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MCF54418 flexCAN porblems

Question asked by Chang Liu on Sep 15, 2017
Latest reply on Sep 20, 2017 by TomE

I have 2 questions about FlexCAN on MCF54418.

There are 2 flexCAN on MCF54418 and the CAN devices can work normally.

Q1.    I must enable "Self reception" function, then  the CAN device can receive the frame sent by itself.

     When the 2 FlexCAN devices are initialized, both of them can receive the frames sent by themselves. But if only 1 of the             them is initialized, the initialized one can not receive the frames from itself.

       I wonder to konw Why ?

 

Q2.  There are 2 FlexCANs on a  CAN bus. The terminating resistance is 120 ohms  x 2. Between the two CAN devices, there is a digital isoltor, theprogagation delay is 60ns. The baudrate is 1MHz. fsys/2=125MHz.  PRESDIV = 4, RJW =0 ,PSEG1=7,  PSEG2 =7,PROPSEG = 7.

       The test case : CAN_A  send only, CAN_B  receive only.    When CAN_A send  one frame, CAN_B receive a lot of same frames, and the error occurs, such as bit1error/bit0error/format error.  

       But if I set  the CANCTRL[RJW] = 3, the CAN communication becomes normal. 

      Why?

 

 

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