ST STM32L4 Series User Manual

Table 45. GPIO_SM_1
SM CODE GPIO_SM_1
Description 1oo2 for input GPIO lines
Ownership End user
Detailed implementation
This method addresses GPIO lines used as inputs. Implementation is done by connecting
the external safety-related signal to two independent GPIO lines. Comparison between the
two GPIO values is executed by Application software each time the signal is used to affect
Application software behavior.
Error reporting Depends on implementation
Fault detection time Depends on implementation
Addressed fault model Permanent/transient
Dependency on Device configuration None
Initialization Permanent/transient
Periodicity On demand
Test for the diagnostic Not applicable
Multiple-fault protection CPU_SM_0: Periodic core self-test software
Recommendations and known limitations
To reduce the potential impact of common cause failure, it is recommended to use GPIO lines:
• belonging to different I/O ports (for instance port A and B)
• with different bit port number (for instance PA1 and PB5)
• mapped to non-adjacent pins on the device package
Table 46. GPIO_SM_2
SM CODE GPIO_SM_2
Description Loopback scheme for output GPIO lines
Ownership End user
Detailed implementation
This method addresses GPIO lines used as outputs. Implementation is done by a loopback
scheme, connecting the output to a different GPIO line programmed as input and by using the
input line to check the expected value on output port. Comparison is executed by Application
software periodically and each time output is updated.
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 Continuous
Test for the diagnostic Not applicable
Multiple-fault protection CPU_SM_0: Periodic core self-test software
Recommendations and known limitations
To reduce the potential impact of common cause failure, it is recommended to use GPIO lines:
• belonging to different I/O ports (for instance port A and B)
• with different bit port number (for instance PA1 and PB5)
• mapped to non-adjacent pins on the device package
Efficiency versus transient failures is linked to final application characteristics. We define as
Tm the minimum duration of GPIO output wrong signal permanence required to violate the
related safety function(s). Efficiency is maximized when execution test frequency is higher
than 1/Tm.
UM2305
Hardware and software diagnostics
UM2305 - Rev 10
page 32/110

ST STM32L4 Series Specifications

General

Brand	ST
Model	STM32L4 Series
Category	Microcontrollers
Language	English