R8C2C datasheet(120/615 Pages) RENESAS

120 / 615 page

R8C/2C Group, R8C/2D Group

10. Clock Generation Circuit

Rev.2.00

Dec 05, 2007

Page 99 of 585

REJ09B0339-0200

Figure 10.3

CM0 Register

System Clock Control Register 0(1)

Symbol

Address

After Reset

CM0

0006h

01101000b

Bit Symbol

Bit Name

Function

NOTES:

b7 b6 b5 b4 b3 b2 b1 b0

—

(b1-b0)

Reserved bits

Set to 0.

CM02

WAIT peripheral function clock

stop bit

0 : Peripheral function clock does not stop

in w ait mode

1 : Peripheral function clock stops in w ait

mode

CM03

XCIN-XCOUT drive capacity

select bit(9)

0 : Low

1 : High

CM04

Port, XCIN-XCOUT sw itch bit(6)

0 : I/O port P4_3, P4_4

1 : XCIN-XCOUT pin(7)

CM05

XIN clock (XIN-XOUT)

stop bit(2, 4)

0 : XIN clock oscillates

1 : XIN clock stops(3)

CM06

System clock division select bit

0(5)

0 : CM16, CM17 enabled

1 : Divide-by-8 mode

CM07

CPU clock select bit(8)

0 : System clock

1 : XCIN clock

When entering stop mode, the CM06 bit is set to 1 (divide-by-8 mode).

Set the PRC0 bit in the PRCR register to 1 (w rite enable) before rew riting the CM0 register.

The CM05 bit stops the XIN clock w hen the high-speed on-chip oscillator mode, low -speed on-chip oscillator mode is

selected. Do not use this bit to detect w hether the XIN clock is stopped. To stop the XIN clock, set the bits in the

follow ing order:

(a) Set bits OCD1 to OCD0 in the OCD register to 00b.

(b) Set the OCD2 bit to 1 (selects on-chip oscillator clock).

During external clock input, only the clock oscillation buffer is turned off and clock input is acknow ledged.

When the CM05 bit is set to 1 (XIN clock stopped) and the CM13 bit in the CM1 register is set to 0 (P4_6, P4_7), P4_6

and P4_7 can be used as input ports.

The MCU enters stop mode, the CM03 bit is set to 1 (high). Rew rite the CM03 bit w hile the XCIN clock oscillation

stabilizes.

The CM04 bit can be set to 1 by a program but cannot be set to 0.

To use the XCIN clock, set the CM04 bit to 1. Also, set ports P4_3 and P4_4 as input ports w ithout pull-up.

Set the CM07 bit to 1 from 0 (XCIN clock) after setting the CM04 bit to 1 (XCIN-XCOUT pin) and allow ing XCIN clock

oscillation to stabilize.

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