NRF52820-QDAA-R datasheet(340/437 Pages) NORDIC

340 / 437 page

Peripherals

Figure 127: TWIS timing diagram, 1 byte transaction

6.24 UART — Universal asynchronous receiver/

transmitter

RXDRDY

TXD

(signal)

RXD-3

TXD

PSEL.CTS

PSEL.TXD

TXDRDY

PSEL.RTS

PSEL.RXD

RXD

(signal)

RXD-2

RXD-1

RXD

RXD-4

RXD-5

STARTRX

STOPRX

RXTO

STARTTX

STOPTX

Figure 128: UART configuration

6.24.1 Functional description

Listed here are the main features of UART.

The UART implements support for the following features:

• Full-duplex operation

• Automatic flow control

• Parity checking and generation for the 9th data bit

As illustrated in UART configuration on page 340, the UART uses the TXD and RXD registers directly to

transmit and receive data. The UART uses one stop bit.

Note: The external crystal oscillator must be enabled to obtain sufficient clock accuracy for stable

communication. See CLOCK — Clock control on page 69 for more information.

6.24.2 Pin configuration

The different signals RXD, CTS (Clear To Send, active low), RTS (Request To Send, active low), and TXD

associated with the UART are mapped to physical pins according to the configuration specified in the

PSEL.RXD, PSEL.CTS, PSEL.RTS, and PSEL.TXD registers respectively.

If the CONNECT field of a PSEL.xxx register is set to Disconnected, the associated UART signal will not

be connected to any physical pin. The PSEL.RXD, PSEL.CTS, PSEL.RTS, and PSEL.TXD registers and their

configurations are only used as long as the UART is enabled, and retained only for the duration the device

is in ON mode. PSEL.RXD, PSEL.CTS, PSEL.RTS, and PSEL.TXD must only be configured when the UART is

disabled.

4463_156 v1.0

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NRF52820-QDAA-R Datasheet(PDF) 340 Page - Nordic Semiconductor

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