请教C6747 串口接收中断进入不了

利用C6747 BIOS的HWI设置URAT1中断后，C6747向PC发消息，PC能收到，但PC向C6747发消息，C6747就进入不了中断服务程序。不知道出了什么问题，我对串口的初始化程序如下：

        uart_handle->regs->DLL = (divisor & 0xff);  // Set baud rate
        uart_handle->regs->DLH = (divisor >> 8);
       
        uart_handle->regs->FCR = 0x0007;            // Clear UART TX & RX FIFOs
        uart_handle->regs->FCR = 0x0001;            // Non-FIFO mode
        uart_handle->regs->IER = 0x0001;            // Enable interrupts
        uart_handle->regs->LCR = 0x0003;            // 8-bit words,
                                                    // 1 STOP bit generated,
                                                    // No Parity, No Stick paritiy,
                                                    // No Break control
        uart_handle->regs->MCR = 0x0000;            // RTS & CTS disabled,
                                                    // Loopback mode disabled,
                                                    // Autoflow disabled

        uart_handle->regs->PWREMU_MGMT = 0xE001;    // Enable TX & RX componenets

  // Clear any pre-existing characters
        dummy = uart_handle->regs->THR;

希望各位大侠出招，谢谢！