[求助] 430的timerA用示波器显示出了怪现象！

aihaiduo 2013-11-18 11:34 楼主

以下是ti提供的TIMERA例程；

//  MSP-FET430P140 Demo - Timer_A, Toggle P3.4, CCR0 Cont. Mode ISR, DCO SMCLK
//
//  Description: Toggle P3.4 using software and TA_0 ISR. Toggles every
//  50000 SMCLK cycles. SMCLK provides clock source for TACLK.
//  During the TA_0 ISR, P3.4 is toggled and 50000 clock cycles are added to
//  CCR0. TA_0 ISR is triggered every 50000 cycles. CPU is normally off and
//  used only during TA_ISR.
//  ACLK = n/a, MCLK = SMCLK = TACLK = default DCO ~800kHz
//
//          MSP430F149
//       ---------------
//    /|\|          XIN|-
//    | |             |
//    --|RST       XOUT|-
//       |             |
//       |          P3.4|-->LED
//
//  Dasheng
//  LiTian Electronic Inc.
//  Feb 2008
//  Built with IAR Embedded Workbench Version: 3.42A
//******************************************************************************
#include
#include  "BoardConfig.h"
void main(void)
{
  WDTCTL = WDTPW + WDTHOLD;                // Stop WDT
  BoardConfig(0xb8);                      //关闭数码管、流水灯和电平转换
  P3DIR |= BIT4;                         // P3.4 output
  CCTL0 = CCIE;                            // CCR0 interrupt enabled
  CCR0 = 2000000;
  TACTL = TASSEL_2 + MC_2;                // SMCLK, contmode
  _BIS_SR(LPM0_bits + GIE);                // Enter LPM0 w/ interrupt
}
// Timer A0 interrupt service routine
#pragma vector=TIMERA0_VECTOR
__interrupt void Timer_A (void)
{
  P3OUT ^= BIT4;                         // Toggle P3.4
  CCR0 += 2000000;                         // Add Offset to CCR0
}

我就在iar上运行了，然后用示波器在p3.4口测试，可是尼玛这是什么问题？明明该是方波啊？？？是示波器有问题还是周围信号有干扰？下图这是哪门子波型？求大神帮小弟解答问题原因及解决措施。