AN3077 datasheet(31/82 Pages) STMICROELECTRONICS

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AN3077

Functional safety requirements for application software

Mandatory: The output write of a redundant PWM channel must be implemented by writing

the new output values to both the PWM channels. The customer can decide whether to use

both eTimers (eTimer_0, eTimer_1) or both FlexPWMs (FlexPWM_0, FlexPWM_1), See

Figure 6.

Note:

Rationale: To write a digital output by exploiting redundancy, and modules must belong to

different lakes to decrease the probability of CCF

3.13.5.1.2

Implementation details

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

●

eTimer_0 channels

●

eTimer_1 channels

●

FlexPWM_0 channels

●

FlexPWM_1 channels

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

(PCRn) in the SIUL module.

Note:

Rationale: To configure pads used by this safety function

3.13.5.2

Single Write PWM Outputs With Read Back

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

to perform a Write PWM Output With Read Back(f). These units must be configured to

implement one PWM output channel and (via internal read back) the eTimer_0 input PWM

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

The software must perform a write operation followed by a read operation. To guarantee the

integrity of the configuration of the channels, the application should test the SIUL

configuration implementing the SIUL_SWTEST_REGCRC (to avoid a common failure

caused by misconfiguration of the pads).

Table 8. Software BIST and/or test

Software BIST or test

Frequency

SIUL_SWTEST_REGCRC

Once after programming3

ETIMER0_SWTEST_REGCRC1

Once after programming

ETIMER1_SWTEST_REGCRC1

Once after programming

FLEXPWM0_SWTEST_REGCRC2

Once after programming

FLEXPWM1_SWTEST_REGCRC2

Once after programming

PWMDW_SWAPP_WRITE

Once every write

This software BIST is needed only if the eTimer channels are used for the safety function

This software BIST is needed only if the FlexPWM channels are used for the safety function

If a change in a single SIUL configuration register is capable of affecting both the output and the read-

back paths, then SIUL_SWTEST_REGCRC must be executed every FTTI. In all other cases

configuration errors are covered by the software comparison.

eTimer_0 and FlexPWM_0 (eTimer_1 and FlexPWM_1) cannot be used in combination due to the same LBIST

partition assignment.

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