7477 datasheet(285/354 Pages) RENESAS

Part #	7477

Description	8-BIT SINGLE-CHIP MICROCOMPUTER 740 FAMILY / 7470 SERIES

PDF	354 Pages

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Manufacturer	RENESAS [Renesas Technology Corp]

Direct Link	http://www.renesas.com

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285 / 354 page

7470/7471/7477/7478 GROUP USER’S MANUAL

2-50

APPLICATION

2.9 Countermeasures against noise

7470

7471

7477

7478

(3) Wiring for the VPP pin of the One Time PROM version and the

EPROM version

q Make the length of wiring which is connected to the

VPP pin as short as possible.

q Connect an approximately 5 k

Ω resistor to the VPP

pin in serial.

q The P33 pin is also used as the VPP pin.

Reason

The VPP pin of the One Time PROM and the EPROM

version is the power source input pin for the built-in

PROM. When programming in the built-in PROM, the

impedance of the VPP pin is low to allow the electric

current for wiring flow into the PROM. Because of

this, noise can enter easily. If noise enters the VPP

pin, abnormal instruction codes or data are read from

the built-in PROM, which may cause a program runaway.

Fig. 2.9.3 Wiring for the VPP pin of the One

Time PROM and the EPROM

version

,,,,

7470/7471/7477/7478 group

P33/VPP

Approximately

Ω

7477 Datasheet(PDF) 285 Page - Renesas Technology Corp