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UM10316_0
© NXP B.V. 2008. All rights reserved.
User manual
Rev. 00.06 — 17 December 2008
270 of 571
1.
How to read this chapter
The contents of this chapter apply to all LPC29xx parts. The modem control features are
pinned out on the LPC2939/30 only. Therefore, registers MCR, MSR and RS485DLY are
available on LPC2939/30 only
2.
Features
•
16 byte Receive and Transmit FIFOs.
•
Register locations conform to ‘550 industry standard.
•
Receiver FIFO trigger points at 1, 4, 8, and 14 bytes.
•
Built-in baud rate generator.
•
Fractional divider for baud rate control, autobaud capabilities and mechanism that
enables software flow control implementation.
•
RS-485/9-bit mode support.
•
DMA support.
•
Standard modem interface signals included (CTS, DCD, DTS, DTR, RI, RTS).
3.
Pin description
UM10316
Chapter 19: LPC29xx Universal Asynchronous
Receiver/Transmitter (UART)
Rev. 00.06 — 17 December 2008
User manual
Table 227. UART0/1 Pin description
Pin
Type
Description
UART0 RXD, UART1 RXD
Input
Serial Input.
Serial receive data.
UART0 TXD, UART1 TXD
Output
Serial Output.
Serial transmit data.
Modem interface pins
UART0/1 CTS
Input
Clear To Send.
Active low signal indicates if the external
modem is ready to accept transmitted data via TXD1 from the
UART1. In normal operation of the modem interface
(MCR[4] = 0), the complement value of this signal is stored in
U1MSR[4]. State change information is stored in MSR[0] and
is a source for a priority level 4 interrupt, if enabled
(IER[3] = 1).
Only CTS1 is also used in auto-cts mode to control the UART1
transmitter.
Clear to send. CTS1 is an asynchronous, active low modem
status signal. Its condition can be checked by reading bit 4
(CTS) of the modem status register. Bit 0 (DCTS) of the
Modem Status Register (MSR) indicates that CTS1 has
changed states since the last read from the MSR. If the
modem status interrupt is enabled when CTS1 changes levels
and the auto-cts mode is not enabled, an interrupt is
generated. CTS1 is also used in the auto-cts mode to control
the transmitter.