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TM4C129ENCZAD: PWM clock maximal frequency

Nissim Varon
Prodigy 10 points
Part Number: TM4C129ENCZAD

Hello,

I am working on a cage that will include a few boards. Every one of them will communicate through Ethernet thanks to the microcontroller TM4C129ENCZAD.

There is some chance to use this microcontroller also as a PWM controller. The examples, included in the datasheet, consider motion control, i.e. are much slower than our application.

May you, please, help me in understanding what is the maximal possible working frequency of the PWM clock.

Thanks in advance,

Nissim

  • 0
    TI__Guru*** 135355 points

    Hello Nissim.

    The maximum PWM clock frequency is 120 MHz as it is possible to clock the PWM directly from the System Clock. This would be done by using the following API:

        //
    // Set the PWM clock to be SysClk.
    //
    MAP_PWMClockSet(PWM0_BASE, PWM_SYSCLK_DIV_1);

    Best Regards,

    Ralph Jacobi

  • 0 in reply to Ralph Jacobi
    Prodigy 10 points

    Hello, Ralph,

    Thank you very much for the fast reaction. 

    Please, let me exploit the opportunity and insist about:

    From the main clock tree diagram (on page 240 of the datasheet) is clear the PWM clock input is connectable directly to the system clock, but this does not say the PWM may work on the maximal possible system clock frequency.

    In the "Clocks" section (par.30.9) of the "Electrical characteristics", on page 1989 appear system clock limitation (specification) tables for usage with specific functions (ADC, USB). May you, please, find such kind of specification (just because deduction from the context does not make me sure enough).

    Thanks in advance,

    Nissim

  • +1 in reply to Nissim Varon
    TI__Guru*** 135355 points

    Hello Nissim,

    I don't think we have an explicit statement in the datasheet about the maximum clock speed so I am speaking from my experience as a device expert, the best 'specification' I can offer is to reference our TivaWare SDK which provides all the software needed to configure peripherals.

    Here are the definitions for the rates the PWM clock can run at, this includes running at System Clock.

    This table only applies for TM4C129x MCUs.

    //*****************************************************************************
//
// Defines that can be passed to the PWMClockSet() API as the ui32Config
// parameter, and can be returned by the PWMClockGet() API.
//
//*****************************************************************************
#define PWM_SYSCLK_DIV_1        0x00000000  // PWM clock is system clock
#define PWM_SYSCLK_DIV_2        0x00000100  // PWM clock is system clock /2
#define PWM_SYSCLK_DIV_4        0x00000101  // PWM clock is system clock /4
#define PWM_SYSCLK_DIV_8        0x00000102  // PWM clock is system clock /8
#define PWM_SYSCLK_DIV_16       0x00000103  // PWM clock is system clock /16
#define PWM_SYSCLK_DIV_32       0x00000104  // PWM clock is system clock /32
#define PWM_SYSCLK_DIV_64       0x00000105  // PWM clock is system clock /64

    Best Regards,

    Ralph Jacobi