Operating Mode Switching - Holtek HT67F2350 Manual

HT67F2350/HT67F2360
HT67F2370/HT67F2390
Advanced A/D Flash MCU with LCD & EEPROM

Operating Mode Switching

These devices can switch between operating modes dynamically allowing the user to select the best
performance/power ratio for the present task in hand. In this way microcontroller operations that
do not require high performance can be executed using slower clocks thus requiring less operating
current and prolonging battery life in portable applications.
In simple terms, Mode Switching between the FAST Mode and SLOW Mode is executed using the
CKS2~CKS0 bits in the SCC register while Mode Switching from the FAST/SLOW Modes to the
SLEEP/IDLE Modes is executed via the HALT instruction. When a HALT instruction is executed,
whether the device enters the IDLE Mode or the SLEEP Mode is determined by the condition of the
FHIDEN and FSIDEN bits in the SCC register.
SLEEP
HALT instruction executed
CPU stop
FHIDEN=0
FSIDEN=0
f off
H
f off
SUB
Rev. 1.60
FAST
f =f ~f /64
SYS H H
f on
H
CPU run
f on
SYS
f on
SUB
IDLE2
HALT instruction executed
CPU stop
FHIDEN=1
FSIDEN=0
f on
H
f off
SUB
91
SLOW
f =f
SYS SUB
f on
SUB
CPU run
f on
SYS
f on/off
H
IDLE0
HALT instruction executed
CPU stop
FHIDEN=0
FSIDEN=1
f
H
f
SUB
IDLE1
HALT instruction executed
CPU stop
FHIDEN=1
FSIDEN=1
f on
H
f on
SUB
May 16, 2019
off
on