258 Run-time System CODESYS 2.3
WAGO-I/O-SYSTEM 750
750-8207 PFC200 CS 2ETH RS 3G
Manual
Draft version 1.2.1 from 2017-09-13, valid from FW Version 02.06.20(09)
8.9.3
Case 3: CODESYS Task Interval Greater than Twice the
Internal Data Bus Cycle
The I/O data from the internal data bus are refreshed once prior to the
CODESYS task and once after the CODESYS task.
Prior to processing the CODESYS task, the internal data bus cycle is executed,
which provides the current input data for the CODESYS task. After execution of
the CODESYS task, an additional internal data bus cycle is started, which
provides the output data to the I/O modules.
This ensures that at the start of every CODESYS task, current input data are
available from the internal data bus and the output data from each CODESYS
task are quickly output to the I/O modules. This prevents processing of internal
data bus cycles that would unnecessarily use a great deal of computing time on
the CPU.
Figure 94: I/O Module Synchronization 03
CTI: CODESYS Task Interval
CT: CODESYS Task that accesses the I/O module of the internal data bus
KBZ: Internal Data Bus Cycle
Example:
CODESYS task interval (CTI): 5000 µs
Internal data bus cycle (KBZ): 2000 µs
Result:
Execution of the internal data bus cycle 2000 µs prior to the CODESYS
task and once directly after the CODESYS task.
