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LCD and Keyboard Interfacing in 8051 - Unit 12 - Review Questions & Answers from 8051 Microcontrollers & Embedded Systems by Mazidi


1. The RS pin is an __________ (input, output) pin for the LCD.

2. The E pin is an ____________ (input, output) pin for the LCD.

3. The E pin requires an _____________ (H-to-L, L-to-H) pulse to latch in information at the data pins of the LCD. 

4. For the LCD to recognize information at the data pins as data, RS must be set to ____________ (high, low).

5. Give the command codes for line 1, first character, and line 2, first character. 


1. Input 

2. Input

3. H-to-L 

4. High

5. 80H and C0H 


1. True or false. To see if any key is pressed, all rows are grounded.

2. If D3 - DO= 0111 is the data read from the columns, which column does the pressed key belong to? 

3. True or false. Key press detection and key identification require two different processes.

4. In Figure 12-6, if the rows are D3 - DO= 1110 and the columns are D3 - DO= 1110, which key is pressed?

5. True or false. To identify the pressed key, one row at a time is grounded. 


1. True 

2. Column3

3. True

4. 0 

5. True 

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