R8C20 datasheet(77/501 Pages) RENESAS

77 / 501 page

R8C/20 Group, R8C/21 Group

7. Programmable I/O Ports

Rev.2.00 Aug 27, 2008

Page 61 of 458

REJ09B0250-0200

7.5

Unassigned Pin Handling

Table 7.48 lists Unassigned Pin Handling.

NOTES:

1. If these ports are set to output mode and left open, they remain input mode until they are switched to

output mode by a program. The voltage level of these pins may be undefined and the power current

may increase while the ports remain input mode.

The content of the direction registers may change due to noise or program runaway caused by

noise. In order to enhance program reliability, the program should periodically repeat the setting of

the direction registers.

2. Connect these unassigned pins to the MCU using the shortest wire length (2 cm or less) as

possible.

3. When power-on reset function is in use.

Figure 7.13

Unassigned Pin Handling

Table 7.48

Unassigned Pin Handling

Pin Name

Connection

Ports P0 to P2, P3_0,

P3_1, P3_3 to P3_7,

P4_3 to P4_5, P6

• After setting to input mode, connect every pin to VSS via a resistor (pull-

down) or connect every pin to VCC via a resistor (pull-up).(2)

• After setting to output mode, leave these pins open.(1, 2)

Ports P4_6, P4_7

Connect to VCC via a resistor (pull-up)(2)

Port P4_2/VREF

Connect to VCC

RESET(3)

Connect to VCC via a resistor (pull-up)(2)

MCU

Port P0 to P2, P3_0,

P3_1, P3_3 to P3_7,

P4_3 to P4_5, P6

(Input mode )

(Input mode)

(Output mode)

Port P4_6, P4_7

RESET(1)

Port P4_2/VREF

Open

NOTE:

1. When power-on reset function is in use.

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