RM0082
LS_Universal asynchronous receiver/transmitter (UART)
Doc ID 018672 Rev 1
597/844
27.4.3 UARTFR
register
The UARTFR (flag) is a RO register which indicates the flag status. The UARTFR bit
assignments are given in
.
Table 524.
UARTFR register bit assignments
Bit
Name
Reset value Description
[15:09]
Reserved
-
Read: as zero.
[08]
RI
1’h0
Ring indicator.
This bit is set when the modem status input is 1‘b0
(
). Specifically, it is the complement of the UART
data carrier detect nUARTRI modem status input.
[07]
TXFE
1’h1
Transmit FIFO empty.
This bit depends on the state of the FEN bit in the UARTLCR_H
register (
). If FIFOs are disabled (FEN set to
1‘b0), the TXFE bit is set when the transmit holding register is
empty. if FIFOs are enabled (FEN set to 1‘b1), it is set when the
Transmit FIFO is empty. This bit does not indicate if there is data
in the transmit shift register.
[06]
RXFF
1’h0
Receive FIFO full.
This bit depends on the state of the FEN bit in the UARTLCR_H
register. If FIFOs are disabled, RXFF is set when the receive
holding register is full, whereas (FIFOs enabled) it is set when
the receive FIFO is full.
[05]
TXFF
1’h0
Transmit FIFO full.
This bit depends on the state of the FEN bit in the UARTLCR_H
register. If FIFOs are disabled, TXFF is set when the transmit
holding register is full, whereas (FIFOs enabled) it is set when
the transmit FIFO is full.
[04]
RXFE
1’h1
Receive FIFO empty.
This bit depends on the state of the FEN bit in the UARTLCR_H
register. If FIFOs are disabled, RXFE is set when the receive
holding register is empty, whereas (FIFOs enabled) it is set
when the receive FIFO is empty.
[03]
BUSY
1’h0
UART busy.
If this bit is set to 1‘b1, the UART is busy transmitting data. This
bit remains set until the complete byte, including all the stop
bits, has been sent from the shift register. This bit is set as soon
as the transmit FIFO becomes non-empty (regardless of
whether the UART is enabled or not).
[02]
DCD
1’h0
Data carrier detect.
This bit is set to 1‘b1 when the modem status input is 1‘b0
(
). Specifically, it is the complement of the UART
data carrier detect nUARTDCD modem status input.