
UM10850
All information provided in this document is subject to legal disclaimers.
© NXP B.V. 2016. All rights reserved.
User manual
Rev. 2.4 — 13 September 2016
277 of 464
NXP Semiconductors
UM10850
Chapter 21: LPC5410x USARTs (USART0/1/2/3)
21.7.4.2 Software flow control
Software flow control could include XON / XOFF flow control, or other mechanisms. these
are supported by the ability to check the current state of the CTS input, and/or have an
interrupt when CTS changes state (via the CTS and DELTACTS bits, respectively, in the
STAT register), and by the ability of software to gracefully turn off the transmitter (via the
TXDIS bit in the CTL register).
21.7.5 Autobaud function
The autobaud functions attempts to measure the start bit time of the next received
character. For this to work, the measured character must have a 1 in the least significant
bit position, so that the start bit is bounded by a falling and rising edge. The measurement
is made using the current clocking settings, including the oversampling configuration. The
result is that a value is stored in the BRG register that is as close as possible to the correct
setting for the sampled character and the current clocking settings. The sampled
character is provided in the RXDAT and RXDATSTAT registers, allowing software to
double check for the expected character.
Autobaud includes a time-out that is flagged by ABERR if no character is received at the
expected time. It is recommended that autobaud only be enabled when the USART
receiver is idle. Once enabled, either RXRDY or ABERR will be asserted at some point, at
which time software should turn off autobaud.
Autobaud has no meaning, and should not be enabled, if the USART is in synchronous
mode.
21.7.6 RS-485 support
RS-485 support requires some form of address recognition and data direction control.
This USART has provisions for hardware address recognition (see the AUTOADDR bit in
the CFG register in
), as well as
software address recognition (see the ADDRDET bit in the CTL register in
Fig 45. Hardware flow control using RTS and CTS
7UDQVPLWWHU
5HFHLYHU
&)* >&76(1@
8QB&76
8QB576
FKDQJH GHWHFW
67$7 >&76@
67$7 >'(/7$&76@
&)* >/223@