Renesas M32R/ECU Series, User Manual

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Appendix 4
Appendix
4-27
32180 Group User's Manual (Rev. 1.0)
SUMMARY OF PRECAUTIONS
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 unsusceptible to influences from other signals.
(1) Avoidance from large-current signal lines
Signal lines that conduct a large current 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 a microcomputer have signal lines to control a motor, LED or thermal head, for example.
When a large current flows in these signal lines, it generates noise due to mutual inductance (M).
Figure 4.13.7 Example Wiring of a Large-Current Signal Line
OSC-VSS
XIN
XOUT
VCNT
Large current
Noise is generated by
mutual inductance between
the microcomputer and
an adjacent signal line
GND
M
Large current
M
OSC-VSS
XIN
XOUT
VCNT
GND
A signal line that conducts a large current
exists near the microcomputer.
Locate a signal line that conducts a large
current apart from the microcomputer.
Appendix 4.13 Precautions about Noise