UM10503
All information provided in this document is subject to legal disclaimers.
© NXP B.V. 2015. All rights reserved.
User manual
Rev. 2.1 — 10 December 2015
1165 of 1441
NXP Semiconductors
UM10503
Chapter 41: LPC43xx/LPC43Sxx 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
Inactive. Parity error status is inactive.
1
Active. 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
Inactive. Framing error status is inactive.
1
Active. 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
Not empty. THR contains valid data.
1
Empty. 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
Not empty. THR and/or the TSR contains valid data.
1
Empty. 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
No error. RBR contains no UART1 RX errors or FCR[0]=0.
1
Error. UART1 RBR contains at least one UART1 RX error.
31:8
-
Reserved, the value read from a reserved bit is not defined.
NA
Table 962: UART1 Line Status Register (LSR, address 0x4008 2014) bit description
Bit
Symbol
Value
Description
Reset
value