AN3077 datasheet(44/82 Pages) STMICROELECTRONICS

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Functional safety requirements for application software

AN3077

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DocID16384 Rev 10

Mandatory: The shared channels (AN[11:14]) suffer from CCF because they share pads

between each ADC module. Therefore, they are omitted (considered not safe) for double

reads. The comparison of the results is performed by application software (See Figure 14).

Note:

Rationale: ADC_0 and ADC_1 share a pad for the channels (AN[11:14]). Omitting them

from double read eliminates a possible source of CCF.

Mandatory: After boot but before executing the safety function the following tests shall be

executed to detect latent faults (See Section 3.15.1.1.3, Hardware BIST and

Section 3.15.1.1.3.1, Hardware BIST implementation):

●

SUPPLY SELF-TEST

●

RESISTIVE-CAPACITIVE SELF-TEST

●

CAPACITIVE SELF-TEST

Note:

Rationale: To check the integrity of the ADC modules

Mandatory: Before running the HW self-test, the customer must copy the threshold values

of the analog watchdogs from test sector into the watchdog registers (See “Self test analog

watchdog” section of the “Analog-to-Digital Converter (ADC)” chapter in Device_Number

Reference Manual).

Note:

Rationale: To set the correct threshold for the self-test

3.15.1.2.2

Safety Integrity Functions

Safety integrity is achieved by replicated acquisition with separate analog input channels

and software comparison by the processing function (See Figure 14).

Mandatory: The following software test must be implemented by the application software:

ADC0_SWTEST_REGCRC, ADC1_SWTEST_REGCRC, SIUL_SWTEST_REGCRC

Note:

Rationale: To verify that the configuration of the module used by this safety function

corresponds with what is expected

Note:

Rationale: To avoid CCF caused by improper configuration of the pads

Mandatory: In addition, the software test ADC_SWTEST_CMP must be implemented to

compare the channel reads.

Note:

Rationale: To verify that the two sets of read data compare

It is important to note that this safety integrity function might be applied in addition to Single

Analog Read Inputs, which increases diagnostic coverage.

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