Assembling An S7-400; Rack Fitted With Modules In The S7-400 System - Siemens S7-400 Installation Manual

Installing the S7-400
2.1

Assembling an S7-400

Introduction
An S7-400 programmable controller consists of a central rack (CR) and one or
more expansion racks (ERs), as required. You use ERs when there are insufficient
slots in the CR for your application, or when you wish to operate signal modules
separated from the CR (e.g. in the immediate vicinity of your process).
When using ERs, you need interface modules (IMs) as well as the additional racks,
and additional power supply modules if necessary. When using interface modules,
you must always use the appropriate partners: you insert a send IM in the CR, and
the matching receive IM in each connected ER (see Reference Manual,
Chapter 7).
The M7-400 modules function similarly to the S7-400 modules and also use the
racks in the S7-400 range. Any differences in function or data can be found directly
at the relevant point or in Section 8.1 "Mechanical Configuration."
Central Rack (CR) and Expansion Rack (ER)
The rack containing the CPU is known as the central rack (CR). The racks
containing modules in the system and connected to the CR are the expansion
racks (ERs).
Shown in Figure 2-1 is a rack with 18 slots configured as a CR.
PS CPU
Figure 2-1
2-2
SMs

Rack Fitted with Modules in the S7-400 System

S7-400 and M7-400 Programmable Controllers Hardware and Installation
A5E00069481-04