68
Function Description
WAGO-I/O-SYSTEM 750
750-806 Fieldbus Controller DeviceNet
TM
Manual
Version 2.0.0
7
Function Description
7.1
Operating System
7.1.1
Run-up
The mode selector switch may not be located in the lower position!
The mode selector switch may not be set at the bottom position during run-
up!
The fieldbus controller begins running up after switching on the power supply or
after a reset. The internal PFC program is then transferred to the RAM.
During the initialization phase, the fieldbus controller detects the I/O modules and
the current configuration and sets the variables to 0 or FALSE, or to an initial
value specified by the PFC program. The flags retain their status. During this
phase the I/O LED will flash red.
When run-up is successful, the I/O LED then stays lit continuously in green.
More information about the LED Signaling
Read the detailed description for the evaluation of the displayed LED state in the
section “Diagnostics” > … > “LED Signaling”.
7.1.2
PFC Cycle
After error-free run-up, the PFC cycle starts with the mode selector switch at the
top position, or on a Start command from WAGO-I/O-
PRO
. The input and output
data for the fieldbus, I/O modules and the timer values are read. The PFC program
contained in the RAM is then processed, after which the output data for the
fieldbus and I/O modules is written to the process image. At the end of the PFC
cycle, the operating system functions are executed for diagnostics and
communication (among other things) and the timer values are updated. The new
cycle begins by reading in of the input and output data and the timer values.
The operating mode is changed (“STOP”/“RUN”) at the end of a PFC cycle.
The cycle time is the time from the beginning of the PFC program up to the next
beginning of the cycle. If a loop is programmed within the PFC program, the PFC
runtime and the PFC cycle time will be extended accordingly.
The inputs, outputs and timer values are not updated while the PFC program is
being processed. Updating is performed only as defined at the end of the PFC
program. As a result, it is not possible to wait on an event from the process or a
set period to expire while a loop is in progress.
