On 09.05.2023 13:16:08, Vincent MAILHOL wrote: > > The diagram in https://www.can-cia.org/can-knowledge/can/can-fd/ > > suggests that IMF is part of the frame. > > ISO 11898-1:2015 section 10.4.6 "Specification of inter-frame space" > makes it clear that the intermission is not part of the frame but part > of the "Inter-frame space". For this reason, it is good to have open standards...oh wait! > To close the discussion, I would finally argue that the intermission > occurs after the EOF bit. Something after an "End of Frame" is not > part of the frame, right? > > I agree with and will follow Thomas's suggestion. [...] > > > /* > > > * Size of a CAN-FD Standard Frame > > > @@ -69,17 +87,17 @@ > > > * Error Status Indicator (ESI) 1 > > > * Data length code (DLC) 4 > > > * Data field 0...512 > > > - * Stuff Bit Count (SBC) 0...16: 4 20...64:5 > > > + * Stuff Bit Count (SBC) 4 > > > > ACK > > > > > * CRC 0...16: 17 20...64:21 > > > * CRC delimiter (CD) 1 > > > + * Fixed Stuff bits (FSB) 0...16: 6 20...64:7 > > > > As far as I understand > > https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=8338047 the FSB > > is 5 or 6. > > Reading the ISO, the fixed bit stuff applies to the CRC field (which, > in the standard nomenclature, includes both the stuff count and the > CRC sequence). > The CRC field starts with a fixed stuff bit and then has another fixed > stuff bit after each fourth bit. > > So the formula would be: > > FSB count = 1 + round_down(len(CRC field)/4) > = 1 + round_down((len(stuff count) + len(CRC sequence))/4) > > In case of CRC_17: > > FSB count = 1 + round_down((4 + 17)/4) > = 6 > > This is coherent with the last figure of > https://www.can-cia.org/can-knowledge/can/can-fd/ which shows 6 FSB > for CRC_17. > > In case of CRC_21: > > FSB count = 1 + round_down((4 + 21)/4) > = 7 > > So, ACK for Thomas, NACK for Marc (sorry :)) It seems that the reviewers of this paper missed some parts :) Marc -- Pengutronix e.K. | Marc Kleine-Budde | Embedded Linux | https://www.pengutronix.de | Vertretung Nürnberg | Phone: +49-5121-206917-129 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-9 |
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