Renesas 7700 FAMILY User Manual page 486

Table 2 Example for processing unused pins in memory expansion mode or microprocessor mode
Ports P4 to P4 , P5 to P8
2 7
____
BHE (Note 2)
ALE (Note 3)
_____
HLDA, φ
1
X (Note 5)
OUT
_____ ____
HOLD, RDY
AVcc
AVss, V
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 "H" level is input to the BYTE pin.
3: This applies when "H" level is input to the BYTE pin and the access space is 64 Kbytes.
4: When supplying Vss level to the CNVss pin, these pins remain set to the input mode until they
are switched to the output mode by software after reset (until the pin function is switched in the
case of the φ
consequently, voltage levels of pins are unstable, and a power source current can increase.
5: This applies when a clock externally generated is input to the X
Appendix 5. Example for processing unused pins
Pin name
pin in the memory expansion mode). While pins remain set to the input mode,
1
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 them open. (Note 4)
Leave it open.
Connect these pins to Vcc via a resistor (pull-up).
Connect this pin to Vcc.
Connect these pins to Vss.
IN
APPENDIX
pin.
20–35