UM10462
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© NXP B.V. 2016. All rights reserved.
User manual
Rev. 5.5 — 21 December 2016
250 of 523
NXP Semiconductors
UM10462
Chapter 12: LPC11U3x/2x/1x USART
12.5.8 USART Modem Control Register
The MCR enables the modem loopback mode and controls the modem output signals.
3
PE
Parity Enable
0
0
Disable parity generation and checking.
1
Enable parity generation and checking.
5:4
PS
Parity Select
0
0x0
Odd parity. Number of 1s in the transmitted character and the
attached parity bit will be odd.
0x1
Even Parity. Number of 1s in the transmitted character and the
attached parity bit will be even.
0x2
Forced 1 stick parity.
0x3
Forced 0 stick parity.
6
BC
Break Control
0
0
Disable break transmission.
1
Enable break transmission. Output pin USART TXD is forced to
logic 0 when LCR[6] is active high.
7
DLAB
Divisor Latch Access Bit
0
0
Disable access to Divisor Latches.
1
Enable access to Divisor Latches.
31:8 -
-
Reserved
-
Table 238. USART Line Control Register (LCR - address 0x4000 800C) bit description
Bit
Symbol Value Description
Reset
Value
Table 239. USART Modem Control Register (MCR - address 0x4000 8010) bit description
Bit
Symbol
Value Description
Reset
value
0
DTRCTRL
Source for modem output pin DTR. This bit reads as 0 when
modem loopback mode is active.
0
1
RTSCTRL
Source for modem output pin RTS. This bit reads as 0 when
modem loopback mode is active.
0
3:2
-
Reserved, user software should not write ones to reserved bits.
The value read from a reserved bit is not defined.
0
4
LMS
Loopback Mode Select. The modem loopback mode provides a
mechanism to perform diagnostic loopback testing. Serial data
from the transmitter is connected internally to serial input of the
receiver. Input pin, RXD, has no effect on loopback and output
pin, TXD is held in marking state. The DSR, CTS, DCD, and RI
pins are ignored. Externally, DTR and RTS are set inactive.
Internally, the upper four bits of the MSR are driven by the
lower four bits of the MCR. This permits modem status
interrupts to be generated in loopback mode by writing the
lower four bits of MCR.
0
0
Disable modem loopback mode.
1
Enable modem loopback mode.
5
-
Reserved, user software should not write ones to reserved bits.
The value read from a reserved bit is not defined.
0