EFM32WG842 Datasheet, PDF (5/78 Pages) Silicon Laboratories – Operation from backup battery when main power drains out

...the world's most energy friendly microcontrollers
process and close to automatic transfers. Automatic recognition of slave addresses is provided in all
energy modes.
2.1.11 Universal Synchronous/Asynchronous Receiver/Transmitter (US-
ART)
The Universal Synchronous Asynchronous serial Receiver and Transmitter (USART) is a very flexible
serial I/O module. It supports full duplex asynchronous UART communication as well as RS-485, SPI,
MicroWire and 3-wire. It can also interface with ISO7816 SmartCards, IrDA and I2S devices.
2.1.12 Pre-Programmed UART Bootloader
The bootloader presented in application note AN0003 is pre-programmed in the device at factory. Auto-
baud and destructive write are supported. The autobaud feature, interface and commands are described
further in the application note.
2.1.13 Low Energy Universal Asynchronous Receiver/Transmitter
(LEUART)
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. The LEUART includes all necessary hardware support to make asynchronous serial communication
possible with minimum of software intervention and energy consumption.
2.1.14 Timer/Counter (TIMER)
The 16-bit general purpose Timer has 3 compare/capture channels for input capture and compare/Pulse-
Width Modulation (PWM) output. TIMER0 also includes a Dead-Time Insertion module suitable for motor
control applications.
2.1.15 Real Time Counter (RTC)
The Real Time Counter (RTC) contains a 24-bit counter and is clocked either by a 32.768 kHz crystal
oscillator, or a 32.768 kHz RC oscillator. In addition to energy modes EM0 and EM1, the RTC is also
available in EM2. This makes it ideal for keeping track of time since the RTC is enabled in EM2 where
most of the device is powered down.
2.1.16 Backup Real Time Counter (BURTC)
The Backup Real Time Counter (BURTC) contains a 32-bit counter and is clocked either by a 32.768 kHz
crystal oscillator, a 32.768 kHz RC oscillator or a 1 kHz ULFRCO. The BURTC is available in all Energy
Modes and it can also run in backup mode, making it operational even if the main power should drain out.
2.1.17 Low Energy Timer (LETIMER)
The unique LETIMER^TM, the Low Energy Timer, is a 16-bit timer that is available in energy mode EM2
in addition to EM1 and EM0. Because of this, it can be used for timing and output generation when most
of the device is powered down, allowing simple tasks to be performed while the power consumption of
the system is kept at an absolute minimum. The LETIMER can be used to output a variety of waveforms
with minimal software intervention. It is also connected to the Real Time Counter (RTC), and can be
configured to start counting on compare matches from the RTC.
2.1.18 Pulse Counter (PCNT)
The Pulse Counter (PCNT) can be used for counting pulses on a single input or to decode quadrature
encoded inputs. It runs off either the internal LFACLK or the PCNTn_S0IN pin as external clock source.
The module may operate in energy mode EM0 – EM3.
2014-06-13 - EFM32WG842FXX - d0196_Rev1.40
5
www.silabs.com