1. //***********************************************************************
   // MSP-FET430P140 Demo - Timer_A0, Capture of ACLK/8 using SMCLK
   //
   // Description: Input capture of ACLK/8 on P1.1(TA0)
   // Run to breakpoint at the _NOP() instruction to see 16 capture
   // values and the differences.
   // ACLK = 32768Hz, MCLK = SMCLK = default ~800kHz
   // //* An external watch crystal on XIN XOUT is required for ACLK *//
   //
   // MSP430F149
   // -----------------
   // /|| XIN|-
   // | | | 32kHz
   // --|RST XOUT|-
   // | |
   // | P2.0/ACLK|---+
   // | | |
   // | P1.1/TA0|<--+
   // | |
   // | P1.0|--->LED
   
   //
   // H. Grewal
   // Texas Instruments Inc.
   // Feb 2005
   // Built with CCE Version: 3.2.0 and IAR Embedded Workbench Version: 3.21A
   //******************************************************************************
   
   #include <msp430x14x.h>
   
   unsigned int new_cap=0;
   unsigned int old_cap=0;
   unsigned int cap_diff=0;
   
   unsigned int diff_array[16]; // RAM array for differences
   unsigned int capture_array[16]; // RAM array for captures
   unsigned char index=0;
   unsigned char count = 0;
   
   void main(void)
   {
   volatile unsigned int i;
   WDTCTL = WDTPW + WDTHOLD; // Stop watchdog timer
   for (i=0; i<20000; i++) // Delay for crystal stabilization
   {
   }
   P1DIR = 0x01; // Set P1.0 out,1.1 input dir
   P1OUT &= ~0x01; // LED off
   P1SEL = 0x02; // Set P1.1 to TA0
   P2DIR = 0x01; // P2.0-ACLK
   P2SEL |= 0x01;
   BCSCTL1 |= DIVA_3; // ACLK/8
   
   CCTL0 = CM_1 + SCS + CCIS_0 + CAP + CCIE; // Rising edge + CCI0A (P1.1)
   // + Capture Mode + Interrupt
   
   TACTL = TASSEL_2 + MC_2; // SMCLK + Continuous Mode
   
   _BIS_SR(LPM0_bits + GIE); // LPM0 + Enable global ints
   }
   
   #pragma vector=TIMERA0_VECTOR
   __interrupt void TimerA0(void)
   {
   new_cap = TACCR0;
   cap_diff = new_cap - old_cap;
   
   diff_array[index] = cap_diff; // record difference to RAM array
   capture_array[index++] = new_cap;
   if (index == 16)
   {
   index = 0;
   P1OUT ^= 0x01; // Toggle P1.0 using exclusive-OR
   }
   old_cap = new_cap; // store this capture value
   count ++;
   if (count == 32)
   {
   count = 0;
   _NOP(); // SET BREAKPOINT HERE
   }
   
   }

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