//******************************************************************************
//  MSP-FET430P140 Demo - USART0, Ultra-Low Pwr 9600 Echo ISR, 32kHz ACLK
//
//  Description: Echo a received character, RX ISR used. Normal mode is LPM3,
//  USART0 RX interrupt triggers TX Echo.
//  Baud rate divider with 32768Hz XTAL @9600 = 32768Hz/9600 = 3.41 (0003h 4Ah )
//  ACLK = UCLK0 = LFXT1 = 32768Hz, MCLK = SMCLK = default DCO ~800kHz
//  //* An external watch crystal is required on XIN XOUT for ACLK *//	
//
//
//              MSP430F12x(2)
//            -----------------
//        /|\|              XIN|-
//         | |                 | 32kHz
//         --|RST          XOUT|-
//           |                 |
//           |             P3.4|----------->
//           |                 | 9600 - 8N1
//           |             P3.5|<-----------
//
//
//  M. Buccini
//  Texas Instruments Inc.
//  Feb 2005
//  Built with IAR Embedded Workbench Version: 3.21A
//******************************************************************************

#include  <msp430x12x2.h>

void main(void)
{
  WDTCTL = WDTPW + WDTHOLD;                 // Stop WDT
  P3SEL |= 0x30;                            // P3.4,5 = USART0 TXD/RXD
  ME2 |= UTXE0 + URXE0;                     // Enable USART0 TXD/RXD
  UCTL0 |= CHAR;                            // 8-bit character
  UTCTL0 |= SSEL0;                          // UCLK = ACLK
  UBR00 = 0x03;                             // 32k/9600 - 3.41
  UBR10 = 0x00;                             //
  UMCTL0 = 0x4A;                            // Modulation
  UCTL0 &= ~SWRST;                          // Initialize USART state machine
  IE2 |= URXIE0;                            // Enable USART0 RX interrupt

  _BIS_SR(LPM3_bits + GIE);                 // Enter LPM3 w/ interrupt
}

#pragma vector=UART0RX_VECTOR
__interrupt void usart0_rx (void)
{
  while (!(IFG2 & UTXIFG0));                // USART0 TX buffer ready?
  TXBUF0 = RXBUF0;                          // RXBUF0 to TXBUF0
}