Nxp Semiconductors UM10237 用户手册
UM10237_2
© NXP B.V. 2008. All rights reserved.
User manual
Rev. 02 — 19 December 2008
453 of 792
NXP Semiconductors
UM10237
Chapter 17: LPC24XX Universal Asynchronous Receiver/Transmitter
4.8 UART1 Modem Control Register (U1MCR - 0xE001 0010)
The U1MCR enables the modem loopback mode and controls the modem output signals.
5:4
Parity
Select
Select
00
Odd parity. Number of 1s in the transmitted character and the
attached parity bit will be odd.
attached parity bit will be odd.
0
01
Even Parity. Number of 1s in the transmitted character and the
attached parity bit will be even.
attached parity bit will be even.
10
Forced "1" stick parity.
11
Forced "0" stick parity.
6
Break
Control
Control
0
Disable break transmission.
0
1
Enable break transmission. Output pin UART1 TXD is forced to
logic 0 when U1LCR[6] is active high.
logic 0 when U1LCR[6] is active high.
7
Divisor
Latch
Access
Bit
(DLAB)
Latch
Access
Bit
(DLAB)
0
Disable access to Divisor Latches.
0
1
Enable access to Divisor Latches.
Table 405: UART1 Line Control Register (U1LCR - address 0xE001 000C) bit description
Bit
Symbol Value Description
Reset
Value
Value
Table 406: UART1 Modem Control Register (U1MCR - address 0xE001 0010) bit description
Bit
Symbol
Value Description
Reset
value
value
0
DTR
Control
Control
Source for modem output pin, DTR. This bit reads as 0 when
modem loopback mode is active.
modem loopback mode is active.
0
1
RTS
Control
Control
Source for modem output pin RTS. This bit reads as 0 when
modem loopback mode is active.
modem loopback mode is active.
0
3-2
-
NA
Reserved, user software should not write ones to reserved bits.
The value read from a reserved bit is not defined.
The value read from a reserved bit is not defined.
0
4
Loopback
Mode
Select
Mode
Select
0
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,
RXD1, has no effect on loopback and output pin, TXD1 is held in
marking state. The four modem inputs (CTS, DSR, RI and DCD)
are disconnected externally. Externally, the modem outputs (RTS,
DTR) are set inactive. Internally, the four modem outputs are
connected to the four modem inputs. As a result of these
connections, the upper four bits of the U1MSR will be driven by
the lower four bits of the U1MCR rather than the four modem
inputs in normal mode. This permits modem status interrupts to
be generated in loopback mode by writing the lower four bits of
U1MCR.
diagnostic loopback testing. Serial data from the transmitter is
connected internally to serial input of the receiver. Input pin,
RXD1, has no effect on loopback and output pin, TXD1 is held in
marking state. The four modem inputs (CTS, DSR, RI and DCD)
are disconnected externally. Externally, the modem outputs (RTS,
DTR) are set inactive. Internally, the four modem outputs are
connected to the four modem inputs. As a result of these
connections, the upper four bits of the U1MSR will be driven by
the lower four bits of the U1MCR rather than the four modem
inputs in normal mode. This permits modem status interrupts to
be generated in loopback mode by writing the lower four bits of
U1MCR.
0
Disable modem loopback mode.
1
Enable modem loopback mode.
5
-
NA
Reserved, user software should not write ones to reserved bits.
The value read from a reserved bit is not defined.
The value read from a reserved bit is not defined.
0