Communication
4.2 Communication services
S7-400 Automation System, CPU Specifications
Manual, 10/2006, 6ES7498-8AA04-8BA0
4-9
4.2.5 S7 communication
Properties
A CPU can always operate as a server or client in S7 communication: A connection is
configured permanently. The following connections are:
● One-sided configured connections (for PUT/GET only)
● Two-side configured connections (for USEND, URCV, BSEND, BRCV, PUT, GET)
S7-400 PN CPUs provide an integrated Industrial Ethernet port on the CPU module, allowing
you to use S7 communication over Industrial Ethernet without going through a
communications processor (CP). Use a CP 443 for S7 communication for other S7-CPUs.
The S7-400 features integrated S7 communication services that allow the user program in
the controller to initiate reading and writing of data. The S7 communication functions are
called via SFBs in the user program. These functions are independent of the specific
network, allowing you to program S7 communication over PROFINET, Industrial Ethernet,
PROFIBUS, or MPI.
S7 communication services provide the following features:
● During system configuration, you configure the connections used by the
S7 communication. These connections remain configured until you download a new
configuration.
● You can establish several connections to the same partner. The number of
communication partners accessible at any time is restricted to the number of connection
resources available.
S7 communication allows you to transfer a block of up to 64 KB per call to the SFB. An
S7-400 transfers a maximum of 4 variables per block call.
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