RX Family
Hardware Design Guide
R01AN1411EJ0110 Rev.1.10
Page 23 of 32
Oct.26.21
2.6 Signal Pins with Large Current Flows
When a large current exceeding the current range supported by the MCU flows in a signal line, place the
signal line as far from the MCU (and the oscillators in particular) as possible, and do not arrange the signal
line in parallel with or across the traces of the reset pin, clock I/O pins, or analog input pins.
Board design hint
In systems using an MCU there are signal lines to control motors, LEDs, thermal heads, etc. If large
currents flow in these signal lines, mutual inductance with parallel wiring traces can cause noise.
2.7 Signal Pins with Rapid Level Changes
Place signal lines with rapid level changes as far from the oscillators and the wiring traces of the oscillators
as possible. Do make such signal lines any longer than necessary and ensure they do not run parallel to or
across the clock-related signal lines or other lines that are easily affected by noise.
Board design hint
Signal lines with rapid level changes can easily affect other signal lines when the level changes at the
rising and falling edges. In particular, when such signal lines cross clock-related signal lines, the clock
waveform can be distorted, possibly resulting in malfunction or program runaway.
