msp430f5529简单uart源程序(用串口助手发什么回复什么) -

/*****用串口助手发什么回复什么****/
#include "msp430f5529.h"
// ACLK = REFO = 32768Hz, MCLK = SMCLK = default DCO/2 = 1048576Hz
// P3.4，5——USCI_A0 TXD/RXD；P9.4,5——USCI_A2 TXD/RXD；P10.4,5——USCI_A3 TXD/RXD；
void main(void)
{
WDTCTL = WDTPW + WDTHOLD; // Stop WDT
P4SEL |=BIT4+BIT5 ; // P5.6,7 = USCI_A1 TXD/RXD
UCA1CTL1 |= UCSWRST; // **Put state machine in reset**
UCA1CTL1 |= UCSSEL_2; // SMCLK
UCA1BR0 = 9; // 1MHz 115200 (see User's Guide)
UCA1BR1 = 0; // 1MHz 115200
UCA1MCTL |= UCBRS_1 + UCBRF_0; // Modulation UCBRSx=1, UCBRFx=0
UCA1CTL1 &= ~UCSWRST; // **Initialize USCI state machine**
UCA1IE |= UCRXIE; // Enable USCI_A1 RX interrupt
__bis_SR_register(LPM0_bits + GIE); // Enter LPM0, interrupts enabled
}
// Echo back RXed character, confirm TX buffer is ready first，发送数据之前确定发送缓存准备好
#pragma vector=USCI_A1_VECTOR
__interrupt void USCI_A1_ISR(void)
{
switch(__even_in_range(UCA1IV,4))
{
case 0:break; // Vector 0 - no interrupt
case 2: // Vector 2 - RXIFG
while (!(UCA1IFG&UCTXIFG)); // USCI_A1 TX buffer ready? UCTXIFG(USCI Transmit Interrupt Flag)
//等待数据发送完成完成UCTXIFG置1 跳出循环
UCA1TXBUF = UCA1RXBUF; // TX -> RXed character
break;
case 4:break; // Vector 4 - TXIFG
default: break;
}
}
// UCTXIFG=0x02，UCA1IFG&UCTXIFG，当UCA1IFG的UCTXIFG位为1时，说明UCA1TXBUF为空，
//跳出while循环循环；当UCTXIFG位为0时UCA1TXBUF不为空，停在循环。

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