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TMS570LS20216 Bit rate calculation Excel Sheet

Rohini DR
Prodigy 150 points

Other Parts Discussed in Thread: TMS570LS20216, TMS320F28335

Hi All,

Is there any Excel sheet where I can get the value of Prescalar for CAN of TMS570LS20216 and TMS320F28335 . Please let me know.

Thanks

Rohini

  • 0
    TI__Expert 8950 points

    Rohini,

    There's no frequency requirement for the CAN bit clock in either device. The prescaler value you need depends on the bit rate and other timing configuration. If you tell me about your requirements, I can suggest a specific value.

  • 0 in reply to Adam Haun
    Prodigy 150 points
    Hello Adam,

    I need to set CAN bit rate for 1MBps and 83.3 Kbps.
    Could you pls provide the specific values 150Mhz clock .

    Thanks
    Rohini
  • 0 in reply to Rohini DR
    TI__Expert 8950 points
    Rohini,

    There are often multiple valid choices for the prescaler. The CAN bit rate is given by the equation:

    Bit rate = CAN clock frequency / (Prescaler * (1 + Tseg1 + Tseg2))

    The bus length and oscillator tolerance also affects the choices. I'll give you some example values. These assume that the CAN bit clock frequency is equal to SYSCLK/2 on the F28335 and GCLK on the LS20216, and that the bus length is less than 50 meters.

    Prescaler: 5 (on the F28335), 10 (on the LS20216)
    Tseg1: 9
    Tseg2: 5
    SJW: 4
    Bit rate: 1000 kbps
    Oscillator tolerance: 1.3%

    Prescaler: 75 (on the F28335), 150 (on the LS20216)
    Tseg1: 6
    Tseg2: 5
    SJW: 4
    Bit rate: 83.3333 kbps
    Oscillator tolerance: 1.6%

    I've been working on a calculation tool for CAN bit timing configuration which I hope to publish soon.
  • 0 in reply to Rohini DR
    TI__Expert 8950 points
    The CAN modules aren't like I2C; you don't need a specific module clock frequency to meet timing requirements.
  • 0 in reply to Adam Haun
    Prodigy 150 points

    Thanks Adam.