LPC 1114 UART help...

Hi there Keil forums, I have a question about how my LPC 1114 responds to data over a Uart connection.

This is my UART interrupt code:

/* UART Data Received Interrupt */
void UART_IRQHandler(void) {
        static NetworkLayerState networkState = Network_Idle;
        unsigned int interruptId = LPC_UART->IIR;

        while((interruptId & 1) == 0)
        {
                switch((interruptId >> 1) & 0x07)
                {

                        case 0x02: //Receive Data Available
                        case 0x06: //Character time-out indicator (buffer flush)
                                networkState = NetworkStateMachine(LPC_UART->RBR & 0xFF, networkState);
                                break;

                        case 0x03: //Receive Line Status interrupt
                                break; //Not handling frame errors
                }

                interruptId = LPC_UART->IIR;
        }
}

My computer and mcu are connected via a usb to uart cable. I want to know what kind of data I need to send to my mcu in order to trigger this interrupt. For example if I want to send the integer "1" to my mcu how would I do that and then I can store that integer value in a variable within the firmware of the MCU.
My GUI is done in C# and it is what I use to communicate with the mcu.