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MCF8316A: Datasheet is unclear about MAX_SPEED

Brian Dang
Genius 5040 points
Part Number: MCF8316A

Hello,

On page 98, under Register Field Description section, it says:

"MAX_SPEED:  14-bit value for setting maximum value of speed in electrical Hz Maximum motor electrical speed (Hz): {MOTOR_SPEED/6} For example: if MOTOR_SPEED is 0x2710, then maximum motor speed (Hz) = 10000(0x2710)/6 = 1666 Hz."

In the description, I'm not sure if MOTOR_SPEED is another Register Field, or perhaps MOTOR_SPEED  is a typo of MAX_SPEED, as I cannot find MOTOR_SPEED as a register valve in the datasheet.

Also, the equation: maximum motor speed (Hz) = 10000(0x2710)/6 = 1666 Hz is either outright wrong or badly written.

Should it be maximum motor speed (Hz) = (0x2710)/6 = 1666 Hz or 10000/6 = 1666 Hz? Does this mean if MAX_SPEED is set to 10000, then the motor max speed will be claimed at 1666 hz? Why do we need to scale down the register value by 6?

If they are typos, then could someone update the datasheet to correct it?

Regards,

Brian

  • 0
    Genius 5040 points

    Where are the TI engineers?

  • 0 in reply to Brian Dang
    TI__Mastermind 23546 points

    Hey Brian

    I have assigned a member of our team to your thread. We will aim to provide feedback shortly.

    Best,

    Akshay

  • +1
    TI__Genius 9220 points

    Hi Brian,

    After reviewing the datasheet, I can confirm that it is indeed a typo, and the MOTOR_SPEED should be MAX_SPEED in the MAX_SPEED register description.

    You are also correct that the equation is simply indicating that 10000 is also 0x2710 by putting the hex value in parenthesis. I can see how this can be confusing and will provide internal feedback for this, along with the typo, to be updated for clarity.

    The scaling down by 6 is simply a conversion factor that allow us to achieve the finer increment when converted to Hz while storing the MAX_SPEED setting as an integer in the register.

    Regards,
    Eric C.