Datasheet

UM10398 All information provided in this document is subject to legal disclaimers. © NXP B.V. 2014. All rights reserved.
User manual Rev. 12.3 — 10 June 2014 219 of 547
NXP Semiconductors
UM10398
Chapter 13: LPC111x/LPC11Cxx UART
Although Table 202 describes how to use TxEn bit in order to achieve hardware flow
control, it is strongly suggested to let UART hardware implemented auto flow control
features take care of this, and limit the scope of TxEn to software flow control.
Table 202
describes how to use TXEN bit in order to achieve software flow control.
13.5.17 UART RS485 Control register (U0RS485CTRL - 0x4000 804C)
The U0RS485CTRL register controls the configuration of the UART in RS-485/EIA-485
mode.
Table 202. UART Transmit Enable Register (U0TER - address 0x4000 8030) 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 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 can clear this bit
when it detects that the a hardware-handshaking TX-permit
signal (CTS
) has gone false, or with software handshaking,
when it receives an XOFF character (DC3). Software can set
this bit again when it detects that the TX-permit signal has gone
true, or when it receives an XON (DC1) character.
1
31:8 - Reserved -
Table 203. UART RS485 Control register (U0RS485CTRL - address 0x4000 804C) bit
description
Bit Symbol Value Description Reset
value
0 NMMEN NMM enable. 0
0 RS-485/EIA-485 Normal Multidrop Mode (NMM)
is disabled.
1 RS-485/EIA-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.
1 RXDIS Receiver enable. 0
0 The receiver is enabled.
1 The receiver is disabled.
2 AADEN AAD enable. 0
0 Auto Address Detect (AAD) is disabled.
1 Auto Address Detect (AAD) is enabled.
3 SEL Select direction control pin 0
0 If direction control is enabled (bit DCTRL = 1), pin
RTS
is used for direction control.
1 If direction control is enabled (bit DCTRL = 1), pin
DTR
is used for direction control.