fet110_ta_cap01.s43

msp430p1110

#include  "msp430x11x1.h"
;******************************************************************************
;   MSP-FET430x110 Demo - Timer_A Ultra-low Power 1200hz detect, ACLK +/- 5%
;
;   Description; Using Timer_A capture capability.  At 250ms intervals,
;   CCR0 is enabled on P2.2  to detect presence or absence of 1200Hz. If 
;   1200Hz is present, P1.0 is set, if not, reset.  WDT is used for 250ms 
;   wake-up to hunt for tone. System runs normally in LPM3.  
;   //*External watch crystal installed on XIN XOUT is required for ACLK*//	  
;
;        32768Hz = ACLK
;        1200Hz  = 27.3 ACLK clocks
;        1260Hz  = 26 ACLK clocks 
;        1730Hz  = 28 ACLK clock
;
;                 MSP430F1121
;             -----------------
;         /|\|              XIN|-  
;          | |                 | 32k
;          --|RST          XOUT|-
;            |                 |
;    Signal->|P2.2/CCR0    P1.0|-->LED
;            |                 |			 
;
;
;            CPU registers used
#define      Period R15
#define      OldCap R14
;
;   M.Buccini
;   Texas Instruments, Inc
;   January 2002
;******************************************************************************
;------------------------------------------------------------------------------ 
            ORG     0F000h                  ; Program Start
;------------------------------------------------------------------------------ 
RESET       mov.w   #300h,SP		    ; Initialize stackpointer
SetupWDT    mov.w   #WDT_ADLY_250,&WDTCTL   ; WDT 250ms Interval Timer 
            bis.b   #WDTIE,&IE1             ; Enable WDT Interrupt 
SetupP1     mov.b   #0FFh,&P1DIR            ; All P1.x Outputs
            clr.b   &P1OUT                  ; All P1.x Reset
SetupP2     mov.b   #0FBh,&P2DIR            ; P2.2 Input / All P2.x Output
            bis.b   #004h,&P2SEL            ; P2.2 CCR0 input
            clr.b   &P2OUT                  ; All P2.x Reset
            eint                            ; Enable Interrupts
                                            ;													  
Mainloop    bis.w   #LPM3,SR                ; Enter LPM3
            call    #Get_CCR0               ; Capture CCR0 on P2.2 
            cmp.w   #029,Period             ;
            jhs     OFF                     ;
            cmp.w   #026,Period             ;
            jlo     OFF                     ;
                                            ;
ON          bis.b   #001h,&P1OUT            ; P1.0 = 1
            jmp     Mainloop                ;  
OFF         bic.b   #001h,&P1OUT            ; P1.0 = 0
            jmp     Mainloop                ;  
                                            ;
;------------------------------------------------------------------------------ 
Get_CCR0; Subroutine to get CCR0 Capture
;------------------------------------------------------------------------------ 
            clr     Period                  ;
            clr     OldCap                  ;
            mov     #TASSEL0+TACLR,&TACTL   ; ACLK, TAR cleared
SetupC0     mov     #CCIS0+CM0+CAP+CCIE+SCS,&CCTL0  ; CCI0B, CAP, interrupt
            bis     #MC1,&TACTL             ; Start timer in Ccntinous mode
Test_1      cmp     #0112,&TAR              ; Timeout
            jlo     Test_1                  ; jump if 112 > &TAR
            clr     &TACTL                  ; Stop Timer_A
            clr     &CCTL0                  ; Stop CCTL0
            ret                             ;
                                            ;
;------------------------------------------------------------------------------ 
TA0_ISR;    Timer_A C0 ISR
;------------------------------------------------------------------------------ 
            push.w  &CCR0                   ; Captured TAR, rising edge
            mov.w   @SP,Period              ;
            sub.w   OldCap,Period           ; New - old = period
            pop.w   OldCap                  ; For next calculation
            reti                            ;
                                            ; 
;------------------------------------------------------------------------------ 
WDT_ISR;    Exit LPM3 on reti
;------------------------------------------------------------------------------ 
            bic.w    #LPM3,0(SP)            ; Clear LPM3 from TOS
            reti                            ;		 
                                            ; 
;------------------------------------------------------------------------------ 
;           Interrupt Vectors Used MSP430x11x1         
;------------------------------------------------------------------------------ 
            ORG     0FFFEh                  ; MSP430 RESET Vector
            DW      RESET                   ; 
            ORG     0FFF4h                  ; WDT Vector
            DW      WDT_ISR                 ; 
            ORG     0FFF2h                  ; Timer_A0 Vector
            DW      TA0_ISR                 ; 
            END