7220 datasheet(234/303 Pages) RENESAS

Part #	7220

Description	8-BIT SINGLE-CHIP MICROCOMPUTER

PDF	303 Pages

Scroll/Zoom	100%

Manufacturer	RENESAS [Renesas Technology Corp]

Direct Link	http://www.renesas.com

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234 / 303 page

7220 Group User’s Manual

APPENDIX

6.4 Countermeasures against noise

6-15

6.4.5 Setup for I/O ports

Setup I/O ports using hardware and software as follows:

qConnect a resistor of 100

Ω or more to an I/O port in series.

qAs for an input port, read data several times by a program for checking whether input levels are equal

or not.

qAs for an output port, since the output data may reverse because of noise, rewrite data to its data register

at fixed periods.

qRewrite data to direction registers and pull-up control registers (only the product having it) at fixed

periods.

When a direction register is set for input port again at fixed periods, a several-nanosecond short pulse may

be output from this port. If this is undesirable, connect a capacitor to this port to remove the noise pulse.

Fig. 6.4.10 Setup for I/O ports

XIN

XOUT

VSS

XIN

XOUT

VSS

N.G.

O.K.

7220 Datasheet(PDF) 234 Page - Renesas Technology Corp