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UM10375
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© NXP B.V. 2011. All rights reserved.
User manual
Rev. 3 — 14 June 2011
192 of 368
NXP Semiconductors
UM10375
Chapter 12: LPC13xx UART
While starting transmission of the initial character, the CTS signal is asserted.
Transmission will stall as soon as the pending transmission has completed. The UART will
continue transmitting a 1 bit as long as CTS is de-asserted (high). As soon as CTS gets
de-asserted, transmission resumes and a start bit is sent followed by the data bits of the
next character.
12.6.9 UART Line Status Register (U0LSR - 0x4000 8014, Read Only)
The U0LSR is a Read Only register that provides status information on the UART TX and
RX blocks.
Fig 21. Auto-CTS Functional Timing
start
bits0..7
start
bits0..7
stop
start
bits0..7
stop
UART TX
CTS pin
~ ~
~ ~
~ ~
~ ~
stop
Table 205. UART Line Status Register (U0LSR - address 0x4000 8014, Read Only) bit
description
Bit Symbol
Value Description
Reset
Value
0
RDR
Receiver Data Ready. U0LSR[0] is set when the U0RBR holds an
unread character and is cleared when the UART RBR FIFO is
empty.
0
0
U0RBR is empty.
1
U0RBR contains valid data.
1
OE
Overrun Error. The overrun error condition is set as soon as it
occurs. A U0LSR read clears U0LSR[1]. U0LSR[1] is set when
UART RSR has a new character assembled and the UART RBR
FIFO is full. In this case, the UART RBR FIFO will not be
overwritten and the character in the UART 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 U0LSR read clears
U0LSR[2]. Time of parity error detection is dependent on
U0FCR[0].
Note:
A parity error is associated with the character at the top of
the UART RBR FIFO.
0
0
Parity error status is inactive.
1
Parity error status is active.