38D2 datasheet(15/136 Pages) RENESAS

15 / 136 page

Rev.3.02

Apr 10, 2008

Page 15 of 131

REJ03B0177-0302

38D2 Group

Fig. 8 Switch procedure of CPU mode register

After releasing reset

Low-speed/XIN mode ?

Start the oscillation

(bits 4 and 5 of CPUM)

Oscillator starts oscillation.

Do not change bit 3, bit 6 and bit 7

of CPUM until oscillation stabilizes.

Select internal system clock

(bit 3 of CPUM or bit 7, 6 = “01”)

Wait by on-chip oscillator operation until

establishment of oscillator clock

Switch the main clock division ratio

selection bit (bit 7, 6 = “00” or “10”)

Start with an on-chip oscillator.

Initial value of CPUM is E016.

Initial value of CPUM2 is 0016.

As for the details of condition for

transition among each mode,

refer to the state transition of

system clock.

System can operate in on-chip

oscillator mode until oscillation

stabilize.

Select internal system clock.

Do not change bit 3, bit 6 and bit

7 of CPUM at the same time.

Select main clock division ratio.

Switch to frequency/2 or frequency/4 mode here,

if necessary.

Main routine

Reset

OSCSEL ?

After releasing reset

Wait by operation until establishment

The CPU starts its operation

in the built-in XIN mode.

Initial value of CPUM is 4016.

Initial value of CPUM2 is 0116.

After releasing reset

Low-speed/XIN mode ?

Start the oscillation

(bits 4 and 5 of CPUM)

Oscillator starts oscillation.

Do not change bit 3, bit 6 and bit 7 of CPUM until

oscillation stabilizes.

Select internal system clock

(bit 3 of CPUM or bit 7, 6 = “01”)

Wait by on-chip oscillator operation until

establishment of oscillator clock

Switch the main clock division ratio

selection bit (bit 7, 6 = “00” or “10”)

Start with an on-chip oscillator.

Initial value of CPUM is E016.

Initial value of CPUM2 is 0016.

As for the details of condition for

transition among each mode,

refer to the state transition of system clock.

System can operate in on-chip oscillator mode until

oscillation stabilize.

Select internal system clock.

Do not change bit 3, bit 6 and bit 7 of CPUM at the

same time.

Select main clock division ratio.

Switch to frequency/2 or 4 mode here, if necessary.

Main routine

Reset

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