System Configurations With Distributed I/O; Redundant Cpus With A Single-Channel, One-Way Or Switched 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-way 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-way or switched I/O

One-way, 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
Automation System S7-400H Fault-tolerant Systems
Baseline
1
Factor
3 or. 12 *
A5E00068197-07