AN3077 datasheet(46/82 Pages) STMICROELECTRONICS

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Functional safety requirements for application software

AN3077

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3.15.2

Other requirements

Other requirements related to the ADC modules are:

●

When an application needs to access the ADC result FIFO, a 32-bit read access shall

be performed to verify the channel number on which the conversion has been

executed.

●

If the ADC analog watchdog function is used for function-safety relevant signal, two

analog watchdog channels must monitor the same signal.

●

If the Sine Wave Generator (SWG) is used, the ADC (in conjunction with CTU) must be

used to check the output signal.

3.16

Temperature sensors

There are two temperature sensors: temperature sensor 0 (TSENS_0) mapped to ADC_0

and temperature sensor 1 (TSENS_1) mapped to ADC_1.

Mandatory: During power up, the two temperature sensors need to be read by software

(TSENS_0 from ADC_0 channel 15, TSENS_1 from ADC_1 channel 15), which must verify

that the read values are similar as a means of assessing the functionality of the sensors.

However, nothing prohibits reading the temperature sensors during run time if needed.

Note:

Rationale: A means of assessing functionality of the temperature sensors

Mandatory: In addition, the temperature must be acquired from at least one of the

temperature sensors by software every FTTI during run time. In case of a fault, software

must move the system to a safe state.

Note:

Rationale: To detect over-temperature faults

To set a proper threshold the customer must consider that the maximum operating junction

temperature is 150 °C (See the Device_Number data sheet) and the temperature sensor

accuracy is 10° C.

Note:

Implementation hint: See the Device_Number Reference Manual for details on TSENS_x

implementation in relation to the ADC.

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

function. Therefore, it is required that the BIST of the ADC be executed once after boot even

if the ADC is not used by the application.

Table 12. Software BIST and/or test

Software BIST or test

Frequency

SUPPLY SELF-TEST

Once after boot

RESISTIVE-CAPACITIVE SELF-TEST

Once after boot

CAPACITIVE SELF-TEST

Once after boot

ADC0_SWTEST_REGCRC

Once after programming

ADC1_SWTEST_REGCRC

Once after progamming

SIUL_SWTEST_REGCRC

Once after progamming

ADC_SWTEST_CMP

Once for every acquisition

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