Nxp semiconductors – NXP Semiconductors LPC24XX UM10237 User Manual
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UM10237_4
© NXP B.V. 2009. All rights reserved.
User manual
Rev. 04 — 26 August 2009
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NXP Semiconductors
UM10237
Chapter 16: LPC24XX UART0/2/3
4.11 IrDA Control Register for UART3 Only (U3ICR - 0xE007 C024)
The IrDA Control Register enables and configures the IrDA mode for UART3 only. The
value of U3ICR should not be changed while transmitting or receiving data, or data loss or
corruption may occur.
The PulseDiv bits in U3ICR are used to select the pulse width when the fixed pulse width
mode is used in IrDA mode (IrDAEn = 1 and FixPulseEn = 1). The value of these bits
should be set so that the resulting pulse width is at least 1.63 µs.
shows the
possible pulse widths.
4.12 UARTn Fractional Divider Register (U0FDR - 0xE000 C028, U2FDR -
0xE007 8028, U3FDR - 0xE007 C028)
The UART0/2/3 Fractional Divider Register (U0/2/3FDR) controls the clock pre-scaler for
the baud rate generation and can be read and written at the user’s discretion. This
pre-scaler takes the APB clock and generates an output clock according to the specified
fractional requirements.
Important: If the fractional divider is active (DIVADDVAL > 0) and DLM = 0, the value of
the DLL register must be 3 or greater.
Table 390. IrDA Control Register for UART3 only (U3ICR - address 0xE007 C024) bit
description
Bit
Symbol
Value Description
Reset value
0
IrDAEn
0
IrDA mode on UART3 is disabled, UART3 acts as a
standard UART.
0
1
IrDA mode on UART3 is enabled.
1
IrDAInv
When 1, the serial input is inverted. This has no effect
on the serial output. When 0, the serial input is not
inverted.
0
2
FixPulseEn
When 1, enabled IrDA fixed pulse width mode.
0
5:3
PulseDiv
Configures the pulse when FixPulseEn = 1. See text
below for details.
0
31:6
-
NA
Reserved, user software should not write ones to
reserved bits. The value read from a reserved bit is
not defined.
0
Table 391. IrDA Pulse Width
FixPulseEn
PulseDiv
IrDA Transmitter Pulse width (µs)
0
x
3 / (16
× baud rate)
1
0
2
× T
PCLK
1
1
4
× T
PCLK
1
2
8
× T
PCLK
1
3
16
× T
PCLK
1
4
32
× T
PCLK
1
5
64
× T
PCLK
1
6
128
× T
PCLK
1
7
256
× T
PCLK