Siemens CP 343-1 User Manual page 29

Reasons for reinitialization
The PROFINET IO device requests reinitialization by the user program in the
following situations:
S The length information of the input and output areas in the FCs does not match
the information configured for this PROFINET IO device on the PROFINET IO
system. A change in the length in the FC calls in the user program counts as a
configuration change.
S The CPU or CP changes to STOP mode.
S The watchdog time was exceeded (see below).
S Following a connection abort between the PROFINET IO controller and
PROFINET IO device (for example because the PROFINET IO controller was
turned off).
Watchdog
FC11 and FC12 each have their own watchdog. Depending on the average CPU
cycle time, the connection to the PROFINET IO controller is terminated if one of
the two blocks is no longer called following the initialization phase.
CP 343-1 Lean for Industrial Ethernet / Manual Part B3L
Release 03/2007
C79000-G8976-C198-04
6 Configuring and Programming the CP as a PROFINET IO Device
B3L−29