On 13.01.2022 21:30:04, Marc Kleine-Budde wrote: > > Recently we did few experiments with our CANFD network. Stuff error > > observed with different Nominal and Dataphase prescaler configuration > > values, which we get from the frame work. > > > > For lower baud rates separate prescalers are working good, but when we > > switch to high baud rates(like 4Mbps and 5Mbps) observed the BUSOFF > > state(Due to stuff errors) on IP(Xilinx). > > > > With shared prescaler(low prescalers) we are not seeing the issue.. > > > > In Iso spec also mentioned to avoid tolerance, we have to maintain > > common TQ for Nominal and Data phase. This is a known problem with the current arbitration and data bit rate calculation. They are done independently of each other, resulting in not common pre-scalers and thus not common TQ. > > Spec: ISO 11898-1:2015(E) page no :50 > > > > " If the same time quantum length is used in the nominal bit time and > > in the data bit time and the positions of the sample points in the > > nominal bit time are the same in all CAN nodes of a network, then > > optimum clock tolerance is accomplished for networks using FD frames." > > > > CIA: > > https://can-newsletter.org/uploads/media/raw/f6a36d1461371a2f86ef0011a513712c.pdf > > > > From above CAN-newsletter also suggested the same in recommendation 2 and 3. I'll have a look at the newsletter and see what changes need to be done to the existing algorithm. > > Recommendation 2: Set the BRPA bit-rate prescaler equal BRPB > > Recommendation 3: Choose BRPA and BRPD as low as possible > > > > Is there any possibility in framework to use shared prescalars for > > Nominal and Dataphase?. Not yet. > > One more question. How to calculate TDCO ?, is there any generic > > formula for this ?. Vincent (Cc'ed) can help you on this. regards, Marc -- Pengutronix e.K. | Marc Kleine-Budde | Embedded Linux | https://www.pengutronix.de | Vertretung West/Dortmund | Phone: +49-231-2826-924 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 |
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