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M30222

SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER

Mitsumi 

dUevnedloerpment

MITSUBISHI MICROCOMPUTERS

Specifications in this manual are tentative and subject to change

M30222 Group

Rev. G

Clock Generating Circuit

SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER

Clock generating Circuit

The clock generating circuit contains two oscillator circuits that supply the operating clock sources to

the CPU and internal peripheral units. Table 1.10 shows some examples of the main clock and

subclock generating circuits.

Table 1.10. Main clock and sub-clock generating circuits

Main clock generating circuit

Use of clock

Operating clock source for CPU

Operating clock source for Internal

peripheral

Usable oscillator

Ceramic or crystal oscillator

Pins to connect oscillator

Xin, Xout

Oscillation stop/restart function Available

Oscillator status immediately

after Reset

Oscillating

Other

Externally derived clock can be input (Note)

Sub-clock generating circuit

Operating clock source

Count clock source for Timers A/B

Operating clock source for LCD

Crystal oscillator

Xcin, Xcout

Available

Stopped

Note: Max. voltage is the same as VDC

Figure 1.11 shows some examples of the main clock circuit, one using an oscillator connected to the

circuit, and the other one using an externally derived clock for input. Figure 1.12 shows some ex-

amples of sub-clock circuits, one using an oscillator connected to the circuit, and the other one using

an externally derived clock for input. Circuit constants in Figures 1.11 and 1.12 vary with each oscil-

lator used. Use the values recommended by the manufacturer of your oscillator.

Microcomputer

(Built-in feedback resistor)

Xin

Xout

(Note)

Rd

Cin

Cout

Microcomputer

Xin

Xout

Open

Externally derived clock

Vcc

Vss

Note: Insert a damping resistor if required. The resistance will vary depending on the oscillator and the oscillation drive

capacity setting. Use the value recommended by the maker of the oscillator.

When the oscillation drive capacity is set to low, check that oscillation is stable. Also, if the oscillator manufacturer's

data sheet specifies that a feedback resistor be added external to the chip, insert a feedback resistor between Xin

and Xout following the instruction.

Fig. 1.11. Examples of main clock

1-21

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