Basic example msp430-uart for reading 16 bytes and then sending it back at once.

example.c

/*
 * example.c
 */

#include <msp430g2553.h>
#include <uart.h>

#define ARRAY_SIZE 16

/**
 * Read 16 bytes and then send it back. Forever loop.
 */
void test_arrays() {
    char buffer[ARRAY_SIZE];
    unsigned char next = 0;

    while (1) {
        // Get single character from UART stream. If 
        // there is no character - it will wait one and then return it.
        unsigned char ch = uart_getc();
        buffer[next++] = ch;

        if (next == ARRAY_SIZE) {
            // 16 bytes received. Send data chunk 
            // back to the sender and clear 'next' indexer.
            uart_putn(buffer, ARRAY_SIZE);
            next = 0;
        }
    }
}

void main(void) {
    // Holding down the watchdog.
    WDTCTL = WDTPW | WDTHOLD;

    // Before using uart_ functions, you must 
    // initialize uart module.
    uart_init();

    test_arrays();
}