AN4266 datasheet(22/76 Pages) STMICROELECTRONICS

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Functional safety requirements for application software

AN4266

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Doc ID 024283 Rev 2

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.

Double Read Encoder Inputs

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

inputs which have edge detection interrupts (See Figure 3 for details).

Mandatory: One channel must be addressed by eTimer_0, and the other by eTimer_1.

Note:

Rationale: Two different eTimers must be used to avoid CCF (eTimer_0 and eTimer_1

belonging to different lakes).

For each signal, the SIUL can provide additional channels to support interrupt-based

reading.

Mandatory: In this configuration, the SIUL must be correctly configured to forward one or

two interrupt-based event readings.

Note:

Rationale: To configure pads used by this safety function

Mandatory: The input pads must not be physically adjacent (see Section 7, I/O pin/ball

configuration for details).

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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