BS82B12A-3 Datasheet, PDF (46/170 Pages) Holtek Semiconductor Inc – Touch Flash MCU with LED/LCD Driver

BS82B12A-3/BS82C16A-3/BS82D20A-3
Touch Flash MCU with LED/LCD Driver
Oscillator
Various oscillator options offer the user a wide range of functions according to their various
application requirements. The flexible features of the oscillator functions ensure that the best
optimisation can be achieved in terms of speed and power saving. Oscillator selections and operation
are selected through a combination of configuration options and registers.
Oscillator Overview
All the devices include two internal oscillators and the some devices also include an external
oscillator. In addition to being the source of the main system clock the oscillators also provide clock
sources for the Watchdog Timer, Time Bases and TMs. External oscillator requiring some external
components as well as fully integrated internal oscillators requiring no external components, are
provided to form a wide range of both fast and slow system oscillators. For the BS82C16A-3 and
BS82D20A-3 devices, the low speed oscillators are selected through the configuration option. The
higher frequency oscillators provide higher performance but carry with it the disadvantage of higher
power requirements, while the opposite is of course true for the lower frequency oscillators. With
the capability of dynamically switching between fast and slow system clock, the devices have the
flexibility to optimize the performance/power ratio, a feature especially important in power sensitive
portable applications.
Device
BS82B12A-3
BS82C16A-3
BS82D20A-3
BS82C16A-3
BS82D20A-3
Type
Internal High Speed RC
Internal Low Speed RC
External Low Speed Crystal
Name
HIRC
LIRC
LXT
Freq.
8/12/16MHz
32kHz
32768Hz
Pins
—
—
XT1/XT2
Oscillator Types
System Clock Configurations
There are three methods of generating the system clock, a high speed oscillator and two low speed
oscillators. The high speed oscillator is the internal 8MHz, 12MHz, 16MHz RC oscillator. The two
low speed oscillators are the internal 32kHz oscillator, LIRC, and the external 32.768kHz crystal
oscillator, LXT. Selecting whether the low or high speed oscillator is used as the system oscillator is
implemented using the HLCLK bit and CKS2 ~ CKS0 bits in the SMOD register and as the system
clock can be dynamically selected.
For two of the three devices, the actual source clock used for the low speed oscillator is chosen via
configuration option. The frequency of the slow speed or high speed system clock is also determined
using the HLCLK bit and CKS2 ~ CKS0 bits in the SMOD register. Note that two oscillator
selections must be made namely one high speed and one low speed system oscillators. It is not
possible to choose a no-oscillator selection for either the high or low speed oscillator.
Rev. 1.60
46
December 15, 2016