Rev. 1.71
38
April 11, 2017
Rev. 1.71
39
April 11, 2017
HT66F002/HT66F0025/HT66F003/HT66F004
Cost-Effective A/D Flash MCU with EEPROM
HT66F002/HT66F0025/HT66F003/HT66F004
Cost-Effective A/D Flash MCU with EEPROM
HIRC
Prescaler
f
H
LIRC
Low Speed Oscillation
f
H
/2
f
H
/16
f
H
/64
f
H
/8
f
H
/4
f
H
/32
HLCLK
CKS2~CKS0 bits
f
SYS
f
LIRC
High Speed Oscillation
WDT
f
SYS
/4
f
TB
Time Base 0
Time Base 1
TBCK
f
L
f
TBC
IDLEN
System Clock Configurations
Note: When the system clock source f
SYS
is switched to f
L
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.
System Operation Modes
There are six different modes of operation for the microcontroller, each one with its own
special characteristics and which can be chosen according to the specific performance and
power requirements of the application. There are two modes allowing normal operation of the
microcontroller, the NORMAL Mode and SLOW Mode. The remaining four modes, the SLEEP0,
SLEEP1, IDLE0 and IDLE1 modes are used when the microcontroller CPU is switched off to
conserve power.
Operating
Mode
Description
CPU
f
SYS
f
LIRC
f
TBC
NORMAL mode
On
f
H
~f
H
/64
On
On
SLOW mode
On
f
L
On
On
IDLE0 mode
Off
Off
On
On
IDLE1 mode
Off
On
On
On
SLEEP0 mode
Off
Off
Off
Off
SLEEP1 mode
Off
Off
On
Off
NORMAL Mode
As the name suggests this is one of the main operating modes where the microcontroller has all
of its functions operational and where the system clock is provided the high speed oscillator. This
mode operates allowing the microcontroller to operate normally with a clock source will come from
the high speed oscillator HIRC. The high speed oscillator will however first be divided by a ratio
ranging from 1 to 64, the actual ratio being selected by the CKS2~CKS0 and HLCLK bits in the
SMOD register. Although a high speed oscillator is used, running the microcontroller at a divided
clock ratio reduces the operating current.
