TM4C1290NCPDT: UART_RSR errors

Hi,

I am using CCS version 10.1.0.00010 with TivaC EK-TM4C1294XL LaunchPad under Windows 10 x64 professional.

I have a another board connected to the TivaC launchPad on UART4 port (RX,TX,RTS,CTS). I have noticed that UART_RSR break error and framing error bits are set when I enable the UART. I have tried to call UARTRxErrorClear(UART4_BASE) with no effect. I disconnected the TM4C UART4 Rx input still these error bits are set. Below is the code that initializes UART4. I would appreciate any clarification.

Thanks,

Sam

void Configure_UART4(void)
{
    //
    // Enable the GPIO Peripheral used by the UART4 (port K).
    //
    SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOK);

    while(!ROM_SysCtlPeripheralReady(SYSCTL_PERIPH_GPIOK)){}

    //
    // Enable UART4.
    //
    SysCtlPeripheralEnable(SYSCTL_PERIPH_UART4);

    //wait for UART module to be ready
    while(!ROM_SysCtlPeripheralReady(SYSCTL_PERIPH_UART4)){}

    //
    // Configure GPIO Pins for UART mode with flow control
    //
    GPIOPinConfigure(GPIO_PK0_U4RX);
    GPIOPinConfigure(GPIO_PK1_U4TX);
    GPIOPinConfigure(GPIO_PK2_U4RTS);
    GPIOPinConfigure(GPIO_PK3_U4CTS);

    GPIOPinTypeUART(GPIO_PORTK_BASE, GPIO_PIN_0 | GPIO_PIN_1 |GPIO_PIN_2 | GPIO_PIN_3 );
    UARTFlowControlSet(UART4_BASE,UART_FLOWCONTROL_TX | UART_FLOWCONTROL_RX);

    UARTClockSourceSet(UART4_BASE,UART_CLOCK_SYSTEM);


    UARTConfigSetExpClk(UART4_BASE, g_ui32SysClock, 1000000,
                            (UART_CONFIG_WLEN_8 | UART_CONFIG_STOP_ONE |
                             UART_CONFIG_PAR_NONE));


    UARTEnable(UART4_BASE);

    //must be after UARTEnable since UARTEnable enables FIFO
    UARTFIFODisable(UART4_BASE);

    UARTRxErrorClear(UART4_BASE);

    //
    // Enable the UART interrupt.
    //
    IntEnable(INT_UART4);

    UARTIntEnable(UART4_BASE, UART_INT_RX);
}