Siemens SIMATIC S7-CPs, Manual

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8 Further Notes on Operation
B − 39
CP 443-1 for Industrial Ethernet / Manual Part B
Release 07/2010
C79000-G8976-C223
− 06
8.4 Media redundancy
You can use the CP in a ring topology with media redundancy. The CP itself can be
redundancy manager.
You create the configuration in STEP 7 in the properties dialog of the PROFINET
interface in the “Media redundancy” tab (HW Config: Row “X1 (<device name>)”).
For more detailed information on configuration, refer to the online help of the
“Media redundancy” tab and in Part A of the manual.
Notice
If you are using IRT communication, no media redundancy is supported.
8.5 Time-of-day synchronization
General rules
The CP supports the two modes explained below for time-of-day synchronization:
S SIMATIC mode
If the CP receives MMS time-of-day messages, its local time is synchronized
providing the NTP mode was not defined during configuration (MMS =
Manufacturing Message Specification).
The advantage of this mode is that it is generally more accurate than the NTP
mode (guar − 1 ms). In contrast to the NTP mode, it is not possible to
forward the time of day over routers; in other words, to other subnets.
S
NTP mode (NTP: Network Time Protocol)
In the NTP mode, the CP sends time queries (in the client mode) at regular
intervals to the NTP server in the subnet (LAN). Based on the responses of the
server, the most reliable and most accurate time of day is calculated and the
time synchronized on the station (in all modules with time-of-day functionality).
The advantage of this mode is that the time of day can be synchronized beyond
the boundaries of the subnet. The accuracy depends on the quality of the NTP
server used.
Note
No automatic changeover to daylight saving is defined in NTP. As a result, you
may need to implement this changeover using a program application.