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UM10316_0
© NXP B.V. 2008. All rights reserved.
User manual
Rev. 00.06 — 17 December 2008
278 of 571
NXP Semiconductors
UM10316
Chapter 19: LPC29xx Universal Asynchronous Receiver/Transmitter
4.6 UARTn FIFO Control Register
The UnFCR controls the operation of the UARTn Rx and TX FIFOs.
4.7 UARTn Line Control Register
The UnLCR determines the format of the data character that is to be transmitted or
received.
Table 236. UARTn FIFO Control Register (U0FCR - address 0xE004 5008,
U1FCR - 0xE004 6008, Write Only) bit description
Bit
Symbol
Value
Description
Reset Value
0
FIFO Enable 0
UARTn FIFOs are disabled. Must not be used in the
application.
0
1
Active high enable for both UARTn Rx and TX
FIFOs and UnFCR[7:1] access. This bit must be set
for proper UARTn operation. Any transition on this
bit will automatically clear the UARTn FIFOs.
1
RX FIFO
Reset
0
No impact on either of UARTn FIFOs.
0
1
Writing a logic 1 to UnFCR[1] will clear all bytes in
UARTn Rx FIFO and reset the pointer logic. This bit
is self-clearing.
2
TX FIFO
Reset
0
No impact on either of UARTn FIFOs.
0
1
Writing a logic 1 to UnFCR[2] will clear all bytes in
UARTn TX FIFO and reset the pointer logic. This bit
is self-clearing.
3
DMA mode
1
When in FIFO mode multiple-character transfers are
performed until the transmitter FIFO is filled or the
receiver FIFO is empty. The receiver direct-memory
access becomes active when the receive-FIFO
trigger level is reached or a character time-out
occurs
0
0
Only single-character transfers are done as default
in 450 mode
5:4
-
0
Reserved, user software should not write ones to
reserved bits. The value read from a reserved bit is
not defined.
NA
7:6
RX Trigger
Level
These two bits determine how many receiver
UARTn FIFO characters must be written before an
interrupt is activated.
0
00
Trigger level 0 (1 character or 0x01)
01
Trigger level 1 (4 characters or 0x04)
10
Trigger level 2 (8 characters or 0x08)
11
Trigger level 3 (14 characters or 0x0E)