msp430x54x_clks_02.c

MSP430F5系列TI官方源码

//*****************************************************************************
//  msp430FG5438 Demo - FLL+, Output 32kHz Xtal + HF Xtal + Internal DCO
//
//  Description:  This program demonstrates using an external 32kHz crystal to
//  supply ACLK, and using a high speed crystal or resonator to supply SMCLK.
//  MLCK for the CPU is supplied by the internal DCO.  The 32kHz crystal
//  connects between pins Xin and Xout. The high frequency crystal or
//  resonator connects between pins XT2IN and XT2OUT.  The DCO clock is
//  generated internally and calibrated from the 32kHz crystal.  ACLK is
//  brought out on pin P11.0, SMCLK is brought out on P11.2, and MCLK is
//  brought out on pin P11.1.
//  ACLK = LFXT1 = 32768Hz, MCLK = default DCO = 32 x ACLK = 1048576Hz
//  SMCLK = HF XTAL
//  //* An external watch crystal between XIN & XOUT is required for ACLK *//	
//
//  NOTE: External matching capacitors must be added for the high
//       speed crystal or resonator as required.
//
//                msp430FG5438
//             -----------------
//        /|\ |              XIN|-
//         |  |                 | 32kHz
//         ---|RST          XOUT|-
//            |                 |
//            |                 |
//            |            XT2IN|-
//            |                 | HF XTAL or Resonator (add capacitors)
//            |           XT2OUT|-
//            |                 |
//            |            P11.0|--> ACLK = 32kHz Crystal Out
//            |                 |
//            |            P11.2|--> SMCLK = High Freq Xtal or Resonator Out
//            |                 |
//            |            P11.1|--> MCLK = Default DCO Frequency
//            |                 |
//            |                 |
//
//   M Smertneck
//   Texas Instruments Inc.
//   April 2008
//   Built with CCEv3.2 IAR Embedded Workbench Version: 3.42A
//******************************************************************************

#include <msp430x54x.h>

void main(void)
{
  volatile unsigned int i;

  WDTCTL = WDTPW + WDTHOLD;                 // Stop WDT
  P11DIR = BIT2 + BIT1 + BIT0;              // P11.2,1,0 to output direction
  P11SEL = BIT2 + BIT1 + BIT0;              // P11.2 to output SMCLK, P11.1
                                            // to output MCLK and P11.0 to 
                                            // output ACLK                                          
  P5SEL |= 0x0C;                            // XT2
  P7SEL |= 0x03;                            // XT1 
  
  // Loop until 32kHz crystal stabilizes
  while ( (SFRIFG1 &OFIFG))                 // Test oscillator fault flag 
  {    
    UCSCTL7 &= ~(XT2OFFG + XT1LFOFFG + DCOFFG);
    SFRIFG1 &= ~OFIFG;                      // Clear fault flags
  }

  UCSCTL4  |= SELS__XT2CLK + SELA__XT1CLK;  // Select SMCLK source as XT2CLK

  while(1);                                 // Loop in place
}