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UM10360_0
© NXP B.V. 2009. All rights reserved.
User manual
Rev. 00.06 — 5 June 2009
284 of 808
NXP Semiconductors
UM10360
Chapter 14: LPC17xx UART0/2/3
The PulseDiv bits in UnICR 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 - 0x4000 C028, U2FDR -
0x4009 8028, U3FDR - 0x4009 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 2 or greater.
Table 261: UARTn IrDA Control Register (U0ICR - 0x4000 C024, U2ICR - 0x4009 8024, U3ICR -
0x4009 C024) bit description
Bit
Symbol
Value Description
Reset value
0
IrDAEn
0
IrDA mode on UARTn is disabled, UARTn acts as a
standard UART.
0
1
IrDA mode on UARTn 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 262: 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