M16C62_M Datasheet, PDF (610/615 Pages) Renesas Technology Corp – 16-BIT SINGLE-CHIP MICROCOMPUTER M16C FAMILY / M16C/60 SERIES

Appendix 5
Mitsubishi microcomputers
M16C / 62A Group
SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER
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.
An example of Vss patterns on the
underside of a printed circuit board
Oscillator wiring
pattern example
XIN
VSS
XOUT
Oscillator mounting unit Top View (on the component side)
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:
<Hardware>
• 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.
<Software>
• 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.
Data bus
Direction register
Data register
Figure 1.5.1. Setup for I/O ports
Noise
O.K.
Noise
N.G.
I/O port
pin
2-293