SLWSTK6101B Datasheet, PDF (7/84 Pages) Silicon Laboratories – BGM113 Blue Gecko Bluetooth ® Module Data Sheet

3.5 Clocking
BGM113 Blue Gecko Bluetooth ^® Module Data Sheet
System Overview
3.5.1 Clock Management Unit (CMU)
The Clock Management Unit controls oscillators and clocks in the BGM113. Individual enabling and disabling of clocks to all peripheral
modules is perfomed by the CMU. The CMU also controls enabling and configuration of the oscillators. A high degree of flexibility al-
lows software to optimize energy consumption in any specific application by minimizing power dissipation in unused peripherals and
oscillators.
3.5.2 Internal Oscillators
The BGM113 fully integrates two crystal oscillators and four RC oscillators, listed below.
• A 38.4MHz high frequency crystal oscillator (HFXO) provides a precise timing reference for the MCU and radio.
• A 32.768 kHz crystal oscillator (LFXO) provides an accurate timing reference for low energy modes.
• An integrated high frequency RC oscillator (HFRCO) is available for the MCU system, when crystal accuracy is not required. The
HFRCO employs fast startup at minimal energy consumption combined with a wide frequency range.
• An integrated auxilliary high frequency RC oscillator (AUXHFRCO) is available for timing the general-purpose ADC and the Serial
Wire debug port with a wide frequency range.
• An integrated low frequency 32.768 kHz RC oscillator (LFRCO) can be used as a timing reference in low energy modes, when crys-
tal accuracy is not required.
• An integrated ultra-low frequency 1 kHz RC oscillator (ULFRCO) is available to provide a timing reference at the lowest energy con-
sumption in low energy modes.
3.6 Counters/Timers and PWM
3.6.1 Timer/Counter (TIMER)
TIMER peripherals keep track of timing, count events, generate PWM outputs and trigger timed actions in other peripherals through the
PRS system. The core of each TIMER is a 16-bit counter with up to 4 compare/capture channels. Each channel is configurable in one
of three modes. In capture mode, the counter state is stored in a buffer at a selected input event. In compare mode, the channel output
reflects the comparison of the counter to a programmed threshold value. In PWM mode, the TIMER supports generation of pulse-width
modulation (PWM) outputs of arbitrary waveforms defined by the sequence of values written to the compare registers, with optional
dead-time insertion available in timer unit TIMER_0 only.
3.6.2 Real Time Counter and Calendar (RTCC)
The Real Time Counter and Calendar (RTCC) is a 32-bit counter providing timekeeping in all energy modes. The RTCC includes a
Binary Coded Decimal (BCD) calendar mode for easy time and date keeping. The RTCC can be clocked by any of the on-board oscilla-
tors with the exception of the AUXHFRCO, and it is capable of providing system wake-up at user defined instances. When receiving
frames, the RTCC value can be used for timestamping. The RTCC includes 128 bytes of general purpose data retention, allowing easy
and convenient data storage in all energy modes.
3.6.3 Low Energy Timer (LETIMER)
The unique LETIMER is a 16-bit timer that is available in energy mode EM2 Deep Sleep in addition to EM1 Sleep and EM0 Active. This
allows it to 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 wave-
forms with minimal software intervention. The LETIMER is connected to the Real Time Counter and Calendar (RTCC), and can be con-
figured to start counting on compare matches from the RTCC.
3.6.4 Ultra Low Power Wake-up Timer (CRYOTIMER)
The CRYOTIMER is a 32-bit counter that is capable of running in all energy modes. It can be clocked by either the 32.768 kHz crystal
oscillator (LFXO), the 32.768 kHz RC oscillator (LFRCO), or the 1 kHz RC oscillator (ULFRCO). It can provide periodic Wakeup events
and PRS signals which can be used to wake up peripherals from any energy mode. The CRYOTIMER provides a wide range of inter-
rupt periods, facilitating flexible ultra-low energy operation.
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