R01UH0092EJ0110 Rev.1.10
Page 188 of 807
Jul 31, 2012
M16C/64C Group
13. Programmable I/O Ports
13.5
Unassigned Pin Handling
Figure 13.15 Unassigned Pin Handling in Single-Chip Mode
Table 13.14
Unassigned Pin Handling in Single-Chip Mode
Pin Name
Connection
Ports P0 to P5
One of the following:
•
Set to input mode and connect a pin to VSS via a resistor (pull-down)
•
Set to input mode and connect a pin to VCC2 via a resistor (pull-up)
•
Set to output mode and leave the pins open
Ports P6 to P10
One of the following:
•
Set to input mode and connect a pin to VSS via a resistor (pull-down)
•
Set to input mode and connect a pin to VCC1 via a resistor (pull-up)
•
Set to output mode and leave the pins open
XOUT
(4)
Open
XIN
Connect to VCC1 via a resistor (pull-up)
AVCC
Connect to VCC1
AVSS, VREF, BYTE
Connect to VSS
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
undefined, 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 values of the direction registers be regularly reset in software to improve
the reliability of the program.
2.
Make sure unassigned pins are connected with the shortest possible wiring from the MCU pins (maximum 2
cm).
3.
Ports P7_0, P7_1, and P8_5 are N-channel open drain outputs. When ports P7_0, P7_1, and P8_5 are set to
output mode, make sure a low is output from the pins.
4.
This applies when an external clock is input to the XIN pin or when VCC1 is connected via a resistor.
XIN
XOUT
AVCC
BYTE
AVSS
VREF
MCU
VCC1
VSS
Single-chip mode
Open
(Input mode)
.
.
.
(Input mode)
(Output mode)
Open
.
.
.
VCC1
Ports P0 to P10
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