System Configurations With Distributed I/Os - Siemens SIMATIC S7-400H System Manual

A.2.2

System configurations with distributed I/Os

The system with two fault-tolerant CPUs 417-4 H and one-sided I/Os described below is
taken as a basis for calculating a reference factor which specifies the multiple of the
availability of the other systems with distributed I/Os compared with the base line.
Redundant CPUs with single-channel, one-sided or switched I/Os
One-sided distributed I/Os
Switched distributed I/O, CCF = 2 %
S7-400H
System Manual, 09/2007, A5E00267695-03
Characteristic values of redundant automation systems
A.2 Comparison of MTBF for selected configurations
Base line
1
Factor
15
317