TI中文支持网//******************************************************************************
// MSP430F20xx Demo – Timer_A, Toggle P1.0-2, Cont. Mode ISR, 32kHz ACLK
//
// Description: Use Timer_A CCRx units and overflow to generate four
// independent timing intervals. For demonstration, CCR0 and CCR1 output
// units are optionally selected with port pins P1.1 and P1.2 in toggle
// mode. As such, these pins will toggle when respective CCRx registers match
// the TAR counter. Interrupts are also enabled with all CCRx units,
// software loads offset to next interval only – as long as the interval offset
// is aded to CCRx, toggle rate is generated in hardware. Timer_A overflow ISR
// is used to toggle P1.0 with software. Proper use of TAIV interrupt vector
// generator is demonstrated.
// ACLK = TACLK = 32kHz, MCLK = SMCLK = Default DCO
// As coded and with TACLK = 32768Hz, toggle rates are:
// P1.1 = CCR0 = 32768/(2*4) = 4096Hz
// P1.2 = CCR1 = 32768/(2*16) = 1024Hz
// P1.0 = overflow = 32768/(2*65536) = 0.25Hz
// //* External watch crystal on XIN XOUT is required for ACLK *//
//
// MSP430F20xx
// —————
// /|\| XIN|-
// | | | 32kHz
// –|RST XOUT|-
// | |
// | P1.1/TA0|–> CCR0
// | P1.2/TA1|–> CCR1
// | P1.0|–> Overflow/software
//
// M. Buccini / L. Westlund
// Texas Instruments Inc.
// October 2005
// Built with CCE Version: 3.2.0 and IAR Embedded Workbench Version: 3.40A
//******************************************************************************
#include <msp430x20x3.h>
void main(void)
{
WDTCTL = WDTPW + WDTHOLD; // Stop WDT
P1SEL |= 0x06; // P1.1 – P1.2 option select
P1DIR |= 0x07; // P1.0 – P1.2 outputs
CCTL0 = OUTMOD_4 + CCIE; // CCR0 toggle, interrupt enabled
CCTL1 = OUTMOD_4 + CCIE; // CCR1 toggle, interrupt enabled
TACTL = TASSEL_1 + MC_2 + TAIE; // ACLK, contmode, interrupt enabled
_BIS_SR(LPM3_bits + GIE); // Enter LPM3 w/interrupt
}
// Timer A0 interrupt service routine
#pragma vector=TIMERA0_VECTOR
__interrupt void Timer_A0 (void)
{
CCR0 += 4; // Add Offset to CCR0
}
// Timer_A2 Interrupt Vector (TAIV) handler
#pragma vector=TIMERA1_VECTOR
__interrupt void Timer_A1(void)
{
switch( TAIV )
{
case 2: CCR1 += 16; // Add Offset to CCR1
break;
case 10: P1OUT ^= 0x01; // Timer_A3 overflow
break;
}
}
这个程序是什么意思？
Peter_Zheng：
这程序上面有英文解释，// P1.1 = CCR0 = 32768/(2*4) = 4096Hz
// P1.2 = CCR1 = 32768/(2*16) = 1024Hz
// P1.0 = overflow = 32768/(2*65536) = 0.25Hz
Hardy Hu：
在P1.0，1.1,1.2，上输出方波，频率如下面这几句话所示：
// P1.1 = CCR0 = 32768/(2*4) = 4096Hz
// P1.2 = CCR1 = 32768/(2*16) = 1024Hz
// P1.0 = overflow = 32768/(2*65536) = 0.25Hz
