topic Re: Disconnecting the external OSC. in S32K

Disconnecting the external OSC.

aboeini — Tue, 01 Jun 2021 06:53:24 GMT

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

Re: Disconnecting the external OSC.

danielmartynek — Tue, 01 Jun 2021 13:36:24 GMT

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