7733 datasheet(800/940 Pages) RENESAS

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APPENDIX

7735 Group User’s Manual

21-12

2. In memory expansion mode

Table 2 Examples of handling unused pins in memory expansion mode

Pins

P42–P47, P5–P8

(Note 5)

_________

________

WEH

, WEL, RDE,

_____

__________

HLDA, CS0–CS4, RSMP

XOUT (Note 4)

_____

____

HOLD

, RDY

AVcc

AVss, VREF

Handling example

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

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

set to the output mode (Notes 1 and 2).

Leave these pins open. (Note 3)

Leave this pin open.

Connect these pins to pin Vcc via resistors after these pins are

set to the input mode. (These pins are pulled high.) (Note 2)

Connect this pin to pin Vcc.

Connect these pins to pin Vss.

Notes 1: When leaving these pins open after they are set to the output 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 source current may increase while these

pins function as input ports. Software reliability can be enhanced when the contents of the above

ports’ direction registers are set periodically. This is because these contents may be changed by

noise, a program runaway which occurs owing to noise, etc.

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

3: When Vss level is applied to pin CNVss, note the following: these pins function as input ports from

reset until the processor mode is switched to the memory expansion mode by software. Therefore,

a voltage level of this pin is undefined and the power source current may increase while this pin

functions as an input port.

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

5: Set pin P42/

φ1 as pin P42. (Clock φ1 output is disabled.) And then, for this pin, do the same

handling as that for pins P43 to P47 and P5 to P8.

Fig. 10 Examples of handling unused pins in memory expansionmode

P42–P47, P5–P8

HOLD

RDY

Vcc

Vss

AVcc

XOUT

CS0

–CS4

P42–P47, P5–P8

HOLD

RDY

Vss

AVcc

XOUT

CS0

–CS4

Vcc

When setting ports to input mode

When setting ports to output mode

Left open

AVss

VREF

AVss

VREF

WEH

WEL

RDE

HLDA

RSMP

WEH

WEL

RDE

HLDA

RSMP

Appendix 7. Examples of handling unused pins

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