AN3077 datasheet(37/82 Pages) STMICROELECTRONICS

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AN3077

Functional safety requirements for application software

3.14.1.3

Other requirements for CTU module usage

Mandatory: The only other requirement related to the CTU is that if the CTU is used to read

an analog signal through the ADC, the software shall verify the Invalid Command Error flag

(CTU_CTUEFR[ICR]) after programming the ADC command lists.

Note:

Rationale: To check the presence of invalid commands

3.15

ADC

If the ADC is used in a safety function, the following sections must be observed if an ADC

BIST is to be performed.

It is important to note that the ADC is part of the temperature measuring safety integrity

function, and it is therefore required that the HWBIST functions be executed once after the

boot even if the ADC is not in application use.

3.15.1

Read Analog Inputs

The customer has two options for reading analog inputs:

●

Single Read Analog Inputs

●

Double Read Analog Inputs

3.15.1.1

Single Read Analog Inputs

3.15.1.1.1

Hardware elements

The single-read analog input uses a single-analog-input channel either of ADC_0 or ADC_1

to acquire an analog voltage signal (See Figure 8).

To support a high diagnostic coverage two known reference supply voltages are utilized by

two software tests which are described in the following sections (ADC_SWTEST_TEST1

and ADC_SWTEST_TEST2).

The reference supply voltages are the following:

●

VDD_HV_ADR0 (ADC_0 high reference voltage)

●

VDD_HV_ADR1 (ADC_1 high reference voltage)

●

VSS_HV_ADR0 (ADC_0 low reference voltage)

●

VSS_HV_ADR1 (ADC_1 low reference voltage)

The SIUL unit must be configured properly to correctly enable the input pads. The pads

used for analog inputs are only of type INPUTS.

3.15.1.1.2

Safety Integrity Functions

Mandatory: The safety integrity is achieved by dedicated hardware BIST(g):

Note:

Rationale: Hardware BIST to check the integrity of the ADC, both analog and digital parts:

●

SUPPLY SELF-TESTRESISTIVE-CAPACITIVE SELF-TESTCAPACITIVE SELF-TEST

These hardware BISTs need some software to activate them. This software shall be developed by the

customer.

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