Appendix 5. Example For Processing Unused Pins - Renesas 7700 FAMILY User Manual

APPENDIX

Appendix 5. Example for processing unused pins

Appendix 5. Example for processing unused pins
Table 1 Example for processing unused pins in single-chip mode
Ports P0 to P8
_
E
X (Note 2)
OUT
AVcc
AVss, V , BYTE
REF
Notes 1: When setting these ports to the output mode and leave them open, they remain set to the input
mode until they are switched to the output mode by software after reset. While ports remain set
to the input mode, consequently, voltage levels of pins are unstable, and a power source current
can increase.
The contents of the direction register can be changed by noise or a program runaway generated
by noise. To improve its reliability, we recommend to periodically set the contents of the direction
register by software.
When processing unused pins, use the possible shortest wiring (within 20 mm from the microcomputer).
2: This applies when a clock externally generated is input to the X
20–34
Pin name
7751 Group User's Manual
Example of processing
Set for input mode and connect these pins to Vcc or
Vss via a resistor; or set for output mode and leave
these pins open. (Note 1)
Leave it open.
Connect this pin to Vcc.
Connect these pins to Vss.
IN
pin.