ST STM32L4 Series User Manual

Table 115. RTC_SM_1
SM CODE RTC_SM_1
Description Application check of running RTC
Ownership End user
Detailed implementation
Application software implements some plausibility check on RTC calendar or timing data,
mainly after a power-up and further date reading by RTC.
The guidelines for the implementation of the method are the following:
• RTC backup registers are used to store coded information in order to detect the
absence of VBAT during power-off period.
• RTC backup registers are used to periodically store compressed information on current
date or time
• Application software executes minimal consistence checks for date reading after power-
on (detecting “past” date or time retrieve).
• Application software periodically checks that RTC is actually running, by reading RTC
timestamp progress and comparing with an elapsed time measurement based on
STM32 internal clock or timers.
Error reporting Depends on implementation
Fault detection time Depends on implementation
Addressed fault model Permanent/transient
Dependency on Device configuration None
Initialization Depends on implementation
Periodicity Periodic
Test for the diagnostic Not applicable
Multiple-fault protection CPU_SM_0: Periodic core self-test software
Recommendations and known limitations
This method provides a limited diagnostic coverage for RTC failure modes. In case of End
user application where RTC timestamps accuracy can affect in severe way the safety function
(for example, medical data storage devices), it is strongly recommended to adopt more
efficient system-level measures.
Table 116. 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/transient
Dependency on Device configuration None
Initialization Depends on implementation
Periodicity Periodic/On demand
Test for the diagnostic Not applicable
Multiple-fault protection CPU_SM_0: Periodic core self-test software
Recommendations and known limitations None
UM2305
Hardware and software diagnostics
UM2305 - Rev 10
page 66/110

ST STM32L4 Series Specifications

General

Brand	ST
Model	STM32L4 Series
Category	Microcontrollers
Language	English