UM11029
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© NXP Semiconductors N.V. 2017. All rights reserved.
User manual
Rev. 1.0 — 16 June 2017
294 of 515
NXP Semiconductors
UM11029
Chapter 17: LPC84x USART0/1/2/3/4
17.6.2 USART Control register
The CTL register controls aspects of USART operation that are more likely to change
during operation.
Table 324. USART Control register (CTL, address 0x4006 4004 (USART0), 0x4006 8004
(USART1), 0x4006 C004 (USART2), 0x4007 0004 (USART3), 0x4007 4004
(USART4)) bit description
Bit
Symbol
Value
Description
Reset
value
0
-
Reserved. Read value is undefined, only zero should be
written.
NA
1
TXBRKEN
Break Enable.
0
0
Normal operation.
1
Continuous break is sent immediately when this bit is set,
and remains until this bit is cleared.
A break may be sent without danger of corrupting any
currently transmitting character if the transmitter is first
disabled (TXDIS in CTL is set) and then waiting for the
transmitter to be disabled (TXDISINT in STAT = 1) before
writing 1 to TXBRKEN.
2
ADDRDET
Enable address detect mode.
0
0
Disabled. The USART presents all incoming data.
1
Enabled. The USART receiver ignores incoming data that
does not have the most significant bit of the data (typically
the 9th bit) = 1. When the data MSB bit = 1, the receiver
treats the incoming data normally, generating a received
data interrupt. Software can then check the data to see if
this is an address that should be handled. If it is, the
ADDRDET bit is cleared by software and further incoming
data is handled normally.
5:3
-
Reserved. Read value is undefined, only zero should be
written.
NA
6
TXDIS
Transmit Disable.
0
0
Not disabled. USART transmitter is not disabled.
1
Disabled. USART transmitter is disabled after any
character currently being transmitted is complete. This
feature can be used to facilitate software flow control.
7
-
Reserved. Read value is undefined, only zero should be
written.
NA
8
CC
Continuous Clock generation. By default, SCLK is only
output while data is being transmitted in synchronous
mode.
0
0
Clock on character. In synchronous mode, SCLK cycles
only when characters are being sent on Un_TXD or to
complete a character that is being received.
1
Continuous clock. SCLK runs continuously in synchronous
mode, allowing characters to be received on Un_RxD
independently from transmission on Un_TXD).