Renesas R8C/20 User Manual

R8C/20 Group, R8C/21 Group 10. Clock Generation Circuit
Rev.2.00 Aug 27, 2008 Page 78 of 458
REJ09B0250-0200
10.4.2.5 Reducing Internal Power Consumption
Internal power consumption can be reduced by using low-speed on-chip oscillator mode.
Figure 10.10 shows the Procedure for Enabling Reduced Internal Power Consumption Using VCA20 bit.
When enabling reduced internal power consumption using the VCA20 bit, follow Figure 10.10 Procedure for
Enabling Reduced Internal Power Consumption Using VCA20 bit.
Figure 10.10 Procedure for Enabling Reduced Internal Power Consumption Using VCA20 bit
NOTES:
1. Execute this handling to all interrupt handlings generated around the WAIT instruction. If it is not necessary to start the high-speed
clock or the high-speed on-chip oscillator in the interrupt handling, it does not need to be started.
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 entering wait mode, follow 10.6.2 Wait Mode.
Handling procedure of internal power
low consumption enabled by VCA20 bit
Enter low-speed on-chip oscillator mode
Stop XIN clock and high-speed on-chip
oscillator clock
VCA20 ← 1 (internal power low consumption
enabled)
(2)
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 oscillation stabilizes)
Enter high-speed clock mode or high-speed
on-chip oscillator mode
In interrupt handling routine
VCA20 ← 0 (internal power low consumption
disabled)
(2)
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 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 oscillation stabilizes)
Step (1)
Step (2)
Step (3)
If it is necessary to start
the high-speed clock or
the high-speed on-chip
oscillator in the interrupt
handling routine, execute
steps (5) to (7) in the
interrupt routine.
If the high-speed clock or
high-speed on-chip
oscillator is started in the
interrupt handling routine,
execute steps (1) to (3) at
the last of the interrupt
routine.
(Note 1)
Interrupt handling
VCA20: Bit in VCA2 register

Renesas R8C/20 Specifications

General

Brand	Renesas
Model	R8C/20
Category	Control Unit
Language	English