msp430x24x_hfxt2_nmi.c

来自「这是关于430单片机的一些应用示例程序」· C语言 代码 · 共 40 行

//******************************************************************************
//   MSP430x24x Demo - Basic Clock, MCLK Sourced from HF XTAL XT2, NMI
//
//   Description: Proper selection of an HF XTAL XT2 for MCLK is shown with
//   enabled OSC fault interrupt - if HF XTAL fails, NMI interrupt is requested.
//   HF XTAL can only source MCLK when OSC fault is clear. For demonstration
//   purposes P1.0 is set during OSC fault. MCLK/10 is on P1.1.
//   ACLK = n/a; MCLK = HFXTAL XT2
//   //* HF XTAL XT2 NOT INSTALLED ON FET *//
//   //* Min Vcc required varies with MCLK frequency - refer to datasheet *//
//
//                MSP430xG249
//             -----------------
//         /|\|              XIN|-
//          | |                 |
//          --|RST          XOUT|-
//            |                 |
//            |            XT2IN|-
//            |                 | HF XTAL (400kHz - 16MHz)
//            |           XT2OUT|-
//            |                 |
//            |             P1.1|-->MCLK/10
//            |             P1.0|-->LED
//
//  B. Nisarga
//  Texas Instruments Inc.
//  September 2007
//  Built with CCE Version: 3.2.0 and IAR Embedded Workbench Version: 3.42A
//******************************************************************************

#include  <msp430x24x.h>

void main(void)
{
  WDTCTL = WDTPW+WDTHOLD;                   // Stop WDT
  P1DIR |= 0x03;                            // P1.0,1 = output direction
  P1OUT &= ~0x01;                           // P1.0 = reset
  
  BCSCTL1 &= ~XT2OFF;                       // Activate XT2 high freq xtal
  BCSCTL3 |= XT2S_2;                        // 3