MC80F0424 Datasheet, PDF (103/135 Pages) List of Unclassifed Manufacturers – 8-BIT SINGLE-CHIP MICROCONTROLLERS

Preliminary
MC80F0424/0432/0448
20.1 Operation Mode Switching
In the Main active mode, only the high-frequency clock oscillator
is used. In the Sub active mode, the low-frequency clock oscilla-
tion is used, so the low power voltage operation or the low power
consumption operation can be enabled. Instruction execution
does not stop during the change of operation mode. In this case,
some peripheral hardware capabilities may be affected. For de-
tails, refer to the description of the relevant operation.
The following describes the switching between the Main active
mode and the Sub active mode. During reset, the system clock
mode register is initialized at the Main active mode. It must be set
to the Sub active mode for reducing the power consumption.
Switching from Main active to Sub active 1
First, write “02_H” into SCMR to switch the main system clock to
the sub-frequency clock of Sub Active mode 1.
Example:
LDM
SCMR,#02_H ;Switch to sub active1
Switching from Main active to Sub active 2
First, write “06_H” into SCMR to switch the main system clock to
the sub-frequency clock of Sub Active mode 2.
Example:
LDM
SCMR,#06_H ;Switch to sub active2
Returning from Sub active 1 to Main active
First, write “01_H” into SCMR to turn on the main-frequency os-
cillation. Sub active mode can also be released by setting the RE-
SET pin to low, which immediately performs the reset operation.
After reset, the MC80F0424/0432/0448 is placed in Main active
mode.
Example:
LDM
SCMR,#01_H ;Switch to main-clock
Switching from Sub active 1 to Sub active 2
First, set SCMR.2 to switch the main system clock to the sub-fre-
quency clock of Sub Active mode 2.
Example:
SET1 SCMR.2 ;Switch to sub active2
Returning from Sub active 2 to Main active
First, set the SCMR.2 bit clear, and wait for a while for oscillation
stabilization time. Secondly, write “01_H” into the SCMR to turn
on the main-frequency oscillation. This time, the stabilization
(warm-up) time needs to be taken by the software delay routine
with the length of two or more NOP instruction. Sub active mode
can also be released by setting the RESET pin to low, which im-
mediately performs the reset operation. After reset, the
MC80F0424/0432/0448 is placed in Main active mode.
Example:
CLR1 SCMR.2 ;Turn on main-clock
NOP ;for OSC stabilization time
NOP ;for OSC stabilization time
LDM SCMR,#01h ;Move to main active
Returning from Sub active 2 to Sub active 1
First, clear SCMR.2 to switch the main system clock to the sub-
frequency clock of Sub Active mode 2.
Example:
CLR1 SCMR.2 ;Switch to sub active1
Shifting from the Normal operation to the SLEEP
mode
If the SLEEP mode is invoked, the external clock oscillation does
not stops but the CPU clock stops while other peripherals are op-
erate normally.
The ways of release from this mode are by setting the RESET pin
to low and all available interrupts. For more detail, See "21.
POWER SAVING OPERATION" on page 101.
Shifting from the Normal operation to the STOP
mode
If the STOP mode is invoked, the main-frequency clock oscilla-
tion stops and the CPU clock stops and other peripherals are stop
too. But sub-frequency clock oscillation operate continuously if
enabled previously. After the STOP operation is released by re-
set, the operation mode is changed to Main active mode.
The methods of release from this mode are Reset, Watch Timer,
RC watchdog timer, Event counter, SIO(External clock), UART,
and External Interrupt.
For more details, see "21. POWER SAVING OPERATION" on
page 101.
Note: In the STOP and SLEEP operating modes, the pow-
er consumption by the oscillator and the internal hardware
is reduced. However, the power for the pin interface (de-
pending on external circuitry and program) is not directly
associated with the low-power consumption operation. This
must be considered in system design as well as interface
circuit design.
MAR. 2005 Ver 0.2
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