APD-32A025A Vishay, APD-32A025A Datasheet - Page 5

• Manufacturer Part Number: APD-32A025A
• Description: Intelligent Plasma Display
• Manufacturer: Vishay

To scan more than 16 switches, a 4 line to 16 line decoder must be added, which will allow scanning up to 64 keys. In this mode
the keyboard outputs (KO0-KO3) will work as a 4 bit binary counter.
The keyboards can be scanned by using a 4-bit code to select one of up to 16 switches. The lines are driven by a 4 to 16
decoder, which supplies a ground return to the selected switch. The switch common line is then read to sense the condition to
that switch. (see keyboard with common pole).
If two or more keys are depressed simultaneously, only one key will be detected. After that key is released the second will be
encoded, and etc. Note that if three keys are depressed simultaneously to form and “L” configuration, an erroneous input could
occur. If this presents a potential problem, a diode (IN914) should be added to the column pole of each switch.
Document Number: 37081
Revision 24-May-05
K03
K02
K01
K00
K13
K12
K11
K10
D
C
B
A
0
0
1
1
2
2
3
3
4
4
KEYBOARD WITH COMMON POLE
5
1 OF 16 DECODER
6
7
8
9
10
11
12
13
APD-32A025A
14
15
15
Vishay Dale
www.vishay.com
17