7733 datasheet(926/940 Pages) RENESAS

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Appendix 7. Examples of handling unused pins

APPENDIX

7736 Group User’s Manual

20–14

Appendix 7. Examples of handling unused pins

The following are examples of handling unused pins.

These are, however, just examples. In actual use, make the necessary adaptations and properly evaluate

performance according to the user’s application.

1. In single-chip mode

Table 1 Examples of handling unused pins in single-chip mode

Handling example

Connect these pins to pin Vcc or Vss via resistors after the

pins are set to the input mode, or leave these pins open after

they are set to the output mode (Note 1).

Leave these pins open after writing data to the port P9 register (Note 3).

Leave this pin open.

Connect this pin to pin Vcc.

Connect these pins to pin Vss.

Connect this pin to pin Vcc or Vss.

Pins

P0–P8, P10

____

, RDE

EVL0, EVL1

XOUT (Note 2)

AVcc

AVss, VREF, BYTE

BSEL

Notes 1: When leaving these pins open after they are set to the outpu

t mode, note the following:

these pins

function as input ports from reset until they are switched to the output mode by software. Therefore,

voltage levels of these pins are undefined and the power sou

rce current may increase while these

ports function as input ports.

Software reliability can be enhanced when the contents of th

e above ports

’ direction registers are

set periodically. This is because these contents may be chan

ged by noise, a program runaway

which occurs owing to noise, etc.

For unused pins, use the shortest possible wiring (within 20 mm from the microcomputer’s pins).

2: This is applied when an external clock is input to pin XIN.

3: When leaving port P9 pins open after writing data to the port P9 register, note the following: these

pins are in a floating state from reset until the data is written to the port P9 register by software.

Therefore, voltage levels of these pins are undefined and the power source current may increase

while they are in a floating state.

Fig. 9 Examples of handling unused pins in single-chip mode

P0–P8,P10

AVSS

VREF

BYTE

BSEL

VSS

AVCC

E/RDE

XOUT

EVL0

EVL1

Left open



When setting ports to input mode

VCC

P0–P10

AVSS

VREF

BYTE

BSEL

VSS

AVCC

E/RDE

XOUT

EVL0

EVL1

Left open



When setting ports to output mode

Left open

VCC

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