Am Mittwoch, 11. August 2010 17:59:17 schrieb Marc Kleine-Budde: > Bit timing parameters for flexcan with 24.576000 MHz ref clock > nominal real Bitrt nom real SampP > Bitrate TQ[ns] PrS PhS1 PhS2 SJW BRP Bitrate Error SampP SampP > Error CAN_CTRL 1000000 40 8 8 8 1 1 983040 1.7% 75.0% > 68.0% 9.3% 0x003f0007 1000000 81 4 4 3 1 2 1024000 2.4% > 75.0% 75.0% 0.0% 0x011a0003 1000000 122 2 3 2 1 3 > 1024000 2.4% 75.0% 75.0% 0.0% 0x02110001 >
Hello Wolfgang, Marc, I was not aware that the clock is 24.576000 MHz, always thought 24.000000. It is often the case that the crystal clock is chosen to get a perfect bit rate for UARTS, not for CAN. But a UART frame, having only 10 bits, can live with a much higher deviation from the nominal bit clock. I see that you typical use a sample point at 75%. CANopen has a "Recommended location of sample point" at 87.5%. (CiA 301). -- with best regards / mit freundlichen Grüßen Heinz-Jürgen Oertel port - Professionals in Industrial Communication +=========================================================== | port GmbH phone +49 345 77755-0 | D-06132 Halle/Saale mailto:[email protected] | Germany http://www.port.de | CAN Wiki http://www.CAN-Wiki.info/ | Newsletter: http://www.port.de/subscribe +=========================================================== port Gesellschaft für computergestützte Automation mbH Geschäftsführer: Christian Bornschein, Heinz-Jürgen Oertel, Marcus Tangermann Sitz der Gesellschaft: Halle/Saale Registergericht Sachsen-Anhalt Stendal HRB 212667
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