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UM10375
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© NXP B.V. 2011. All rights reserved.
User manual
Rev. 3 — 14 June 2011
193 of 368
NXP Semiconductors
UM10375
Chapter 12: LPC13xx UART
3
FE
Framing Error. When the stop bit of a received character is a logic
0, a framing error occurs. A U0LSR read clears U0LSR[3]. The
time of the framing error detection is dependent on U0FCR0.
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 UART 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 U0LSR read clears this status bit. The time of break
detection is dependent on U0FCR[0].
Note:
The break interrupt is associated with the character at the
top of the UART 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 UART THR and is cleared on a
U0THR write.
1
0
U0THR contains valid data.
1
U0THR is empty.
6
TEMT
Transmitter Empty. TEMT is set when both U0THR and U0TSR
are empty; TEMT is cleared when either the U0TSR or the
U0THR contain valid data.
1
0
U0THR and/or the U0TSR contains valid data.
1
U0THR and the U0TSR are empty.
7
RXFE
Error in RX FIFO. U0LSR[7] is set when a character with a RX
error such as framing error, parity error or break interrupt, is
loaded into the U0RBR. This bit is cleared when the U0LSR
register is read and there are no subsequent errors in the UART
FIFO.
0
0
U0RBR contains no UART RX errors or U0FCR[0]=0.
1
UART RBR contains at least one UART RX error.
31:
8
-
-
Reserved
-
Table 205. UART Line Status Register (U0LSR - address 0x4000 8014, Read Only) bit
description
…continued
Bit Symbol
Value Description
Reset
Value