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M30220

SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER

MITSUBISHI ELECTRIC  

Unddeevrelopment

Clock

Tentative Specifications REV.E

Specifications in this manual are

Generating Circuit

tentative

and

subject

to

change.

SINGLE-CHIP

16-BIT

Mitsubishi microcomputers

M30220 Group

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 1.9.1. Main clock and sub-clock generating circuits

Main clock generating circuit

Sub-clock generating circuit

Use of clock

• CPU’s operating clock source • CPU’s operating clock source

• Internal peripheral units’

• Timer A/B’s count clock

operating clock source

source

• Intermittent pullup operation

clock source of key input

• LCD operation clock source

Usable oscillator

Ceramic or crystal oscillator

Crystal oscillator

Pins to connect oscillator

XIN, XOUT

XCIN, XCOUT

Oscillation stop/restart function Available

Available

Oscillator status immediately after reset Oscillating

Stopped

Other

Externally derived clock can be input

Example of oscillator circuit

Figure 1.9.1 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 1.9.2 shows some examples 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 1.9.1 and 1.9.2 vary with each oscillator used. Use the

values recommended by the manufacturer of your oscillator.

Microcomputer

(Built-in feedback resistor)

XIN

XOUT

(Note)

Rd

CIN

COUT

Microcomputer

(Built-in feedback resistor)

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.

Figure 1.9.1. Examples of main clock

Microcomputer

(Built-in feedback resistor)

XCIN

XCOUT

(Note)

RCd

CCIN

CCOUT

Microcomputer

(Built-in feedback resistor)

XCIN

XCOUT

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 XCIN

and XCOUT following the instruction.

Figure 1.9.2. Examples of sub-clock

20

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