AN3077 datasheet(28/82 Pages) STMICROELECTRONICS

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Functional safety requirements for application software

AN3077

28/82

DocID16384 Rev 10

Figure 5. Double Write Digital Output

3.13.4.2.1

Software test implementation

●

SIUL_SWTEST_REGCRC

The configuration registers of the SIUL are read and a CRC is computed. This CRC

value is compared with what is expected.

Note:

Implementation hint: The eDMA and CRC modules should be used to implement this SIF

to avoid overloading the CPU.

●

GPODW_SWAPP_WRITE

Mandatory: The output write of a redundant channel must be implemented following this

guideline:

●

The two outputs are written with a single instruction to the appropriate register.

●

The output register is read back.

Note:

Rationale: To minimize CCF of the SIUL

Note:

Implementation hint: To write two or more GPIOs with a single instruction, the Masked

Parallel GPIO Pad Data Out register (MPGPDOx) register can be used.

Application software shall verify that the two GPIOs used are in the same MPGPDOx

To protect the value of the other GPIOs that belong to the same MPGPDOx, the MASK field

of the MPGPDOx register needs to be properly configured.

3.13.4.2.2

Implementation details

The only hardware element that can be used for the safety function is the GPIO.

Note:

Every pad that is not dedicated to a single function can be configured as GPIO. ADCs are

an exception to this rule, as they can be configured as inputs only.

SIUL

Digital Out Double

Configuration

GPO[y]

GPO[x]

= Output Pad

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