MSP430G2553: SPI on msp430g2553 using MPU6050 slave

#include <msp430.h>
#include <stdlib.h>
#include <stdio.h>

unsigned char MST_Data;
unsigned char SLV_Data;
/**
* main.c
*/
int main(void)
{

WDTCTL = WDTPW | WDTHOLD; // stop watchdog timer
P1OUT |= BIT5;
P1DIR |= 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; // No modulation
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
}
// Test for valid RX and TX character
#pragma vector=USCIAB0RX_VECTOR
__interrupt void USCIA0RX_ISR(void)
{
volatile unsigned int i;

while (!(IFG2 & UCA0TXIFG)); // USCI_A0 TX buffer ready?

if (UCA0RXBUF == SLV_Data) // Test for correct character RX'd
P1OUT |= BIT0; // If correct, light LED
else
P1OUT &= ~BIT0; // If incorrect, clear LED

MST_Data++; // Increment master value
SLV_Data++; // Increment expected slave value
UCA0TXBUF = MST_Data; // Send next value

__delay_cycles(50); // Add time between transmissions to
} // make sure slave can keep up

So I am testing this MPU6050 accelerometer as an spi slave to my msp430g2553 micro controller and i tried to use the above code to test the SPI connection. upon running the code the tx registry data increments until reaching some hex limit, but the rx registry doesn't change from 0xff. the forum post on this website i found the majority of the above code on had an answer that mentioned slaves returning a 0xff value as an idle value but didn't address what to do when this happens. any help would be appreciated