AN4266 datasheet(37/76 Pages) STMICROELECTRONICS

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AN4266

Functional safety requirements for application software

Doc ID 024283 Rev 2

37/76

To enable the interrupt in case of error during reload, the IEE flag in the CTUIR register shall

be asserted.

This interrupt is shared between several sources of error. The user can discriminate among

them by reading the CTUEFR register.

Implementation details

The following hardware elements shall be used for the safety function:

●

CTU

●

One eTimer channel

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

Table 10.

Software BIST and/or test

Software BIST or test

Frequency

CTU_HWSWTEST_TRIGGERNUM

Once for every control period (< FTTI)

CTU_SWTEST_TRIGGERTIME

Once for every CTU control period (triggered

mode) or every trigger (sequential mode)

CTU_HWSWTEST_TRIGGEROVERRUN

Once for every trigger

CTU_HWSWTEST_ADCCOMMAND

Once for every ADC command

CTU_SWTEST_ETIMERCOMMAND

Once for every control period (< FTTI)

CTU_HW_CFGINTEGRITY

Once for every control period (< FTTI)

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