
DR
AFT
DR
AFT
DRAFT
DR
D
RAFT
DRAFT
DRA
FT DRAF
D
RAFT DRAFT DRAFT DRAFT DRAFT D
DRAFT
D
RAFT DRA
FT DRAFT DRAFT DRAFT DRA
UM10360_0
© NXP B.V. 2009. All rights reserved.
User manual
Rev. 00.06 — 5 June 2009
299 of 808
NXP Semiconductors
UM10360
Chapter 15: LPC17xx UART1
It is the lowest priority interrupt and is activated whenever there is any state change on
modem inputs pins, DCD, DSR or CTS. In addition, a low to high transition on modem
input RI will generate a modem interrupt. The source of the modem interrupt can be
determined by examining U1MSR[3:0]. A U1MSR read will clear the modem interrupt.
4.6 UART1 FIFO Control Register (U1FCR - 0x4001 0008, Write Only)
The U1FCR controls the operation of the UART1 RX and TX FIFOs.
4.6.1 DMA Operation
The user can optionally operate the UART transmit and/or receive using DMA. The DMA
mode is determined by the DMA Mode Select bit in the FCR register. This bit only has an
affect when the FIFOs are enabled via the FIFO Enable bit in the FCR register.
UART receiver DMA
In DMA mode, the receiver DMA request is asserted on the event of the receiver FIFO
level becoming equal to or greater than trigger level, or if a character timeout occurs. See
the description of the RX Trigger Level above. The receiver DMA request is cleared by the
DMA controller.
Table 276: UART1 FIFO Control Register (U1FCR - address 0x4001 0008, Write Only) bit
description
Bit
Symbol
Value Description
Reset
Value
0
FIFO
Enable
0
UART1 FIFOs are disabled. Must not be used in the application.
0
1
Active high enable for both UART1 Rx and TX FIFOs and
U1FCR[7:1] access. This bit must be set for proper UART1
operation. Any transition on this bit will automatically clear the
UART1 FIFOs.
1
RX FIFO
Reset
0
No impact on either of UART1 FIFOs.
0
1
Writing a logic 1 to U1FCR[1] will clear all bytes in UART1 Rx
FIFO, reset the pointer logic. This bit is self-clearing.
2
TX FIFO
Reset
0
No impact on either of UART1 FIFOs.
0
1
Writing a logic 1 to U1FCR[2] will clear all bytes in UART1 TX
FIFO, reset the pointer logic. This bit is self-clearing.
3
DMA
Mode
Select
When the FIFO enable bit (bit 0 of this register) is set, this bit
selects the DMA mode. See
0
5:4
-
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 UART1 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).