Listing for "Digital countdown timer may never need battery replacement", EDN Magazine, June 23, 2005


#include  "msp430x41x.h"
;******************************************************************************
; MSP430F412 Demo: Ultra-Low Power Digital Countdown Timer
;
;                                                3.5 digit, Static LCD
;                                                VARITRONIX
;                 /|\       MSP430x41x MCU       # VI-302-DP
;                  |        ---------------       --------------
;         +-o\-+(100k)-----| RST      COM2 |     |              |
;         |                |          COM1 |     |              |
;        \|/               |          COM0 |-----|COM           |
;                          |          SEG0 |-----|21            |
;                          |          SEG1 |-----|20            |
;                          |           .   |-----|.             |
;                          |           .   |-----|.             |
;                          |          SEG23|-----|3             |
;                          |               |     |              |
;                 	   |               |      --------------
;                           ---------------
;
; M.Buccini
; Texas Instruments, Inc
; March 2005
;******************************************************************************
            ORG     0F000h                  ; Program Start
RESET       mov.w   #300h,SP                ; Initialize '412 stackpointer
StopWDT     mov.w   #WDTPW+WDTHOLD,&WDTCTL  ; Stop Watchdog Timer
SetupFLL    bis.b   #XCAP18PF,&FLL_CTL0     ; Select load Caps
SetupLCD    mov.b   #LCDSG0_3+LCDON+LCDSTATIC,&LCDCTL ; Static LCD, segs0-23
SetupBT     mov.b   #BT_fLCD_DIV256+BT_ADLY_1000,&BTCTL; fLCD= ACLK/256, 1 sec
            bis.b   #BTIE,&IE2              ; Enable Basic Timer interrupt
SetupPx     mov.b   #0FFh,&P1DIR            ; P1.x output
            clr.b   &P1OUT                  ;
            mov.b   #0FFh,&P2DIR            ; P2.x output direction
            clr.b   &P2OUT                  ;
            mov.b   #0FFh,&P5DIR            ; R5.x outputs
            clr.b   &P5OUT                  ;
            mov.b   #0FFh,&P6DIR            ; P6.x output direction
            clr.b   &P6OUT                  ;
ClearLCD    mov.w   #20,R15                 ; Clear 20 bytes of LCD RAM
Clear1      clr.b   LCDMEM-1(R15)           ; Clear LCD RAM to clear
            dec.w   R15                     ; All 20 bytes of LCD RAM?
            jnz     Clear1                  ; Not done?
            mov.w   #01459h,&200h           ;
                                            ;
Mainloop    call    #Display                ;
            bis.w   #LPM3+GIE,SR            ;
            clrc                            ;
            dadd.b  #099h,&200h             ;
            jc      Mainloop                ;
            mov.b   #059h,&200h             ;
            clrc                            ;
            dadd.b  #099h,&201h             ;
            jc      Mainloop                ;
                                            ;
            mov.w   #0000h,&200h            ;
            call    #Display                ;
TimeOut     xor.b   #LCDON,&LCDCTL          ;
            bis.w   #LPM3+GIE,SR            ;
            jmp     TimeOut                 ;
                                            ;
Display     mov.w   &200h,R14               ; Copy BCD value
            mov.w   #LCDM1,R15              ; R15 points to first LCD location
OutLCD      mov.w   R14,R13                 ; Copy BCD value in R14 to R13
            and.b   #0Fh,R13                ; R13 = Nibble
            mov.b   LCD_Tab(R13),R13        ; R13 = LCD segment information
            mov.b   R13,0(R15)              ; Segments a & b to LCD
            rra.w   R13                     ;
            mov.b   R13,1(R15)              ; Segments c & d to LCD
            rra.w   R13                     ;
            mov.b   R13,2(R15)              ; Segments e & f to LCD
            rra.w   R13                     ;
            mov.b   R13,3(R15)              ; Segments g & h to LCD
            rra.w   R14                     ; Right Shift
            rra.w   R14                     ; Right Shift
            rra.w   R14                     ; Right Shift
            rra.w   R14                     ; Right Shift
            add.b   #04h,R15                ; R15 points to next LCD location
            cmp.b   #LCDM13,R15             ;
            jne     OutLCD                  ;
            bit.w   #00001h,R14             ; Third digit
            jnc     Disp_end                ;
            bis.b   #010h,&LCDM12           ;
Disp_end    bis.b   #010h,&LCDM4            ; ":"
            ret                             ;
                                            ;
BT_ISR      bic.w   #LPM3,0(SP)             ; Exit LPM3 on reti
            reti                            ;
                                            ;
LCD_Tab     DB      077h                    ; "0"
            DB      012h                    ; "1"
            DB      03Dh                    ; "2"
            DB      03Bh                    ; "3"
            DB      05Ah                    ; "4"
            DB      06Bh                    ; "5"
            DB      06Fh                    ; "6"
            DB      013h                    ; "7"
            DB      07Fh                    ; "8"
            DB      07Bh                    ; "9"
                                            ;
            ORG     0FFFEh                  ; MSP430 RESET Vector
            DW      RESET                   ;
            ORG     0FFE0h                  ; BT Vector
            DW      BT_ISR                  ;
            END