UART Registers
19.5.1.37 Enhanced Feature Register (EFR)
The enhanced feature register (EFR) enables or disables enhanced features. Most enhanced functions
apply only to UART modes, but EFR[4] enables write accesses to FCR[5:4], the TX trigger level, which is
also used in IrDA modes. The enhanced feature register (EFR) is shown in
and described in
.
Figure 19-70. Enhanced Feature Register (EFR)
15
8
Reserved
R-0
7
6
5
4
3
0
AUTOCTSEN
AUTORTSEN
SPECIALCHARDETECT
ENHANCEDEN
SWFLOWCONTROL
R/W-0
R/W-0
R/W-0
R/W-0
R/W-0
LEGEND: R/W = Read/Write; R = Read only; -n = value after reset
Table 19-68. Enhanced Feature Register (EFR) Field Descriptions
Bit
Field
Value
Description
15-8
Reserved
0
Reserved.
7
AUTOCTSEN
Auto-CTS enable bit (UART mode only).
0
Normal operation.
1
Auto-CTS flow control is enabled; transmission is halted when the CTS pin is high
(inactive).
6
AUTORTSEN
Auto-RTS enable bit (UART mode only).
0
Normal operation.
1
Auto-RTS flow control is enabled; RTS pin goes high (inactive) when the receiver FIFO
HALT trigger level, TCR[3:0], is reached and goes low (active) when the receiver FIFO
RESTORE transmission trigger level is reached.
5
SPECIALCHARDETECT
Special character detect (UART mode only).
0
Normal operation.
1
Special character detect enable. Received data is compared with XOFF2 data. If a
match occurs, the received data is transferred to RX FIFO and the IIR[4] bit is set to 1 to
indicate that a special character was detected.
4
ENHANCEDEN
Enhanced functions write enable bit.
0
Disables writing to IER[7:4], FCR[5:4], and MCR[7:5].
1
Enables writing to IER[7:4], FCR[5:4], and MCR[7:5].
3-0
SWFLOWCONTROL
0-Fh
Combinations of software flow control can be selected by programming this bit. XON1
and XON2 should be set to different values if the software flow control is enabled. See
. In IrDA mode, EFR[1:0] selects the IR address to check. See IR Address
Checking.
3537
SPRUH73H – October 2011 – Revised April 2013
Universal Asynchronous Receiver/Transmitter (UART)
Copyright © 2011–2013, Texas Instruments Incorporated