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UM10503
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© NXP B.V. 2015. All rights reserved.
User manual
Rev. 2.1 — 10 December 2015
1168 of 1441
NXP Semiconductors
UM10503
Chapter 41: LPC43xx/LPC43Sxx UART1
UART1 baud rate can be calculated as (n = 1):
(10)
Where PCLK is the peripheral clock, DLM and DLL are the standard UART1 baud rate
divider registers, and DIVADDVAL and MULVAL are UART1 fractional baud rate generator
specific parameters.
The value of MULVAL and DIVADDVAL should comply to the following conditions:
1. 1
MULVAL
15
2. 0
DIVADDVAL
14
3. DIVADDVAL < MULVAL
The value of the FDR should not be modified while transmitting/receiving data or data may
be lost or corrupted.
If the FDR register value does not comply to these two requests, then the fractional divider
output is undefined. If DIVADDVAL is zero then the fractional divider is disabled, and the
clock will not be divided.
41.6.14 UART1 RS485 Control register
The RS485CTRL register controls the configuration of the UART in RS-485/EIA-485
mode.
UART1
baudrate
PCLK
16
256
DLM
DLL
+
1
DivAddVal
MulVal
-----------------------------
+
------------------------------------------------------------------------------------------------------------------
=
Table 967: UART1 RS485 Control register (RS485CTRL - address 0x4008 204C) bit description
Bit
Symbol
Value Description
Reset value
0
NMMEN
Multidrop mode select.
0
0
Disabled. RS-485/EIA-485 Normal Multidrop Mode (NMM) is disabled.
1
Enabled. RS-485/EIA-485 Normal Multidrop Mode (NMM) is enabled. In this mode,
an address is detected when a received byte causes the USART to set the parity
error and generate an interrupt.
1
RXDIS
Receive enable.
0
0
Enabled. The receiver is enabled.
1
Disabled.The receiver is disabled.
2
AADEN
Auto Address Detect enable.
0
0
Disabled. Auto Address Detect (AAD) is disabled.
1
Enabled. Auto Address Detect (AAD) is enabled.
3
SEL
Direction control.
0
0
RTS. If direction control is enabled (bit DCTRL = 1), pin RTS is used for direction
control.
1
DTR. If direction control is enabled (bit DCTRL = 1), pin DTR is used for direction
control.