fet140_tb_08.c

天祥电子-10天学会MSP430单片机开发板资源TI提供的例程

//*******************************************************************************
//  MSP-FET430P140 Demo - Timer_B, PWM TB1-2, Up Mode, HF XTAL ACLK
//
//  Description: This program generates two PWM outputs on P4.1,2 using
//  Timer_B configured for up mode. The value in CCR0, 512-1, defines the PWM
//  period and the values in CCR1 and CCR2 the PWM duty 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 *//
//  //* Min Vcc required varies with MCLK frequency - refer to datasheet *//	
//
//               MSP430F149
//            -----------------
//        /|\|              XIN|-
//         | |                 | HF XTAL (455k - 8MHz)
//         --|RST          XOUT|-
//           |                 |
//           |         P4.1/TB1|--> CCR1 - 75% PWM
//           |         P4.2/TB2|--> CCR2 - 25% PWM
//
//  M. Buccini
//  Texas Instruments Inc.
//  Feb 2005
//  Built with IAR Embedded Workbench Version: 3.21A
//******************************************************************************

#include  <msp430x14x.h>

void main(void)
{
  volatile 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
}