BC68F2420BC68F2420 Datasheet, PDF (36/116 Pages) Holtek Semiconductor Inc – 315/433MHz RF Super-regenerative Receiver SoC Flash MCU

BC68F2420
315/433MHz RF Super-regenerative
Receiver SoC Flash MCU
Operating Modes and System Clocks
Present day applications require that their microcontrollers have high performance but often still
demand that they consume as little power as possible, conflicting requirements that are especially
true in battery powered portable applications. The fast clocks required for high performance will
by their nature increase current consumption and of course vice-versa, lower speed clocks reduce
current consumption. As Holtek has provided this device with both high and low speed clock
sources and the means to switch between them dynamically, the user can optimise the operation of
their microcontroller to achieve the best performance/power ratio.
System Clocks
The device has many different clock sources for both the CPU and peripheral function operation. By
providing the user with a wide range of clock options using register programming, a clock system
can be configured to obtain maximum application performance.
The main system clock, can come from either a high frequency fH or low frequency fSUB source,
and is selected using the CKS2~CKS0 bits in the SCC register. The high speed system clock can
be sourced from the HIRC oscillator. The low speed system clock source can be sourced from the
LIRC oscillator. The other choice, which is a divided version of the high speed system oscillator has
a range of fH/2~fH/64.
High Speed
Oscillator
HIRCEN
HIRC
IDLE0
SLEEP
Low Speed
Oscillator
LIRC
fLIRC
IDLE2
SLEEP
fLIRC
fH
fH/2
fH/4
fH/8
Prescaler _fH/16
fSYS
fH/32
fH/64
CKS2~CKS0
fSUB
fSUB
fSYS
fSYS/4
fSUB
fPSC
Prescaler
TB1[2:0] TB0[2:0]
CLKSEL[1:0]
WDT
Time Base 0
Time Base 1
fLIRC
LVR
Device Clock Configurations
Note: When the system clock source fSYS is switched to fSUB from fH, the high speed oscillator can be stopped to
conserve the power or continue to oscillate to provide the clock source, fH ~ fH/64, for peripheral circuit to
use, which is determined by configuring the corresponding high speed oscillator enable control bit.
Rev. 1.00
36
May 24, 2017