4518 datasheet(68/160 Pages) RENESAS

68 / 160 page

Rev.3.01

2005.06.15

page 68 of 157

REJ03B0008-0301

4518 Group

Fig. 57 Switch to ceramic resonance/RC oscillation/quartz-crystal oscillation

Reset

On-chip oscillator operation

CMCK instruction

CRCKinstruction

• Main clock: ceramic resonance

• On-chip oscillator: operating

• System clock: on-chip oscillator clock

CYCK instruction

• Set the main clock (f(XIN)) oscillation by bit 1 of register MR.

• Switch the system clock by bit 0 of register MR.

Also, when system clock is switched after main clock oscillation is started,

generate the oscillation stabilizing wait time by program if necessary.

• Set the on-chip oscillator clock oscillation by register RG.

• Main clock: RC oscillation circuit

• On-chip oscillator: operating

• System clock: on-chip oscillator clock

• Main clock: Quartz-crystal circuit

• On-chip oscillator: operating

• System clock: on-chip oscillator clock

(1) Main clock generating circuit (f(XIN))

The ceramic resonator, RC oscillation or quartz-crystal oscillator

can be used for the main clock of this MCU.

After system is released from reset, the MCU starts operation by

the clock output from the on-chip oscillator which is the internal os-

cillator.

When the ceramic resonator is used, execute the CMCK instruc-

tion. When the RC oscillation is used, execute the CRCK

instruction. When the quartz-crystal oscillator is used, execute the

CYCK instruction. The oscillation start/stop of main clock f(XIN) is

controlled by bit 1 of register MR. The system clock is selected by

bit 0 of register MR. The oscillation circuit by the CMCK, CRCK or

CYCK instruction can be selected only at once. The oscillation cir-

cuit corresponding to the first executed one of these instructions is

valid.

Execute the CMCK, CRCK or CYCK instruction in the initial setting

routine of program (executing it in address 0 in page 0 is recom-

mended). Also, when the CMCK, CRCK or CYCK instruction is not

executed in program, this MCU operates by the on-chip oscillator.

4518 Datasheet(PDF) 68 Page - Renesas Technology Corp

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