Siemens Simatic S7-400

Configuration Variants of the S7-400
6-8
Automation System S7-400 Configuration and Use
A5E0044271 1-02
6.5 Segmented and Split Rack
Introduction
The S7-400 allows you to install two CPUs in one rack and thereby centrally
control two processes independently.
Two Central Controllers in a Segmented Rack
Segmented racks makes it possible to install two CPUs in a single rack. The I/O
bus is divided into two segments in such a rack. A CPU can be installed in each
segment.
The CPUs operate independent of one another and access separate signal
modules. Operating state transitions of one CPU do not affect the other CPU.
The CPUs can access each other via the MPI interface without addition hardware
because they share the communication bus.
Figure 6-4 shows a segmented rack with two I/O segments and the common
communication bus.
123456789123456789
123456789101112131415161718
C bus
I/O bus
segment 2
I/O bus
segment 1
Figure 6-4 Segmented rack
Advantages
Integrating two CPUs in a single rack not only results in a compact assembly, it
also saves on costs since only one rack and one power supply are needed.