R8C/18 Group, R8C/19 Group
19. Usage Notes
Rev.1.30
Apr 14, 2006
Page 227 of 233
REJ09B0222-0130
19.7
Notes on Noise
19.7.1
Inserting a Bypass Capacitor between VCC and VSS Pins as a
Countermeasure against Noise and Latch-Up
Connect
a bypass capacitor (at least 0.1
µ
F) using the shortest and thickest wire possible.
19.7.2
Countermeasures against Noise Error of Port Control Registers
During rigorous noise testing or the like, external noise (mainly power supply system noise) can
exceed the capacity of the MCU’s internal noise control circuitry. In such cases the contents of the
port related registers may be changed.
As a firmware countermeasure, it is recommended that the port registers, port direction registers, and
pull-up control registers be reset periodically. However, examine the control processing fully before
introducing the reset routine as conflicts may be created between the reset routine and interrupt
routines.