Introduction - Siemens SIMATIC S7-400H Manual

Using I/O on the S7-400H
6.1

Introduction

I/O configuration types
In addition to the power supplies and central processing units, which are always
redundant, there are the following configuration types for the I/O, which are
supported by the operating system:
Single-channel, one-sided configuration with normal availability
Single-channel, switched configuration with enhanced availability
A two-channel redundant configuration is similarly possible. However, you have to
implement the high degree of availability in the user program (refer to Section 6.4).
Addressing
No matter whether you are using a single-channel, one-sided or switched I/O, you
always specify the same address for the I/O.
Limits of I/O configuration
If there are insufficient slots in the central controllers, you can add up to 20
expansion units to the configuration of the S7-400H.
You can assign even-numbered mounting racks only to central controller 0,
whereas odd-numbered mounting racks can be assigned only to central
controller 1.
For using distributed I/O you can connect up to 12 DP master systems in each of
the subsystems (2 DP master systems to the integrated interfaces of the CPU and
10 more via external DP master systems).
You can operate up to 32 slaves on the integrated MPI/DP interface. You can
connect up to 125 distributed I/O devices to the integrated DP master interface
and the external DP master systems.
6-2
S7-400H Programmable Controller Fault-Tolerant Systems
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