master.c

//Master device SPI code
#include <msp430.h>
unsigned char MST_Data, SLV_Data;
int main(void)
{
 volatile unsigned int i;
 WDTCTL = WDTPW + WDTHOLD; // Stop watchdog timer
 P1OUT = 0x00; // P1 setup for LED & reset output
 P1DIR |= BIT0 + BIT5; //
 P1SEL = BIT1 + BIT2 + BIT4;
 P1SEL2 = BIT1 + BIT2 + BIT4;
 UCA0CTL0 |= UCCKPL + UCMSB + UCMST + UCSYNC; // 3-pin, 8-bit SPI master
 UCA0CTL1 |= UCSSEL_2; // SMCLK
 UCA0BR0 |= 0x02; // /2
 UCA0BR1 = 0; //
 UCA0MCTL = 0; 
 UCA0CTL1 &= ~UCSWRST; // **Initialize USCI state machine**
 IE2 |= UCA0RXIE; // Enable USCI0 RX interrupt
 P1OUT &= ~BIT5; // Now with SPI signals initialized,
 P1OUT |= BIT5; // reset slave
__delay_cycles(75); // Wait for slave to initialize
 MST_Data = 0x01; // Initialize data values
 SLV_Data = 0x00;
 UCA0TXBUF = MST_Data; // Transmit first character
 __bis_SR_register(LPM0_bits + GIE); // CPU off, enable interrupts
}

// Master RX ISR
#pragma vector=USCIAB0RX_VECTOR
__interrupt void USCIA0RX_ISR(void)
{
 while (!(IFG2 & UCA0TXIFG)); // USCI_A0 TX buffer ready for next transmission?
//Code for Master TX goes here
__delay_cycles(50); // Add time between transmissions to make sure slave can keep up
}