topic S32K344 CAN FD setup in S32K

S32K344 CAN FD setup

Ayaz — Thu, 04 Jul 2024 11:01:38 GMT

I am currently working on setup the CAN FD on my project, i have some confusion regarding the CAN clock.

I am using AIPS_PLAT_CLK to provide a clock to FLEXCAN.

In the reference manual it mentioned that the FLEXCAN uses tow clock source .

Is the FlexCANprotocol clock is same CAN_PE_CLK? what is the clock source for FlexCANprotocol clock and CAN_PE_CLK ? and what the Prescaler division factor role is?

Re: S32K344 CAN FD setup

Julián_AragónM — Thu, 04 Jul 2024 17:21:11 GMT

Hi @Ayaz,

The module clock is the control host interface clock, while the PE clock is the functional clock. The module clock is only used for the register access of the peripheral and is usually sourced from a fixed clock source. For the PE clock, you can select whether the internal clock is connected to the output of a crystal oscillator (Oscillator Clock) or to the Peripheral Clock. The oscillator clock should be selected whenever a tight tolerance (up to 0.1%) is required in the CAN bus timing. The crystal oscillator clock has better jitter performance than the peripheral clock.

The Serial Clock (Sclock) period defines the 'time quantum' used to compose the CAN waveform, so the CAN bitrate is computed based on the frequency of the PE clock.

Please look at the following overview:

Best regards,
Julián

Re: S32K344 CAN FD setup

Ayaz — Thu, 04 Jul 2024 18:20:19 GMT

Thanks for explanation

How to select the frequency for the module frequency (CHI) and the PE clock frequency ?

Which clock is this one ?

Re: S32K344 CAN FD setup

Julián_AragónM — Thu, 04 Jul 2024 22:18:18 GMT

Hi @Ayaz,

You can look at the source for FlexCAN0_CLK from the Peripheral Clock View:

Best regards,
Julián

Re: S32K344 CAN FD setup

Ayaz — Fri, 05 Jul 2024 08:38:04 GMT

As I understood there are two different clock frequencies for FlexCAN.

1. CHI clock, which can be selected according to the photo you have sent.

2. how do select the PE clock frequency?

One last question which clock source is this one? Is it a CHI or PE clock?? should be the same as a module clock?

Re: S32K344 CAN FD setup

Julián_AragónM — Fri, 05 Jul 2024 18:29:11 GMT

Hi @Ayaz,

FlexCAN has the following unique clocks:

CAN_CHI_CLK—FlexCAN controller host interface clock
CAN_PE_CLK—FlexCAN protocol engine clock

CHI_CLK is fed by AIPS_PLAT_CLK, and PE_CLK can be selected as shown in my previous reply with the peripheral view.

The one in config tools refers to PE_CLK

Best regards,
Julián

Re: S32K344 CAN FD setup

Ayaz — Fri, 05 Jul 2024 19:05:39 GMT

One last question which clock source is this one? Is it a CHI or PE clock?? should be the same as a module clock?

Re: S32K344 CAN FD setup

Julián_AragónM — Fri, 05 Jul 2024 20:36:34 GMT

Hi @Ayaz,

That refers to the PE Clock. Yes, it should be the same as the module clock.

Re: S32K344 CAN FD setup

Ayaz — Fri, 05 Jul 2024 20:37:57 GMT

Thanks for the explanation