S32KのトピックFlexcan bit timing configuration

Flexcan bit timing configuration

eason_chen — Tue, 22 Jan 2019 03:47:46 GMT

Hi,

I am writing flexcan driver on S32K144 development kit.

But i don't know how to calculate the bit timing(prop seg, phase seg1, phase seg2... ).

Which document could i refer to?

Thanks.

Re: Flexcan bit timing configuration

PetrS — Tue, 22 Jan 2019 10:08:18 GMT

Hi,

you can try e.g this simple guide(https://community.nxp.com/docs/DOC-330446 ) for nominal bit timing calculation. Just consider min/max values of each segments as given in the reference manual.

Regarding the FD bit time calculation; it is calculated in similar way as nominal timing considering segments length. It is recommended to have the same prescaler for both nominal and data bit time. No bus propagation is assumed, just propagation delay of single transceiver is taken into account for propagation phase calculation. Thus there is more freedom for sample point placing, but it is usually placed somewhere in the middle of the data bit time.

In case of transceiver propagation delay is bigger then bit time a TDC (Transceiver Delay Compensation) should be enabled and TDC offset properly set.

BR, Petr

Re: Flexcan bit timing configuration

eason_chen — Tue, 22 Jan 2019 10:25:25 GMT

Hi Petr,

First at all, thank you for your answer.

Another question about propagation delay.

In page 6, how do i get the bus propagation delay and physical interface transmitter plus receiver propagation?

Are they constant? if yes, where can i find them? If no, how do i know these two parameters?

Thanks.

BR,
Eason