Siemens SIMATIC S7 F Manual page 245

Fail-Safe Blocks
Error Information in Diagnostic Buffer
Error Code (W#16#...)
75DAH
75E1H
75E1H
...
75E1H
75E1H
75E1H
Fail-Safe Systems
A5E00085588-03
Description
Error in the safety data format of the input MAX_CYC or
the output DIFF (error due to online modification of the
Safety Program or internal CPU fault)
Power failure
Internal CPU fault
Maximum permissible F cycle time exceeded or internal
CPU fault
Internal CPU fault
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