R8C2C datasheet(137/615 Pages) RENESAS

137 / 615 page

R8C/2C Group, R8C/2D Group

10. Clock Generation Circuit

Rev.2.00

Dec 05, 2007

Page 116 of 585

REJ09B0339-0200

10.5.2.5

Reducing Internal Power Consumption

Internal power consumption can be reduced by using low-speed clock mode 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 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 entering wait mode, follow 10.7.2 Wait Mode.

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 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 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 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

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 routine, execute

steps (1) to (3) at the last of

the interrupt routine.

(Note 1)

Interrupt handling

VCA20: Bit in VCA2 register

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