EFM32WG Datasheet, PDF (493/834 Pages) List of Unclassifed Manufacturers – The EFM32WG Wonder Gecko is the ideal choice for demanding 8-, 16-, and 32-bit energy sensitive applications.

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19 LEUART - Low Energy Universal Asynchronous
Receiver/Transmitter
What?
Quick Facts
0123 4
DMA
controller
RAM
The LEUART provides full UART
communication using a low frequency 32.768
kHz clock, and has special features for
communication without CPU intervention.
Why?
It allows UART communication to be
performed in low energy modes, using only a
few µA during active communication and only
150 nA when waiting for incoming data.
LEUART
RX
TX
How?
A low frequency clock signal allows
communication with less energy. Using
DMA, the LEUART can transmit and receive
data with minimal CPU intervention. Special
UART-frames can be configured to help
control the data flow, further automating data
transmission.
19.1 Introduction
The unique LEUART^TM, the Low Energy UART, is a UART that allows two-way UART communication
on a strict power budget. Only a 32.768 kHz clock is needed to allow UART communication up to 9600
baud/s.
Even when the EFM is in low energy mode EM2 (with most core functionality turned off), the LEUART
can wait for an incoming UART frame while having an extremely low energy consumption. When a UART
frame is completely received, the CPU can quickly be woken up. Alternatively, multiple frames can be
transferred via the Direct Memory Access (DMA) module into RAM memory before waking up the CPU.
Received data can optionally be blocked until a configurable start frame is detected. A signal frame can
be configured to generate an interrupt to indicate e.g. the end of a data transmission. The start frame and
signal frame can be used in combination for instance to handle higher level communication protocols.
Similarly, data can be transmitted in EM2 either on a frame-by-frame basis with data from the CPU or
through use of the DMA.
The LEUART includes all necessary hardware support to make asynchronous serial communication
possible with minimum of software intervention and energy consumption.
19.2 Features
• Low energy asynchronous serial communications
• Full/half duplex communication
• Separate TX / RX enable
• Separate double buffered transmit buffer and receive buffer
• Programmable baud rate, generated as a fractional division of the LFBCLK
2013-05-08 - Wonder Gecko Family - d0233_Rev0.50
493
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