TMS570LC4357: How to throw initial TX interrupt (TX INT) from SCI UART using Halcogen

static unsigned char command;

void main(void)
{
    /* Enable IRQ */
    _enable_IRQ();

    /* Initialize SCI module */
    sciInit();

    /* Send user prompt */
    sciSend(scilinREG, 21, (unsigned char *)"please press a key!\r\n");

    /* Await user character */
    sciReceive(scilinREG, 1, (unsigned char *)&command);

    /* Infinite loop */
    while (1);
} 

void sciNotification(sciBase_t *sci, unsigned flags)
{
    /* Echo received character */
    sciSend(sci, 1, (unsigned char *)&command);

    /* Await further character */
    sciReceive(sci, 1, (unsigned char *)&command);
}

In the tutorial the interrupt service routine (sciNotification) is triggered because in the main method sciSend is called and at the end of the sciSend call the ISR will be called. I would like to know how to throw or trigger a TX INT from the UART whenever the UART is empty so that the ISR gets called without having to first send something using sciSend.

In my ISR I will have a list of messages that I append to in other places in my application and I want the UART to get those messages out whenever it is idle. In order to do this I need to know how to trigger a TX INT from the UART.