;*******************************************************************************
;   MSP430F20xx Demo - Timer_A, Toggle P1.0, Overflow ISR, 32kHz ACLK
;
;   Description: Toggle P1.0 using software and the Timer_A overflow ISR.
;   In this example an ISR triggers when TA overflows. Inside the ISR P1.0
;   is toggled. Toggle rate is exactly 0.5Hz.
;   ACLK = TACLK = LFXT1 = 32768Hz, MCLK = SMCLK = default DCO
;   //* An external watch crystal on XIN XOUT is required for ACLK *//	
;
;                 MSP430F20xx
;             -----------------
;         /|\|              XIN|-
;          | |                 | 32kHz
;          --|RST          XOUT|-
;            |                 |
;            |             P1.0|-->LED
;
;   P.Thanigai
;   Texas Instruments Inc.
;   May 2007
;   Built with Code Composer Essentials Version: 2.0
;*******************************************************************************
 .cdecls C,LIST,  "msp430x20x3.h"

;------------------------------------------------------------------------------
            .text                           ; Progam Start
;------------------------------------------------------------------------------
RESET       mov.w   #0280h,SP               ; Initialize stackpointer
StopWDT     mov.w   #WDTPW+WDTHOLD,&WDTCTL  ; Stop WDT
SetupP1     bis.b   #001h,&P1DIR            ; P1.0 output
SetupTA     mov.w   #TASSEL_1+MC_2+TAIE,&TACTL  ; ACLK, contmode interrupt
                                            ;													
Mainloop    bis.w   #LPM3+GIE,SR            ; Enter LPM3, interrupts enabled
            nop                             ; Required only for debugger
                                            ;
;-------------------------------------------------------------------------------
TAX_ISR;    Common ISR for CCR1-4 and overflow
;-------------------------------------------------------------------------------
            add.w   &TAIV,PC                ; Add Timer_A offset vector
            reti                            ; CCR0 - no source
            reti                            ; CCR1
            reti                            ; CCR2
            reti                            ; CCR3
            reti                            ; CCR4
TA_over     xor.b   #001h,&P1OUT            ; Toggle P1.0
            reti                            ; Return from overflow ISR		
                                            ;
;------------------------------------------------------------------------------
;           Interrupt Vectors
;------------------------------------------------------------------------------
            .sect   ".reset"                ; MSP430 RESET Vector
            .short  RESET                   ;
            .sect   ".int08"                ; Timer_AX Vector
            .short  TAX_ISR                 ;
            .end