DocID024464

Rev 2

13/27

AN4287

Functional safety requirements for application software

Figure 1. Block scheme of external/internal read-back

Single write PWM output with read-back

Implementation hint: Two pins are used to implement this function. One pin to generate

the PWM output and another pin to read-back this PWM to check its integrity.

Each single write with read-back can be implemented using pads configured as eMIOS200

channel by the SIU unit and configured as PWM by eMIOS200 module.

PWM set of data (duty cycle and period) shall be applied by software. The read-back shall

be done using the external configuration or the internal. SIU pads shall be configured as

follows:

•

External read-back: one SIU pad is configured as eMIOS200 channel by the SIU unit

and configured with input capture feature by eMIOS200 module to allow read-back of

the output written on the output pad. The loop-back is done with an external connection

outside the device. In case of External read-back, the two selected pads shall not be

physically adjacent;

•

and configured with input capture feature by eMIOS200 module to allow read-back of

the output write on the selected pad. The loop-back is done via an internal read path.

The two selected pads shall not be physically adjacent to minimize CCFs. SIU pads can be

configured via the relevant pad configuration registers (PCRn). eTPU2 channels instead of

eMIOS200 channels can be used.

d.

Internal read back does not cover package faults (e.g. wire bond). Refer to the specific reference manual to

verify the availability of the internal read path.

SIUL

O

I

External Readback

Configuration

SIUL

O

Internal Readback

Configuration