MPS430F5529 mapping P4.1 P4.2 SPI模式应该怎么配置？

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//******************************************************************************
//   MSP430F552x Demo - USCI_A0, SPI 3-Wire Slave Data Echo
//
//   Description: SPI slave talks to SPI master using 3-wire mode. Data received
//   from master is echoed back.  USCI RX ISR is used to handle communication,
//   CPU normally in LPM4.  Prior to initial data exchange, master pulses
//   slaves RST for complete reset.
//   ACLK = ~32.768kHz, MCLK = SMCLK = DCO ~ 1048kHz
//
//   Use with SPI Master Incremented Data code example.  If the slave is in
//   debug mode, the reset signal from the master will conflict with slave's
//   JTAG; to work around, use IAR's "Release JTAG on Go" on slave device.  If
//   breakpoints are set in slave RX ISR, master must stopped also to avoid
//   overrunning slave RXBUF.
//
//                   MSP430F552x
//                 -----------------
//            /|\ |                 |
//             |  |                 |
//    Master---+->|RST              |
//                |                 |
//                |             P3.3|-> Data Out (UCA0SIMO)
//                |                 |
//                |             P3.4|<- Data In (UCA0SOMI)
//                |                 |
//                |             P2.7|-> Serial Clock Out (UCA0CLK)
//
//
//   Bhargavi Nisarga
//   Texas Instruments Inc.
//   April 2009
//   Built with CCSv4 and IAR Embedded Workbench Version: 4.21
//******************************************************************************

#include <msp430.h>

int main(void)
{
  WDTCTL = WDTPW+WDTHOLD;                   // Stop watchdog timer

  while(!(P2IN&0x80));                      // If clock sig from mstr stays low,
                                            // it is not yet in SPI mode
  P3SEL |= BIT3+BIT4;                       // P3.3,4 option select
  P2SEL |= BIT7;                            // P2.7 option select
  UCA0CTL1 |= UCSWRST;                      // **Put state machine in reset**
  UCA0CTL0 |= UCSYNC+UCCKPL+UCMSB;          // 3-pin, 8-bit SPI slave,
                                            // Clock polarity high, MSB
  UCA0CTL1 &= ~UCSWRST;                     // **Initialize USCI state machine**
  UCA0IE |= UCRXIE;                         // Enable USCI_A0 RX interrupt

  __bis_SR_register(LPM4_bits + GIE);       // Enter LPM4, enable interrupts
}

// Echo character
#if defined(__TI_COMPILER_VERSION__) || defined(__IAR_SYSTEMS_ICC__)
#pragma vector=USCI_A0_VECTOR
__interrupt void USCI_A0_ISR(void)
#elif defined(__GNUC__)
void __attribute__ ((interrupt(USCI_A0_VECTOR))) USCI_A0_ISR (void)
#else
#error Compiler not supported!
#endif
{
  switch(__even_in_range(UCA0IV,4))
  {
    case 0:break;                             // Vector 0 - no interrupt
    case 2:                                   // Vector 2 - RXIFG
      while (!(UCA0IFG&UCTXIFG));             // USCI_A0 TX buffer ready?
      UCA0TXBUF = UCA0RXBUF;
      break;
    case 4:break;                             // Vector 4 - TXIFG
    default: break;
  }
}