
R8C/3GM Group
32. Reducing Power Consumption
R01UH0284EJ0100 Rev.1.00
Aug 09, 2011
Figure 32.2
Setting Procedure for Reducing Internal Power Consumption Using VCA20 Bit when
WAIT Instruction is Executed to Enter Wait Mode
Notes:
1. Execute this routine to handle all interrupts generated in wait mode.
However, this does not apply if it is not necessary to start the high-speed clock or high-speed on-chip oscillator during the interrupt routine.
2. Do not set the VCA20 bit to 0 with the instruction immediately after setting the VCA20 bit to 1. Also, do not do the opposite.
3. When the VCA20 bit is set to 1, do not set the CM10 bit to 1 (stop mode).
4. When the MCU enters wait mode, follow 9.7.2 Wait Mode.
Procedure for enabling reduced internal
power consumption using VCA20 bit
Enter low-speed clock mode or
low-speed on-chip oscillator mode
Stop XIN clock and
high-speed on-chip oscillator clock
VCA20
← 1
(internal power low consumption enabled) (2, 3)
Enter wait mode (4)
VCA20
← 0
(internal power low consumption disabled) (2)
Start XIN clock or
high-speed on-chip oscillator clock
(Wait until XIN clock or high-speed on-chip
oscillator clock oscillation stabilizes)
Enter high-speed clock mode or
high-speed on-chip oscillator mode
In interrupt routine
VCA20
← 0
(internal power low consumption disabled) (2)
(This is automatically set when exiting wait mode)
Start XIN clock
or high-speed on-chip oscillator clock
Enter high-speed clock mode or
high-speed on-chip oscillator mode
Enter low-speed clock mode or
low-speed on-chip oscillator mode
Exit wait mode by interrupt
Stop XIN clock and
high-speed on-chip oscillator clock
VCA20
← 1
(internal power low consumption enabled) (2, 3)
Interrupt handling completed
Step (1)
Step (2)
Step (3)
Step (4)
Step (5)
Step (6)
Step (7)
Step (8)
Step (5)
Step (6)
Step (7)
Step (8)
(Wait until XIN clock or high-speed on-chip
oscillator clock oscillation stabilizes)
Step (1)
Step (2)
Step (3)
If it is necessary to start
the high-speed clock or
high-speed on-chip oscillator
during the interrupt routine,
execute steps (6) to (7)
in the routine.
If the high-speed clock or
high-speed on-chip oscillator
starts during the interrupt
routine, execute steps (1) to
(3) at the end of the routine.
(Note 1)
Interrupt handling
VCA20: Bit in VCA2 register