21. LETIMER - Low Energy Timer
4
3
2
1
0
LETIMER
RTC
Quick Facts
What?
The LETIMER is a down-counter that can keep track
of time and output configurable waveforms. Running
on a 32768 Hz clock, the LETIMER is available in
EM0 Active, EM1 Sleep, EM2 Deep Sleep, and EM3
Stop.
Why?
The LETIMER can be used to provide repeatable
waveforms to external components while remaining
in EM2 Deep Sleep. It is well suited for applications
such as metering systems or to provide more com-
pare values than available in the RTC.
How?
With buffered repeat and top value registers, the LE-
TIMER can provide glitch-free waveforms at fre-
quencies up to 16 kHz. It can be coupled with RTC
using PRS, allowing advanced time-keeping and
wake-up functions in EM2 Deep Sleep and EM3
Stop
21.1 Introduction
The unique LETIMER
TM
, the Low Energy Timer, is a 16-bit timer that is available in energy mode EM0 Active, EM1 Sleep, EM2 Deep
Sleep, and EM3 Stop. 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 can also be connected to the Real
Time Counter (RTC) using PRS, and can be configured to start counting on compare matches from the RTC.
21.2 Features
• 16-bit down count timer
• 2 Compare match registers
• Compare register 0 can be top timer top value
• Compare registers can be double buffered
• Double buffered 8-bit Repeat Register
• Same clock source as the Real Time Counter
• LETIMER can be triggered (started) by an RTC event via PRS or by software
• LETIMER can be started, stopped, and/or cleared by PRS
• 2 output pins can optionally be configured to provide different waveforms on timer underflow:
• Toggle output pin
• Apply a positive pulse (pulse width of one LFACLK
LETIMER
period)
• PWM
• Interrupt on:
• Compare matches
• Timer underflow
• Repeat done
• Optionally runs during debug
• PRS Output
Reference Manual
LETIMER - Low Energy Timer
silabs.com
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