Unassigned Pin Handling - Renesas M16C/64A Series User Manual

M16C/64A Group
13.5

Unassigned Pin Handling

Table 13.14 Unassigned Pin Handling in Single-Chip Mode
Pin Name
Ports P0 to P5
Ports P6 to P10
(4)
XOUT
XIN
AVCC
AVSS, VREF, BYTE
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.
Figure 13.15 Unassigned Pin Handling in Single-Chip Mode
R01UH0136EJ0210 Rev.2.10
Jul 31, 2012
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
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
Open
Connect to VCC1 via a resistor (pull-up)
Connect to VCC1
Connect to VSS
MCU
Ports P0 to P10 (Input mode)
.
.
.
(Input mode)
(Output mode)
XOUT
AVCC
BYTE
AVSS
VREF
Single-chip mode
(2)
Connection
(1)
(1, 3)
.
.
.
Open
VCC1
XIN
Open
VCC1
VSS
13. Programmable I/O Ports
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