UART/Autobaud Control and Status Registers
12-27
UART Devices
Table 12–21. Modem Control Register (MCR) (Continued)
Bit
Reset
Value
R/W
Function
Value
Name
2
RESERVED
Reserved. This bit must always be written as
0.
R/W
0
1
RTS
0
0: Forces RTS output to inactive (high)
R/W
0
1
Forces RTS output to active (low)
In loopback mode controls MSR4.
If automatic RTS is enabled, the RTS output
is controlled by hardware flow control.
0
DTR
0
Forces DTR output to inactive (high)
R/W
0
1
Forces DTR output to active (low)
Note:
Bits 5, 6, and 7 can be written only when EFR[4] = 1.
The modem status register (MSR) provides information about the current state
of the control lines from the modem, data set, or peripheral device to the host
(MPU or DSP). It also indicates when a control input from the modem changes
state.
Table 12–22. Modem Status Register (MSR)
Bit
Name
Function
R/W
Reset
Value
7–6
RESERVED
Reserved
R
Input signal
5
NDSR_STS
This bit is the complement of the DSR input. In loop-
back mode it is equivalent to MCR0
R
Input signal
4
NCTS_STS
This bit is the complement of the CTS input. In loopback
mode it is equivalent to MCR1
R
Input signal
3–2
RESERVED
Reserved
R
0
1
DSR_STS
1: Indicates that DSR input (or MCR0 in loopback) has
changed state. Cleared on a read
R
0
0
CTS_STS
1: Indicates that CTS input (or MCR1 in loopback) has
changed state. Cleared on a read.
R
0