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2.4 Oscillators and Clocks
EFR32 has six different oscillators integrated, as shown in
Table 2.1 EFR32 Oscillators on page 32
Table 2.1. EFR32 Oscillators
Oscillator
Frequency
Optional?
External
components
Description
HFXO
38 MHz - 40 MHz
No
Crystal
High accuracy, low jitter high frequency crystal oscillator. Tun-
able crystal loading capacitors are fully integrated. The HFXO
is required for all types of RF communication to be active.
HFRCO
1 MHz - 38 MHz
No
-
Medium accuracy RC oscillator, typically used for timing dur-
ing startup of the HFXO and as a clock source as long as no
RF communication is active.
AUXHFRCO
1 MHz - 38 MHz
No
-
Medium accuracy RC oscillator, typically used as alternative
clock source for Analog to Digital Converter or Debug Trace.
LFRCO
32768 Hz
No
-
Medium accuracy frequency reference typically used for medi-
um accuracy RTCC timing.
LFXO
32768 Hz
Yes
Crystal
High accuracy frequency reference typically used for high ac-
curacy RTCC timing. Tunable crystal loading capacitors are
fully integrated.
ULFRCO
1000 Hz
No
-
Ultra low frequency oscillator typically used for the watchdog
timer.
The RC oscillators can be calibrated against either of the crystal oscillators in order to compensate for temperature and voltage supply
variations. Hardware support is included to measure the frequency of various oscillators against each other.
Oscillator and clock management is available through the Clock Management Unit (CMU), see section
2.5 RF Frequency Synthesizer
The Fractional-N RF Frequency Synthesizer (SYNTH) provides a low phase noise LO signal to be used in both receive and transmit
modes.
The capabilities of the SYNTH include:
• High performance, low phase noise
• Fast frequency settling
• Fast and fully automated calibration
• Sub 100 Hz frequency resolution across the supported frequency bands
2.6 Modulation Modes
EFR32 supports a wide range of modulation modes in transmit and receive:
• 2-FSK, 2-GFSK, 4-FSK, 4-GFSK, MSK, GMSK, O-QPSK with half-sine shaping, ASK / OOK, DBPSK TX
• NRZ or Manchester support
• UART mode over air for legacy protocols
• Data rates ranging from 600 bps up to 2 Mbps
• Configurable frequency deviation
• Configurable Direct Sequence Spread Spectrum (DSSS), with spread sequences up to 32 chips encoding up to 4 information bits
• Configurable 4-FSK symbol encoding
Reference Manual
System Overview
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