AN3077 datasheet(22/82 Pages) STMICROELECTRONICS

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Functional safety requirements for application software

AN3077

22/82

DocID16384 Rev 10

Note:

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

SIFs to avoid overloading the CPU.

●

ETIMERI_SWTEST_CMP

This software BIST is used to execute the comparison between the double reads

performed by a channel on eTimer_0 and another channel on eTimer_1. The

comparison must take into account possible approximation because of different

capturing of the input asynchronous signals.

3.13.2.1.4

Implementation details

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

●

eTimer_0 channels

●

eTimer_1 channels

Mandatory: The user must select one channel from the eTimer_0 module and another from

the eTimer_1.

Note:

Rationale: To avoid CCF (eTimer_0 and eTimer_1 belonging to different lakes)

Mandatory: The pads shall be configured via the appropriate pad configuration registers

(SIUL_PCRn).

Note:

Rationale: To configure pads used by this safety function

3.13.3

Read Encoder Inputs

For ASIL D applications, encoder inputs used for safety purposes are assumed to be

acquired redundantly as described in the following section.

Read Encoder Input means any input read related to signal transitions (rise or fall). This

may also include signals coming from an encoder.

3.13.3.1

Double Read Encoder Inputs

3.13.3.1.1

Hardware elements

A Double Read Encoder Input is implemented using two channels that can be provided by:

●

eTimer_0

●

eTimer_1

●

SIUL

When both channels are provided by the timer units, the signals of one encoder must be

addressed to eTimer_0 and the signals of the other encoder must be addressed to

eTimer_1. Alternatively, one or both channels can be provided by the SIUL, which supports

interrupt based reading of encoder signals. This means the SIUL must use general purpose

Table 4. Software BIST and/or test

Software BIST or test

Frequency

ETIMER0_SWTEST_REGCRC

Once after programming

ETIMER1_SWTEST_REGCRC

Once after programming

SIUL_SWTEST_REGCRC

Once after programming

ETIMERI_SWTEST_CMP

Once for every acquisition

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