UM10503
All information provided in this document is subject to legal disclaimers.
© NXP B.V. 2012. All rights reserved.
User manual
Rev. 1.3 — 6 July 2012
960 of 1269
NXP Semiconductors
UM10503
Chapter 37: LPC43xx USART0_2_3
Table 831. USART Line Status Register Read Only (LSR - addresses 0x4008 1014 (USART0),
0x400C 1014 (USART2), 0x400C 2014 (USART3)) bit description
Bit Symbol
Value Description
Reset
Value
0
RDR
Receiver Data Ready.
LSR[0] is set when the RBR holds an unread character and is
cleared when the USART RBR FIFO is empty.
0
0
RBR is empty.
1
RBR contains valid data.
1
OE
Overrun Error.
The overrun error condition is set as soon as it occurs. A LSR
read clears LSR[1]. LSR[1] is set when USART RSR has a new
character assembled and the USART RBR FIFO is full. In this
case, the USART RBR FIFO will not be overwritten and the
character in the USART RSR will be lost.
0
0
Overrun error status is inactive.
1
Overrun error status is active.
2
PE
Parity Error.
When the parity bit of a received character is in the wrong state, a
parity error occurs. A LSR read clears LSR[2]. Time of parity error
detection is dependent on FCR[0].
Note:
A parity error is associated with the character at the top of
the USART RBR FIFO.
0
0
Parity error status is inactive.
1
Parity error status is active.
3
FE
Framing Error.
When the stop bit of a received character is a logic 0, a framing
error occurs. A LSR read clears LSR[3]. The time of the framing
error detection is dependent on FCR0. Upon detection of a
framing error, the RX will attempt to re-synchronize to the data
and assume that the bad stop bit is actually an early start bit.
However, it cannot be assumed that the next received byte will be
correct even if there is no Framing Error.
Note:
A framing error is associated with the character at the top
of the USART RBR FIFO.
0
0
Framing error status is inactive.
1
Framing error status is active.
4
BI
Break Interrupt.
When RXD1 is held in the spacing state (all zeros) for one full
character transmission (start, data, parity, stop), a break interrupt
occurs. Once the break condition has been detected, the receiver
goes idle until RXD1 goes to marking state (all ones). A LSR read
clears this status bit. The time of break detection is dependent on
FCR[0].
Note:
The break interrupt is associated with the character at the
top of the USART RBR FIFO.
0
0
Break interrupt status is inactive.
1
Break interrupt status is active.