Diagnostics; Reactions To Faults - Siemens SIMATIC ET 200S Installation And Operating Manual

Diagnostics

5.1

Reactions to Faults

5.1
Safe State (Safety Concept)
The basic principle behind the safety concept is the existence of a safe state for all process
variables. For digital F-modules, the safe state is, for example, the value "0". This applies to
both sensors and actuators.
Reactions to Faults and Startup of F-System
The safety function requires that fail-safe values (safe state) be applied to a fail-safe module
instead of process data (passivation of the fail-safe module) in the following situations:
• When the F-system is started up
• In the case of errors during safety-related communication between the F-CPU and
• If F-I/O or channel faults occur (e.g., wire break, short circuit, discrepancy error)
Detected faults are entered in the diagnostic buffer of the F-CPU and the safety program in
the F-CPU is informed.
F-modules cannot save data as retentive data. When the system is powered down and then
back up, any faults still existing are detected again during startup. However, you have the
option of saving faults in your safety program.
Warning
For channels that you set to "deactivated" in
handling if a channel fault occurs, not even when this channel is affected indirectly by a
channel group fault ("Channel activated/deactivated" parameter).
ET 200S Distributed I/O System - Fail-Safe Modules
Hardware Installation and Operating Manual, 07/2005, A5E00103686-04
F-module via the PROFIsafe safety protocol (communication fault).
STEP 7
, there is no diagnostic reaction or error
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