UM10413
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© NXP B.V. 2011. All rights reserved.
User manual
Rev. 1 — 16 December 2011
94 of 268
NXP Semiconductors
UM10413
MPT612 User manual
15. Universal Asynchronous Receiver/Transmitter 1 (UART1)
15.1 Features
•
UART1 is identical to UART0 with the addition of a modem interface
•
UART1 contains 16 byte receive and transmit FIFOs
•
Register locations conform to ‘550 industry standard
•
Receiver FIFO trigger points at 1, 4, 8, and 14 bytes
•
Fractional baud rate generator with auto-bauding capabilities is built in
•
Mechanism enables software and hardware flow control implementation
•
Standard modem interface signals are included, and flow control (auto-CTS/RTS) is
fully supported in hardware
15.2 Pin
description
15.3 Register
description
UART1 contains registers organized as shown in
. The Divisor Latch Access Bit
(DLAB) is contained in U1LCR[7] and enables access to the divisor latches.
Table 98.
UART1 pin description
Pin
Type
Description
RXD1
input
serial input. Serial receive data.
TXD1
output
serial output. Serial transmit data.
CTS1
input
clear to send. Active LOW signal indicates if external modem is ready to accept transmitted data
via TXD1 from UART1. In normal operation of modem interface (U1MCR[4] = 0), complement
value of this signal is stored in U1MSR[4]. If enabled (U1IER[3] = 1), state change information is
stored in U1MSR[0] and is a source for a priority level 4 interrupt.
DCD1
input
data carrier detect. Active LOW signal indicates if external modem has established a
communication link with UART1 and data can be exchanged. In normal operation of modem
interface (U1MCR[4]=0), complement value of this signal is stored in U1MSR[7]. If enabled
(U1IER[3] = 1), state change information is stored in U1MSR3 and is a source for a priority level 4
interrupt.
DSR1
input
data set ready. Active LOW signal indicates if external modem is ready to establish a
communications link with UART1. In normal operation of modem interface (U1MCR[4] = 0),
complement value of this signal is stored in U1MSR[5]. If enabled (U1IER[3] = 1), state change
information is stored in U1MSR[1] and is a source for a priority level 4 interrupt.
DTR1
output
data terminal ready. Active LOW signal indicates that UART1 is ready to establish connection with
external modem. Complement value of this signal is stored in U1MCR[0].
RI1
input
ring indicator. Active LOW signal indicates that telephone ringing signal is detected by modem. In
normal operation of modem interface (U1MCR[4] = 0), complement value of this signal is stored in
U1MSR[6]. If enabled (U1IER[3] = 1), state change information is stored in U1MSR[2] and is a
source for a priority level 4 interrupt.
RTS1
output
request to send. Active LOW signal indicates that UART1 wants to transmit data to external
modem. Complement value of this signal is stored in U1MCR[1].