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AN3077

Functional safety requirements for application software

The pads shall be configured via the appropriate pad configuration registers (PCRn) in the

SIUL module.

3.13.5

Write PWM Outputs

For ASIL D applications, PWM outputs used for safety purposes are assumed to be written

either redundantly or with read back as described in the following section.

The element safety function Write PWM Output is implemented as Double Write PWM

Outputs or Single Write PWM Outputs With Read Back.

3.13.5.1

Double Write PWM Outputs

The hardware elements eTimer_0 and eTimer_1 or FlexPWM_0 and FlexPWM_1 are used

to perform a Double Write PWM Output.

Mandatory: These units must be configured to implement two PWM channels. The SIUL

must be configured to define the configuration of the output pads used. The software must

perform a double write.

Mandatory: Redundant pads must not be adjacent and pad configuration/data registers

must be separate SIUL registers (see Section 7, I/O pin/ball configuration for details).

Note:

Rationale: To avoid CCF

Mandatory: To guarantee the integrity of the two output channels, the application should

test the SIUL configuration implementing the SIUL_SWTEST_REGCRC.

Note:

Rationale: To avoid CCF caused by incorrect configuration of the pads

Mandatory: The application software must implement a test for the eTimer_0 and eTimer_1

configuration (ETIMER0_SWTEST_REGCRC, ETIMER1_SWTEST_REGCRC) or for the

FlexPWM_0 and FlexPWM_1 configuration (FLEXPWM0_SWTEST_REGCRC,

FLEXPWM1_SWTEST_REGCRC) and a software write (PWMDW_SWAPP_WRITE).

Note:

Rationale: To verify that the configuration of the modules used by this safety function

adhere to the expected configuration

Table 7. Software BIST and/or test

Software BIST or test

Frequency

SIUL_SWTEST_REGCRC

Once after programming

GPODW_SWAPP_WRITE

Once every write

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