;*******************************************************************************
;   MSP430F20xx Demo - USICNT Used as a One-Shot Timer Function, DCO SMCLK
;
;   Description: USI conunter is used as a one-shot timer. The USI
;   conunter ISR toggles P1.0 using software. As coded ACLK is pre-divided by
;   128 and the USICNT loaded with 32, for a total divided of 4096 or
;   12-bits. USICNT must be reloaded after each interrupt which also clears
;   interrupt flag.
;   ACLK = VLO, MCLK = SMCLK = default DCO
;
; 		  MSP430F20xx
;              -----------------
;          /|\|              XIN|-
;           | |                 |
;           --|RST          XOUT|-
;             |                 |
;             |             P1.0|-->LED
;
;   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 watchdog timer
SetupP1     bis.b   #01h,&P1DIR             ; P1.1 output direction

SetupBC     bis.b   #LFXT1S_2,&BCSCTL1      ; ACLK = VL0
SetupUSI    bis.b   #USIMST,&USICTL0        ; SPI master
            bis.b   #USIIE,&USICTL1         ; Counter interrupt, flag remains
            mov.b   #USIDIV_7+USISSEL_1,&USICKCTL    ; /128 ACLK
            bic.b   #USISWRST,&USICTL0      ; Enable USI
            mov.b   #08h,&USICNT            ; init-load counter
                                            ;
Mainloop    bis.w   #LPM0+GIE,SR            ; Enter LPM0, enable interrupts
            jmp     Mainloop                ; Again
                                            ;
;-------------------------------------------------------------------------------
USI_ISR  ;
;-------------------------------------------------------------------------------
            xor.b   #01h,&P1OUT             ; Toggle P1.0
            bis.b   #01Fh,&USICNT           ; re-load counter
            reti                            ;
                                            ;
;-------------------------------------------------------------------------------
;           Interrupt Vectors Used MSP430x2013
;-------------------------------------------------------------------------------
            ORG     0FFFEh                  ; MSP430 RESET Vector
            DW      RESET                   ;
            ORG     0FFE8h                  ; USICNT
            DW      USI_ISR                 ;
            END