
UM10800
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© NXP Semiconductors N.V. 2016. All rights reserved.
User manual
Rev. 1.2 — 5 October 2016
189 of 487
NXP Semiconductors
UM10800
Chapter 13: LPC82x USART0/1/2
The Baud Rate Generator block divides the incoming clock to create a 16x baud rate
clock in the standard asynchronous operating mode. The BRG clock input source is the
shared Fractional Rate Generator that runs from the common USART peripheral clock
U_PCLK).
In synchronous slave mode, data is transmitted and received using the serial clock
directly. In synchronous master mode, data is transmitted and received using the baud
rate clock without division.
Status information from the transmitter and receiver is saved and provided via the Stat
register. Many of the status flags are able to generate interrupts, as selected by software.
Remark:
The fractional value and the USART peripheral clock are shared between all
USARTs.
U_PCLK = FRGCLKDIV/(1+MULT/DIV)
Fig 21. USART block diagram
USART2 block
USART1 block
Transmitter
Shift
Regi ster
Transmitter
Holding
Regi ster
Transmitter
Receiver
Shift
Regi ster
Receiver
U
n
_TXD
Un_RXD
Un_SCLK
SCLK
OUT
SCLK
IN
Receiver
Buffer
Regi ster
Un_CTS
Un_RTS
Baud Rate and
Clocking Generation
Interrupt Generation, Status,
Flow Control, Break & parity
gene ration & detection,
FRGCLKDIV
FRG
SYSCON block
USART0 block
main clock
USARTn interrupt
U_PCLK
system clock
RS-485 support