UM11029
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© NXP Semiconductors N.V. 2017. All rights reserved.
User manual
Rev. 1.0 — 16 June 2017
283 of 515
17.1 How to read this chapter
Five USARTs are available on all parts depending on the switch matrix configuration.
UART3 and UART4 do not support RTS/CTS hardware signaling for automatic flow
control.
17.2 Features
•
7, 8, or 9 data bits and 1 or 2 stop bits
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Synchronous mode with master or slave operation. Includes data phase selection and
continuous clock option.
•
Multiprocessor/multidrop (9-bit) mode with software address compare.
•
RS-485 transceiver output enable.
•
Parity generation and checking: odd, even, or none.
•
Software selectable oversampling from 5 to 16 clocks in asynchronous mode.
•
One transmit and one receive data buffer.
•
RTS/CTS for hardware signaling for automatic flow control. Software flow control can
be performed using Delta CTS detect, Transmit Disable control, and any GPIO as an
RTS output.
•
Received data and status can optionally be read from a single register
•
Break generation and detection.
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Receive data is 2 of 3 sample "voting". Status flag set when one sample differs.
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Built-in Baud Rate Generator with autobaud function.
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A fractional rate divider is shared among all USARTs.
•
Interrupts available for Receiver Ready, Transmitter Ready, Receiver Idle, change in
receiver break detect, Framing error, Parity error, Overrun, Underrun, Delta CTS
detect, and receiver sample noise detected.
•
Loopback mode for testing of data and flow control.
•
USARTn transmit and receive functions can operated with the system DMA
controller.
17.3 Basic configuration
Configure the USARTs for receiving and transmitting data:
•
In the SYSAHBCLKCTRL register, set bit 14 to 16, bit 30, and 31 (
enable the clock to the register interface.
•
Clear the USART peripheral resets using the PRESETCTRL register (
•
Enable or disable the USART interrupts in slots #3, #4, #5, #30, and #31 in the NVIC.
See
•
Configure the USART pin functions through the switch matrix.
UM11029
Chapter 17: LPC84x USART0/1/2/3/4
Rev. 1.0 — 16 June 2017
User manual