R8C/13 Group
19. Usage Notes
19.8 Noise
(1) Bypass Capacitor between VCC and VSS Pins
Insert a bypass capacitor (at least 0.1 µF) between VCC and VSS pins as the countermeasures against
noise and latch-up. The connecting wires must be the shortest and widest possible.
(2) Port Control Registers Data Read Error
During severe noise testing, mainly power supply system noise, and introduction of external noise, the
data of port related registers may changed. As a firmware countermeasure, it is recommended to
periodically reset the port registers, port direction registers and pull-up control registers. However, you
should fully examine before introducing the reset routine as conflicts may be created between this
reset routine and interrupt routines (i. e. ports are switched during interrupts).
(3) CNVss Pin Wiring
In order to improve the pin tolerance to noise, insert a pull down resistance (about 5 kΩ) between
CNVss and Vss, and placed as close as possible to the CNVss pin.
Rev.1.20 Jan 27, 2006 page 198 of 205
REJ09B0111-0120
RENESAS [ RENESAS TECHNOLOGY CORP ]
