Siemens SIMATIC NET S7-300 Manual page 27

1.4 S7 Communication on Industrial Ethernet
Application
S7 communication via Industrial Ethernet allows program-controlled
communication using communication SFBs/FBs via configured S7 connections.
Per job, up to 64 Kbytes of user data can be transmitted.
The Ethernet CP acts as an "S7 communication relay" by passing on the S7
functions via Industrial Ethernet. Depending on the configuration of the Ethernet
CP, data transfer is on the basis of the ISO transport or the ISO-on-TCP protocol
(TCP/IP with RFC 1006).
From the perspective of the user, S7 communication is identical over PROFIBUS
and Industrial Ethernet.
Nodes
Two situations can occur depending on device type and plant configuration:
S Client and server functionality at both ends
S7 connections can be operated between the following nodes with the entire
functionality of S7 communication:
- between S7 stations S7-300 and S7-400;
- between S7 stations and PC/PG stations with an Ethernet CP.
S7 - 400
Ethernet
PC/PG with Ethernet CP
Figure 1-3 Nodes Communicating on S7 Connections over Industrial Ethernet
S7-CPs for Industrial Ethernet Configuring and Commissioning
Release 01/2007
C79000-G8976-C182-07
1 Communication via Ethernet CPs in S7 Stations
Ethernet CP
S7 - 300
WAN *
* only TCP/IP
S7 - 300 / 400
Ethernet CP
M7
PUT / GET
BSEND / BRECV
USEND / URECV
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