Technical data

Table Of Contents
System Software for S7-300/400 System and Standard Functions - Volume 2/2
A5E00739858-01
20-1
20 Overview over the S7 Communication and
the S7 Basic Communication
20.1 Differences between the Blocks of the S7
Communication and the S7 Basic Communication
Selection Criteria
Apart from global data communication, there are two other methods of exchanging
data between CPUs/FMs of SIMATIC S7 programmable controllers:
Data exchange using communication SFCs for non-configured S7 connections
Data exchange using communication SFBs for configured S7 connections
Which method you choose, depends on the SIMATIC S7 programmable controller
you are using (S7-300, S7-400) and on other parameters for data exchange. The
following table contains a list of criteria on which you can base your selection.
Criteria Communication SFCs for Non-
Configured S7 Connections
Communication SFBs for
Configured S7 Connections
Availability of the blocks S7-300 and S7-400 as SFCs S7-300 as FBs and FC
S7-400 as SFBs and SFC
Communication
connections
The connection is not configured. It is
established when the SFC is active.
The connection either remains established
after the data have been transferred or it is
terminated parameter-controlled.
If a connection cannot be established
temporarily, the corresponding job cannot be
sent.
Connections are configured
permanently in the system
configuration.
Change to the STOP
mode
If the CPU that initiated the data transfer
changes to STOP mode, all the connections
it established are terminated.
The connection is maintained in
the STOP mode.
Several connections to a
partner
At any one time, a maximum of one
connection is possible to a communication
partner.
You can establish several
connections to the same partner.
Address range Modules can be addressed in the local
station or in the MPI subnet
Modules can be addressed on the
MPI network, on PROFIBUS or on
Industrial Ethernet