On 4/30/19 10:52 AM, Joakim Zhang wrote: > I am confused about the range limitation of a CAN bit time in flexcan > driver. Could you help me understand this issue? > > 1)ISO 11898-1:2003(E) show that : > > 12.4.1.2 Programming of bit time > > *The total number of time quanta in a bit time shall be > programmable at least from 8 to 25*. > > 2)CAN2.0 spec show that: > > 8 BIT TIMING REQUIREMENTS > > *The total number of TIME QUANTA in a bit time has to > be programmable at least from 8 to 25.* [...] > It means that the minimum value of 1 CAN bit time is 7 (1 + tseg1_min + > tseg2_min). But the minimum value of a CAN bit time is 8 according to > CAN spec. I don't come to the same conclusion as you. I read the above quoted paragraph as: If you implement a spec conforming CAN core, the time quanta has to programmable in a certain range (according to CAN2.0, while SO 11898-1:2003(E) says it "shall be"). That range must be at least 8...25. To my understanding you might implement a wider range. Marc -- Pengutronix e.K. | Marc Kleine-Budde | Industrial Linux Solutions | Phone: +49-231-2826-924 | Vertretung West/Dortmund | Fax: +49-5121-206917-5555 | Amtsgericht Hildesheim, HRA 2686 | http://www.pengutronix.de |
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