![]() ![]() When that key is pressed, no other counter output will cause That's the code corresponding to that key. Pressed, and if the counter output is 0110, the output from the selector becomes 1: For example, if the switch second from the top and right is But if a particular key is pressed, at a particular 4-bit counter output If no keys are pressed, none of the inputs to the selector can be 1. The outputs of the 4-bit counter are the select inputs of both a 2-Line-to-4-Line Decoder and a 4-Lineto-1-Line Data Selector. Must be fast enough to cycle through all the codes faster than a person can press and release a key. A 4-īit counter repetitively and very quickly cycles through the 16 codes corresponding to the keys. The 16 keys of the keyboard are shown as simple switches in the lower left area of this diagram. ![]()
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