UM10503
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© NXP B.V. 2012. All rights reserved.
User manual
Rev. 1.3 — 6 July 2012
998 of 1269
NXP Semiconductors
UM10503
Chapter 38: LPC43xx UART1
38.6.15 UART1 RS485 Control register
The RS485CTRL register controls the configuration of the UART in RS-485/EIA-485
mode.
Table 864: UART1 Transmit Enable Register (TER - address 0x4008 2030) 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
Transmit enable bit.
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, user software should not write ones to reserved bits. The value read from a
reserved bit is not defined.
NA
Table 865: UART1 RS485 Control register (RS485CTRL - address 0x4008 204C) bit description
Bit
Symbol
Value Description
Reset value
0
NMMEN
Multidrop mode select.
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
Receive enable.
0
0
The receiver is enabled.
1
The receiver is disabled.
2
AADEN
Auto Address Detect enable.
0
0
Auto Address Detect (AAD) is disabled.
1
Auto Address Detect (AAD) is enabled.
3
SEL
Direction control.
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.
4
DCTRL
Direction control enable.
0
0
Disable Auto Direction Control.
1
Enable Auto Direction Control.
5
OINV
Polarity.
This bit reverses the polarity of the direction control signal on the RTS (or DTR) pin.
0
0
The direction control pin will be driven to logic ‘0’ when the transmitter has data to
be sent. It will be driven to logic ‘1’ after the last bit of data has been transmitted.
1
The direction control pin will be driven to logic ‘1’ when the transmitter has data to
be sent. It will be driven to logic ‘0’ after the last bit of data has been transmitted.
31:6
-
-
Reserved, user software should not write ones to reserved bits. The value read
from a reserved bit is not defined.
NA