R29 datasheet(111/473 Pages) RENESAS

111 / 473 page

R8C/28 Group, R8C/29 Group

10. Clock Generation Circuit

Rev.2.10

Sep 26, 2008

Page 92 of 441

REJ09B0279-0210

10.5.2.5

Reducing Internal Power Consumption

Internal power consumption can be reduced by using low-speed clock mode (for N, D version only) or low-

speed on-chip oscillator mode. Figure 10.14 shows the Procedure for Enabling Reduced Internal Power

Consumption Using VCA20 bit.

When enabling reduced internal power consumption using the VCA20 bit, follow Figure 10.14 Procedure for

Enabling Reduced Internal Power Consumption Using VCA20 bit.

Figure 10.14

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 10.7.2 Wait Mode.

VCA20: Bit in VCA2 register

Handling procedure of internal power

low consumption enabled by 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 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 mode other than low-speed clock mode

or low-speed on-chip oscillator mode

Enter low-speed clock mode or

low-speed on-chip oscillator mode

Exit wait mode by

interrupt

Interrupt handling

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)

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