[求助] MSP430F5438的DCO怎么设置

dageliu 2015-6-17 10:19 楼主

DCO怎么设置，怎么知道频率是多少

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沙发 LeoMe

void SetVcoreUp (unsigned int level)
{
PMMCTL0_H = PMMPW_H; /* Open PMM registers for write */
SVSMHCTL = SVSHE + SVSHRVL0 * level + SVMHE + SVSMHRRL0 * level; /* Set SVS/SVM high side new level */
SVSMLCTL = SVSLE + SVMLE + SVSMLRRL0 * level; /* Set SVM low side to new level */
while ((PMMIFG & SVSMLDLYIFG) == 0); /* Wait till SVM is settled */
PMMIFG &= ~(SVMLVLRIFG + SVMLIFG); /* Clear already set flags */
PMMCTL0_L = PMMCOREV0 * level; /* Set VCore to new level */
if ((PMMIFG & SVMLIFG)) /* Wait till new level reached */
while ((PMMIFG & SVMLVLRIFG) == 0);
SVSMLCTL = SVSLE + SVSLRVL0 * level + SVMLE + SVSMLRRL0 * level; /* Set SVS/SVM low side to new level */
PMMCTL0_H = 0x00; /* Lock PMM registers for write access */
}
void UcsInit (void)
{
// Increase Vcore setting to level3 to support fsystem=25MHz
// NOTE: Change core voltage one level at a time..
SetVcoreUp (0x01);
SetVcoreUp (0x02);
SetVcoreUp (0x03);
UCSCTL3 = SELREF_2; // Set DCO FLL reference = REFO
UCSCTL4 |= SELA_2; // Set ACLK = REFO
__bis_SR_register(SCG0); // Disable the FLL control loop
UCSCTL0 = 0x0000; // Set lowest possible DCOx, MODx
UCSCTL1 = DCORSEL_7; // Select DCO range 50MHz operation
UCSCTL2 = FLLD_1 + 762; // Set DCO Multiplier for 25MHz
// (N + 1) * FLLRef = Fdco
// (762 + 1) * 32768 = 25MHz
// Set FLL Div = fDCOCLK/2
__bic_SR_register(SCG0); // Enable the FLL control loop
// Worst-case settling time for the DCO when the DCO range bits have been
// changed is n x 32 x 32 x f_MCLK / f_FLL_reference. See UCS chapter in 5xx
// UG for optimization.
// 32 x 32 x 25 MHz / 32,768 Hz ~ 780k MCLK cycles for DCO to settle
__delay_cycles(782000);
// Loop until XT1,XT2 & DCO stabilizes - In this case only DCO has to stabilize
do
{
UCSCTL7 &= ~(XT2OFFG + XT1LFOFFG + DCOFFG);// Clear XT2,XT1,DCO fault flags
SFRIFG1 &= ~OFIFG; // Clear fault flags
}while (SFRIFG1&OFIFG); // Test oscillator fault flag
}