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DEDICATED SWITCHES
DEDICATED SWITCH CIRCUIT
The dedicated switches operate similar to switches in the matrix except that instead of a column circuit there is a direct tie to
ground. Therefore, the column side is constantly active (low).
When a switch closes the row side (dedicated input) of the circuit activates. The "+" input to the LM339 drops below +5V causing
its output to go low. Since the row circuit (dedicated input) is tied directly to ground through the switch, the switch is considered
closed by the microprocessor. When the switch opens, the "+" input to the LM339 is about +5V, its output is high and the row is
inactive.
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