1.  Keyboards, LCDs most widely used input/output devices of the 8051  Contents to be covered:  keyboard fundamentals  key press and key detection mechanisms  Details of keyboard interfacing to 8051. 1

2. 1 C1 R1 P2.0 P2.4 8051 Key not pressed 1 C1 R1 P2.0 P2.4 8051 Key pressed

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4.  Keyboards organized in a matrix of rows and columns.  The CPU accesses both rows and column through ports  When a key pressed, a row and column make a connect; otherwise, there is no connection between row and column.  Microcontroller scans the keys continuously to identify which one has been activated 4