STM32H743 reference manual FDCAN_NBTP description

[EMonj.1]

Hi,

depend on reference manual RM0433 Rev 8 for STM32H743 p.56.5.7 "FDCAN nominal bit timing and prescaler register" the CAN bit time can be programmed max. 81 time quanta. Is documentation correct on this place?

Due to described time quantum range [1...1024] this documentation part can be copypasted.

The question is only about documentation.

I know it was a similar question about STM32G0B1.

Best regards.

[Sarra.S]

Hello @EMonj.1, 

There is no contradiction between the CAN bit time value and the CAN time quantum value -if that's what you mean- since the bit time is the overall time taken to transmit a single bit, while the time quantum is the smallest unit of time used to define the length of each segment of a bit time. 

 

 

[EMonj.1]

Hello @Sarra.S,

what I mean here is the time quantum can't be programmed to 1024 FDCAN kernel clock periods due the size of NBRP in FDCAN_NBTP register.

My actual question is about CAN nominal bit time. Is it really max. 81tq?

[EMonj.1]

@Sarra.S,

a similar question: NSJW description in p.56.5.7 FDCAN_NBTP

NSJW "should be smaller than TNSEG2" but valid values for NSJW and NTSEG2 are both up to 127.

Is hier mean should be not bigger or max. value of 127 for NSJW is wrong?