Rules For The Assembly Of Fault-Tolerant Stations; Configuring Hardware - Siemens SIMATIC S7-400H System Manual

Configuring with STEP 7
12.2 Configuring with STEP 7
12.2.1

Rules for the assembly of fault-tolerant stations

The following rules have to be complied with for a fault-tolerant station, in addition to the
rules that generally apply to the arrangement of modules in the S7-400:
● The CPUs always have to be inserted in the same slots.
● Redundantly used external DP master interfaces or communication modules must be
● External DP master interface modules for redundant DP master systems should only be
● Redundantly used modules (for example, CPU 417-4H, DP slave interface module IM 153-2)
Installation rules
● A fault-tolerant station may contain up to 20 expansion racks.
● Even-numbered mounting racks can be assigned only to central unit 0, whereas
● Modules with communication bus interface can be operated only in mounting racks 0
● Communication-bus capable modules are not permissible in switched I/Os.
● Pay attention to the mounting rack numbers when operating CPs for redundant
● A rack number is also assigned for DP master no. 9 onwards if the central unit contains
Compliance with the rules is monitored automatically by STEP 7 and taken into account in
an appropriate manner during configuration.
12.2.2

Configuring hardware

The simplest way of achieving a redundant hardware configuration consists in initially
equipping one rack with all the redundant components, assigning parameters to them and
then copying them.
You can then specify the various addresses (for one-sided I/Os only!) and arrange other,
non-redundant modules in individual racks.
Special features in presenting the hardware configuration
In order to enable quick recognition of a redundant DP master system, it is represented by
two closely parallel DP cables.
180
inserted in the same slots in each case.
inserted in central units, rather than in expansion units.
must be identical, i.e. they must have the same order number, the same version, and the
same firmware version.
odd-numbered mounting racks can be assigned only to central unit 1.
through 6.
communication in expansion racks:
The numbers must be directly sequential and begin with the even number - for example,
mounting racks numbers 2 and 3, but not mounting racks numbers 3 and 4.
DP master modules. The number of possible expansion racks is reduced as a result.
System Manual, 09/2007, A5E00267695-03
S7-400H