
DESCRIPTION
7702/7703 Group User’s Manual
1–9
1.3 Pin description
1.3.1 Example for processing unused pins
Examples for processing unused pins are described below. These descriptions are just examples. The user
shall modify them according to the user’s actual application and test them.
(1)
In single-chip mode
Table 1.3.4 Example for processing unused pins in single-chip mode
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. (Notes 1, 3)
Leave it open.
Connect this pin to Vcc.
Connect these pins to Vss.
Pin name
Ports P0 to P8
_
E
XOUT (Note 2)
AVcc
AVss, VREF, BYTE
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 XIN pin.
3: In the 7703 Group, the following ports does not have the corresponding pins and have only the
direction registers. Fix the bit of these direction registers to “1” (output mode).
Ports P33, P43–P46, P60, P61, P66, P67, P73–P76, P84, P85
P0–P8
AVSS
VREF
BYTE
M37702
VSS
AVCC
E
XOUT
VCC
P0–P8
AVSS
VREF
M37702
VSS
AVCC
E
XOUT
VCC
Left open
q When setting ports for input mode
q When setting ports for output mode
Left open
BYTE
Fig. 1.3.1 Example for processing unused pins in single-chip mode