M16C1N Datasheet, PDF (229/238 Pages) Renesas Technology Corp – RENESAS 16-BIT SINGLE-CHIP MICROCOMPUTER M16C FAMILY / M16C/10 SERIES

M16C/1N Group
20. Precautionary Notes in Using the Device
20.7 Noise
1. Bypass Capacitor between VCC and VSS Pins
Insert a bypass capacitor (at least 0.1 µF) between VCC and VSS pins as noise and latch-up
countermeasures. In addition, make sure that connecting lines are the shortest and widest pos-
sible.
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 re-set the port registers, port direction registers and pull-up control registers. How-
ever, you should fully examine before introducing the re-set routine as conflicts may be created
between this re-set routine and interrupt routines (i. e. ports are switched during interrupts).
3. CNVss pin wiring
CNVSS pin functions as a pin to change to shipment examination mode or flash memory rewrite
mode in the flash memory version.
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.1.00 Oct 20, 2004 page 217 of 222
REJ090007-0100Z