4282 datasheet(21/69 Pages) RENESAS

21 / 69 page

Rev.1.33

Mar 18, 2004

page 21 of 67

4282 Group

Fig. 26 Clock control circuit structure

System clock signal f(XIN) is obtained by externally connecting a

ceramic resonator. Connect this external circuit to pins XIN and

XOUT at the shortest distance as shown Figure 27.

A feedback resistor is built-in between XIN pin and XOUT pin.

ROM ORDERING METHOD

Please submit the information described below when ordering

Mask ROM.

(1) Mask ROM Order Confirmation Form*

(2) Mark Specification Form

(3) Data to be written to ROM, in EPROM form (three identical

copies) or one floppy disk.

* For the mask ROM confirmation and the mark specifications,

refer to the “Renesas Technology Corp.” Homepage

(http://www.renesas.com/en/rom).

Fig. 27 Ceramic resonator external circuit

CLOCK CONTROL

The clock control circuit consists of the following circuits.

• System clock generating circuit

• Control circuit to stop the clock oscillation

• Control circuit to return from the RAM back-up state

4282

XIN

XOUT

CIN

COUT

Use the resonator

manufacturer’s

recommended value

because constants

such as capacitance

depend on the

resonator.

OSC

POF instruction

XIN

XOUT

Ports E0,E1,G0–G3

Pull-down control

Port E2

Internal clock

generation circuit

(divided by 4)

Frequency

divider

(divided by 8)

CCK instruction

STCK

INSTCK

Internal power-on reset circuit

Ports D4–D7

Pull-down control

Multi-

plexer

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