Assigning Parameters To Modules In A Fault-Tolerant Station; Central Processing Unit (Exception); Modules In The I/O Address Area; Recommendations For Setting The Cpu Parameters - Siemens SIMATIC S7-400H Manual

9.2.3

Assigning Parameters to Modules in a Fault-Tolerant Station

Introduction
Assigning parameters to modules in a fault-tolerant station is no different to
assigning parameters to modules in S7-400 standard stations.
Procedure
All the parameters of the redundant components (with the exception of MPI and
communication addresses) must be identical.

Central processing unit (exception)

CPU parameters can only be set for CPU0 (CPU on rack 0). Any values that you
specify for it are automatically allocated to CPU1 (CPU on rack 1). The settings of
CPU1 cannot be changed with the exception of the following parameters:
• MPI address of the CPU
• Station and diagnostics addresses of the integrated PROFIBUS DP interfaces

Modules in the I/O address area

A module that is addressed in the I/O address area must either be completely
within or completely outside the process image. Otherwise, consistency cannot be
guaranteed, and the data may be corrupted.
9.2.4

Recommendations for Setting the CPU Parameters

CPU parameters that determine cyclic behavior
You specify the CPU parameters that determine the cyclic behavior of the system
on the "Cycle/Clock memory" tab.
Recommended settings:
• As long a scan cycle monitoring time as possible (e.g.6000 ms)
• As small a process input image as possible (slightly larger than the number of
inputs actually used)
• As small a process output image as possible (slightly larger than the number of
outputs actually used)
• OB 85 call when there is an I/O access error: only with incoming and outgoing
errors
Automation System S7-400H Fault-tolerant Systems
A5E00068197-07
Configuring with STEP 7
9-5