R8C23 datasheet(97/549 Pages) RENESAS

97 / 549 page

R8C/22 Group, R8C/23 Group

10. Clock Generation Circuit

Rev.2.00 Aug 20, 2008

Page 77 of 501

REJ09B0251-0200

Figure 10.6

FRA2 Register

Figure 10.7

VCA2 Register

High-Speed On-Chip Oscillator Control Register 2

(1)

Symbol

Address

After Reset

FRA2

0025h

00h

Bit Symbol

Bit Name

Function

NOTES:

b7 b6 b5 b4 b3 b2 b1 b0

0000

The division of high-speed on-chip

oscillator clock can be selected.

b2 b1 b0

0 0 0 : Divide-by-2 mode(3)

0 0 1 : Divide-by-3 mode(3)

0 1 0 : Divide-by-4 mode

0 1 1 : Divide-by-5 mode

1 0 0 : Divide-by-6 mode

1 0 1 : Divide-by-7 mode

1 1 0 : Divide-by-8 mode

1 1 1 : Divide-by-9 mode

FRA22

High-speed on-chip oscillator

frequency sw itching bits(2)

FRA20

Do not set on the K version products.

FRA21

Set the PRC0 bit in the PRCR register to 1 (enables w riting) before rew riting to the FRA2 register.

Since the value after reset is 000b, set 010b to 111b on the K version products.

—

(b7-b3)

Reserved bits

Set to 0

Voltage Detection Register 2

(1)

Symbol

Address

VCA2

0032h

Bit Symbol

Bit Name

Function

NOTES:

b2 b1 b0

b7 b6 b5 b4 b3

When using the voltage monitor 1 reset, set the VCA26 bit to 1.

After the VCA26 bit is set from 0 to 1, the voltage detection circuit elapses for td(E-A) before starting operation.

000

—

(b5-b1)

Reserved bits

VCA27

After Reset(4)

Set the PRC3 bit in the PRCR register to 1 (enables w riting) before w riting to the VCA2 register.

Set to 0

VCA26

Voltage detection 2 enable bit(3)

0 : Voltage detection 2 circuit disabled

1 : Voltage detection 2 circuit enabled

The LVD1ON bit in the OFS register is set to 1: 00h

Power-on reset, v oltage monitor 1 reset or the LVD1ON

bit in the OFS register is set to 0: 01000000b

Use the VCA20 bit only w hen entering to w ait mode. To set the VCA20 bit, follow the procedure show n in Figure

10.11 Procedure for Enabling Reduced Internal Pow er Consum ption Using VCA20 bit.

VCA20

Internal pow er low consumption

enable bit(5)

0 : Disables low consumption

1 : Enables low consumption

When using the voltage monitor 2 interrupt/reset or the VCA13 bit in the VCA1 register, set the VCA27 bit to 1.

After the VCA27 bit is from 0 to 1, the voltage detection circuit elapses for td(E-A) before starting operation.

The VCA27 bit remains unchanged after softw are reset, w atchdog timer reset, and voltage monitor 2 reset.

Voltage detection 1 enable bit(2)

0 : Voltage detection 1 circuit disabled

1 : Voltage detection 1 circuit enabled

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