JNTU B.Tech II Semester Examinations, MICROPROCESSORS AND MICRO CONTROLLERS, Apr/May 2008
(Electrical & Electronic Engineering)
Time: 3 hours Max Marks: 80
Answer any FIVE Questions
All Questions carry equal marks
1. (a) Discuss about the interface signals of the 8086 processor in maximum mode
(b) Discuss SBB, AAD, TEST, SCAS instructions of 8086. [8+8]
2. (a) Explain the following Assembler Directives
(b) Write an ALP to Subtract two 16-bit numbers. [10+6]
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) Explain the priorities of DMA requests
(b) Explain the interfacing if 8257 with 8086. [6+10]
5. (a) List and briefly describe the function of the three signal groups of the GPIB.
(b) Draw the data transfer and handshake waveforms. [10+6]
6. (a) Discuss in detail about 8051 instruction set.
(b) Give the comments for the following instructions.
i. MOV @RP , #n
ii. MOV A, 80h
iii. MOV 0A8h, 77h
iv. MOV A, add
v. MOV add, @RP
vi. MOV A, @R0 [10+6]
7. (a) Write 8051 program as an example of interrupt call to a routine, timer 0 is
used in mode 0 to overflow and set the timer 0 interrupt flag. When the
interrupt is generated, the program vectors to the interrupt routine, resets the
timer 0 interrupt flag, stops the timer, and returns.
1 of 2
(b) Discuss the bit format of IP register of 8051? [8+8]
8. (a) Draw the circuit diagram to interface the DAC to the microcontroller and
(b) Give the differences between microprocessors and microcontrollers? [8+8]