Clock Sources; Rc Oscillators Clock References; High-Precision Clock References; Khz Crystal - Semtech LR1110 User Manual

6. Clock Sources

The LR1110 uses both low frequency (32 kHz) and high frequency (32 MHz) clock sources. For each frequency, the clock
signal can be obtained by either a RC oscillator, or a Crystal oscillator. RC oscillators allow optimized power consumption
and faster switching times. Crystal oscillators provide a more precise frequency, in cases when frequency accuracy is
needed.
RF operations require 32 MHz high precision clock reference, which can be provided by either an external crystal oscillator
or by a TCXO.

6.1 RC Oscillators Clock References

Two RC oscillators are available: 32 kHz and 32 MHz RC oscillators:
•
The 32 kHz RC oscillator is optionally used by the circuit in Sleep mode to wake-up the device when performing
periodic or duty cycled operations. Several commands make use of this 32 kHz RC oscillator (RTC) to generate
time-based events.
•
The 32 MHz RC oscillator is enabled for all SPI communication to permit configuration of the device without the need
to start the 32MHz crystal oscillator.

6.2 High-Precision Clock References

6.2.1 32.768 kHz Crystal

A 32.768 kHz crystal oscillator can be used instead of the 32.768 kHz RC oscillator as low frequency clock source. The
configuration of the 32 kHz source is done through the command ConfigLfClock( ) . By default, the 32.768 kHz RC oscillator
is used.

Table 6-1: ConfigLfClock Command

Byte
Data from Host
Data to Host
LfClkConfig parameter:
•
bit 0-1: LF clock selection
0: use 32.768 kHz RC oscillator

1: use 32.768 kHz Crystal oscillator

2: use externally provided 32.768kHz signal on DIO11 pin

3: RFU

•
bit 2: Wait for Xtal 32k ready. If 1 will wait for the Xtal 32k to be ready before releasing the busy.
LR1110
User Manual Rev.1.0
UM.LR1110.W.APP March 2020
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