UM10503
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© NXP B.V. 2012. All rights reserved.
User manual
Rev. 1.3 — 6 July 2012
994 of 1269
NXP Semiconductors
UM10503
Chapter 38: LPC43xx UART1
2
PE
Parity Error.
When the parity bit of a received character is in the wrong state, a parity error
occurs. An 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 UART1 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. An
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 resynchronize 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 UART1
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 zeroes) 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). An 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 UART1
RBR FIFO.
0
0
Break interrupt status is inactive.
1
Break interrupt status is active.
5
THRE
Transmitter Holding Register Empty.
THRE is set immediately upon detection of an empty UART1 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 UART1 FIFO.
0
0
RBR contains no UART1 RX errors or FCR[0]=0.
1
UART1 RBR contains at least one UART1 RX error.
31:8
-
Reserved, the value read from a reserved bit is not defined.
NA
Table 859: UART1 Line Status Register (LSR - address 0x4008 2014) bit description
Bit
Symbol
Value Description
Reset
value