msp430g2x21 usi 01

The USI // conunter ISR toggles P1.0 using software.. USICNT must be reloaded after each interrupt which also clears // interrupt flag.. Dang // Texas Instruments Inc.

//****************************************************************************** // MSP430G2x21/G2x31 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

//

// MSP430G2x21/G2x31

//

-// /|\|

XIN|-// | | |

// |RST

XOUT|-// | |

// | P1.0| >LED

//

// D Dang

// Texas Instruments Inc

// October 2010

// Built with CCS Version 4.2.0 and IAR Embedded Workbench Version: 5.10

//******************************************************************************

#include <msp430g2221.h>

void main(void)

{

WDTCTL = WDTPW + WDTHOLD; // Stop watchdog timer

BCSCTL3 |= LFXT1S_2; // ACLK = VLO

P1DIR |= 0x01; // Set P1.0 to output direction USICTL0 |= USIMST; // Master mode

USICTL1 |= USIIE; // Counter interrupt, flag remains set

USICKCTL = USIDIV_7 + USISSEL_1; // /128 ACLK

USICTL0 &= ~USISWRST; // USI released for operation

_BIS_SR(LPM3_bits + GIE); // Enter LPM3 w/ interrupt

}

// USI interrupt service routine

#pragma vector=USI_VECTOR

interrupt void universal_serial_interface(void)

{

P1OUT ^= 0x01; // Toggle P1.0 using exclusive-OR USICNT = 0x1F; // re-load counter

}