HT66F25D View Datasheet(PDF) - Holtek Semiconductor
Part Name
Description
MFG CO.
'HT66F25D' PDF : 177 Pages View PDF
A/D Flash Type 8-bit MCU with EEPROM
HT66F24D/HT66F25D
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 Mode are used when the microcontroller CPU is switched off to
conserve power.
Description
Operating Mode
CPU
fSYS
fSUB
fS
fTBC
NORMAL Mode
On
fH ~ fH/64
On
On
On
SLOW Mode
On
fL
On
On
On
IDLE0 Mode
Off
Off
On
On
On
IDLE1 Mode
Off
On
On
On
On
SLEEP0 Mode
Off
Off
Off
Off
Off
SLEEP1 Mode
Off
Off
On
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 by one of the high speed oscillators.
This mode operates allowing the microcontroller to operate normally with a clock source will come
from one of the high speed oscillators, either the HXT or HIRC oscillators. 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.
SLOW Mode
This is also a mode where the microcontroller operates normally although now with a slower
speed clock source. The clock source used will be from the low speed oscillator LIRC. Running
the microcontroller in this mode allows it to run with much lower operating currents. In the SLOW
Mode, the fH is off.
SLEEP0 Mode
The SLEEP Mode is entered when a HALT instruction is executed and the IDLEN bit in the SMOD
register is low. In the SLEEP0 mode the CPU will be stopped, and the fSUB and fS clocks will be
stopped too, and the Watchdog Timer function is disabled. In this mode, the LVDEN is must set to 0.
If the LVDEN is set to 1, it won’t enter the SLEEP0 Mode.
SLEEP1 Mode
The SLEEP Mode is entered when a HALT instruction is executed and the IDLEN bit in the SMOD
register is low. In the SLEEP1 mode the CPU will be stopped. However, the fSUB and fS clocks will
continue to operate if the LVDEN is set to 1 or the Watchdog Timer function is enabled and if its
clock source is chosen via configuration option to come from the fSUB.
Rev. 1.10
41
March 25, 2013
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