Fail-Safe signal module (SM) diagnostics
6.1 Reactions to faults
S7-1200 Functional Safety Manual
116 Manual, 02/2015, A5E03470344-AA
Time-out of the PROFIsafe message (F-monitoring time exceeded) passivates all module
channels.
Table 6- 1 Signal module type and passivation result
SM 1226 F-DI 16 x 24 VDC
• Tests are evaluated per channel, in order to allow chan-
nel-granular passivation of defective inputs.
• If a channel fault occurs for a 1oo1 configuration, only
the affected channel is passivated. For a 1oo2, the
channel group of two inputs in the 1oo2 configuration are
passivated.
SM 1226 F-DQ 4 x 24 VDC
• Tests are evaluated per channel, in order to allow chan-
nel-granular passivation of defective outputs.
• Diagnostic evaluations are performed separately for
each of the two switches of a channel. Failure detection
for one switch leads to passivation of the channel.
SM 1226 F-DQ 2 x Relay
• Tests are evaluated per channel, in order to allow chan-
nel-granular passivation of defective outputs.
• Diagnostic evaluations are performed separately for
each of the two relays of a channel. Failure detection for
one relay leads to passivation of the channel.
Response to faults in the fail-safe system
You should prepare maintenance procedures for your system to assure that return to
operation after a detected fault is controlled and documented.
The following steps must be performed:
1. Diagnosis and repair of the fault
2. Revalidation of the safety function
3. Recording in the service report
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