.

• The response of motor control and digital outputs can be set under

Project➞

➞➞

➞Exception handling.

(also refer associated system organization unit description in the manual for the respective

Lenze automation system.)

• The program can only be restarted after a TRIP reset or mains switching.

A TRIP reset (Keypad: STOPàRUN key; GDC: Code C0043) resets the Lenze automation system

after a task overflow, and the error message “Task overflow” is acknowledged.The automation

system must be corrected to prevent further task overflows.

The watchdog time is set as follows:

• Use the task dialog box Properties, input field Watchdog time to enter the maximum runtime

for the task.

• Interval: The watchdog time is between 0-100 % of the interval time (default=90 % ) and can

be set between 1 ms and 300 ms.

(Witha1mstask,thewatchdogtimeis1ms=100%fixed.)

• Event/Interrupt: The watchdog time can only be set less than 300 ms (default=100 ms).

• Use the dialog box

Exception handling

(ProjectWException handling), input field

Watchdog time to enter the maximum runtime for the cyclical task (PLC_PRG).

Tripping the watchdog time

• Tripping the watchdog time activates an error message in the PLC.

• This error message is displayed on the Keypad/in GDC in code C0168.

• After TRIP reset, error message and PLC program will be reset. Use the DDS start command

or C2108=1 to restart the program.

8.8.5 Task declaration

A task declaration consists of the task name, the entry for task priority and the condition for its

execution.

The condition can be a time interval (1 ms to 16 s) after which the task is to be executed, an event

(rising edge at the digital input or FALSE/TRUE change of a global variable) or a hardware interrupt.

Every task can now be assigned a list of programs (Program-type POUs) to be called by the task.

These programs are processed in the listed order.

Tip!

The task settings (properties) cannot be changed in online mode!

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Lenze DDS v2.3 Manual de usuario Pagina 221

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