JNTU previous papers III B -Tech – Microprocessors and micro controllers – Aug/Sep 2008

JNTU III B.Tech Supplimentary Examinations, Aug/Sep 2008

Microprocessors and micro controllers

(Electrical & Electronic Engineering)


1. What is a machine cycle? Explain the basic 8086 system timing with a neat timing



2. Write an 8086 Assembler program to decide the parity of a given number? If the

parity is even, set DL to 00H, else set DL to 01H. The given number may be a multibyte number with a maximum length of 8 bytes.


3. Interface a 4 x 4 key board with 8086 using 8255 and write an ALP for detecting the key closure and return the key code in AL. The debouncing period for a key is

10 ms.Use software key debouncing technique. DEBOUNCE is an available 1 ms delay routine.


4. (a) What are the registers available in 8257? What are their functions

(b) Explain the functions of following signals of 8257


ii. AEN

iii. MARK

iv. MEMR.


5. (a) Explain why serial data transfer is mostly preferred over parallel data transfer.

Give reasons.

(b) Distinguish between data formats used for Synchronous and Asynchronous serial data transfer modes.


6. (a) Draw the oscillator circuit and also draw the 8051 timing diagram.

(b) Discuss in detail about parallel I/O ports in 8051 micro controller and explain how these ports are accessible for specific applications.


7. (a) Discuss in detail about serial port operation in 8051 microcontroller.

(b) Discuss about various modes of operations of timer in 8051.


8. Give the hardware and software details of interfacing of 7-segment displays to 8051 Microcontroller with time-multiplexing and display select mechanism.

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