UNIT I

2 MARKS

1. What is Microprocessor?

Microprocessor is a multipurpose, programmable clock driven register based electronic device that reads binary information from a storage device called memory; accepts binary data as input and processes data according to those instructions, and provides results.

 

2. What are the basic units of a microprocessor?

 The basic units or blocks of a microprocessor are,

¬  ALU

¬  An array of registers

¬  Control unit

 

3. Define hardware and software?

      Hardware:

            Te physical components of a system are called hardware

       Software:

            A set of instructions written to perform a particular task is called a program, 

        and a group of programs is called software.

 

4.What is an assembly language?

An assembly language is a language which uses English – like words.  Assembly language is microprocessor specific i.e programs written in assembly language are not transferable from one machine to another assembly language is machine dependent.  Eg; 8085

 

5. What is a low –level language?

Low level language is a language which user the binary 0 and 1.  All the microprocessor understands only the binary.

 

6. What is a high level language?

Programming languages that are intended to be machine independent are high level languages. Instruction used in those languages is known as statements.

            Example:         BASIC, C, C++ and Java

 

7.Differentiate compiler and an interpreter?

Compiler or an interpreter programs accept English like statements as their input, called the source code and translates it into the machine language called the object code.

The primary difference between compiler and an assembler is that, The compiler reads the entire program first and translates it into the object

code that is executed by the microprocessor. Interpreter reads are instruction at a time, produces its object code and

executes the instruction before reading the next instruction.

 8. What is assembler?

The assembler is a program that translates the mnemonics entered by the ASCII keyboard into the corresponding binary machine codes of the microprocessor.

 9. What is cross assembler programs?

Cross – assemblers can be used to translate the 8085 mnemonics into appropriate machine codes.

 

10. Define operating system?

The interaction between the hardware and the software is managed by set of programs called an operating system of a computer, it overseas all the operation of the computer.

 

11. What is Microcomputer?

It is a computer that is designed using a microprocessor as its CPU.  It include microprocessor, memory and I / O (Input / Output)

 

12. What are the advantages of an assembly language in comparison with high level languages?

Te assembly language programs are compact and require less space.  They are more efficient than the high – level language programs.

 

13. What are the advantages of high level language in comparison with the assembly languages.?

The primary advantage of high – level language is in troubleshooting (debugging ) programs.  It is much easier to find errors in a program written in a high – level language than to find them in a program written in an assembly language.

 

14. Draw the block diagram of a microcomputer

It is possible to build the CPU on single chip, this came to be known as microprocessor.  A computer with a microprocessor as its CPU is known as a microcomputer.        

 

15. Define bit, byte, word and instruction    

            Bit       :           Bit is a binary digit  0  or 1.

            Byte    :           Byte is a group of  8 bits.

            Nibble :           Nibble is a group of bits the computer recognizes and process at                              a time.

            Instruction:      A instruction is a binary pattern designed inside a microprocessor to perform a specific function.

 

16. What is a bus?

Bus is a group of conducting lines that carries data, address and control signals.

 

17. Define MPU

The terms microprocessor and microprocessor unit (MPU) are often used synonymously.  MPU implies a complete processing unit width the necessary control signals.  Because of the limited number of available pins on a microprocessor package, some of signals (Such as control and multiplexed signals) need to be generated by using discrete devices to make the microprocessor a complete functional unit or MPU.

 

18.       List the four operations commonly performed by the MPU?

The MPU performs primarily operations

1.         Memory Read:            Reads data (or instructions) from memory.

2.         Memory Write:            Write data (or instructions) into memory

3.         I / O Read       :           Accept data from input devices.

4.         I / O Write       :           Sends data to output devices.

 

 

19. Define the address bus:

The address bus is a group of 16 lines ( A0 to A15)  used to identify a peripheral or a memory location.  It carries a 16 bit address.

 

20.Mention the steps, the MPU needs to communicate with the peripheral.

1. Identify the peripheral or  the memory location (with its address)2. Transfer binary information (data and instructions)3. Provide timing or synchronization signals.

            These functions are performed by a three sets of communication lines called 

                buses.

1.  address bus2. Data bus3. Control bus

 21. Define data bus:

The data bus is a group of eight lines used for data flow.  It performs the transferring of binary information.

 

22. Why 8085 is known as 8 – bit microprocessor?

8085 Microprocessor has 8 data lines.  So it is known as 8 – bit microprocessor.

 

23. Define control bus?

Control bus is not a group of lines like address or data buses, but  individual lines that provide a pulse to indicate an MPU operation.

These signals are used to identify a device type with which the MPU intends to communicate.

 

24. Why is the data bus bidirectional?

The data bus are bidirectional since the data flow is in both directions between the MPU and memory and peripheral.

 

25. Why is the address bus unidirectional

The address bus is unidirectional since the bits flow in one direction – from the MPU to peripheral devices.

26.How many memory location can be addressed by a microprocessor with n address lines.

The 8085 MPU with its n address lines is capable of addressing 2n memory locations.

Example :8 bit microprocessor addresses

 

27. Specify the four control signals commonly used by the 8085 MPU?

The four control signals are generated by combining the signals  and  

 IO / .  They are

i.           (Memory Read)

ii.          (Memory write)

iii.            (I / O Read)

iv.         (I / O write )

 

28. How a 8085 microprocessor can qualify as an MPU.

1. The low – order address bus of the 8085 microprocessor is multiplexed with the data bus.  The buses need to be demultiplexed

2. Interface memory and I / O with the 8085.

 

29. List the four categories of 8085 instructions that manipulate data.

1. Data Transfer (copy) Instructions2. Arithmetic instructions.3. Logical instructions.4. Branch Instructions

 

30. How many instructions are available in 8085 instruction set?

8085 microprocessor has 74 operation codes that result in a 246 instructions.

 

31. How 8085 microprocessor operations are classified?

The 8085 microprocessor are classified into five major groups.  They are data  transfer  (copy), arithmetic, logic, branch and machine control.

32. Define opcode and operand?

       An instruction has two parts

1. Opcode (Operation to be performed)2. Operand  (data to be operated on)

        Opcode:

            Operation code is the task to be performed.

       Operand:

            Operand is the data to be operated on

        Example:

            MOV C, A Operand [C, A]®            Opcode[MOV]

 

33.     How 8085 instructions are classified according to the work size or byte size.?

            Instruction set is classified according to the word size as,

1. 1 -  byte instructions2. 2 – byte instructions3. 3 – byte instructions

 

34.What is addressing and what are the addressing modes available in 8085

Every instruction of a program has to operate on a data.  Te method of specifying the data to be operated by the instruction is called addressing (i.e the various way of specifying data are called addressing modes)

            The 8085 supports five addressing modes and they are,

1. Immediate addressing2. Direct addressing

3. Register addressing4. Register indirect addressing5. Implied addressing.

 

35. Explain the immediate addressing with an example

In immediate addressing mode, the data is specified in the instruction itself.  The data will be a part of the program instruction.

            Example:         MVI B, 3 E H

            Move the data 3 E given in the instruction to B – register.

 

36. Direct Addressing

In direct addressing mode, the address of the data is specified in the instruction.  The data will be in memory.  In this addressing mode, the program instructions and data can be stored in different memory locations.

            Example: LDA 1050 H – load the data available in memory location 1050 H in accumulator.

 37.       Explain register addressing with an example?

In register addressing mode, the instruction specifies the name of the register in which the data is available.

            Example:MOV A, B   -Move the content of B register to A register.

 

38.       What is register indirect addressing.  Give an example

In register indirect addressing mode, the instruction specifies the name of the register I which the address of the data is available.. Here the data will be in memory w and the address will be in a register pair

  Example:  MOV A, M – The memory data addressed by  HL pair is moved to

                             A – register.

 

39. Explain the implied addressing with an example

In implied addressing mode, the instruction itself specifies the data to be operated.

            Example:         CMA   -           Complement the content of the accumulator.

 

40. In which unit arithmetic and logical operations are performed and where the result is stored?

The arithmetic and logical operations are performed in ALU.  After the operation the result will be stored in accumulator.

 

41. Which group of instruction affects the flag?

The flags are altered after execution of arithmetic and logical instructions

 

42. What are the arithmetic instructions that do not effect the flag?

The 16 - bit increment and decrement instructions (IN X  rp and DCX rp) will not affect any flags.

 

43. What are the flags affected by 8 – bit increment and decrement instructions?

Except carry, all other flags are affected by 8 – bit increment and decrement instructions.

 

44. List the instructions that effect only carry flag.

The instructions that effect only carry flag are the following

1. CMC2. DAD rP

3. RAL4. RAR5. RLC6. RRC7. STC

45. List the various instruction that can be used to clear accumulator?

The accumulator can be cleared by the following instruction.

1. MVI A,  00H

2. SUB A3. ANI OOH4. XRA A

46. Why the program counter and the stack pointer are 16 – Bit registers?

Program counter (Pc) and stack pointer (Sp) are 16 – bit registers used to hold memory addresses.  The size of these registers is 16 bits, because the memory addresses are 16 bits.

 

47.       What is machine cycle?

Each instruction of the 8085 microprocessor can be divided into a few basic operations called machine cycle and each machine cycle can be divided into T – states.

 

48. What are the machine cycles available in 8085 microprocessor?

The various machine cycles of 8085 are

1. Opcode fetch cycle

2. Memory Read cycle3. Memory Write cycle4. I / O Read cycle5. I / O Write cycle6. Interrupt acknowledge cycle7. Bus idle cycle

 

49. What is T - State?

The T- state is the time period of the internal clock of the processor.  The time taken by the processor to execute a machine cycle is expressed in T – State.

 

50.       What is flag?

The data conditions, after an arithmetic or logical operation are indicated by setting or resetting the flip-flops called flags.

 

51.       Write the 8085 machine cycle status and control signals.

            Machine cycle             Status                          Control signals

                                                 S,   S0

                Opcode fetch              0            1    1             

            Memory read               0            1    1             

            Memory Write             0            0    1             

            I / O Read                   1            1    0             

            I / O Write                   1            0    1             

            Interrupt

Acknowledge              1          1          1         

Halt                                     0          0

Hold                                    X         X          and

Reset                                   X         X                    

52. How 8085 can be used as an MPU?

8085 Microprocessor can be used as an MPU but with the following tow limitations.

1. The low –order address bus of the 8085 multiplexer is multiplexed with the data bus.  Te buses need to be demultiplexed.

2. Appropriate control signals need to be generated to interface memory and I/O  with the 8085.

 

 53. Define mnemonics?

The short hand form of describing the instructions are called mnemonics.  They are given by manufacturer of [company] microprocessors and programmable devices.

Example:  Intel corporation.

 

54. What is Opcode fetch cycle?

The opcode fetch cycle is a machine cycle executed to fetch the opcode of an instruction stored in memory.  The first machine cycle of every instruction is opcode fetch machine cycle.