It is very useful for BE (EEE) students. The answer key prepared as per the anna university End semester question (April/May - 2015)

1. B.E / B.Tech DEGREE EXAMINATION, APRIL/MAY - 2015
Sixth Semester
Electrical and Electronics Engineering
EE 2354 – MICROPROCESSORS AND MICROCONTROLLER
Regulation 2008
Answer Key
PART – A
1. What is the function of ALE in 8085 microprocessor?
ALE is a control signal of 8085 MPU. 8085 is a 8-bit microprocessor which have 16-bit
address bus among them lower 8-bit are multiplexed. So while MPU executes read or
write operation it needs to de multiplexed. ALE control signal used to de multiplexed the lower order
address and data bus.
2. What is the maximum number of byte of memory addressable by the 8086
microprocessor?
1 M since the 8088/ 8086 has 20 bit address lines so 220
= 1M
3. What is the function of Rotate Instructions? Give an example.
Rotate instructions are similar to shift instructions, except that rotate instructions are
circular, with the bits shifted out one end returning on the other end. Rotates can be to the left or
right. Rotates can also employ an extend bit for multi-precision rotates.
Example: RRC, RLC
4. How is time delay generated using subroutines.
Subroutine is one that generates a programmable Time delay. Time delays may be done by
using software loops that essentially do nothing for some period.
5. What are the internal Registers available in 8259 PIC?
 In service Register
 Priority Resolver
 Interrupt Mask Register
 Interrupt Request Register
6. Distinguish between synchronous and asynchronous transmission.
Synchronous transmission:
• Supports high data transfer rate
• Needs clock signal between the sender and the receiver
• Requires master/slave configuration
Asynchronous transmission:
• Does not need clock signal between the sender and the receiver
• Slower data transfer rate
7. Write down the instruction format for 8051 microcontroller.
 One Byte Instruction
 Two Byte Instruction
 Three Byte Instruction
8. What is the purpose of timing diagram in 8051 microcontroller?
The graphical representation of all steps which are performed in a machine cycle is known as
the timing diagram. Timing diagram consist of op code fetch, memory read, memory write, I/O read
and I/O write operations.
9. How pulse is generated using 8051 microcontroller.
 Sequential Approach
 Time multiplexed Approach

2. 10. What are the control signals from 8051 microcontroller required for washing machine
control?
Inputs:
 Start
 Prewash Input
 Cloth Type
Outputs:
 Prewash Output
 Main Wash1
 Main Wash 2
 Rinse1
 Rinse 2
 Graduated Spin
 Spin
PART – B
11. (a) i. Explain with a neat block diagram, the hardware architecture of 8085
microprocessor.

3. Architecture:
Register Structure

4. General Purpose Register
Temporary Register
Special Purpose Register

5. 16 Bit Register

6. ALU (Arithmetic Logic Unit)
Instruction Decoder
Address Buffer
Address / Data Buffer
Incrementer / Decrementer Address Latch

7. This 16 bit register is used to increment or decrement the contents of program counter as a
part of execution of instructions related to them.
Interrupt Control
Serial I/O Control
Timing and Control Circuitry
11. (a) ii. Describe the Interrupt Structure of 8085 Microprocessor from the
order their priority.

11. 11. (b) i. Describe the data transfer concepts in 8086 microprocessor.

16. (b) ii. Draw the timing diagram of memory READ and WRITE operations in
8086 microprocessor.
Memory Read:

18. Memory Write:

20. 12. (a) i. Describe the 8085 Assembly Language Program for the Loop Structure
with counting 10 numbers.

21. (a) ii. Describe the different addressing modes of 8085 microprocessor.

23. 12. (b) i. Write an assembly Language program using 8085 instructions to find
the biggest number in a block of data stored in the locations from 70H – 7FH.
(b) ii. Write short notes on Look up table and its usage.

25. 13. (a) i. With a neat functional block diagram, explain the functions of 8255 PPI.
Data Bus Buffer:
Control Logic:

26. Group A and Group B Control:
Operation Modes:
Bit Set – Reset Mode (BSR):
I /O Modes:

27. 13. (a) ii. With a neat functional block diagram, explain the functions of 8279
keyboard controller.

28. It consists of Four Main sections:
 CPU Interface and Control Section
 Scan Section
 Keyboard Section
 Display Section
CPU Interface and Control Section:

29. It consists of Four Main sections:
 CPU Interface and Control Section
 Scan Section
 Keyboard Section
 Display Section
CPU Interface and Control Section:

30. Scan Section:
Key Board Section:

31. 13. (b) i. With a neat functional block diagram, explain the function of 8259 PIC.

33. (b) ii. Explain with neat sketch, the A/D converter interfacing with 8085
microprocessor.
Pin Diagram:

34. Interfacing Diagram:
Timing Diagram:

35. 14. (a) i. Explain with a neat functional block diagram, the 8051 Microcontroller
hardware.
Central Processing Unit (CPU):
On Chip Data Memory and Register Bank:

36. On Chip Program Memory:

37. I/O Ports:
Register Set:

38. Stack and Stack Pointer:
Data Pointer (DPTR)

39. Program Counter
Special Function Register (SFR)
(a) ii. Describe the interrupt structure of 8051 Microcontroller.

41. Priority Level Structure

42. External Interrupts:
Single Step Operation

43. 14. (b) i. Explain various I/O ports and its functions of 8051 Microcontroller.

45. (b) ii. Explain how the internal timers are used to generate time delay by
using 8051 microcontroller.

49. 15. (a) i. Write an 8051 Assembly Language Program to copy 10 bytes of data
stored from location 30H to another location starting from 50H.

50. (a) ii. Explain with a neat diagram the stepper motor control using 8051
microcontroller.

52. 15. (b) i. Explain with a neat diagram, a 4X4 key board interfacing with 8051
microcontroller.

53. Program:
(b) ii. Describe with a neat diagram, the washing machine control using 8051
microcontroller.