ST STM32F2 Series - Table 75. GPIO_SM_3

SM CODE GPIO_SM_2
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 and Transient
Dependency on MCU
configuration
None
Initialization Depends on implementation
Periodicity Continuous
Test for the diagnostic Not needed
Multiple faults protection CPU_SM_0: periodical 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 number (for instance PORTA.1 and PORTB.5)
• 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
Table 75. GPIO_SM_3
SM CODE GPIO_SM_3
Description GPIO port configuration lock register
Ownership ST
Detailed implementation
This safety mechanism prevents configuration changes for GPIO registers; it addresses therefore
systematic faults in software application.
The use of this method is encouraged to enhance the end-application robustness for systematic
faults
Error reporting Depends on implementation
Fault detection time Depends on implementation
Addressed fault model None (Systematic only)
Dependency on MCU configuration None
Initialization
The correct write sequence must be applied to bit 16 (LCKK) of GPIOx_LCKR after the final GPIO
configuration has been written by the application software.
Periodicity Continuous
Test for the diagnostic Not needed
Multiple faults protection Not needed
Recommendations and known limitations
This method does not address transient faults (soft errors) that can possibly cause bit-flips on GPIO
registers at running time
UM1845
Description of hardware and software diagnostics
UM1845 - Rev 4
page 53/108