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UM10316_0
© NXP B.V. 2008. All rights reserved.
User manual
Rev. 00.06 — 17 December 2008
291 of 571
NXP Semiconductors
UM10316
Chapter 19: LPC29xx Universal Asynchronous Receiver/Transmitter
describes how to use TXEn bit in order to achieve software flow control.
4.15 UART0 RS485 Control register
The U0RS485CTRL register controls the configuration of the UART as an addressable
slave. The addressable slave is one of multiple slaves controlled by a single master.
The UART master transmitter will identify an address character by setting the parity (9th)
bit to ‘1’. For data characters, the parity bit is set to ‘0’.
Each UART slave receiver can be assigned a unique address. The slave can be
programmed to either manually or automatically reject data following an address which is
not theirs.
Table 246. UARTn Transmit Enable Register (U0TER - address 0xE004 5030,
U1TER - 0xE004 6030) bit description
Bit
Symbol
Description
Reset
Value
6:0
-
Reserved, user software should not write ones to reserved bits. The
value read from a reserved bit is not defined.
NA
7
TXEN
When this bit is 1, as it is after a Reset, data written to the THR is output
on the TXD pin as soon as any preceding data has been sent. If this bit
is cleared to 0 while a character is being sent, the transmission of that
character is completed, but no further characters are sent until this bit is
set again. In other words, a 0 in this bit blocks the transfer of characters
from the THR or TX FIFO into the transmit shift register. Software
implementing software-handshaking can clear this bit when it receives
an XOFF character (DC3). Software can set this bit again when it
receives an XON (DC1) character.
1
Table 247. UART0 RS485 Control register(U0/2RS485CTRL - 0xE004 504C/0xE004 604C/ bit
description
Bit
Symbol
Value
Description
Reset
value
0
NMMEN
0
RS-485 Normal Multidrop Mode (NMM) is
enabled. In this mode, an address is detected
when a received byte causes the UART to set the
parity error and generate an interrupt.
0
1
RS-485 Normal Multidrop Mode (NMM) is
disabled.
1
RXDIS
0
The receiver is enabled.
0
1
The receiver is disabled.
2
AADEN
0
Auto Address Detect (AAD) is disabled.
0
1
Auto Address Detect (AAD) is enabled.
31:3 -
-
Reserved, user software should not write ones to
reserved bits. The value read from a reserved bit
is not defined.
NA