NXP Semiconductors LPC24XX UM10237 - Manual (Page 452)

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User manual Rev. 04 — 26 August 2009 452 of 792
NXP Semiconductors
UM10237
Chapter 17: LPC24XX 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 - 0xE001 0008, Write Only)
The U1FCR controls the operation of the UART1 RX and TX FIFOs.
4.7 UART1 Line Control Register (U1LCR - 0xE001 000C)
The U1LCR determines the format of the data character that is to be transmitted or
received.
Table 404. UART1 FIFO Control Register (U1FCR - address 0xE001 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 and 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 and reset the pointer logic. This bit is self-clearing.
5:3 - 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
00
These two bits determine how many receiver UART1 FIFO
characters must be written before an interrupt is activated. 0
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).
Table 405. UART1 Line Control Register (U1LCR - address 0xE001 000C) bit description
Bit Symbol Value Description Reset
Value
1:0 Word
Length
Select 00 5 bit character length. 0
01 6 bit character length.
10 7 bit character length.
11 8 bit character length.
2 Stop Bit
Select 0 1 stop bit. 0
1 2 stop bits (1.5 if U1LCR[1:0]=00).
3 Parity
Enable 0 Disable parity generation and checking. 0
1 Enable parity generation and checking.