TM4C123GE6PZ: 串口不是一次只能接收一个字节数据吗？为什么UARTCharGet函数返回的是一个4字节的数据？

串口不是一次只能接收一个字节数据吗？为什么UARTCharGet函数返回的是一个4字节的数据？

//*****************************************************************************
//
//! Waits for a character from the specified port.
//!
//! \param ui32Base is the base address of the UART port.
//!
//! This function gets a character from the receive FIFO for the specified
//! port.  If there are no characters available, this function waits until a
//! character is received before returning.
//!
//! \return Returns the character read from the specified port, cast as a
//! \e int32_t.
//
//*****************************************************************************
int32_t
UARTCharGet(uint32_t ui32Base)

Yale Li：

图片上传失败了，方便重新上传一下吗？