Application - Siemens S5-155U System Manual

Application

2.1

Application

2 - 4
The S5-135U/155U programmable controllers comprise a central
controller (CC) and, if required, one or more expansion units (EUs).
You need EUs when there are insufficient slots in the CC for the
modules to be used.
Various interface modules (IMs) are available for communication
between the CC and the EUs and between the EUs. It is therefore
possible to install an EU or EUs in the immediate vicinity of the CC
(centralized configuration) or at some distance (distributed
configuration). A combination of both types of configuration is also
possible by connecting additional EUs in a centralized configuration
with a distributed EU (see Figure 2-6).
This is clarified on the following pages.
System Manual
C79000-B8576-C199-03