4501 datasheet(126/212 Pages) RENESAS

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2.1 I/O pins

2-9

4501 Group

APPLICATION

Rev.2.01

Feb 07, 2005

REJ09B0192-0201

2.1.3 Port application examples

(1)

Key input by key scan

Key matrix can be set up by connecting keys externally because port D output structure is an N-

channel open-drain and port P0 has the pull-up resistor.

Outline: The connecting required external part is just keys.

Specifications: Port D is used to output “L” level and port P0 is used to input 16 keys.

Figure 2.1.1 shows the key input and Figure 2.1.2 shows the key input timing.

Fig. 2.1.1 Key input by key scan

Fig. 2.1.2 Key scan input timing

SW4SW3

SW2

SW8SW7

SW6

SW9

SW11

SW10

SW12

SW16SW15SW14SW13

P00

P01

P02

P03

SW1

SW5

M34501

IAP0IAP0IAP0IAP0

IAP0

“H”

“L”

“H”

“L”

“H”

“L”

“H”

“L”

Input to

SW1–SW4

Input to

SW13–SW16

Input to

SW9–SW12

Input to

SW5–SW8

Input to

SW1–SW4

Key input period

Switching key input selection port (D

→D )

Stabilizing wait time for input

Reading port (key input)

Note: “H” output of port D becomes high-impedance state.

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