DR
AFT
DR
AFT
DRAFT
DR
D
RAFT
DRAFT
DRA
FT DRAF
D
RAFT DRAFT DRAFT DRAFT DRAFT D
DRAFT
D
RAFT DRA
FT DRAFT DRAFT DRAFT DRA
UM10316_0
© NXP B.V. 2008. All rights reserved.
User manual
Rev. 00.06 — 17 December 2008
271 of 571
NXP Semiconductors
UM10316
Chapter 19: LPC29xx Universal Asynchronous Receiver/Transmitter
4.
Register description
Each UART contains registers as shown in
. The Divisor Latch Access Bit
(DLAB) is contained in UnLCR7 and enables access to the Divisor Latches.
UART0/1 DCD
Input
Data Carrier Detect.
Active low signal indicates if the external
modem has established a communication link with the UART1
and data may be exchanged. In normal operation of the
modem interface (MCR[4]=0), the complement value of this
signal is stored in MSR[7]. State change information is stored
in MSR3 and is a source for a priority level 4 interrupt, if
enabled (IER[3] = 1).
UART0/1 DSR
Input
Data Set Ready.
Active low signal indicates if the external
modem is ready to establish a communications link with the
UART1. In normal operation of the modem interface
(MCR[4] = 0), the complement value of this signal is stored in
MSR[5]. State change information is stored in MSR[1] and is a
source for a priority level 4 interrupt, if enabled (IER[3] = 1).
UART0/1 DTR
Output
Data Terminal Ready. Active low signal indicates that the
UART1 is ready to establish connection with external modem.
The complement value of this signal is stored in MCR[0].
The DTR pin can also be used as an RS-485/EIA-485 output
enable signal.
UART0/1 RI
Input
Ring Indicator.
Active low signal indicates that a telephone
ringing signal has been detected by the modem. In normal
operation of the modem interface (MCR[4] = 0), the
complement value of this signal is stored in U1MSR[6]. State
change information is stored in MSR[2] and is a source for a
priority level 4 interrupt, if enabled (IER[3] = 1).
UART0/1 RTS
Output
Request To Send.
Active low signal indicates that the UART1
would like to transmit data to the external modem. The
complement value of this signal is stored in MCR[1].
Only in the auto-rts mode uses RTS to control the transmitter
FIFO threshold logic.
Request to send. RTS1 is an active low signal informing the
modem or data set that the UART is ready to receive data.
RTS is set to the active (low) level by setting the RTS modem
control register bit and is set to the inactive (high) level either
as a result of a system reset or during loop-back mode
operations or by clearing bit 1 (RTS) of the MCR. In the
auto-rts mode, RTS is controlled by the transmitter FIFO
threshold logic.
The RTS pin can also be used as an RS-485/EIA-485 output
enable signal.
UART0/1 UOUT1/2
Output
<tbd>
Table 227. UART0/1 Pin description
Pin
Type
Description