M34282M1 Datasheet, PDF (22/70 Pages) Mitsubishi Electric Semiconductor – SINGLE-CHIP 4-BIT CMOS MICROCOMPUTER

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.
➂ Timer
• Count source
Stop timer 1 or timer 2 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.
• Timer 1 count operation
When the bit 5 of the watchdog timer (WDT) is selected as
the timer 1 count source, the error of maximum ± 256 µs
(at the minimum instruction execution time : 8 µs) is
generated from timer 1 start until timer 1 underflow. When
programming, be careful about this error.
• Stop of timer 2
Avoid a timing when timer 2 underflows to stop timer 2.
• Writing to reload register R2H
When writing data to reload register R2H while timer 2 is
operating, avoid a timing when timer underflows.
• Timer 2 carrier wave output function
When to expand “H” interval of carrier wave is valid, set “1”
or more to reload register R2H.
➃ Program counter
Make sure that the program counter does not specify after the
last page of the built-in ROM.
MITSUBISHI MICROCOMPUTERS
4282 Group
SINGLE-CHIP 4-BIT CMOS MICROCOMPUTER
MITSUBISHI
22
ELECTRIC