LPC1758 UART Problem

#define  DMA_BUF_ADR 0x2008000

short *DataBuf = (short *)(DMA_BUF_ADR);

short DataOut = 0; 

//usart interrupt routine 

void UART3_IRQHandler(void)

{   

      unsigned char data=0;

     intsrc = (LPC_UART3->IIR & 0x03CF);       

     intsrc &= UART_IIR_INTID_MASK;    /* Interrupt ID mask */

    //THRE

    if (intsrc == UART_IIR_INTID_THRE)

    {

         data = DataBuf[DataOut++];

        pUart->THR  =data; 

        if(DataOut == 300)

        {

              DataOut = 0; 

      UART_IntConfig((LPC_UART_TypeDef *)pUart, UART_INTCFG_THRE, false);  //disable THRE  

        }

    }

}