;******************************************************************************
;   MSP-FET430P140 Demo - USART1, UART 9600 Echo ISR, HF XTAL ACLK
;
;   Description: This program will echo a received character, RX ISR used.
;   ACLK = MCLK = UCLK1 = = XT1 = 3.58MHz
;   Baud rate divider with 3.58Mhz XTAL @9600 = 3.58MHz/9600 = 372 (0174h)
;   //* An external 3.58MHz XTAL on XIN XOUT is required for ACLK *//	
;
;                MSP430F149
;             -----------------
;         /|\|              XIN|-
;          | |                 | 3.58MHz
;          --|RST          XOUT|-
;            |                 |
;            |             P3.6|------------>
;            |                 | 9600 - 8N1
;            |             P3.7|<------------
;
;   M. Buccini
;   Texas Instruments Inc.
;   Feb 2005
;   Built with IAR Embedded Workbench Version: 3.21A
;******************************************************************************
#include  <msp430x14x.h>
;------------------------------------------------------------------------------
            ORG     01100h                  ; Progam Start
;------------------------------------------------------------------------------
RESET       mov.w   #0A00h,SP               ; Initialize stackpointer
StopWDT     mov.w   #WDTPW+WDTHOLD,&WDTCTL  ; Stop WDT
SetupP3     bis.b   #0C0h,&P3SEL            ; P3.6,7 = USART1 option select
SetupBC     bis.b   #XTS,&BCSCTL1           ; LFXT1 = HF XTAL
SetupOsc    bic.b   #OFIFG,&IFG1            ; Clear OSC fault flag
            mov.w   #0FFh,R15               ; R15 = Delay
SetupOsc1   dec.w   R15                     ; Additional delay to ensure start
            jnz     SetupOsc1               ;
            bit.b   #OFIFG,&IFG1            ; OSC fault flag set?
            jnz     SetupOsc                ; OSC Fault, clear flag again
            bis.b   #SELM_3,&BCSCTL2        ; MCLK = LFXT1
SetupUART1  bis.b   #UTXE1+URXE1,&ME2       ; Enable USART1 TXD/RXD
            bis.b   #CHAR,&UCTL1            ; 8-bit characters
            mov.b   #SSEL0,&UTCTL1          ; UCLK1 = ACLK
            mov.b   #074h,&UBR01            ; 3.58Mhz 9600 - 372
            mov.b   #001h,&UBR11            ; 3.58Mhz 9600
            mov.b   #000h,&UMCTL1           ; 3.58MHz no modulation 9600
            bic.b   #SWRST,&UCTL1           ; **Initialize USART state machine**
            bis.b   #URXIE1,&IE2            ; Enable USART1 RX interrupt
                                            ;
Mainloop    bis.b   #CPUOFF+GIE,SR          ; Enter LPM0, interrupts enabled
            nop                             ; Needed only for debugger
                                            ;
;------------------------------------------------------------------------------
USART1RX_ISR;  Echo back RXed character, confirm TX buffer is ready first
;------------------------------------------------------------------------------
TX2         bit.b   #UTXIFG1,&IFG2          ; USART1 TX buffer ready?
            jz      TX2                     ; Jump is TX buffer not ready
            mov.b   &RXBUF1,&TXBUF1         ; TX -> RXed character
            reti                            ;
                                            ;
;------------------------------------------------------------------------------
;           Interrupt Vectors
;------------------------------------------------------------------------------
            ORG     0FFFEh                  ;
            DW      RESET                   ; POR, ext. Reset, Watchdog
            ORG     0FFE6h                  ;
            DW      USART1RX_ISR              ; USART1 Receive
            END