MCQs on Microprocessor

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01․ Inintel 8085A microprocessor ALE signal is made high to
Enable the data bus to be used as low order address bus
To latch data D0-D7 from data bus
To disable data bus
To achieve all the functions listed above

When ALE signal is high all the buses are used as address bus and when it is low lower byte of address bus is used as data bus.
02․ Output of the assembler in machine codes is referred to as
Object program
Source program
Macroinstruction
Symbolic addressing

Input to a assembler is the source program and assembler converts it into object program.
03․ Which of the following statements for intel 8085 is correct?
Program Counter (PC) specifies the address of the instruction last executed
PC specifies the address of the instruction being executed
PC specifies the address of the instruction to be executed
PC specifies the number of instructions executed so far

Program counter contains the address of the instruction to be fetched.
04․ A good assembly language programmer should use general purpose registers rather than memory in maximum possible ways for data processing. This is because:
Data processing with registers is easier than with memory
Data processing with memory requires more instructions in the program than that with registers
Of limited set of instructions for data processing with memory
Data processing with registers takes fewer cycles than that with memory

Data processing with registers takes fewer cycle than with memory which require extra memory read or write signal.
05․ Which one of the following is not correct?
Bus is a group of wires
Bootstrap is a technique or device for loading first instruction
An instruction is a set of bits that defines a computer operation
An interrupt signal is required at the start of every program

Interrupt is required for interruption of main program to perform a subroutine. It may be used at the start of some program as per requirement but it is not mandatory at start of every program.
06․ I)A total of about one million bytes can be directly addressed by the 8086 microprocessor II)8086 has thirteen 16-bit registers III)8086 has eight flags IV)Compared to 8086, the 80286 provides a higher degree of memory protection Which one of the statements given above are correct?
2,3&4
1,3 &4
1,2 & 4
1,2 & 3

→ 8086 has 9 flags i.e. CF, PF, AF, ZF, SF, TF, IF, DF, OF → 8086 has 20 address lines so it can address 220 = 1Mbyte memory location. → 8086 has thirteen 16-bit registers.
07․ The processor status word of 8085 microprocessor has five flags namely:
S, Z, AC, P, CY
S, OV, AC, P, CY
S, Z, OV, P, CY
S, Z, AC, P, OV

8085 microprocessor has 5 status flag S → Sign flag Z → Zero flag AC → Auxiliary carry flag P → Parity flag CY → Carry flag
08․ What are the sets of commands in a program which are not translated into machine instructions during assembly process, called?
Mnemonics
Directives
Identifiers
Operands

Directives are not translated into machine instruction during assembly process.
09․ The cycle required to fetch and execute an instruction in a 8085 microprocessor is which one of the following?
Clock cycle
Memory cycle
Machine cycle
Instruction cycle

One machine cycle is equivalent to one memory access. Clock cycle implies one clock period. Instruction cycle includes fetching and execution of a given instruction.
10․ In an intel 8085A, which is the first machine cycle of an instruction?
An op-code fetch cycle
A memory read cycle
A memory write cycle
An I/O read cycle

In execution of any instruction first cycle is op-code fetch the memory read or write or I/O read or write cycle occur as per instruction given.
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