Two Marks Questions with Answers

Two Marks Questions with Answers

 

Q.1 What is microprocessor ? Give the power supply and clock frequency

Ans. : A microprocessor is a multipurpose, programmable logic device binary instructions from a storage device called memory accepts binary da and processes data according to those instructions and provides result as o power supply of 8085 is +5 V and clock frequency in 3 MHz.

 

Q.2 What are the functions of an accumulator ?

Ans. : The accumulator is the register associated with the ALU open sometimes I/O operations. It is an integral part of ALU. It holds one of processed by ALU. It also temporarily stores the result of the operation per the ALU.

 

Q.3 List the 16 - bit registers of 8085 microprocessor.

Ans. : Stack pointer (SP) and Program counter (PC).

 

Q.4 List the allowed register pairs of 8085.

Ans. : B-C register pair D-E register pair H-L register pair    of 8085 ? that reads :a as input utput. The itions and data to be formed by         

 

Q.5 Mention the purpose of SID and SOD lines.

Ans. : SID (Serial input data line) : It is an input line through which the microprocessor accepts serial data. SOD (Serial output data line): It is an output line through which the microprocessor sends output serial data.

 

Q.6 What is the function of IO/M signal in the 8085 ?

Ans. : It is a status signal. It is used to differentiate between memory locations and I/O operations. When this signal is low it denotes the memory related operations. When this signal is high  it denotes an I/O operation.

 

Q.7 What is the signal classification of 8085 ?

Ans. : All the signals of 8085 can be classified into 6 groups

i) Address bus

ii) Data bus

iii) Control and status signals

iv) Power supply and frequency signals

v) Externally initiated signals

vi) Serial I/O ports

 

Q.8 What is the use of bi-directional buffers ?

Ans. : It is used to increase the driving capacity of the data bus. The data bus of a microcomputer system is bi-directional, so it requires a bi-directional buffer that allows the data to flow in both directions.

 

Q.9 Explain the signals HOLD, READY and SID.

Ans. : HOLD indicates that a peripheral such as DMA controller is requesting the use of address bus, data bus and control bus. READY is used to delay the microprocessor read or write cycles until a slow responding peripheral is ready to send or accept data. SID is used to accept serial data bit by bit.

 

Q.10 What is the need for ALE signal in 8085 microprocessor ?

Ans. : The ALE signal is used to demultiplex (separate) AD₀ - AD₇ lines to Ao - A7 (address lines) and D₀ - D₇ (data lines). The separation of address lines and data lines is achieved by connecting a external latch to AD₀ - AD₇ lines and enabling the latch when ALE signal is active.

 

Q.11 How performance of a microprocessor is measured interms of MIPS ?

Ans. : The performance of a microprocessor is measured interms of MIPS (Million Instructions per Second). It is given as,              

1 MIPS rate = 1/ Average time required for the execution of instruction × 106

 

Q.12 A microprocessor takes n ps for executing an instruction. What design change will make the microprocessor to execute the same instruction in n/2 µs ?

AU : June-07

Ans. : By replacing the crystal of double frequency than that of existing one we can execute the same instruction in half time.

 

Q.13 If a 5 MHz crystal is connected with 8085; what is the value of system clock frequency and one T-state ?

 

Q.14 To obtain a 320 ns clock, what should be the input clock frequency ? What is the frequency of clock signal at CLK OUT ?

Ans. :

 

Q.15 What are the important control signals in 8085 microprocessor ?

Ans. : The important control signals in 8085 microprocessor are : 

 

Q.16 What is tri-state logic ?

Ans. : Logic outputs have two normal states, LOW and HIGH, corresponding to logic values 0 and 1. However, some outputs have a third electrical state that is not logic state at all, called the high-impedance or floating state. In this state the output behaves as if it isn't even connected to the circuit, except for a small leakage current that may flow into or out of the output pin. The circuit having such three states is called tri-state logic.

 

Q.17 What is the function of the Ready signal of 8085 ?

Ans. : It is used by the microprocessor to sense whether a peripheral is ready or not for data transfer. If not, the processor waits. It is thus used to synchronize slower peripherals to the microprocessor.

 

Q.18 List the five interrupt pins available in 8085.

Ans. : The five interrupt pins available in 8085 are : TRAP, RST 7.5, RST 6.5, RST 5.5, and INTR.

 

Q.19 Specify the size of data, address, memory word and memory capacity of 8085 microprocessor.

Ans. : Size of data bus = 8-bits         Size of address bus = 16-bits

Size of memory word = 8-bits Memory capacity = 64 kbytes

 

Q.20 List the special purpose registers of 8085

Ans. : The special purpose registers of 8085 are: 1. A (Accumulator) 2. Flag register 3. Instruction register 4. program counter 5. Stack pointer.

 

Q.21 List the signals provided for DMA operation by 8085 and explain their use.

Ans. : HOLD : This signal indicates that another master is requesting for the use of address bus, data bus and control bus.

HLDA : This active high signal is used to acknowledge HOLD request.

 

Q.22  What are the content of PC and INTE flag after reset ?

Ans. : After reset, PC is loaded with 0000H and INTE flag is cleared.

 

Q.23  What is the need of bus drivers ?

Ans. : Typically, the 8085 buses can source 400 ,µA and sink 2 mA of current, i.e. it can drive only one TTL load. Therefore, it is necessary to increase driving capacity of the 8085 buses. Bus drivers, buffers are used to increase the driving capacity of the buses.

 

Q.24  What is the function of program counter ?

Ans. : Program counter stores the address of the next instruction to be fetched. Thus it is used as pointer to the instruction.

 

Q.25  What is stack and what is the function of stack pointer ? |

Ans. : The stack is a reserved area of the memory in the RAM where temporary information may be stored. A 16-bit stack pointer is used to hold the address of the most recent stack entry.

 

Q.26  What are the various flags used in 8085 ?

Ans. : Various flags in 8085 are : S (Sign flag), Z (Zero flag), AC (Auxiliary carry flag), P (Parity flag), and CY (Carry flag)

 

Q.27  Define the function of parity flag and zero flag in 8085.

 (Refer section 1.2.1)

 

Q.28  List the control and status signals of 8085 microprocessor and mention its need.

(Refer section 1.3.3)

 

Q.29 What is ALE ?

(Refer section 1.3.3)

 

Q.30  Draw the schematic of latching low-order address bus in 8085 microprocessor.

(Refer section 1.4.2)

 

Q.31  Does the 8085 support externally initiated operations. If yes how ?

Ans.: Yes the 8085 does support several externally initiated operations. The possible operations and the corresponding pins for them in the 8085 are as follows :

• It supports resetting ( this is possible with the Reset Pin ).

• Various interruptions ( these are possible through Trap, RST 7.5, 6.5, 5.5 and the interrupt pins. )

• The 8085 also supports readying with the help of the Ready pin.

• It also has a HOLD pin which can basically pause the operation till required/ as required.