UPD784020 Datasheet, PDF (88/90 Pages) NEC – 16/8-BIT SINGLE-CHIP MICROCOMPUTER

mPD784020, 784021
Cautions on CMOS Devices
Countermeasures against static electricity for all MOSs
Caution When handling MOS devices, take care so that they are not electrostatically charged.
Strong static electricity may cause dielectric breakdown in gates. When transporting or storing
MOS devices, use conductive trays, magazine cases, shock absorbers, or metal cases that NEC
uses for packaging and shipping. Be sure to ground MOS devices during assembling. Do not
allow MOS devices to stand on plastic plates or do not touch pins.
Also handle boards on which MOS devices are mounted in the same way.
CMOS-specific handling of unused input pins
Caution Hold CMOS devices at a fixed input level.
Unlike bipolar or NMOS devices, if a CMOS device is operated with no input, an intermediate-
level input may be caused by noise. This allows current to flow in the CMOS device, resulting
in a malfunction. Use a pull-up or pull-down resistor to hold a fixed input level. Since unused
pins may function as output pins at unexpected times, each unused pin should be separately
connected to the VDD or GND pin through a resistor.
If handling of unused pins is documented, follow the instructions in the document.
Statuses of all MOS devices at initialization
Caution The initial status of a MOS device is unpredictable when power is turned on.
Since characteristics of a MOS device are determined by the amount of ions implanted in
molecules, the initial status cannot be determined in the manufacture process. NEC has no
responsibility for the output statuses of pins, input and output settings, and the contents of
registers at power on. However, NEC assures operation after reset and items for mode setting
if they are defined.
When you turn on a device having a reset function, be sure to reset the device first.
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