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Rev. 1.20
�6
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Rev. 1.20
�7
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HT69F30A/HT69F40A/HT69F50A
TinyPower
TM
I/O Flash 8-Bit MCU with LCD & EEPROM
HT69F30A/HT69F40A/HT69F50A
TinyPower
TM
I/O Flash 8-Bit MCU with LCD & EEPROM
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 these devices 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 Clock
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 configuration options and register
programming, a clock system can be configured to obtain maximum application performance.
The main system clock, can come from either a high frequency, f
H
, or low frequency, f
SUB
, source,
and is selected using the HLCLK bit and CKS2~CKS0 bits in the SMOD register. The high speed
system clock can be sourced from an HXT, ERC or HIRC oscillator, selected via a configuration
option. The low speed system clock source can be sourced from the clock, f
SUB
. If f
SUB
is selected
then it can be sourced by either the LXT or LIRC oscillators, selected via a configuration option.
The other choice, which is a divided version of the high speed system oscillator has a range of
f
H
/2~f
H
/64.
The f
SUB
clock is used to provide a substitute clock for the microcontroller just after a wake-up has
occurred to enable faster wake-up times.
HXT
HIRC
P�es�ale�
f
H
LIRC
LXT
High Speed �s�illation
(H�SC)
Low Speed �s�illation
(L�SC)
f
H
/2
f
H
/16
f
H
/64
f
H
/�
f
H
/4
f
H
/32
High Speed �s�illation
Configu�ation �ption
Low Speed �s�illation
Configu�ation �ption
CKS[2:0]� HLCLK
f
SYS
Fast Wake-up f�om SLEEP Mode o�
IDLE Mode Cont�ol (fo� HXT only)
÷
�
LCD D�ive�
f
SYS
/4
f
SUB
f
TB
WDT
Time Base
TBCK
fs
ERC
EC
System Clock Configurations
Note: When the system clock source f
SYS
is switched to f
SUB
from f
H
, the high speed oscillation will stop to
conserve the power. Thus there is no f
H
~f
H
/64 for peripheral circuit to use.