A.2.2 System Configurations With Distributed I/O - Siemens SIMATIC S7-400H Manual

Characteristic Values of Redundant Programmable Logic Controllers
A.2.2 System Configurations With Distributed I/O
The following system with two fault-tolerant CPUs 417-4 H and a one-sided I/O is
taken as a basis for calculating a reference factor which specifies the multiple of the
availability of the other systems with a distributed I/O compared with the baseline.
Redundant CPUs with a single-channel, one-sided or switched I/O
One-sided, distributed I/O
2 fiber-optic cables
ET 200M
Switched distributed I/O
2 fiber-optic cables
ET 200M
* A factor of 3 applies to the condition when the failure of an I/O module has resulted in the entire system
stopping. A factor of 12 applies when the failure of an I/O module has not resulted in the entire system
stopping.
A-6
S7-400H Programmable Controller Fault-Tolerant Systems
Baseline
1
Factor
3 12 *
or
A5E00068197-04