WAGO I/O SYSTEM 750 XTR
Run-time System CODESYS 2.3 275
750-8202/040-001 PFC200 2ETH RS TELE XTR
Manual
Version 1.2.0, valid from FW Version 03.01.07(13)
8.9.5.1 Effect of Update Mode on CODESYS Tasks
8.9.5.1.1 Asynchronous Update Mode
In the asynchronous update mode there is no direct influence on CODESYS task
behavior.
Local bus “freeze” on priority conflicts!
In the asynchronous update mode there is a risk of the local bus “freezing”, as
the local bus thread operates at the same priority as the IEC tasks. The local
bus thread must therefore use a priority higher than that of the IEC task to
prevent this from occurring.
8.9.5.1.2 Synchronous Update Mode
In the synchronous update mode the runtime behavior of CODESYS tasks can
be influenced by the local bus. The minimum task interval that can then be
achieved depends on the duration of a local bus cycle. The duration of a local
bus cycle, on the other hand, is based on the I/O modules connected to the bus.
As a rule of thumb: The shorter the local bus structure, the shorter the cycle time
and digital modules are faster than analog or complex ones.
In the event of a local bus error, the CODESYS tasks are blocked until the error
is rectified, i.e., when a local bus cycle has been successfully executed again.
No call-up of local bus status when local bus errors are present!
If a local bus error has occurred, it is not possible to call up the bus status using
KBUS_ERROR_INFORMATION (mod_com.lib) while in the synchronous update
mode.
