32171 Datasheet, PDF (765/772 Pages) Renesas Technology Corp – 32-BIT RISC SINGLE-CHIP MICROCOMPUTER M32R FAMILY / M32R/ECU SERIES

Appendix 4
SUMMARY OF PRECAUTIONS
Appendix 4.13 Precautions about Noise
Appendix 4.13.4 Consideration about the Oscillator and VCNT Pin
The oscillator that generates the fundamental clock for microcomputer operation requires
consideration to make it less susceptible to influences from other signals.
(1) Avoidance from large-current signal lines
Signal lines in which a large current flows exceeding the range of current values that the
microcomputer can handle must be routed as far away from the microcomputer (especially the
oscillator and VCNT pin) as possible. Also, make sure the circuit is protected with a GND pattern.
<Reasons>
Systems using the microcomputer contain signal lines to control, for example, a motor, LED,
and thermal head. When a large current flows in these signal lines, it generates noise due to
mutual inductance (M).
Noise is generated by
M ^{mutual inductance between}
the microcomputer and
an adjacent signal line
Large current
OSC-VSS
XIN
XOUT
VCNT
GND
A signal line that conducts a large current
exists near the microcomputer.
M
Large current
OSC-VSS
XIN
XOUT
VCNT
GND
Locate a signal line that conducts a large
current apart from the microcomputer.
Figure A4.13.7 Example Wiring of Large-current Signal Lines
Appendix 4-29 32171 Group User's Manual (Rev.2.00)