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M16C/5L Group, M16C/56 Group
11.5
Unassigned Pin Handling
Table 11.11
Unassigned Pin Handling in Single-Chip Mode
Pin Name
Ports P0 to P3, P6 toP10
(3)
XOUT
XIN
AVCC
AVSS, VREF
Notes:
1.
When setting a port to output mode and leaving it open, be aware that the port remains in input mode
until it is switched to output mode by a program after reset. For this reason, the voltage level on the
pin becomes indeterminate, causing the power supply current to increase while the port remains in
input mode.
Furthermore, since the values of the direction registers can be changed by noise or noise-induced
loss of control, it is recommended that the contents of the direction registers be regularly reset in
software to improve the program reliability.
2.
Make sure unused pins are connected with the shortest possible wiring from the MCU pins
(maximum 2 cm).
3.
Leave the XOUT pin open when inputting an external clock to the XIN pin or when connecting VCC
via a resistor.
Figure 11.9
Unassigned Pin Handling
R01UH0127EJ0110 Rev.1.10
Sep 01, 2011
One of the following:
•
Set the pin to input mode and connect a pin to VSS via resistor (pull-down)
•
Set the pin to input mode and connect a pin to VCC via resistor (pull-up)
•
Set the pin to output mode and leave the pin open
Open
Connect to VCC via a resistor (pull-up)
Connect to VCC
Connect to VSS
MCU
Ports P0 to P3,
(Input mode)
P6 to P10
:
:
(Input mode)
(Output mode)
(2)
Connection
:
:
Open
VCC
XIN
Open
XOUT
VCC
AVCC
AVSS
VREF
VSS
11. Programmable I/O Ports
(1)
Page 165 of 803
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