• State Resolved
  • Locked Locked
  • Replies 7 replies
  • Answers 1 answer
  • Subscribers 30 subscribers
  • Views 268 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

MSPM0G3507: Baud Rate Config

Matze
Intellectual 442 points
Part Number: MSPM0G3507
Other Parts Discussed in Thread: SYSCONFIG

Tool/software:

Hi TI-Experts,

I am struggeling with the Baud Rate Config.

I am using normal CAN, not CAN FD. 

But I don't know what is the relevance of 

1a. the "arbitration baud rate" and 

1b. the "data baud rate"?

2. Does the "data baud rate" only apply to CAN FD or is it also relevant for normal CAN?

3. Should I enter something for "desired data rate"?

4. What is the relationship between the CAN CLK frequency, the arbitration and the data baud rate and the corresponding bit timing parameters?

5. I have noticed that with a CAN clock frequency of 80 MHz I do not receive some CAN messages and then the MRAF bit is set in the interrupt register. However, if I reduce the CAN clock frequency to 40 MHz, I achieve very reliable CAN message reception - apparently without MRAF errors. The sysconfig does not give an error when I set the 80 MHz, but is it perhaps still the case that the CAN module cannot process a CAN clock frequency of 80 MHz and can only cope with a maximum of 40 MHz, for example? I didn't find any corresponding information in the TRM.


Thanks a lot for your answers in advance!

Matze

  • 0
    TI__Mastermind 45285 points

    Hi, 

    1&2. If you are not using CAN FD, you can ignore the configuration of data baud rate. The "data baud rate" only apply to CAN FD.

    3. No.

    4. CAN CLK is the clock source for CAN module, it does not determine the baud rate. The arbitration bit rate defines your baud rate here. And the rest bit timing parameters are automatically calculated by the desired sampling point and  arbitration bit rate.

    5. 

    Best regards,

    Cash Hao

  • 0 in reply to Cash Hao11
    Intellectual 442 points

    Hi, Thanks!

    5. I also found that "SYSPLL Usage Example" that you screenshotted for me. But because of the title "example" I did not think that this would be the only possible configuration/frequency.

    a) I would expect that such an important information is to be found in some chapter like "technical data" or somewhere like that and not in the third line below an "Usage Example" for "SYSPLL" in "Chapter 2 - PMCU" without obvious connection to CAN-BUS or in "Chapter 21 - CAN-FD".

    b) I would expect that the sysconfig-SYSCTL or the clock tree issues an error or at least a warning that the set frequency is not recommended and leads to errors in the function of the CAN module.

    Is it possible that both named points are included somewhere and maintained in the TRM and in the sysconfig?

    Or do you think this is not relevant?


    Many thanks in advance! and best regards

    Matze

  • 0 in reply to Matze
    TI__Mastermind 45285 points

    Hi,

    Actually, you can configure the CANCLK to 80MHz. It could due to the CLK source(SYSOSC)'s accuracy is enough for CAN communication and causes you can not receive messages under 80MHz. 

    Best regards,

    Cash Hao

  • 0 in reply to Cash Hao11
    Intellectual 442 points

    sorry, could you please explain in more detail what you mean by this statement? Unfortunately, I can't quite understand what you mean and what conclusions I can draw from your answer.

  • 0 in reply to Matze
    TI__Mastermind 45285 points

    Hi,

    The CAN interface requires a high clock accuracy for each CAN node. Since you are using 80MHz as the CANCLK, I assume you get this 80MHz from SYSOSC through PLL. The internal SYSOSC's accuracy is not good enough for CAN node. It is recommended to source CANCLK from external crystal, and usually the external crystal 's frequency is 40MHz.

    Best regards,

    Cash Hao

  • +1 in reply to Cash Hao11
    Intellectual 442 points

    Hi,

    I tried three different solutions:

    1. INTOSC with PLL

    2. INTOSC with Frequency Correction Loop and External Ref. Resistor ROSC and PLL

    3. HFCLK with 10 MHz and PLL

    No matter which of the three variants I chose, at 40MHz CANCLK I had error-free message reception, at 80 MHz I had unreliable message reception.

    BR

    Matze

  • +1 in reply to Matze
    TI__Mastermind 45285 points

    Hi,

    Okay, some of the customers do feedback that they will get errors at CANCLK 80MHz. But I have tested on my side on LP and can transmit and receive messages without errors under CANCLK 80MHz. I am not sure why. But you can still configure the CANCLK to 40MHz for operation. 

    Best regards,

    Cash Hao