m3819 Renesas Electronics Corporation., m3819 Datasheet - Page 185

• Manufacturer Part Number: m3819
• Description: Mitsubishi 8-bit Single-chip Microcomputer 740 Family / 38000 Series
• Manufacturer: Renesas Electronics Corporation.

3. APPENDIX
3.1.4 Notes on the RESET pin
3.1.5 Notes on input and output pins
<Note 3>
The comparator uses internal capacitors whose charge will be lost if the clock frequency is too low. Thus, make sure
the following during an A-D conversion.
<Note>
n case where the RESET signal rise time is long, connect a ceramic capacitor or others across the RESET pin and
the V
following :
Reason
If the several nanosecond or several ten nanosecond impulse noise enters the RESET pin, it may cause a
microcomputer failure.
<Note 1>
In stand-by state* for low-power dissipation, do not make input levels of an input and an I/O port “undefined,“
especially for the I/O ports of the P-channel and the N-channel open-drain.
Pull-up (connect the port to V
When determining a resistance value, note the following points:
When using built-in pull-up or pull-down resistor as an option, note on varied current values.
Reason
Even when setting as an output port with its direction register, in the following state :
the transistor becomes the OFF state, which causes the ports to be the high-impedance state. Note that the level
becomes “undefined” depending on external circuits.
Accordingly, the potential which is input to the input buffer in a microcomputer is unstable in the state that input levels
of an input and an I/O port are “undefined.” This may cause power source current.
*
Make the length of the wiring which is connected to a capacitor.
Be sure to check the operation of application products on the user side.
External circuit
Variation of output levels during the ordinary operation
When setting as an input port : Fix its input level
When setting as an output port : Prevent current from flowing out to external
P-channel......when the content of the data register (port latch) is “0”
N-channel......when the content of the data register (port latch) is “1”
stand-by state : the stop mode by executing the STP instruction
f(X
Do not execute the STP instruction and WIT instruction.
IN
SS
) is 500 kHz or more .
pin. And use a 1000 pF or more capacitor for high frequency use. When connecting the capacitor, note the
the wait mode by executing the WIT instruction
CC
) or pull-down (connect the port to V
3819 Group USER’S MANUAL
SS
) these ports through a resistor.
3.1 Notes on use
MITSUBISHI MICROCOMPUTER
3819 Group
171