
UART Registers
1635
SLAU723A – October 2017 – Revised October 2018
Copyright © 2017–2018, Texas Instruments Incorporated
Universal Asynchronous Receiver/Transmitter (UART)
26.5.3 UARTFR Register (Offset = 0x18) [reset = 0x90]
UART Flag (UARTFR)
The UARTFR register is the flag register. After reset, the TXFF, RXFF, and BUSY bits are 0, and TXFE
and RXFE bits are 1.
NOTE:
Registers that contain bits for modem control or status only apply to the following UARTs:
•
UART0 (modem flow control and modem status)
•
UART1 (modem flow control and modem status)
•
UART2 (modem flow control)
•
UART3 (modem flow control)
•
UART4 (modem flow control)
UARTFR is shown in
and described in
.
Return to
Figure 26-6. UARTFR Register
31
30
29
28
27
26
25
24
RESERVED
R-0x0
23
22
21
20
19
18
17
16
RESERVED
R-0x0
15
14
13
12
11
10
9
8
RESERVED
RI
R-0x0
R-0x0
7
6
5
4
3
2
1
0
TXFE
RXFF
TXFF
RXFE
BUSY
DCD
DSR
CTS
R-0x1
R-0x0
R-0x0
R-0x1
R-0x0
R-0x0
R-0x0
R-0x0
Table 26-6. UARTFR Register Field Descriptions
Bit
Field
Type
Reset
Description
31-9
RESERVED
R
0x0
8
RI
R
0x0
Ring Indicator
0x0 = The UnRI signal is not asserted.
0x1 = The UnRI signal is asserted.
7
TXFE
R
0x1
UART Transmit FIFO Empty.
The meaning of this bit depends on the state of the FEN bit in the
UARTLCRH register.
0x0 = The transmitter has data to transmit.
0x1 = 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.
6
RXFF
R
0x0
UART Receive FIFO Full.
The meaning of this bit depends on the state of the FEN bit in the
UARTLCRH register.
0x0 = The receiver can receive data.
0x1 = If the FIFO is disabled (FEN is 0), the receive holding register
is full.If the FIFO is enabled (FEN is 1), the receive FIFO is full.
5
TXFF
R
0x0
UART Transmit FIFO Full.
The meaning of this bit depends on the state of the FEN bit in the
UARTLCRH register.
0x0 = The transmitter is not full.
0x1 = 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.