DocID026216 Rev 1

13/27

AN4475

Functional safety requirements for application software

26

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) is applied by software. The read-back is done using the external configuration or

the internal. SIU pads is 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 are not

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 are not 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.

Double Write PWM Outputs

Implementation hint: Each double write can be implemented using two pads configured as

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

e.

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.