Freedom Board 8 Mhz to 48Mhz MCG setup code.

JimDon — Thu, 29 Oct 2020 08:51:07 GMT

Code to set the Freedom Board MCG to 48MHz.

/*
* init_clocks()
* Set the PLL to 48MUz from the 8Mz xtal on the
* Freedom board.
* Returns:
* The freequency set from the divide/multiply register values.
*/


int  init_clocks()
{
    signed char prdiv; signed char vdiv;
    // Set the core/system clock to divide by 2.
    SIM_CLKDIV1 = SIM_CLKDIV1_OUTDIV1(1);
    // 12.2.3 Selects the MCGPLLCLK or MCGFLLCLK clock for various peripheral
    // clocking options.
    SIM_SOPT2 |= SIM_SOPT2_PLLFLLSEL_MASK;
    // 12.2.1 Set OSC32KSEL to 00 to select the System oscillator
    SIM_SOPT1 &= ~(SIM_SOPT1_OSC32KSEL(3));
    // Select MCGFLLCLK clock or MCGPLLCLK/2 fpr TPM
    SIM_SOPT2 &=  ~SIM_SOPT2_TPMSRC(3);
    SIM_SOPT2 |=  SIM_SOPT2_TPMSRC(1);
   
    // Set up for external XTAL. 10.3.1 KL25 Signal Multiplexing and Pin Assignments
    // Set pin function to EXTAL - Clear to 0 (pin 40)
    PORTA_PCR18 &= ~(PORT_PCR_ISF_MASK | PORT_PCR_MUX(7));                                                 
    // Set pin function to XTAL -  Clear to 0
    PORTA_PCR19 &= ~(PORT_PCR_ISF_MASK | PORT_PCR_MUX(7)); 

    // FBE Mode
    OSC0_CR = OSC_CR_ERCLKEN_MASK;                                                 
    MCG_C2 = (MCG_C2_RANGE0(2) | MCG_C2_EREFS0_MASK);                                                 
    MCG_C1 = (MCG_C1_CLKS(2) | MCG_C1_FRDIV(3) | MCG_C1_IRCLKEN_MASK);                                                 
    MCG_C4 &= ~(MCG_C4_DMX32_MASK | MCG_C4_DRST_DRS(3));                                                 
    MCG_C5 = MCG_C5_PRDIV0(3);                                                 
    MCG_C6 = 0x00U;   
    // Wait for FLL extern ref.
    while((MCG_S & MCG_S_IREFST_MASK) != 0)
      ;
    // Wait for external ref. select.
    while((MCG_S & MCG_S_CLKST_MASK) != 8)
      ;
    // PBE
    MCG_C2 = (MCG_C2_RANGE0(2) | MCG_C2_EREFS0_MASK);                                                 
                                               
    MCG_C6 = MCG_C6_PLLS_MASK;
   
    // Wait for lock.
    while((MCG_S & MCG_S_LOCK0_MASK) == 0)
      ;
   
    // PEE Mode
                                               
    MCG_C1 = (MCG_C1_FRDIV(3) | MCG_C1_IRCLKEN_MASK);                                                 
   
    // Wait for PLL select.
    while((MCG_S &MCG_S_CLKST_MASK) !=MCG_S_CLKST_MASK)
      ;
    // Use actual PLL settings to calculate PLL frequency
    prdiv = ((MCG_C5 & MCG_C5_PRDIV0_MASK) + 1);
    vdiv = ((MCG_C6 & MCG_C6_VDIV0_MASK) + 24);
    return ((8000000 / prdiv) * vdiv);

}

Re: Freedom Board 8 Mhz to 48Mhz MCG setup code.

JimDon — Wed, 24 Oct 2012 02:55:02 GMT

Find file with code attached.

Kinetis Microcontrollers中的主题 Freedom Board 8 Mhz to 48Mhz MCG setup code.

Freedom Board 8 Mhz to 48Mhz MCG setup code.

Re: Freedom Board 8 Mhz to 48Mhz MCG setup code.