Tab ‘System Events’

Object: Task Configuration

In the System Events tab, you define which events call which functions and whether or not the configuration is currently activated. You use this tab when a system event (instead of a task) should call a project function.

Add Event Handler Opens the Add Event Handler dialog box
Remove Event Handler Deletes the selected list assignment
Event Info Shows information from the corresponding event library
Open Event Function Opens the editor of the new function for the selected assignment You have selected the implementation language of the new function in the Add Event Handler dialog box.
Assignment of functions to call for events with: Name,Description, Function to call, and Active (activate/deactivate configuration).
Add Event Handler
Adds a new assignment “Event – Function to call” to the list
Event

The list of choices depends on the target device. CODESYS marks unavailable events with a red symbol in front of the name.

A list of all possible system events is located at the end of this section.
Function to call

Function name (POU, type FUNCTION)

You must enter the name of the new function. CODESYS inserts the function to the device tree after you confirm the dialog box.
Scope
  • Application: Function is available for the application
  • POUs: Function is available for the entire project
Implementation language Implementation language for the new function
Description Short description of the selected event

Features in Online Mode

The list of assignments from called functions to events also includes the following information: Event Status, Call Count, and the Online Reset button.

Event Status

0: No error has occurred.

Does not equal 0: error. You must consult the respective runtime system documentation.
Call Count Displays how often the event has occurred or the associated function has been called.
Online Reset CODESYS reinitializes the event lists and resets the counter for the events/function calls. Incorrectly initialized events are displayed with a red status cell.

Possible system events

Event Description Task Debugging
PrepareStart Call before starting the application Communication Task no
StartDone Call after starting the application Communication Task no
PrepareStop Call before stopping the application Communication Task no
StopDone Call after stopping the application Communication Task no
PrepareReset Call before resetting the application Communication Task no
ResetDone Call after resetting the application Communication Task no
PrepareOnlineChange Call before online change of the application Communication Task no
OnlineChangeDone Call after online change of the application Communication Task no
PrepareDownload Call before downloading the application Communication Task no
DownloadDone Call after downloading the application Communication Task no
PrepareDelete Call before deleting the application Communication Task no
DeleteDone Call after deleting the application Communication Task no
PrepareExit Call before exiting the application Communication Task no
ExitDone Call after exiting the application Communication Task no
CodeInitDone Event is sent after Code Init. Called within the safe section task and only for online change (for example, the copy code is executed here for online change). Communication Task no
Exception The event is sent if an exception has occurred in the context of an application. Exception Handling Task (of runtime system) or task itself (if the runtime system does not support exception handling) Depends on the task
Login Logs in a client to this application Communication Task no
Logout Logs out a client from this application Communication Task no
BeforeReadingInputs Call before reading the inputs IEC Task yes
AfterReadingInputs Call after reading the inputs IEC Task yes
BeforeWritingOutputs Call before writing the inputs IEC Task yes
AfterWritingOutputs Call after writing the inputs IEC Task yes
DebugLoop Event is sent in cycles to the debug loop if the IEC task stops at a breakpoint. Communication Task no
PrepareShutdown Event is sent immediately before the runtime system is downloaded. Runtime System Main Loop no
PrepareExitComm Event is sent during download before exiting the communication server. Runtime System Main Loop no
PrepareExitTasks Event is sent during download before exiting all tasks. Runtime System Main Loop no