M16CSLASH62M datasheet(610/615 Pages) RENESAS

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Appendix 5

Mitsubishi microcomputers

M16C / 62A Group

SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER

2-293

1.4.3 Oscillator protection using Vss pattern

As for a two-sided printed circuit board, print a VSS pattern on the underside (soldering side) of the

position (on the component side) where an oscillator is mounted.

Connect the VSS pattern to the microcomputer VSS pin with the shortest possible wiring. Besides, sepa-

rate this VSS pattern from other VSS patterns.

XIN

XOUT

VSS

An example of Vss patterns on the

underside of a printed circuit board

Oscillator wiring

pattern example

Oscillator mounting unit

Top View (on the component side)

Noise

Direction register

Data register

Data bus

I/O port

Noise

N.G.

O.K.

Figure 1.4.3. VSS pattern on the underside of an oscillator

1.5 Setup for I/O ports

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

• Connect a resistor of 100

Ω or more to a signal line which is connected to an I/O port in series. Besides,

connect the resistor to the microcomputer as close as possible.

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

not.

• As for an output port, since the output data may reverse because of noise, rewrite data to its port latch

at fixed periods.

• Rewrite data to direction registers and pull-up control registers at fixed periods.

Figure 1.5.1. Setup for I/O ports

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