Table 78. RTC_SM_2
SM CODE RTC_SM_2
Description Information redundancy on backup registers
Ownership End user
Detailed implementation
Data stored in RTC backup registers must be protected by a checksum with encoding capability (for
instance, CRC). Checksum must be checked by application software before consuming stored
data.
This method guarantees data versus erases due to backup battery failures
Error reporting Depends on implementation
Fault detection time Depends on implementation
Addressed fault model Permanent and Transient
Dependency on MCU configuration None
Initialization Depends on implementation
Periodicity On demand
Test for the diagnostic Not needed
Multiple faults protection CPU_SM_0: periodical core self-test software
Recommendations and known limitations
Implementation of this safety method shows a partial overlap with an already foreseen method for
Cortex
®
-M3 (CPU_SM_1); optimizations in implementing both methods are therefore possible
Table 79. RTC_SM_3
SM CODE RTC_SM_3
Description Application-level measures to detect failures in timestamps/event capture
Ownership End user
Detailed implementation
This method must detect failures affecting the RTC capability to correct execute the timestamps/
event capture functions. Due to the nature strictly application-dependent of this solution, no detailed
guidelines for its implementation are given here
Error reporting Depends on implementation
Fault detection time Depends on implementation
Addressed fault model Permanent and Transient
Dependency on MCU configuration None
Initialization Depends on implementation
Periodicity Periodic/On demand
Test for the diagnostic Not needed
Multiple faults protection CPU_SM_0: Periodical core self-test software
Recommendations and known
limitations
This method must be used only if the timestamps/event capture function is used in the safety function
implementation. It is worth to note that the use of timestamp/event capture in safety related
applications where the MCU is in sleep or stop mode is prevented by the assumed requirement
ASR7 (refer to Section 3.3.1 )
UM1845
Description of hardware and software diagnostics
UM1845 - Rev 4
page 55/108
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