TM4C123gh6pm UARTFR :what is the need of having TXFE ,TXFF also RXFE,RXFF ?

From the User Manual

TxFE

UART Transmit FIFO Empty

The meaning of this bit depends on the state of the FEN bit in the

UARTLCRH register.

Value Description

0 The transmitter has data to transmit.

1 If the FIFO is disabled (FEN is 0), the transmit holding register

is empty.

If the FIFO is enabled (FEN is 1), the transmit FIFO is empty

TxFF

UART Transmit FIFO Full

The meaning of this bit depends on the state of the FEN bit in the

UARTLCRH register.

Value Description

0 The transmitter is not full.

1 If the FIFO is disabled (FEN is 0), the transmit holding register

is full.

If the FIFO is enabled (FEN is 1), the transmit FIFO is full.

Obviously quite different meanings

Four distinct possibilities

TxFE, TxFF both 0 Not empty, not full

TxFE 1, TxFF 0 Empty, not full

TxFE 0, TxFF 1 not Empty, Full

TxFE, TxFF both 1. This would indicate both full and empty and thus is not a legal state. The others all have obvious distinct meanings though

Robert

Thanks Robert !

Yeah I got now.TXFE=1 mean no data in fifo but it does not mean whenever TXFF=0 ,the fifo is completely Empty.

thanks