Siemens NCM S7 Manual page 58

Installing and Starting the Ethernet CP with STEP 7
Table 2-1 Settings in the "Options" Tab , continued
Option
S
Multiplex OP Connections /
Reserve Internal CPU
Connection Resources
Time-of-Day Synchronization Tab
In this tab, you can make the settings for one of the two synchronization modes
explained below:
S SIMATIC mode
If the CP receives MMS time-of-day frames, its local time is synchronized
providing the NTP mode was not configured (MMS = Manufacturing Message
Specification).
The advantage of this mode is the accuracy that is generally higher than
achieved with the NTP mode.
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 replies from the
server, the most reliable and most accurate time is calculated and the time of
day on the station is synchronized.
The advantage of this mode is that the time of day can be synchronized beyond
the boundaries of the subnet.
58
Meaning / Effect
To attach TD/OPs or HMI devices, you can optimize the connection
resources on the S7-300 CPU by having up to 16 of these devices
communication on a single CPU connection resource (multiplex
mode).
If you do not use this option, the number of operable TD/OPs or HMI
devices depends on the number of available connection resources of
the CPU you are using.
As default, this option is deactivated. This means that a CPU
connection resource is used for multiplex only when necessary.
Configured S7 connections over the CP use the same multiplex
channel as you use for multiplexing the HMI connections. If you
configure S7 connections, this means that one CPU connection
resource is already used.
Please note: PG connections do not use the multiplexer; if you use a
PG, one connection resource is always occupied.
Note on Programming:
When you use the multiplex mode, you must specify the rack/slot
assignment of the CP for addressing on TD/OP/HMI connections
instead of the rack/slot assignment of the CPU!
Applications (for example ProAgent) that require block-related
messages (Alarm_S: SFC17-19) are not supported in the multiplex
mode.
SIMATIC NET NCM S7 for Industrial Ethernet
C79000-G8976-C129–06