msp430x24x_of_xt2.s43

步进电机驱动程序msp430f247单片机

;******************************************************************************
;   MSP430x24x Demo - XT2 Oscillator Fault Detection
;
;   Description: System runs normally in LPM3 with Timer A clocked by
;   ACLK.  Basic Timer interrupt causes an exit from LPM3, and toggles P1.0.
;   If an XT2 oscillator fault occurs, NMI is requested, pausing execution and
;   flashing LED quickly until fault is resolved.  Assumed only XT2 as NMI
;   source - code does not check for other NMI sources. MCLK is buffered on 
;   P5.4. If fault occurs for crystal osc sourcing the MCLK, MCLK is 
;   automatically switched to DCO for its clock source
;   MCLK = XT2 = 8MHz normally, within ISRs MCLK = DCO freq ~1045kHz
;   //* An external 8MHx crystal is required between XT2 and XT2OUT , and
;   an external 32kHz crystal is required between XIN and XOUT.  *//	
;
;                MSP430x249
;             -----------------
;         /|\|              XIN|-
;          | |                 | 32KHz
;          --|RST          XOUT|-
;            |                 |
;            |            XT2IN|-
;            |                 | 8MHz
;            |           XT2OUT|-
;            |                 |
;            |             P1.0|-->LED
;            |        P5.4/MCLK|-->MCLK = XT2 HFXTAL
;
;  B. Nisarga
;  Texas Instruments Inc.
;  September 2007
;  Built with IAR Embedded Workbench Version: 3.42A
;******************************************************************************
#include  <msp430x24x.h>
;-------------------------------------------------------------------------------
            RSEG    CSTACK                  ; Define stack segment
;-------------------------------------------------------------------------------
            RSEG    CODE                    ; Assemble to Flash memory
;-----------------------------------------------------------------------------
RESET       mov.w   #SFE(CSTACK),SP         ; Initialize stackpointer
StopWDT     mov.w   #WDTPW+WDTHOLD,&WDTCTL  ; Stop WDT

SetupBC     bic.b   #XT2OFF,&BCSCTL1        ; Activate XT2 high freq xtal
            bis.b   #XT2S_2,&BCSCTL3        ; 3