Help on UART1 configuration on Tiva-C TM4C1294 LaunchPad

Hi,

I am new to Tiva-C hardware, especially peripheral such as UART. The example project uart_echo works as expected. I would like to add UART1 to this project. The first step I want UART1 in loopback mode. Whenever a character is received in UART0, it sends to both UART0 and UART1. Here is the interrupt vector table.

    IntDefaultHandler,                      // GPIO Port A
    IntDefaultHandler,                      // GPIO Port B
    IntDefaultHandler,                      // GPIO Port C
    IntDefaultHandler,                      // GPIO Port D
    IntDefaultHandler,                      // GPIO Port E
    UARTIntHandler,                         // UART0 Rx and Tx
    IntDefaultHandler,          	// for FIFO new usage
    UARTInt1Handler,                        // UART1 Rx and Tx

The main code is shown below. 

int
main(void)
{
    //
    // Set the clocking to run directly from the crystal at 120MHz.
    //
    g_ui32SysClock = MAP_SysCtlClockFreqSet((SYSCTL_XTAL_25MHZ |
                                             SYSCTL_OSC_MAIN |
                                             SYSCTL_USE_PLL |
                                             SYSCTL_CFG_VCO_480), 120000000);
    //
    // Enable the GPIO port that is used for the on-board LED.
    //
    ROM_SysCtlPeripheralEnable(SYSCTL_PERIPH_GPION);

    //
    // Enable the GPIO pins for the LED (PN0).
    //
    ROM_GPIOPinTypeGPIOOutput(GPIO_PORTN_BASE, GPIO_PIN_0);

    //
    // Enable the peripherals used by this example.
    // ???????
    ROM_SysCtlPeripheralEnable(SYSCTL_PERIPH_UART0);
    ROM_SysCtlPeripheralEnable(SYSCTL_PERIPH_UART1);
//  ROM_SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOA);
    ROM_SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOA);


    //
    // Enable processor interrupts.
    //
    ROM_IntMasterEnable();

    //
    // Set GPIO A0 and A1 as UART pins.
    //
    GPIOPinConfigure(GPIO_PA0_U0RX);
    GPIOPinConfigure(GPIO_PA1_U0TX);
    ROM_GPIOPinTypeUART(GPIO_PORTA_BASE, GPIO_PIN_0 | GPIO_PIN_1);

    //
    // Configure the UART for 115,200, 8-N-1 operation.
    //
    ROM_UARTConfigSetExpClk(UART0_BASE, g_ui32SysClock, 115200,
                            (UART_CONFIG_WLEN_8 | UART_CONFIG_STOP_ONE |
                             UART_CONFIG_PAR_NONE));
    ROM_UARTConfigSetExpClk(UART1_BASE, g_ui32SysClock, 115200,
                            (UART_CONFIG_WLEN_8 | UART_CONFIG_STOP_ONE |
                             UART_CONFIG_PAR_NONE));

    //
    // Enable the UART interrupt.
    //
    ROM_IntEnable(INT_UART0);
    ROM_UARTIntEnable(UART0_BASE, UART_INT_RX | UART_INT_RT);
    //
    // This register write will set the UART to operate in loopback mode.  Any
    // data sent on the TX output will be received on the RX input.
    //
    HWREG(UART1_BASE + UART_O_CTL) |= UART_CTL_LBE;

    ROM_IntEnable(INT_UART1);
    ROM_UARTIntEnable(UART1_BASE, UART_INT_RX | UART_INT_RT);

    //
    // Prompt for text to be entered.
    //
    UARTSend((uint8_t *)"\033[2JEnter text: ", 16);

    //
    // Loop forever echoing data through the UART.
    //
    while(1)
    {
    }
}

After it receives one character, it goes to the default handler:

static void
IntDefaultHandler(void)
{
    //
    // Go into an infinite loop.
    //
    while(1)
    {
    }
}


If I disable UART1 interrupt by commenting either line of

ROM_IntEnable(INT_UART1);
ROM_UARTIntEnable(UART1_BASE, UART_INT_RX | UART_INT_RT);

UART0 will work as normal. That is, introducing UART1 makes the program jump to the the default interrupt handler.

I don't know what part of UART1 configuration wrong. Can you tell me the problem?

Thanks,