Disconnecting the external OSC.

[aboeini]

Hello community members,

I am working on S32K, I wanted to disconnect the external oscillator on the HW. I want to just use FIRC as the main clock. But we have issues with this. 

I just want to understand, is this possible? 

I configured SCG_RCCR to use FIRC. which means the system clock is provided by FIRC. When I had to configure the CAN clock source I selected 1 to use SYS_CLK.

Please provide your inputs.

Thank you

[danielmartynek]

Hello @aboeini,

The SOSC clock is recommended because of the FIRC tolerance.

Please refer to: CAN with Flexible Data-Rate Specification Version 1.0 

p. 32 Oscillator Tolerance

FlexCAN Bit Timing Calculation 

STEP 6: Calculate required oscillator tolerance

You can use this calculator to calculate the df(%).

MPC5xxx/S32Kxx: CAN / CAN FD bit timing calculation 

Regards,

Daniel