4507_M Datasheet, PDF (125/216 Pages) Renesas Technology Corp – 4-BIT CISC SINGLE-CHIP MICROCOMPUTER 4500 SERIES

4507 Group
APPLICATION
2.1 I/O pins
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.
M34507
D0
D1
D2
D3
P00
P01
P02
P03
SW4
SW8
SW12
SW16
SW3
SW7
SW11
SW15
SW2
SW6
SW10
SW14
SW1
SW5
SW9
SW13
Fig. 2.1.1 Key input by key scan
Switching key input selection port (D0→D1)
Stabilizing wait time for input
Reading port (key input)
D0 ^{“H”}
“L”
D1 ^{“H”}
“L”
D2 ^{“H”}
“L”
D3 ^{“H”}
“L”
Key input period
IAP0
IAP0
IAP0
IAP0
IAP0
Input to
SW1–SW4
Input to
SW5–SW8
Input to
Input to
SW9–SW12 SW13–SW16
Input to
SW1–SW4
Note: “H” output of port D becomes high-impedance state.
Fig. 2.1.2 Key scan input timing
Rev.2.01 Feb 04, 2005
REJ09B0195-0201
2-10