3 Operating the Ethernet CP with
A-72
S7-CPs for Industrial Ethernet Configuring and Commissioning
Release 01/2007
C79000-G8976-C182-07
Table 3-1 Settings in the “Options” Tab , continued
Option Meaning / Effect
Send keepalives for
connections
Here, you can set the interval at which keepalives are sent to the
partner of a communications connection. This setting decides the
latest time after which the failure of a communications partner is
detected.
For all connection-oriented services, the Ethernet CP is configured so
that keepalives are sent. This guarantees that connections are
closed if a communications partner fails and that the connection
resources are released. The setting made here applies to all TCP
and ISO-on-TCP connections operated via the CP; a
connection-oriented setting is not possible.
Possible values:
Default Setting: 30 seconds
Turn keepalives off 0 seconds
Maximum value: 65535 seconds
Notes / Recommendations:
Remember that the keepalive mechanism can keep underlying
connections established (for example, an ISDN telephone
connection) although no user data are actually being transmitted. If
this is not required, set the interval so high that the underlying
connection is closed down when no further user data are sent before
a keepalive is sent.
Multiplex OP connections /
reserve internal CPU
connection resources
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.
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