Rev. 1.00
36
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Rev. 1.00
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HT66FM5440
Brushless DC Motor A/D Flash MCU
HT66FM5440
Brushless DC Motor A/D Flash MCU
Operating Mode Switching
The device 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 from the NORMAL Mode to the SLEEP/IDLE Modes is executed
via the HALT instruction. When a
n
HALT instruction is executed, whether the device enters the
IDLE Mode or the SLEEP Mode is determined by the condition of the condition of the IDLEN bit in
the SMOD register and the FSYSON bit in the CTRL register.
When the HLCLK bit switches to a low level, which implies that clock source is switched from the
high speed clock source, f
H
, to the clock source, f
H
/2~f
H
/64. The accompanying flowchart shows
what happens when the device moves between the various operating modes.
NORMAL
f
SYS
=f
H
~f
H
/64
f
H
on
CPU r�n
f
SYS
on
f
TBC
on
f
SUB
on
IDLE0
HALT instr�ction exec�ted
CPU stop
IDLEN=1
FSYSON=0
f
SYS
off
f
TBC
on
f
SUB
on
IDLE1
HALT instr�ction exec�ted
CPU stop
IDLEN=1
FSYSON=1
f
SYS
on
f
TBC
on
f
SUB
on
SLEEP
HALT instr�ction exec�ted
f
SYS
off
CPU stop
IDLEN=0
f
TBC
off
f
SUB
on
WDT or LVD on
Entering the SLEEP Mode
There is only one way for the device to enter the SLEEP Mode and that is to execute the "HALT"
instruction in the application program with both the IDLEN bit in the SMOD register equal to "0"
and the WDT or LVD on. When this instruction is executed under the conditions described above,
the following will occur:
• The system clock and the Time Base clock will be stopped and the application program will stop
at the "HALT" instruction, but the WDT or LVD will remain with the clock source coming from
the f
L
clock.
• The Data Memory contents and registers will maintain their present condition.
• The WDT will be cleared and resume counting.
• The I/O ports will maintain their present conditions.
• In the status register, the Power Down flag, PDF, will be set and the Watchdog time-out flag, TO,
will be cleared.