fet140_tb_pwm03.c

来自「msp430f14x 系列片内外设的实例代码」· C语言 代码 · 共 56 行

//*******************************************************************************
//  MSP-FET430P140 Demo - Timer_B PWM TB1-2 upmode, HF XTAL ACLK
//
//  Description; This program will generate two PWM outputs on P4.1/4.2 using
//  Timer_B in upmode.  The value in CCR0, defines the period and the 
//  values in CCR1 and CCR1 the duty PWM cycles.  Using HF XTAL ACLK as TBCLK,
//  the timer period is HF XTAL/512 with a 75% duty cycle on P4.1 and 25% on P4.2. 
//  ACLK = MCLK = TBCLK = HF XTAL 
//  //** HF XTAL REQUIRED AND NOT INSTALLED ON FET **//
//
//               MSP430F149
//            -----------------
//        /|\|              XIN|-  
//         | |                 | HF XTAL (455k - 8Mhz) 
//         --|RST          XOUT|-
//           |                 |
//           |             P4.1|--> CCR1 - 75% PWM
//           |             P4.2|--> CCR2 - 25% PWM
//
//  M.Buccini
//  Texas Instruments, Inc
//  September 2003
//  Built with IAR Embedded Workbench Version: 1.26B
//  June 2004
//  Updated for IAR Embedded Workbench Version: 2.21B
//******************************************************************************

#include <msp430x14x.h>

void main(void)
{ 
  unsigned int i;
  WDTCTL = WDTPW + WDTHOLD;             // Stop WDT
  BCSCTL1 |= XTS;                       // ACLK = LFXT1 = HF XTAL

  do 
  {
  IFG1 &= ~OFIFG;                       // Clear OSCFault flag
  for (i = 0xFF; i > 0; i--);           // Time for flag to set
  }
  while ((IFG1 & OFIFG));               // OSCFault flag still set?                

  BCSCTL2 |= SELM_3;                    // MCLK= LFXT1 (safe)
  P4DIR |= 0x06;                        // P4.1 and P4.2 output
  P4SEL |= 0x06;                        // P4.2 and P4.2 TB1/2 otions
  TBCCR0 = 512-1;                       // PWM Period
  TBCCTL1 = OUTMOD_7;  			// CCR1 reset/set
  TBCCR1 = 384;                         // CCR1 PWM duty cycle
  TBCCTL2 = OUTMOD_7;  			// CCR2 reset/set
  TBCCR2 = 128;                         // CCR2 PWM duty cycle
  TBCTL = TBSSEL_1 + MC_1;              // ACLK, up mode

  _BIS_SR(CPUOFF);                      // Enter LPM0
}