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

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



1. (a) Draw the block diagram of 8086 and explain each block?

(b) Discuss the addressing modes provided by 8086 and explain with examples?


2. (a) Develop a far procedure declared as PUBLIC to convert a 4-digit BCD number

to its equivalent hex number?

(b) Develop a near procedure to find the GCD of two numbers of 2-digit Hex. Use this procedure to find the GCD of three numbers?


3. The I/O circuitry in an 8086 based system consists of five I/O devices with one status signal for each device. Design the required hardware providing two address locations to each device, one for status and other for data. In the range 0F00H to

0FOFH. Write an instruction sequence to test the status of each device and store it.


4. Interface a 12-bit DAC to 8255 with an address map of 0C00H to 0C03H. The DAC provides output in the range of +5V to -5V. Write the instruction sequence.

(a) For generating a square wave with a peak to peak voltage of 4V and the frequency will be selected from memory location ‘F’.

(b) For generating a triangular wave with a maximum voltage of +3V and a minimum of 2V.


5. (a) Draw the command register and mode register format of 8237 and explain each bit?

(b) Show how 8237’s are cascaded to provide more number of DRQ’s and explain the operation?

(c) Explain how memory to memory transfer is performed with 8237?


6. (a) Discuss the sequence of operations performed in the interrupt acknowledge cycle?

(b) What is the difference between RET and IRET? Discuss the result, if RET instruction is placed at the end of the interrupt service routine?

(c) What is the vector address of type 50H interrupt?


7. It is necessary to interface 128KB SRAM and 32KB EPROM to an 8086 based system. The size of SRAM and EPROM chips is 16KB. Address map of SRAM is fixed from 00000H to 1FFFFH and that of EPROM is from F8000H to FFFFFH. Design the entire memory interface? Give the address map of individual chip?


8. (a) Enlist salient features of 8051 family of microcontrollers?

(b) Explain with waveforms different modes of counter/timer in 8051?

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