UM10503
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© NXP B.V. 2012. All rights reserved.
User manual
Rev. 1.3 — 6 July 2012
961 of 1269
NXP Semiconductors
UM10503
Chapter 37: LPC43xx USART0_2_3
37.6.9 USART Scratch Pad Register
The SCR has no effect on the USART operation. This register can be written and/or read
at user’s discretion. There is no provision in the interrupt interface that would indicate to
the host that a read or write of the SCR has occurred.
37.6.10 USART Auto-baud Control Register
The USART Auto-baud Control Register (ACR) controls the process of measuring the
incoming clock/data rate for the baud rate generation and can be read and written at
user’s discretion.
5
THRE
Transmitter Holding Register Empty.
THRE is set immediately upon detection of an empty USART
THR and is cleared on a THR write.
1
0
THR contains valid data.
1
THR is empty.
6
TEMT
Transmitter Empty.
TEMT is set when both THR and TSR are empty; TEMT is
cleared when either the TSR or the THR contain valid data.
1
0
THR and/or the TSR contains valid data.
1
THR and the TSR are empty.
7
RXFE
Error in RX FIFO.
LSR[7] is set when a character with a RX error such as framing
error, parity error or break interrupt, is loaded into the RBR. This
bit is cleared when the LSR register is read and there are no
subsequent errors in the USART FIFO.
0
0
RBR contains no USART RX errors or FCR[0]=0.
1
USART RBR contains at least one USART RX error.
8
TXERR
Error in transmitted character.
A NACK response is given by the receiver in Smart card T=0
mode. This bit is cleared when the LSR register is read.
0
0
No error (normal default condition).
1
A NACK response is received during Smart card T=0 operation.
31:
9
-
-
Reserved
-
Table 831. USART Line Status Register Read Only (LSR - addresses 0x4008 1014 (USART0),
0x400C 1014 (USART2), 0x400C 2014 (USART3)) bit description
…continued
Bit Symbol
Value Description
Reset
Value
Table 832. USART Scratch Pad Register (SCR - addresses 0x4008 101C (USART0), 0x400C
101C (USART2), 0x400C 201C (USART3)) bit description
Bit
Symbol
Description
Reset Value
7:0
PAD
Scratch pad. A readable, writable byte.
0x00
31:8
-
Reserved
-