描述下列程序的功能。 void USART_Configuration(void) { RCC_APB2PeriphClockCmd(RCC_APB2Periph_USART1, ENABLE); USART_InitStructure.USART_BaudRate = 9600; USART_InitStructure.USART_WordLength = USART_WordLength_8b; USART_InitStructure.USART_StopBits = USART_StopBits_1; USART_InitStructure.USART_Parity = USART_Parity_No; USART_InitStructure.USART_HardwareFlowControl = USART_HardwareFlowControl_None; USART_InitStructure.USART_Mode = USART_Mode_Rx|USART_Mode_Tx; USART_Init(USART1,&USART_InitStructure); USART_Cmd(USART1, ENABLE); USART_ITConfig(USART1,USART_IT_RXNE,ENABLE); USART_ITConfig(USART1,USART_IT_TXE ,ENABLE); }