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This keypad can detect one or two key-pressed simultaneously with any combination. Figure 3.12.3
shows one key pressed condition. Figure 3.12.4(a) and Figure 3.12.4(b) illustrate two keys pressed cases.
Since the key press detection depends on the HIGH or LOW level of the external keypad interface, if keys
are pressed at the same time and there exists a key that is on the same column and the same row with
the other keys, the pressed key cannot be correctly decoded. For example, if there are three key presses:
key1 = (x1, y1), key2 = (x2, y2), and key3 = (x1, y2), then both key3 and key4 = (x2, y1) are detected, and
therefore they cannot be distinguished correctly. Hence, the keypad can detect only one or two keys
pressed simultaneously at any combination. More than two keys pressed simultaneously in a specific
pattern retrieve the wrong information.
Figure 3.12.3 One key pressed with de-bounce mechanism denoted
Figure 3.12.4 Two keys pressed, case 1 (b) Two keys pressed, case 2
Copyright © 2010 LG Electronics. Inc. All right reserved.
Only for training and service purposes
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3. TECHNICAL BRIEF
3. TECHNICAL BRIEF
LGE Internal Use Only
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