;*******************************************************************************
;   MSP430F20xx Demo - Timer_A, Toggle P1.0-2, Cont. Mode ISR, 32kHz ACLK
;
;   Description: Use Timer_A CCRx units and overflow to generate four
;   independent timing intervals. For demonstration, CCR0 and CCR2
;   output units are optionally selected with port pins P1.1 and P1.2
;   in toggle mode. As such, these pins will toggle when respective CCRx
;   registers match the TAR counter. Interrupts are also enabled with all
;   CCRx units, software loads offset to next interval only - as long as the
;   interval offset is added to CCRx, toggle rate is generated in hardware.
;   Timer_A overflow ISR is used to toggle P1.0 with software. Proper use
;   of the TAIV interrupt vector generator is demonstrated.
;   ACLK = TACLK = 32kHz, MCLK = SMCLK = default DCO
;   //* An external watch crystal on XIN XOUT is required for ACLK *//	
;
;   As coded and with TACLK = 32768Hz, toggle rates are:
;   P1.1= CCR0 = 32768/(2*4) = 4096Hz
;   P1.2= CCR1 = 32768/(2*16) = 1024Hz
;   P1.0= overflow = 32768/(2*65536) = 0.25Hz
;
;                MSP430F20xx
;             -----------------
;         /|\|              XIN|-
;          | |                 | 32kHz
;          --|RST          XOUT|-
;            |                 |
;            |         P1.1/TA0|--> CCR0
;            |         P1.2/TA1|--> CCR1
;            |             P1.0|--> Overflow/software
;
;   M. Buccini / L. Westlund
;   Texas Instruments Inc.
;   October 2005
;   Built with IAR Embedded Workbench Version: 3.40A
;*******************************************************************************
#include  "msp430x20x3.h"
;-------------------------------------------------------------------------------
            ORG     0F800h                  ; Program Reset
;-------------------------------------------------------------------------------
RESET       mov.w   #0280h,SP               ; Initialize stackpointer
StopWDT     mov.w   #WDTPW+WDTHOLD,&WDTCTL  ; Stop WDT
SetupP1     bis.b   #006h,&P1SEL            ; P1.1 - P1.2 option select
            bis.b   #007h,&P1DIR            ; P1.0-2 outputs
SetupC0     mov.w   #OUTMOD_4 +CCIE,&CCTL0  ; CCR0 toggle, interrupt enabled
SetupC1     mov.w   #OUTMOD_4 +CCIE,&CCTL1  ; CCR1 toggle, interrupt enabled
SetupTA     mov.w   #TASSEL_1+MC_2+TAIE,&TACTL   ; ACLK, contmode, interrupt
                                            ;													
Mainloop    bis.w   #LPM3+GIE,SR            ; Enter LPM3, interrupts enabled
            nop                             ; Required for debug
                                            ;
;-------------------------------------------------------------------------------
TA0_ISR;
;-------------------------------------------------------------------------------
            add.w   #4,&CCR0                ; Offset until next interrupt
            reti                            ;		
                                            ;
;-------------------------------------------------------------------------------
TAX_ISR;    Common ISR for CCR1-4 and overflow
;-------------------------------------------------------------------------------
            add.w   &TAIV,PC                ; Add Timer_A offset vector
            reti                            ; CCR0 - no source
            jmp     CCR1_ISR                ; CCR1
            reti                            ; CCR2
            reti                            ; CCR3
            reti                            ; CCR4
TA_over     xor.b   #001h,&P1OUT            ; Toggle P1.0
            reti                            ; Return from overflow ISR		
                                            ;
CCR1_ISR    add.w   #16,&CCR1               ; Offset until next interrupt
            reti                            ; Return ISR		
                                            ;
;-------------------------------------------------------------------------------
;           Interrupt Vectors
;-------------------------------------------------------------------------------
            ORG     0FFFEh                  ; MSP430 RESET Vector
            DW      RESET                   ;
            ORG     0FFF2h                  ; Timer_A0 Vector
            DW      TA0_ISR                 ;
            ORG     0FFF0h                  ; Timer_AX Vector
            DW      TAX_ISR                 ;
            END