UART Registers
19.5.1.11 Modem Control Register (MCR)
Bits 3-0 control the interface with the modem, data set, or peripheral device that is emulating the modem.
The modem control register (MCR) is shown in
and described in
.
Figure 19-44. Modem Control Register (MCR)
15
8
Reserved
R-0
7
6
5
4
3
2
1
0
Reserved
TCRTLR
XONEN
LOOPBACKEN
CDSTSCH
RISTSCH
RTS
DTR
R-0
R/W-0
R/W-0
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 19-40. Modem Control Register (MCR) Field Descriptions
Bit
Field
Value
Description
15-7
Reserved
0
Reserved.
6
TCRTLR
Can be written only when EFR[4] = 1.
0
No action.
1
Enables access to the TCR and TLR registers.
5
XONEN
Can be written only when EFR[4] = 1.
0
Disable XON any function.
1
Enable XON any function.
4
LOOPBACKEN
Loopback mode enable.
0
Normal operating mode.
1
Enable local loopback mode (internal). In this mode, the MCR[3:0] signals are looped back into
MSR[7:4]. The transmit output is looped back to the receive input internally.
3
CDSTSCH
0
In loopback mode, forces DCD input high and IRQ outputs to INACTIVE state.
1
In loopback mode, forces DCD input low and IRQ outputs to INACTIVE state.
2
RISTSCH
0
In loopback mode, forces RI input inactive (high).
1
In loopback mode, forces RI input active (low).
1
RTS
In loopback mode, controls MSR[4]. If auto-RTS is enabled, the RTS output is controlled by
hardware flow control.
0
Force RTS output to inactive (high).
1
Force RTS output to active (low).
0
DTR
0
Force DTR output (used in loopback mode) to inactive (high).
1
Force DTR output (used in loopback mode) to active (low).
3516
Universal Asynchronous Receiver/Transmitter (UART)
SPRUH73H – October 2011 – Revised April 2013
Copyright © 2011–2013, Texas Instruments Incorporated