Siemens Simatic S7-300 CPU 31xC and CPU 31x S7-300 - Manual (Page 34)

Communication
3.2 Communication services
CPU 31xC and CPU 31x, Technical data
3-6
Manual, Edition 08/2004, A5E00105475-05
3.2 Communication services
3.2.1 Overview of communication services
Selecting the communication service
You need to decide on a communication service, based on functionality requirements. Your
choice of communication service will have no effect on:
•
the functionality available,
• whether an S7 connection is required or not, and
• the time of connecting.
The user interface can vary considerably (SFC, SFB, ...), and is also determined by the
hardware used (SIMATIC CPU, PC, ...).
Overview of communication services
The table below provides an overview of communication services offered by the CPUs.
Table 3-2 Communication services of the CPUs
Communication service Functionality Time at which the S7
connection is established ...
via MPI via DP via
PtP
via
PN
PG communication Commissioning, test,
diagnostics
From the PG, starting when
the service is being used
X X – X
OP communication Monitor and modify via OP at POWER ON X X – X
S7 basic communication Data exchange is programmed at the blocks
(SFC parameters)
X – – –
S7 communication Data exchange in server
and client mode:
Configuration of
communication required.
via active partner at POWER
ON.
Only in
server
mode
Only in
server
mode
– X
Global data
communication
Cyclic data exchange (for
example, flag bits)
does not require an S7
connection
X – – –
Routing PG functions
(only for CPUs with
DP or PN interface)
for example testing,
diagnostics on other
networks also
from the PG, starting when the
service is being used
X X – X
PtP communication Data exchange via serial
interface
does not require an S7
connection
– – X –
SNMP
(Simple Network
Management Protocol)
Standard protocol for
network diagnostics and
configuration
does not require an S7
connection
– – – X
open communication by
means of TCP/IP
Data exchange via
Industrial Ethernet with
TCP/IP protocol (by means
of loadable FBs)
Does not require an S7
connection, is handled in the
user program by means of
loadable FBs
– – – X