Syste� Ope�Ation Modes - Holtek HT66F488 Manual

System Operation Modes
There are 6 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 three modes allowing normal operation of the
microcontroller, the NORMAL, SLOW0 and SLOW1 Mode. The remaining three modes, the
SLEEP, IDLE0 and IDLE1 Modes are used when the microcontroller CPU is switched off to
conserve power.
Operating
Mode
�ORMAL �ode
SLOW� �ode
SLOW1 �ode
ILDE� �ode
IDLE1 �ode
SLEEP �ode
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, HXT or HIRC.
SLOW0 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 or LXT. Running
the microcontroller in this mode allows it to run with much lower operating currents. In the SLOW
Mode 0, the f is off.
H
SLOW1 Mode
This is also a mode where the microcontroller operates normally although now with a slower speed
clock source. The high speed oscillator will however first be divided by a ratio ranging from 2 to 64,
the actual ratio being selected by the CKS2~CKS0 bits in the SMOD register. Although a high speed
oscillator is used, running the microcontroller at a divided clock ratio reduces the operating current.
SLEEP Mode
The SLEEP Mode is entered when an HALT instruction is executed and the IDLEN bit in the SMOD
register is low. In the SLEEP mode the CPU will be stopped. However the f
to operate as the Watchdog Timer clock.
IDLE0 Mode
The IDLE0 Mode is entered when a HALT instruction is executed and when the IDLEN bit in the
SMOD register is high and the FSYSON bit in the CTRL register is low. In the IDLE0 Mode the
system oscillator will be inhibited from driving the CPU but some peripheral functions will remain
operational such as the Watchdog Timer and TMs. In the IDLE0 Mode, the system oscillator will be
stopped.
Rev. 1.21
A/D Flash MCU with EEPROM
Description
CPU f
SYS
On f ~f /64
H H
On f
L
On f /2~f /64
H H
Off Off
Off On
Off Off
4�
HT66F488/HT66F489
f f
SUB TBC
On On
On On
On On
On On
On On
On Off
clock will continue
SUB
�ove��e� ��� 2�1�