MSP430G2553 P1.4口无法输出高电平

你用的什么开发板？外部电路是怎么样的？有没有被强拉到gnd？

给SEL置零之后还是输出为低电平啊，在手册上标注了SEL置零为I/O功能的

建议您试一下例程

 *******************************************************************************
 * 
 *                       MSP430 CODE EXAMPLE DISCLAIMER
 *
 * MSP430 code examples are self-contained low-level programs that typically
 * demonstrate a single peripheral function or device feature in a highly
 * concise manner. For this the code may rely on the device's power-on default
 * register values and settings such as the clock configuration and care must
 * be taken when combining code from several examples to avoid potential side
 * effects. Also see www.ti.com/grace for a GUI- and www.ti.com/msp430ware
 * for an API functional library-approach to peripheral configuration.
 *
 * --/COPYRIGHT--*/
//******************************************************************************
//  MSP430G2xx3 Demo - Software Poll P1.4, Set P1.0 if P1.4 = 1
//
//  Description: Poll P1.4 in a loop, if hi P1.0 is set, if low, P1.0 reset.
//  ACLK = n/a, MCLK = SMCLK = default DCO
//
//               MSP430G2xx3
//            -----------------
//        /|\|              XIN|-
//         | |                 |
//         --|RST          XOUT|-
//     /|\   |                 |
//      --o--|P1.4         P1.0|-->LED
//     \|/
//
//  D. Dang
//  Texas Instruments, Inc
//  December 2010
//   Built with CCS Version 4.2.0 and IAR Embedded Workbench Version: 5.10
//******************************************************************************

#include <msp430.h>

int main(void)
{
  WDTCTL = WDTPW + WDTHOLD;                 // Stop watchdog timer
  P1DIR |= 0x01;                            // Set P1.0 to output direction

  while (1)                                 // Test P1.4
  {
    if ((0x10 & P1IN)) P1OUT |= 0x01;       // if P1.4 set, set P1.0
    else P1OUT &= ~0x01;                    // else reset
  }
}