msp430x261x_of_xt2.c

来自「MSP430F241x, MSP430F261x的各外设功能模块的C语言开发源程」· C语言 代码 · 共 41 行

//******************************************************************************
//   MSP430x26x Demo - XT2 Oscillator Fault Detection
//
//   Description: System runs normally in LPM3 with Timer A clocked by
//   ACLK.  TimerA0 interrupt causes an exit from LPM3, and toggles P1.0.
//   If an XT2 oscillator fault occurs, NMI is requested, pausing execution and
//   flashing LED quickly until fault is resolved.  Assumed only XT2 as NMI
//   source - code does not check for other NMI sources. MCLK is buffered on 
//   P5.4. If fault occurs for crystal osc sourcing the MCLK, MCLK is 
//   automatically switched to DCO for its clock source
//   MCLK = XT2 = 8MHz normally, within ISRs MCLK = DCO freq ~1025kHz
//   //* An external 8MHx crystal is required between XT2 and XT2OUT , and
//   an external 32kHz crystal is required between XIN and XOUT.  *//	
//
//             MSP430F261x/241x
//             -----------------
//         /|\|              XIN|-
//          | |                 | 32KHz
//          --|RST          XOUT|-
//            |                 |
//            |            XT2IN|-
//            |                 | 8MHz
//            |           XT2OUT|-
//            |                 |
//            |             P1.0|-->LED
//            |        P5.4/MCLK|-->MCLK = XT2 HFXTAL
//
//  B. Nisarga
//  Texas Instruments Inc.
//  September 2007
//  Built with CCE Version: 3.2.0 and IAR Embedded Workbench Version: 3.42A
//******************************************************************************
#include  <msp430x26x.h>

void main(void)
{
  volatile unsigned int i;

  WDTCTL = WDTPW+WDTHOLD;                   // Stop WDT
  BCSCTL1 &= ~XT2OFF;                       // Activate XT2 high freq xtal
  BCSCTL3 |= XT2S_2;                        // 3