R28 datasheet(97/473 Pages) RENESAS

97 / 473 page

R8C/28 Group, R8C/29 Group

10. Clock Generation Circuit

Rev.2.10

Sep 26, 2008

Page 78 of 441

REJ09B0279-0210

Figure 10.6

Registers FRA2, FRA4, FRA6, and FRA7

High-Speed On-Chip Oscillator Control Register 2

(1)

Symbol

Address

After Reset

FRA2

0025h

00h

Bit Symbol

Bit Name

Function

NOTES:

2. Do not set in K version.

FRA22

—

(b7-b3)

Reserved bits

Set to 0.

High-speed on-chip oscillator

frequency sw itching bits

FRA21

Selects the dividing ratio for the high-

speed on-chip oscillator clock.

b2 b1 b0

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

0 0 1: Divide-by-3 mode(2)

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

FRA20

00 00

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

b7 b6 b5 b4 b3 b2 b1 b0

High-Speed On-Chip Oscillator Control Register 4 (for N, D version only)

Symbol

Address

After Reset

FRA4

0029h

When Shipping

b7 b6 b5 b4 b3 b2 b1 b0

Function

Stores data for frequency correction w hen VCC = 2.7 to 5.5 V. (The value is the same as that

of the FRA1 register after a reset.) Optimal frequency correction to match the voltage

conditions can be achieved by transferring this value to the FRA1 register.

High-Speed On-Chip Oscillator Control Register 6 (for N, D version only)

Symbol

Address

After Reset

FRA6

002Bh

When Shipping

b7 b6 b5 b4 b3 b2 b1 b0

Function

Stores data for frequency correction w hen VCC = 2.2 to 5.5 V. Optimal frequency correction

to match the voltage conditions can be achieved by transferring this value to the FRA1

High-Speed On-Chip Oscillator Control Register 7 (For N, D Version Only)

Symbol

Address

After Reset

FRA7

002Ch

When Shipping

Function

36.864 MHz frequency correction data is stored.

The oscillation frequency of the high-speed on-chip oscillator can be adjusted to 36.864 MHz

by transferring this value to the FRA1 register.

b3 b2 b1 b0

b7 b6 b5 b4

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