SPI question

Hello!

I just figured out how to make a SPI link to work in a way that just the Master MCU sends out an 8 bit valeu to the Slave MCU.

But know, what I'm looking forward to do is to make them both send and recieve 8 bits values.

Well I tried to do it with no sucess. I would like to know what steps I need to take in order to make it work.

Here is my code for both the Master and Slave MCUs in wich the masters sends out a value and the slave recieves it.

 MSP430 G2553 (SLAVE)

#include <msp430.h>

volatile unsigned char RECEP = 0;

void main(void)
{
    WDTCTL = WDTPW + WDTHOLD;

    P1DIR = 0x40;
    P1SEL = 0x40;
    TACCR0 = 255;
    TACCTL1 = OUTMOD_7;
    TACCR1 = 0;
    TACTL = TASSEL_2 + MC_1;

    P1DIR |= BIT0;
    P1OUT &= ~BIT0;

  	P1SEL |= BIT1 + BIT2 + BIT4;
    P1SEL2 |= BIT1 + BIT2 + BIT4;
    UCA0CTL0 |= UCCKPL + UCMSB + UCSYNC;
    

    UCA0CTL1 &= ~UCSWRST;
    IE2 |= UCA0RXIE;

    __bis_SR_register(GIE);

    while(1){

    	TACCR1 = RECEP;
    	IE2 |= UCA0RXIE;}
  }


  #pragma vector=USCIAB0RX_VECTOR
  __interrupt void USCIA0RX_ISR(void)
  {
	P1OUT ^= BIT0;
  	RECEP = UCA0RXBUF;
}


MSP430 FR5739 (MASTER) code:

#include <msp430.h>

unsigned char TXData;
volatile unsigned char a =0;

int main(void)
{
  WDTCTL = WDTPW+WDTHOLD;

  P3DIR |= BIT4;
  P3OUT |= BIT4;
  
  
  P1SEL1 |= BIT5; 
  P2SEL1 |= BIT0 + BIT1;
  UCA0CTLW0 |= UCSWRST;
  UCA0CTLW0 |= UCMST+UCSYNC+UCCKPL+UCMSB;

  UCA0CTLW0 |= UCSSEL_2;
  UCA0BR0 = 0x16;
  UCA0BR1 = 0;
  UCA0MCTLW = 0;
  UCA0IE |= UCRXIE;
  UCA0CTLW0 &= ~UCSWRST;
  TXData = 0;


  //TIMER_B2 CONFIGURATION

      P3DIR |= BIT6 + BIT7;
      P3SEL0 |= BIT6 + BIT7;

      TB2CCTL1 = OUTMOD_7;
      TB2CCTL2 = OUTMOD_7;
      TB2CCR0 = 256;
      TB2CCR1 = 0;
      TB2CCR2 = 0;
      TB2CTL = TBSSEL_2 + MC_1;

  while(1){
    UCA0IE |= UCTXIE;
    __bis_SR_register(GIE);
    __no_operation();
    __delay_cycles(80000);
    if( a < 256 ){
        a += 2;
        TXData++;
        TB2CCR1 = TXData;
        TB2CCR2 = TXData;}
    else{
        a=0;
        TXData = 0;}
}}

#pragma vector=USCI_A0_VECTOR
__interrupt void USCI_A0_ISR(void)
{

  switch(__even_in_range(UCA0IV,0x04))
  {
    case 0: break;
    case 2: break;
    case 4:
          P3OUT ^= BIT4;
          UCA0TXBUF = TXData;
          UCA0IE &= ~UCTXIE;
          break;
    default: break;
}}