WAGO 750-830 Manual page 100

100 • BACnet/IP Controller 750-830
Programming the PFC Using WAGO-I/O-PRO CAA
3.1.8.4.1 IEC Task Sequence
1. Determine the system time (tStart).
2. If no full internal bus cycle has run since the last time the outputs were
3. Reading of inputs and reading back of the outputs from the process image.
4. If the application program has been started.
5. Writing of the outputs to the process image.
6. Determine the system time (tEnd).
3.1.8.4.2 Overview of Most Important Task Priorities
Internal bus task/fieldbus task (internal)
The internal bus task matches the process image to the input/output data of the
modules in defined cycles.
The fieldbus tasks are performed as triggered by events and only require com-
puting time when communication is performed via fieldbus (MODBUS).
Normal task (IEC tasks 1-10)
IEC tasks with this priority may be interrupted by the internal bus tasks.
Therefore, configuration for the connected modules and communication via
fieldbus with the watchdog activated for the task call interval must be taken
into account here.
PLC-Comm task (internal)
The PLC-Comm task is active when logged in and takes up communication
with the WAGO-I/O-PRO CAA gateway.
Background task (IEC tasks 11-31)
All internal tasks have a priority higher than that for the IEC background
tasks. These tasks are therefore very well suited for performing time-intensive
and non-critical time tasks, such as calling up functions in the SysLibFile.lib.
written:
! Wait until the next internal bus cycle is completed.
! Execute the program codes for this task.
! tEnd - tStart = runtime for the IEC task
WAGO-I/O-SYSTEM 750
BACnet/IP Controller