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UM10360_0
© NXP B.V. 2009. All rights reserved.
User manual
Rev. 00.06 — 5 June 2009
303 of 808
NXP Semiconductors
UM10360
Chapter 15: LPC17xx UART1
While starting transmission of the initial character the CTS1 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 CTS1 is de-asserted (high). As soon as CTS1 gets
de-asserted transmission resumes and a start bit is sent followed by the data bits of the
next character.
4.10 UART1 Line Status Register (U1LSR - 0x4001 0014, Read Only)
The U1LSR is a Read Only register that provides status information on the UART1 TX and
RX blocks.
Fig 47. Auto-CTS Functional Timing
start
bits0..7
start
bits0..7
stop
start
bits0..7
stop
UART1 TX
CTS1 pin
~ ~
~ ~
~ ~
~ ~
stop
Table 280: UART1 Line Status Register (U1LSR - address 0x4001 0014, Read Only) bit
description
Bit Symbol
Value Description
Reset
Value
0
Receiver
Data
Ready
(RDR)
U1LSR[0] is set when the U1RBR holds an unread character and
is cleared when the UART1 RBR FIFO is empty.
0
0
U1RBR is empty.
1
U1RBR contains valid data.
1
Overrun
Error
(OE)
The overrun error condition is set as soon as it occurs. An U1LSR
read clears U1LSR[1]. U1LSR[1] is set when UART1 RSR has a
new character assembled and the UART1 RBR FIFO is full. In
this case, the UART1 RBR FIFO will not be overwritten and the
character in the UART1 RSR will be lost.
0
0
Overrun error status is inactive.
1
Overrun error status is active.
2
Parity
Error
(PE)
When the parity bit of a received character is in the wrong state, a
parity error occurs. An U1LSR read clears U1LSR[2]. Time of
parity error detection is dependent on U1FCR[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.