Using I/O on the S7-400H
7-2
Automation System S7-400H Fault-tolerant Systems
A5E00068197-07
7.1 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:
I/O Type Configuration Availability
Digital input Single channel one-way
Single channel switched
Dual channel redundant
normal
increased
high
Digital output Single channel one-way
Single channel switched
Dual channel redundant
normal
increased
high
Analog input Single channel one-way
Single channel switched
Dual channel redundant
normal
increased
high
Analog output Single channel one-way
Single channel switched
normal
increased
A two-channel redundant configuration on the user level is similarly possible.
However, you have to implement the high degree of availability in the user program
(refer to Section 7.4).
Addressing
No matter whether you are using a single-channel, one-way 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.
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