;******************************************************************************
;   MSP-FET430P140 Demo - USART0 UART Ultra-low Power 9600 String, 32kHz ACLK 
;
;   Description: This program demonstrates a full-duplex 9600-baud UART using 
;   USART0 and a 32kHz crystal.  The program will wait in LPM3, and will
;   respond to a received 'u' character using 8N1 protocol. The response will
;   be the string 'Hello World'. 
;   ACLK = LFXT1 = UCLK0, MCLK = SMCLK = default DCO ~ 800KHz
;   Baud rate divider with 32768hz XTAL @9600 = 32768Hz/9600 = 3.41 (000Dh 4Ah )
;  //*An external watch crystal is required on XIN XOUT for ACLK*//	  
;              
;                MSP430F149
;             -----------------
;         /|\|              XIN|-  
;          | |                 | 32kHz  
;          --|RST          XOUT|-
;            |                 |
;            |             P3.4|-----------> 
;            |                 | 9600 - 8N1
;            |             P3.5|<-----------
;
;   CPU registers used
#define      Pointer  R4
;
LF           equ    0ah                     ; ASCII Line Feed
CR           equ    0dh                     ; ASCII Carriage Return
;
;    M.Buccini
;    Texas Instruments, Inc
;    January 2004
;******************************************************************************
#include "msp430x14x.h"
;----------------------------------------------------------------------------- 
            ORG     0F000h                  ; Program Reset
;----------------------------------------------------------------------------- 
RESET       mov.w   #0A00h,SP               ; Initialize stackpointer
StopWDT     mov.w   #WDTPW+WDTHOLD,&WDTCTL  ; Stop WDT
SetupP3     bis.b   #030h,&P3SEL            ; P3.4,5 = USART0 TXD/RXD
SetupUART0  bis.b   #UTXE0+URXE0,&ME1       ; Enable USART0 TXD/RXD
            bis.b   #CHAR,&UCTL0            ; 8-bit characters
            mov.b   #SSEL0,&UTCTL0          ; UCLK = ACLK
            mov.b   #003h,&UBR00            ; 32k/9600 - 3.41
            mov.b   #000h,&UBR10            ; 
            mov.b   #04Ah,&UMCTL0           ; Modulation 
            bic.b   #SWRST,&UCTL0           ; **Initialize USART state machine**
            bis.b   #URXIE0+UTXIE0,&IE1     ; Enable USART0 RX/TX interrupt
            bic.b   #UTXIFG0,&IFG1          ; Clear inital flag on POR
                                            ;             
Mainloop    bis.w   #LPM3+GIE,SR            ; Enter LPM3 w/ int until Byte RXed
            nop                             ; Required only for debugger
                                            ;
;------------------------------------------------------------------------------ 
USART0TX_ISR; 
;------------------------------------------------------------------------------ 
            cmp.w   #String1+13,Pointer     ;
            jeq     Done                    ;
            mov.b   @Pointer+,&TXBUF0       ;
Done        reti                            ; 
                                            ;
;----------------------------------------------------------------------------- 
USART0RX_ISR; 
;----------------------------------------------------------------------------- 
            cmp.b   #'u',&RXBUF0            ;
            jne     USART_Done              ;
            mov.w   #String1,Pointer        ;
            mov.b   @Pointer+,&TXBUF0       ;
USART_Done  reti                            ;		 
                                            ;
String1      DB 'Hello World',CR,LF  

;------------------------------------------------------------------------------ 
;           Interrupt Vectors Used MSP430x13x/14x/15x/16x         
;------------------------------------------------------------------------------ 
            ORG     0FFFEh                  ; 
            DW      RESET                   ; POR, ext. Reset, Watchdog
            ORG     0FFF2h                  ; 
            DW      USART0RX_ISR            ; USART0 receive
            ORG     0FFF0h                  ; 
            DW      USART0TX_ISR            ; USART0 transmit
            end