CHAPTER 2 PIN FUNCTIONS
17
2.3 HANDLING UNUSED PINS
In normal operation mode, it is recommended to process the unused pins as follows:
Table 2-1. Handling Unused Pins
Recommended Measures
Inside Microcontroller
Outside Microcontroller
P0A, P0B, P0C
–
Does not incorporate a pull-up
resistor by the mask option
Incorporates a pull-up resistor
by the mask option.
P0A, P0BP0C
(CMOS port)
Outputs low level without
incorporating pull-up resistor by
the mask option.
Outputs high level with a pull-up
resistor incorporated by the
mask option.
External Interrupt (INT)
Note2
–
Directly connected to GND
Does not incorporate a pull-up
resistor by the mask option
Incorporates a pull-up resistor
by the mask option.
Notes
1.
When externally pulling up (connecting to V
DD
through a resistor) or pulling down (connecting to the
GND through a resistor), make sure to pay attention to the port's driving ability and current
consumption. When pulling up or pulling down at a high resistance value, be careful to ensure that
no noise is caused in the relevant pin. Although it depends on the applied circuit as well, it is usual
to choose several tens of k
as the resistance value for pull-up or pull-down.
2.
The INT pin is for the test mode setting function as well; connect it directly to the GND when unused.
3.
If the applied circuit requires a high level of reliability, be sure to design it so that the RESET signal
is input externally. Also, since the RESET pin is for the test mode setting function as well, connect
it directly to the V
DD
when unused.
Caution The output levels of the input/output mode and pins are recommended to be fixed by being set
repeatedly in their respective loops in the program.
Remark
The
μ
PD17P132 and 17P133 do not contain pull-up resistors by the mask option.
Each pin is connected to V
DD
or
GND through the resistor.
Note1
Open
Pin Name
Input mode
P0D, P0E
–
P
Output mode
Open
P0D and P0E (N-ch
open drain port)
RESET
Note3
when using only the built-in
power-ON/power-DOWN reset
Directly connected to V
DD