7549 datasheet(49/86 Pages) RENESAS

49 / 86 page

Rev.2.02

Mar 31, 2009

Page 47 of 81

REJ03B0202-0202

7549 Group

Fig 64. Structure of clock mode register

•Note

• Switching to XIN/XCIN Oscillator

After a reset is cleared, operation starts using the low-speed on-

chip oscillator. When switching to XIN/XCIN oscillator, make

sure to set a sufficient wait duration with the on-chip oscillator to

allow the XIN/XCIN oscillator to stabilize.

Low-speed on-chip oscillator oscillation control bit

(Notes 1, 2, and 4)

0: Oscillation start

1: Oscillation stop

High-speed on-chip oscillator oscillation control bit

(Notes 2 and 4)

0: Oscillation start

1: Oscillation stop

XIN/XCIN oscillation control bit (Notes 2 and 4)

0: Oscillation start

1: Oscillation stop

Oscillation stabilization time set bit after release of the

STP instruction

0: Timer 1 set to “0116” and prescaler 12 to “FF16”

automatically

1: Un-automatically

Clock selection bits (Notes 3 and 4)

b5 b4

0 0 : Low-speed on-chip oscillator

0 1 : High-speed on-chip oscillator

1 0 : XIN/XCIN oscillation, External clock

1 1 : Not available

Clock division ratio selection bit

b7 b6

0 0 :

φSOURCE/8 (low-speed mode)

0 1 :

φSOURCE/4 (middle-speed mode)

1 0 :

φSOURCE/2 (high-speed mode)

1 1 : No division (double-speed mode)

Clock mode register

(CLKM: address 003716, initial value: 0216)

Notes 1: When stopping the low-speed on-chip oscillator is disabled by setting the low-speed

on-chip oscillator control bit (bit 4 in FSROM2), “1” cannot be written to this bit.

The low-speed on-chip oscillator does not stop even in stop mode.

2: “1” cannot be written to the oscillation control bits (bits 2 to 0) of the clock selected

φSOURCE by the clock selection bits.

3: When “oscillation pins not used” is set by the oscillation method selection bits (bits 1

and 0 in FSROM1), “102” cannot be written to these bits.

4: Do not change the values of the clock selection bits and the clock oscillation control

bits at the same time using a single instruction. Always use different instructions to

rewrite these values.

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