MITSUBISHI MICROCOMPUTERS
4280 Group
SINGLE-CHIP 4-BIT CMOS MICROCOMPUTER for INFRARED REMOTE CONTROL TRANSMITTERS
LIST OF PRECAUTIONS
➀ Noise and latch-up prevention
Connect a capacitor on the following condition to prevent noise
and latch-up;
•
connect a bypass capacitor (approx. 0.01 µF) between pins
VDD and VSS at the shortest distance,
equalize its wiring in width and length, and
use the thickest wire.
•
•
In the One Time PROM version, port E2 is also used as VPP
pin. Connect this pin to VSS through the resistor about 5 kΩ
which is assigned to E2/VPP pin as close as possible at the
shortest distance.
➁ Notes on unused pins
(Note in order to set the output latch to “0” to make pins open)
•
After system is released from reset, a port is in a high-
impedance state until the output latch of the port is set to
“0” by software.
Accordingly, the voltage level of pins is undefined and the
excess of the supply current may occur.
•
To set the output latch periodically is recommended
because the value of output latch may change by noise or
a program run away (caused by noise).
(Note when connecting to VSS and VDD)
•
Connect the unused pins to VSS and VDD at the shortest
distance and use the thick wire against noise.
➂Timer
•
Count source
Stop timer 1 counting to change its count source.
Watchdog timer
•
Be sure that the timing to execute the WRST instruction in
order to operate WDT efficiently.
•
Writing to reload register R1
When writing data to reload register R1 while timer 1 is
operating, avoid a timing when timer 1 underflows.
➃Program counter
Make sure that the program counter does not specify after the
last page of the built-in ROM.
MITSUBISHI
ELECTRIC
21
MITSUBISHI [ Mitsubishi Group ]
