CS1304-mp

1.What is Microprocessor ?

It is a program controlled semiconductor device (IC}, which fetches,

decode and executes instructions.

2. What are the basic units of a microprocessor ?

The basic units or blocks of a microprocessor are ALU, an array of

registers and control unit.

3.What is Software and Hardware?

The Software is a set of instructions or commands needed for

performing a specific task by a programmable device or a computing

machine.

The Hardware refers to the components or devices used to form

computing machine in which the software can be run and tested.

Without software the Hardware is an idle machine.

4. What is assembly language?

The language in which the mnemonics (short -hand form of

instructions) are used to write a program is called assembly language.

The manufacturers of microprocessor give the mnemonics.

5. What are machine language and assembly language programs?

The software developed using 1's and 0's are called machine language,

programs. The software developed using mnemonics are called

assembly language programs.

6. What is the drawback in machine language and assembly language,

programs?

The machine language and assembly language programs are machine

dependent. The programs developed using these languages for a

particular machine cannot be directly run on another machine .

7. Define bit, byte and word.

A digit of the binary number or code is called bit. Also, the bit is the

fundamental storage unit of computer memory.

The 8-bit (8-digit) binary number or code is called byte and 16-bit

binary number or code is called word. (Some microprocessor

manufactures refer the basic data size operated by the processor as

word).

8. What is a bus?

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

signals.

9. Why data bus is bi-directional?

The microprocessor has to fetch (read) the data from memory or input

device for processing and after processing, it has to store (write) the

data to memory or output device. Hence the data bus is bi-directional.

10. Why address bus is unidirectional?

The address is an identification number used by the microprocessor to

identify or access a memory location or I / O device. It is an output

signal from the processor. Hence the address bus is unidirectional.

11. What is the function of microprocessor in a system?

The microprocessor is the master in the system, which controls all the

activity of the system. It issues address and control signals and fetches

the instruction and data from memory. Then it executes the instruction

to take appropriate action.

12. Why interfacing is needed for 1/0 devices?

Generally I/O devices are slow devices. Therefore the speed of I/O

devices does not match with the speed of microprocessor. And so an

interface is provided between system bus and I/O devices.

13. What is the difference between CPU bus and system bus?

The CPU bus has multiplexed lines but the system bus has separate

lines for each signal. (The multiplexed CPU lines are demultiplexed by

the CPU interface circuit to form system bus).

14..What does memory-mapping mean?

The memory mapping is the process of interfacing memories to

microprocessor and allocating addresses to each memory locations.

15..What is interrupt 1/0?

If the 1/0 device initiate the data transfer through interrupt then the 1/0

is called interrupt driven 1/0.

16. Why EPROM is mapped at the beginning of memory space in 8085

system?

In 8085 microprocessor, after a reset, the program counter will have

OOOOH address. If the monitor program is stored from this address

then after a reset, it will be executed automatically. The monitor

program is a permanent program and stored in EPROM memory. If

EPROM memory is mapped at the beginning of memory space, i.e., at

OOOOH, then the monitor program will be executed automatically

after a reset.

17. What is the need for system clock and how it is generated in 8085?

The system clock is necessary for synchronizing various internal

operations or devices in the microprocessor and to synchronize the

microprocessor with other peripherals in the system.

18. What is multiplexing and what is its advantage? How the address and

data lines are demultiplexed in 8085?

Multiplexing is transferring different information at different well

defined times through same lines. A group of such lines is called

multiplexed bus. The advantage of multiplexing is that fewer pins are

required for microprocessors to communicate with outside world.

The low order address and data lines of 8085 are demultiplexed

using an external 8-bit D-Latch (74LS373) and the ALE signal of

8085, as shown in fig.

Ao – A7 D0 - D7

Fig : Demultiplexing of address and data lines in 8085 processor

At the beginning of every machine cycle, ALE is asserted high and

then low. Also the low byte of address is given out through ADo -

AD7 lines. Since the ALE is connected to Enable of Latch, when

ALE is asserted high and then low the addresses are latched into the

output lines of the latch. Now the lines ADo -AD7 are free for data

transfer.

19. Explain the function of IO/M, READY , HOLD and HLDA

in 8085.

The IO/M is used to differentiate memory access and I/O

access. For IN and OUT instruction it is high. For memory reference

instructions it is low.

READY is an input signal to the processor, used by the

memory or I/O devices to get extra time for data transfer or to

introduce wait states in the bus cycles.

8085 ADo – AD7 ALE

74LS373 LATCH EN

HOLD and HLDA signals are used for the Direct

Memory Access (DMA) type of data transfer. The DMA controller

place a high on HOLD pin in order to take control of the system bus.

The HOLD request is acknowledged by the 8085 by driving all its

tristated pins to high impedance state and asserting HLDA signal high.

20. What is a flag? List the flags of 8085.

Flag is a flip flop used to store the information about the status

of the processor and the status of the instruction executed most

recently.

There are five flags in 8085. They are sign flag, zero flag,

Auxiliary carry flag, parity flag and carry flag.

21. Define mnemonics.

The short-hand form of describing the instructions are called

mnemonics. The mnemonics are given by the manufacturers of

microprocessors and programmable devices.

22. What is processor cycle (Machine cycle) ,Instruction cycle, fetch and

execute cycle?

The processor cycle or machine cycle is the basic operation

performed by the processor. To execute an instruction, the processor

will run one or more machine cycles in a particular order.I

The sequence of operations that a processor has to carry out

while executing the instruction is called Instruction cycle. Each

instruction cycle of a processor in tum consists of a number of

machine cycles.

In general, the instruction cycle of an instruction can be

divided into fetch and execute cycles. The fetch cycle is executed to

fetch the opcode from memory. The execute cycle is executed to

decode the instruction and to perform the work instructed by the

instruction.

23. List the various machine cycles of 8085

The various machine cycles of8085 are

(i) Opcode fetch cycle

(ii) Memory read cycle

(iii) Memory write cycle

(iv) I/0 read cycle

(v) I/0 write cycle

(vi) Interrupt acknowledge cycle

(vii) Bus idle cycle.

24. What is the need for timing diagram?

The timing diagram provides information regarding the status

of various signals, when a machine cycle is executed. The knowledge

of timing diagram is essential for system designer to select matched

peripheral devices like memories, latches, ports, etc., to form a

microprocessor system.

25. What is T -state?

The T-state is the time period of the internal clock signal of the

processor. The time taken by the processor to execute the machine

cycle is expressed in T-state.

26. Define opcode and operand.

Opcode (Operation code) is the part of an instruction / directive

that identifies a specific operation.

Operand is a part of an instruction / directive that represents

a value on which the instruction acts.

27. What is addressing? What are the various addressing modes

available in 8085?

The method of specifying the data to be operated by the

instruction is called addressing.

The 8085 has the following five different types of addressing.

1. Immediate addressing

2. Direct addressing

3. Register addressing

4. Register indirect addressing

5. Implied addressing

28. What is meant by memory mapping? What is memory access time ?

The memory mapping is the process of interfacing memories

to microprocessor and allocating addresses to each memory

locations. The memory access time is the time taken by the

processor to read or write a memory location. During read

operation it is the time between a valid address on the bus and end

of read control signal. During write operation it is the time

between a valid address on the bus and the end of write control

signal.

28. Compare the memory mapped I/0 and standard I/0 mapped I/0.

Memory Mapped 1/0 Standard 1/0 mapped 1/0

1. 16-bit address is allotted to 1. 8 -bit address is allotted to an I/O

an I/O device device.

2. The devices are accessed by 2. The devices are accessed by

I/O read or I/O write cycle. memory read or memory write

cycle.

3. All instructions related to 3. Only IN and OUT instructions

memory can be used for can be used for data transfer

data transfer.

4 . A large number of I/O ports 4. Only 256 ports can be interfaced.

can be interfaced.

29. What is an Interrupt ? Haw the interrupt are classified ?

Interrupt is a signal send by an external device to the processor

so as to request the processor to perform a particular task or work.

They are three methods of classifying interrupts

Method I :The interrupts are classified into Hardware and

Software interrupts

Method II:The interrupts are classified into vectored and

Non- Vectored interrupt

30. What is Vectored and Non- Vectored interrupt?

When an interrupt is accepted, if the processor control

branches to a specific address defined by the manufacturer then the

interrupt is called vectored interrupt.

In Non-vectored interrupt there is no specific address

for storing the interrupt service routine. Hence the interrupted device

should give the address of the interrupt service routine.

31. List the Software and Hardware interrupts of 8085 ?

Software interrupts :

RST 0, RSTl, RST 2,

RST 3, RST 4, RST 5,

RST 6 and RST 7.

Hardware interrupts:

TRAP, RST 7.5, RST 6.5,

RST 5.5 and INTR.

32. What is Polling ? What are the different types of Polling?

Polling is a scheme or an algorithm to identify the devices

interrupting the processor. Polling is employed when multiple

devices interrupt the processor through one interrupt pin of the

processor.

The polling can be classified into software and hardware

polling. In software polling the entire polling process is govern by a

prograrn.1n hardware polling, the hardware takes care of checking

the status of interrupting devices and allowing one by one to the

processor.

33. Write 8085 assembly language instructions to store the contents of the

flag register in memory location 2000H.

PUSH PSW POP B MOV A,C STA 2000H. HLT

34. Draw the flow chart of a counter.

No Is this

Final

Count

Yes

35. Write an 8085 program to generate a time delay of 0.4sec given

crystal frequency 5MHZ.

Operating frequency = 5/2 = 2.5MHZ.

Time for one T-state = 1/ 2.5MHZ = 0.4msec.

Number of T-states required = Required Time/Time for 1T-state

= 0.4sec/ 0.4msec

= 1 x 106

Initialize

Display Update

Delay program:

LXI B,COUNT

Loop : DCX B

MOV A,C

ORA B

JNZ Loop

1 x 106 = 10 + (count – 1) x24 +21

count = 4166610

= A2C2H.

36. What is masking and why it is required?

Masking is preventing the interrupt from disturbing the current

program execution. When the processor is performing an

important job (process) and if the process should not be

interrupted then all the interrupts should be masked or disabled.

In processor with multiple 'interrupts, the lower priority interrupt

can be masked so as to prevent it from interrupting, the execution

of interrupt service routine of higher priority interrupt.

37. When the 8085 processor accept hardware interrupt?

The processor keeps on checking the interrupt pins at the second T

-state of last Machine cycle of every instruction. If the processor

finds a valid interrupt signal and if the interrupt is unmasked and

enabled then the processor accepts the interrupt. The acceptance

of the interrupt is acknowledged by sending an OOA signal to the

interrupted device.

38. When the 8085 processor will disable the interrupt system?

The interrupts of 8085 except TRAP are disabled after anyone of the

following operations

1. Executing El instruction.

2. System or processor reset.

3. After reorganization (acceptance) of an interrupt.

39. How the vector address is generated for the INTR interrupt of 8085?

For the interrupt INTR, the interrupting device has to place either RST

opcode or CALL opcode followed by l6-bit address. I~RST opcode is

placed then the corresponding vector address is generated by the

processor. In case of CALL opcode the given l6-bit address will be the

vector address.

40. How clock signals are generated in 8085 and what is the frequency of

the internal clock?

The 8085 has the clock generation circuit on the chip but an

external quartz crystal or L C circuit or RC circuit should be

connected at the pins XI and X2. The maximum internal clock

frequency of 8085A is 3.03 MHz.

1. What are the modes in which 8086 can operate?

The 8086 can operate in two modes and they are minimum ( or

uniprocessor) mode and maximum ( or multiprocessor) mode.

2 .What are the interrupts of 8086?

The interrupts of 8085 are INTR and NMI. The INTR is general

maskable interruput and NMI is non-maskable interrupt.

.

3. How clock signal is generated in 8086? What is the maximum internal

clock frequency of 8086?

The 8086 does not have on-chip clock generation circuit. Hence

the clock generator chip, 8284 is connected to the CLK pin of8086.

The clock signal supplied by 8284 is divided by three for internal use.

The maximum internal clock frequency of8086 is 5MHz.

4. What is pipelined architecture?

In pipelined architecture the processor will have number of

functional units and the execution time of functional units are

overlapped. Each functional unit works independently most of the

time.

5. What are the functional units available in 8086 architecture?

The bus interface unit and execution unit are the two functional

units available in 8086 architecture.

6. List the segment registers of 8086.

The segment registers of 8086 are Code segment, Data

segment, Stack segment and Extra segment registers.

7. What is the difference between segment register and general purpose register?

The segment registers are used to store 16 bit segment base

address of the four memory segments. The general purpose registers

are used as the source or destination register during data transfer and

computation, as pointers to memory and as counters.

8. What is queue? How queue is implemented in 8086?

A data structure which can be accessed on the basis of fIrst in

fIrst out is called queue. The 8086 has six numbers of 8-bit FIFO

registers, which is used for instruction queue.

9. Write the special functions carried by the general purpose registers of

8086.

The special functions carried by the registers of 8086 are the

following.

Register Special function

AX 16-bit Accumulator

AL 8-bit Accumulator

BX Base Register

CX Count Register

DX .Data Register

10. Write the flags of 8086.

The 8086 has nine flags and they are

1. Carry Flag (CF) 6. Overflow Flag (OF)

2. Parity Flag (PF) 7. Trace Flag (TF)

3. Auxiliary carry Flag (AF) 8. Interrupt Flag (IF)

4. Zero Flag (ZF) 9. Direction Flag (DF)

5. Sign Flag (SF)

11. What are control bits?

The flags TF, IF and DF of8086 are used to control the

processor operation and so they are called control bits.

12. Describe the difference between the instructions MOV AX,2437H and

MOV AX,[2437H].

Difference between the instructions MOV AX,2437H

and MOV AX,[2437H] are former instruction takes 2437 as 16-bit

data and latter instruction takes 2437 as 16-bit address.

13. State the function of Direction flag in 8086.

Direction flag is used with string instructions. If DF= 0, the string is

processed from its beginning with the first element having the lowest

address. Otherwise, the string is processed from the high address towards the

low address.

14. In 8086 processor the code segment contains 4000H and instruction

pointer contains 9F20H. Find the memory location addressed by the

processor.

Segment address 4000 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0

Shifted to left by 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

four bits + Offset address 1 0 0 1 1 1 1 1 0 0 1 0 0 0 0 0 0 1 0 0 1 0 0 1 1 1 1 1 0 0 1 0 0 0 0 0 Physical address 49F20H

15. Mention the three operating modes of Intel 80386 processor.

i. Real Mode.

ii. Protected Mode.

iii. Virtual 8086 Mode.

16. What happens in 8086 processor, when

a. overflow of sum occurs during addition of signed numbers.

b. overflow of quotient occurs during division operation.

a. When overflow of sum occurs during addition of signed numbers,

overflow flag is set to one (OVF =1).

b. When overflow of quotient occurs during division operation, type

0 (divide by zero ) interrupt is generated.

17. Discuss the functions of the following prefixes:

LOCK, ESCAPE

LOCK :

In a multiprocessor system each microprocessor has its own

local buses and memory. The individual microprocessors are

connected together by a system bus so that each can access system

resources such as disk drives or memory. Each microprocessor only

takes control of the system bus when it needs to access some system

resources. The LOCK prefix allows a microprocessor to make sure

that another processor does not take control of the system bus while it

is in the middle of a critical instruction which uses the system bus.

ESCAPE:

This instruction is used to pass instructions to a coprocessor

such as the 8087 math coprocessor which shares the address and data

bus with an 8086.

18. What are the flag manipulation instructions of 8086.

59. LAHF : Load AH from low byte of flag register.

60. SAHF : Store AH to low byte of flag register

61. PUSHF : Push content of flag to the stack.

62. POPF : Pop content of stack and load it in the

flag register.

19.Give the contents of the flag register after execution of following

addition.

0 1 1 0 0 1 0 1 1 1 0 1 0 0 0 1 + 0 0 1 0 0 0 1 1 0 1 0 1 1 0 0 1

1 0 0 0 1 0 0 1 0 0 1 0 1 0 1 0 SF = 1, ZF = 0, PF = 1, CF = 0, AF = 0, OF=1.

1. What are the three groups of signals in 8086 ?

The 8086 signals are categorized in three groups. They are :

i. The signals having common function in minimum and maximum

mode.

ii. The signals having special functions for minimum mode,

iii. The signals having special functions for maximum mode.

2. What are the uses of AD0 – AD15 lines ?

These are the time multiplexed memory 15 address and data lines.

Address remains on the line during T I state ,while data is available on the

data bus during T2, T3, TW and T4. Here Ti' T2, T3, T4 and Tw are the

clock states of a machine , cycle. Tw is a wait state. These lines are active

high and float to a tristate during interrupt acknowledge and local bus hold

acknowledge cycles.

3. What is the operation of RD signal ?

Read signal RD when low, indicates the peripherals that the processor is

performing a memory (or) I/O read operation.

4. What is the function of READY signal?

This is the acknowledgment from the slow devices (or) memory that

they have completed the data transfer. The signal made available by the

devices is synchronized by the 8284A clock generator to provide ready

input to the 8086. The signal is active high.

5.What is the function of INTR signal ?

INTR- Interrupt Request: This is a level triggered input. This is

sampled during the last clock cycle of each instruction to determine

the availability of the request, If any interrupt request is pending, the

processor enters the interrupt acknowledge cycle. This can be

internally masked by resetting he interrupt enable flag. This signal is

active high and 1ternally synchronized.

6. What is the operation performed when TEST .input in low ?

If the TEST input goes low, execution will continue, else, the processor

remains in an idle state. The input is synchronized internally during each

clock cycle on leading edge of clock.

7. What is the purpose of ALE signal in minimum mode?

ALE -Address Latch Enable: This output signal indicates the

availability of the valid address on the address / data lines, and is

connected to latch enable input of latches. This signal is active high and is

never tristated.

8. What is the function of RESET pin ?

RESET input causes the processor to terminate the current activity and start

execution from FFFFOH. This signal is active high and must be active for at

least four clock cycles. It restarts execution when the RESET return low.

RESET is also internally synchronized.

9. What is the function of DEN signal in minimum mode ?

This signal indicates the availability of valid data over the address /

data lines. It is used to enable the Transceivers to separate the data from

the multiplexed address / data signal.It is active from the middle of T2

until the middle of T4 DEN is tristated during hold acknowledge

cycle.

10. What are the differences between maximum mode and minimum mode

Minimum mode Maximum mode

1 A processor is in minimum mode when MN /MX pin is strapped to +5v

A processor is in maximum mode when MN /MX is grounded

2. All control signals are given out by. microprocessor chip it self

The processor derive the status signals S2, Sl and So. Another chip called bus controller derives control signals using this status information

3. There is a single micro processor

There may be more than one microprocessor

11. What is the fabrication technology used for 8086?

The 8086 is fabricated using the HMOS (High density n-type metal

oxide silicon field effect transistors) technology and contains

approximately 29,000 transistors. The 8086 packed in a 40 pin DIP and

requires a single 5V supply.

12. What is multimicro-processor architecture ?

The maximum clock frequency at which a system operate may be

considered as one of the measure of the processor capability of the system.

An appropriate system involving several microprocessors connected using a

certain topology ma provide high processing capacity. The study of such a

system known as multi micro processor architecture.

13. What are the functional parts of simple multi micro processor system ?

The simplest type of multimicroprocessor system is one containing a

CPU and a numeric data processor (NDP) and/or an Input / Output

processor (IOP).

14. Give the interconnection topology classification oj multiprocessor

system.

Some of the interconnection topologies are: (Based on he mode of

communication)

i. Shared bus

ii. Linked Input I Output

iii. Multiport memory

Based on the physical interconnections between the processors:

i. Star configuration

ii. Loop configuration

iii. Complete interconnection

iv. Regular topologies

v. Irregular topologies.

15. What is the fabrication technology used for 8087 (NDP) ?

Numeric processor packed in a 40 pin ceramic DIP package, it is

available in 5MHZ, 8MHZ and 10MHZ versions compatible with 8086,

8088, 80186 and 80188 processors.

16. What is meant by numeric processor ?

.The numeric processor 8087 is a coprocessor which has been designed to

work under the control of the processor 8086 and offer it additional numeric

processing capabilities.

17. What are the functional parts of coprocessor ?

The 8087 is divided into two sections internally. They are :

i. Control Unit (CU)

ii. Numeric Extension Unit (NEU)

18. What is the purpose of control unit ?

The control unit is mainly responsible for establishing communication

between the CPU and memory and also for co-coordinating the internal co-

processor execution.

19. What is the function of INT pin in 8087 ?

The interrupt output is used by 8087 to indicate that an unmasked

exception has been received during execution. This is usually handled by

8259A.

20. What is the function of busy signal in 8087 ?

This output signal, when high, indicates to the CPU that it is busy with

the execution of an allotted instruction. This is usually connected to the

TEST pin of 8086/8088.

21. Give the register classification of 8087.

In 8087 registers are divided into three fields.

They are: (i) sign (1 bit) (ii) exponent ( 15 bits)

(iii) significant (64 bit)

22. What is the use of instruction and data pointer (8087)?

The instruction and data pointers are used to enable the programmers

to write their own exception handling subroutines.

23. What is the. use of control word register (8087) ?

The control word register of 8087 allows the programmer to select the

required processing options out of available ones. In other words, the

16-bit control word register is used to control the operation of the

8087.

24. Give the additional instructions supported by 8087.

The additional instructions supported by 8087 can be categorized into the

following types.

i. Data transfer instruction

ii. Arithmetic instructions

iii. Comparison instructions

iv. Transcendental operations

v. Constant operations

vi. Coprocessor control operation.

25. Give the classification of multimicroprocessor system.

The multimicroprocessor systems are also classified as tightly

(closely) coupled or loosely coupled systems, depending upon whether the

microprocessor share a common memory and common system bus or not

26. Explain the tightly coupled (closely coupled) system.

!n a tightly coupled system. the microprocessor (either coprocessor or

independent processors) may share a common clock and bus control logic

The two processors in a closely coupled system may communicate using a

common system bus or common memory The microprocessor in a closely

coupled system either uses a status bit in memory (or) interrupt the host to

inform it about the completion of the task allotted to it

Explain the loosely coupled multiprocessor system

In a loosely coupled multiprocessor system. on the other hand. each

CPU may have its own bus control logic The bus arbitration is handled by

an external circuit. Common to all the processor The loosely coupled

system configurations like LAN and WAN can be spreaded over a large

area

27. Give the advantage of loosely coupled system over the tightly coupled

system.

The loosely coupled system have the following advantage over the

tightly coupled system,

i. More number of CPUs can be added in a loosely coupled system to

improve the system performance.

ii. The system structure is modular and hence easy to maintain and

troubleshoot.

iii. A fault in a single module does not lead to a complete system

breakdown.

iv. Due to the independent processing modules used in

the system, it is more fault -tolerant.

v. More suitable to parallel applications due to its modular organization.

1. What is the need for interrupt controller?

The interrupt controller is employed to expand the interrupt

inputs. It can handle the interrupt request from various devices and

allow one by one to the processor.

2. List some of the features of INTEL 8259 (Programmable Interrupt

Controller )

i) It manage eight interrupt request.

ii) The interrupt vector addresses are programmable.

iii) The priorities of interrupts are programmable.

iv) The interrupt can be masked or unmasked individually.

3. Write the various functional blocks of INTEL 8259 ?

The various functional blocks of 8259 are

Control logic, Read/ Write logic, Data bus buffer, IRR, ISR,

IMR, Priority resolver and cascade buffer

IRR - Interrupt Request Register

ISR - In-Service Register

IMR Interrupt Mask Register,

4. What is Master and Slave 8259 ?

When 8259's are connected in cascade, one 8259 will be

directly interrupting 8085 and it is called master 8259, To each

interrupt request input of master 8259, one slave 8259 can be

connected, The 8259 's interrupting the master 8259 are called slave

8259.

5. How 8259 is programmed?

The 8259 is programmed by sending

i) Initialization Command Words (ICWs) and

ii)Operational Command Words (OCWs).

6. What is a programmable peripheral device ?

If the functions performed by a peripheral device can be altered

or changed by a program instruction then the peripheral device is

called programmable device. Usually the programmable devices will

have control registers. The device can be programmed by sending

control word in the prescribed format to the control register.

7. What is handshake port ? Explain the working of a handshake input port

and output port.

In handshake port, signals are exchanged between I/O device

and port or port and processor for checking or informing various

condition of the device.

In handshake input operation, the input device will check whether the

port is empty or not. If the port is empty then it will load data to port.

When the port receives the data, it will inform the processor for read

operation. Once the data have been read by the processor, the port will

signal the input device that it is empty. Now the input device can load

another data to port and the above process is repeated.

In handshake output operation, the processor will load a data

to port. When the port receives the data, it will inform the output

device to collect the data. Once the output device accepts the data,

the port will inform the processor that it is empty. Now the

processor can load another data to port and the above process is

repeated.

8. What are the internal devices of 8255 ?

The internal devices of 8255 are port-A, port-B and port-C.

The ports can be programmed for either input or output function in

different operating modes.

9. What are the operating modes of port -A 8255?

The port-A of 8255 can be programmed to work in anyone of

the following operating modes as input or output port.

Mode-0 : Simple 1/0 port.

Mode-l: Handshake 1/0 port

Mode-2 : Bidirectional 1/0 port

10. What are the functions performed by port-C of8255?

1. The port-C pins are used for handshake signals.

2. Port-C can be used as an 8-bit parallel 1/0 port in mode-0.

3. It can be used as two numbers of 4-bit parallel port in mode-0.

4. The individual pins of port-C can be set or reset for various control

applications.

11. What are the different scan modes of of8279?

The different scan modes of8279 are decoded scan and encoded

scan. In decoded scan mode, the output of scan lines will be similar to

a 2-to-4 decoder. In encoded scan mode, the output of scan lines will

be binary count, and so an external decoder should be used to convert

the binary count to decoded output.

!

12. What is baud rate ?

The baud rate is the.rate at which the serial data are transmitted.

Baud rate is defined as l/(The time for a bit cell). In some systems one

bit cell has one data bit, then the baud rate and bits/sec are same.

13 . What is USART ? What are the functions performed by INTEL 8251A?

The device which can be programmed to perform Synchronous

or Asynchronous serial communication is called USART (Universal

Synchronous Asynchronous Receiver Transmitter). The INTEL

8251A is an example of USART.

The INTEL 825lA is used for converting parallel data to serial

or vice versa. The data transmission or reception can be either

asynchronously or synchronously. The 8251A can be used to interface

MODEM and establish serial communication through MODEM over

telephone lines.

14 . What are the control words of 8251A and what are its functions ?

The control words of 8251A are Mode word and Command

word. The mode word informs 8251 about the baud rate, character

length, parity and stop bits. The command word can be send to

enable the data transmission and reception.

15. What is debouncing ?

When a key is, pressed it bounces for a short time. If a key

code is generated immediately after sensing a key actuation, then the

processor will generate the same keycode a number of times.(A key

typically bounces for 10 to 20 msec). Hence the processor has to wait

for the key bounces to settle before reading the keycode. This process

is called keyboard debouncing.

16. What is the difference in programming the 8279 for encoded scan and

decoded scan?

If the 8279 is programmed for decoded scan then the output of

scan lines will be decoded output and if it is programmed for,

encoded scan then the output of scan lines will be binary count. In

encoded mode, an external decoder should be used to decode the scan

lines.

17. What are the different types of ADC?

The different types of ADC are successive approximation

ADC, counter type ADC flash type ADC, integrator converters and

voltage-to-frequency converters.

18. What is DMA Controller?

Direct Memory Access is an I/O technique used for high speed

data transfer. In DMA, the MPU releases the control of the buses to a

device called a DMA controller. The controller manages data transfer

between memory and a peripheral under its control, thus bypassing

the MPU.

19. Explain the function of the signal ADSTB in DMA controller?

The 8257 has eight address lines, but requires 16 address lines to

address a memory location. The additional eight lines are generated

by using the signal ADSTB to strobe a high-order memory address

into the 8212 from the data bus.

20. Explain the function of inservice register, masking register and

interrupt request register of 8259?

Inservice Register: ISR stores all the levels that are currently being

serviced.

Masking Register: IMR stores the masking bits of the interrupt lines

to be masked.

Interrupt Request Register: IRR stores the interrupt request , when

interrupt request lines goes high.

21. What is a Simulator?

Simulator is a debugging tool used for microcomputer based

system. The simulator program shows all internal registers, entire

memory and peripheral on the monitor. The simulator is supported

with single step and breakpoint facilities which help user to debug

their programs

22. How DMA is initiated?

When the I/O device needs a DMA transfer, it will send a

DMA request signal to DMA controller. The DMA controller in turn

sends a HOLD request to the processor. When the processor receives

a HOLD request, it will drive its tri-stated pins to high impedance

state at the end of current instruction execution and send an

acknowledge signal to DMA controller. Now the DMA controller

will perform DMA transfer.

23. What is scanning in keyboard and what is scan time?

The process of sending a zero to each row of a keyboard matrix and

reading the columns for key actuation is called scanning. The scan time

is the time taken by the processor to scan all the rows one by one

starting from first row and coming back to the first row again.

24 What is synchronous data transfer scheme?

For synchronous data transfer scheme, the processor does not check the

readiness of the device after a command have been issued for

read/write operation. fu this scheme the processor will request the

device to get ready and then read/W1.ite to the device immediately

after the request. In some synchronous schemes a small delay is

allowed after the request.

25. What is asynchronous data transfer scheme?

In asynchronous data transfer scheme, first the processor sends a

request to the device for read/write operation. Then the processor

keeps on polling the status of the device. Once the device is ready, the

processor execute a data transfer instruction to complete the process.

26. What is the need for Port?

The I/O devices are generally slow devices and their timing

characteristics do not match with processor timings. Hence the I/O

devices are connected to system bus through the ports

27. List some of the features of INTEL 8259 (Programmable Interrupt

Controller)

1. It manage eight interrupt request

2. The interrupt vector addresses are programmable.

3. The priorities of interrupts are programmable.

The interrupt can be masked or unmasked individually

28. What are the functions performed by INTEL 8251A?

The INTEL 825lA is used for converting parallel data to serial

or vice versa. The data transmission or reception can be either

asynchronously or synchronously. The 8251A can be used to

interface MODEM and establish serial communication through

MODEM over telephone lines

29. What are the information that can be obtained from the status word of

8251 ?

The status word can be read by the CPU to check the readiness of the

transmitter or receiver and to check the character synchronization in

synchronous reception. It also provides information regarding various

errors in the data received. The various error conditions that can be

checked from the status word are parity error, overrun error and

framing error.

30. What are the tasks involved in keyboard interface?

The task involved in keyboard interfacing are sensing a key actuation,

Debouncing the key and Generating key codes (Decoding the key).

These task are performed software if the keyboard is interfaced

through ports and they are performed by hardware if the keyboard is

interfaced through 8279.

31. How a keyboard matrix is formed in keyboard interface using 8279?

The return lines, RLo to RL7 of 8279 are used to form the columns of

keyboard matrix. In decoded scan the scan lines SLo to SL3 of 8279

are used to form the rows of keyboard matrix. In encoded scan mode,

the output lines of external decoder are used as rows of keyboard

matrix

32. . What is scanning in display and what is the scan time?

In display devices, the process of sending display codes to 7 -segment

LEDs to display the LEDs one by one is called scanning ( or

multiplexed display). The scan time is the time taken to display all the

7-segment LEDs one by one, starting from first LED and coming back

to the first LED again.

33. What is settling or conversion time in DAC?

The time taken by the DAC to convert a given digital data to

corresponding analog signal is called conversion time.

34. What are the different types of ADC?

The different types of ADC are successive approximation ADC,

counter type ADC flash type ADC, integrator converters and voltage-

to-frequency converters.

35. How the microprocessor is synchronized with peripherals?

The timing and control unit synchronizes all the microprocessor

operations with clock and generates control signals necessary for

communication between the microprocessor and peripherals.

1. What is mean by microcontroller?

A device which contains the microprocessor with

integrated peripherals like memory, serial ports, parallel ports,

timer/counter, interrupt controller, data acquisition interfaces like

ADC,DAC is called microcontroller.

2. Explain DJNZ instructions of intel 8051 microcontroller?

a. DJNZ Rn, rel

Decrement the content of the register Rn and jump if not

zero.

b. DJNZ direct , rel

Decrement the content of direct 8-bit address and jump if

not zero.

3. Explain the contents of the accumulator after the execution ot the

following program segments:

MOV A,#3CH

MOV R4,#66H

ANL A,R4

A 3C R4 66 A 24

4. State the function of RS1 and RS0 bits in the flag register of intel 8051

microcontroller?

RS1 , RS0 – Register bank select bits

RS1 RS0 Bank

Selection

0

0

1

1

0

1

0

1

Bank 0

Bank 1

Bank 2

Bank 3

5. Write a program using 8051 assembly language to change the date

55H stored in the lower byte of the data pointer register to AAH using

rotate instruction.

MOV DPL,#55H

MOV A, DPL

RL A

Label :SJMP Label

6. Give the alternate functions for the port pins of port3?

RD WR T1 T0 INT1 INT0 TXD RXD

RD – Read data control output.

WR – Write data control output.

T1 – Timer / Counter1 external input or test pin.

T0 – Timer / Counter0 external input or test pin.

INT1- Interrupt 1 input pin.

INT 0 – Interrupt 0 input pin.

TXD – Transmit data pin for serial port in UART mode.

RXD - Receive data pin for serial port in UART mode.

7. Specify the single instruction, which clears the most significant bit of

B register of 8051, without affecting the remaining bits.

Single instruction, which clears the most significant bit of B

register of 8051, without affecting the remaining bits is CLR B.7.

8. Explain the function of the pins PSEN and EA of 8051.

PSEN :

PSEN stands for program store enable. In 8051 based

system in which an external ROM holds the program code, this pin is

connected to the OE pin of the ROM.

EA :

EA stands for external access. When the EA pin is

connected to Vcc, program fetched to addresses 0000H through

0FFFH are directed to the internal ROM and program fetches to

addresses 1000H through FFFFH are directed to external

ROM/EPROM. When the EA pin is grounded, all addresses fetched

by program are directed to the external ROM/EPROM.

9. Explain the 16-bit registers DPTR and SP of 8051.

DPTR:

DPTR stands for data pointer. DPTR consists of a high

byte (DPH) and a low byte (DPL). Its function is to hold a 16-

bit address. It may be manipulated as a 16-bit data register or as

two independent 8-bit registers. It serves as a base register in

indirect jumps, lookup table instructions and external data

transfer.

SP:

SP stands for stack pointer. SP is a 8- bit wide register. It

is incremented before data is stored during PUSH and CALL

instructions. The stack array can reside anywhere in on-chip

RAM. The stack pointer is initialized to 07H after a reset. This

causes the stack to begin at location

08H.

10. Name the special functions registers available in 8051.

a. Accumulator

b. B Register

c. Program Status Word.

d. Stack Pointer.

e. Data Pointer.

f. Port 0

g. Port 1

h. Port 2

i. Port 3

j. Interrupt priority control register.

k. Interrupt enable control register.

11. Write down the different operating modes for serial communication of

8051.

Serial communication of 8051 operate under four modes. They

are mode 0 , mode 1, mode 2 and mode3 .SM0 and SM1 bits of

SCON register specifies the mode.

SM0 SM1 Mode

0 0 0 Baud rate fixed.

0 1 1 8-bit data, 1 stop bit, 1 start bit. Baud rate variable.

1 0 2 8-bit data, 9th programmable bit,1 stop bit, 1 start bit, Baud rate fixed. 1 1 3 8-bit data, 9th programmable bit,1 stop bit, 1 start bit, Baud rate variable.

12. Explain the register IE format of 8051.

EA - ET2 ES ET1 EX1 ET0 EX0

EA- Enable all control bit. ET2- Timer 2 interrupt enable bit. ES – Enable serial port control bit. ET1 – Enable Timer1 control bit. EX1- Enable external interrupt1 control bit. ET0 – Enable Timer0 control bit. EX0- Enable external interrupt0 control bit.

13. Compare Microprocessor and Microcontroller.

Sl.

No

Microprocessor Microcontroller

1 Microprocessor contains

ALU,general purpose

registers,stack pointer,

Microcontroller contains the

circuitry of microprocessor and in

addition it has built- in ROM,

program counter, clock

timing circuit and interrupt

circuit.

RAM, I/O devices, timers and

counters.

2 It has many instructions to

move data between memory

and CPU.

It has one or two instructions to

move data between memory and

CPU.

3 It has one or two bit handling

instructions.

It has many bit handling

instructions.

4 Access times for memory and

I/O devices are more.

Less access times for built-in

memory and I/O devices.

5 Microprocessor based system

requires more hardware.

Microcontroller based system

requires less hardware reducing

PCB size and increasing the

reliability.

14. Name the five interrupt sources of 8051?.

The interrupts are:

Vector address

· External interrupt 0 : IE0 : 0003H

· Timer interrupt 0 : TF0 : 000BH

· External interrupt 1 : IE1 : 0013H

· Timer Interrupt 1 : TF1 : 001BH

· Serial Interrupt

Receive interrupt : RI : 0023H

Transmit interrupt: TI : 0023H

15. Write a program to load accumulator A, DPH and DPL with 30H.

MOV A,#30

MOV DPH,A

MOV DPL,A

16. Write a program to subtract the contents of R1 of Bank0 from the

contents of R0 of Bank2.

MOV PSW,#10

MOV A,R0

MOV PSW,#00

SUBB A,R1

17.How the RS -232C serial bus is interfaced to TTL logic device ?

The RS-232C signal voltage levels are not compatible with

TTL logic levels. Hence for interfacing TTL devices to RS-

232C serial bus, level converters are used. The popularly used

level converters are MC 1488 & MC 1489 or MAX 232.

18. List some of the features of 8096 microcontroller.

a. The 8096 is a 16-bit microcontroller.

b. The 8096 is designed to use in applications which require high

speed calculations and fast I/O operations.

c. The high speed I/O section of an 8096 includes a 16 bit timer, a

16 bit counter, a 4 input programmable edge detector, 4

software timers and a 6-output programmable event generator.

d. It has 100 instructions, which can operate on bit,byte,word

,double words.

e. The bit operations are possible and these can be performed on

any bit in the register file or in the special function register.

19. What is HS0 of 8096?

HS0:

The High Speed Output unit (HS0) is used to

trigger events at specific times with minimal CUP

overhead. These events include : starting an A to D

conversion, resetting Timer2, setting 4 software flags,

and switching up to 6 output lines.

20. List the features of 8051 microcontroller?

The features are

*single_supply +5 volt operation using HMOS technology.

*4096 bytes program memory on chip(not on 8031)

*128 data memory on chip.

*Four register banks.

*Two multiple mode,16-bit timer/counter.

*Extensive boolean processing capabilities.

*64 KB external RAM size

*32 bidirectional individually addressible I/O lines.

*8 bit CPU optimized for control applications.

21 .Explain the operating mode0 of 8051 serial ports?

In this mode serial enters &exits through RXD, TXD outputs

the shift clock.8 bits are transmitted/received:8 data bits(LSB first).The

baud rate is fixed at 1/12 the oscillator frequency.

22. Explain the operating mode2 of 8051 serial ports?

In this mode 11 bits are transmitted(through TXD)or received

(through RXD):a start bit(0), 8 data bits(LSB first),a programmable 9th data

bit ,& a stop bit(1).ON transmit the 9th data bit (TB* in SCON)can be

assigned the value of 0 or 1.Or for eg:, the parity bit(P, in the PSW)could be

moved into TB8.On receive the 9th d ata bit go in to the RB8 in Special

Function Register SCON, while the stop bit is ignored. The baud rate is

programmable to either 1/32or1/64 the oscillator frequency.

23. .Write A program to perform multiplication of 2 nos using 8051? MOV A,#data 1 MOV B,#data 2 MUL AB MOV DPTR,#5000 MOV @DPTR,A(lower value) INC DPTR MOV A,B MOVX @ DPTR,A 24. Write a program to mask the 0th &7th bit using 8051? MOV A,#data ANL A,#81 MOV DPTR,#4500 MOVX @DPTR,A LOOP SJMP LOOP

25.Write about CALL statement in 8051? There are two subroutine CALL instructions. They are

*LCALL(Long CALL)

*ACALL(Absolute CALL)

Each increments the PC to the 1st byte of the instruction & pushes them

in to the stack.

26. .Write about the jump statement? There are three forms of jump. They are

LJMP(Long jump)-address 16 AJMP(Absolute Jump)-address 11 SJMP(Short Jump)-relative address

27. .Write program to load accumulator ,DPH,&DPL using 8051?

MOV A,#30 MOV DPH,A MOV DPL,A

28.Write a program to find the 2’s complement using 8051? MOV A,R0 CPL A INC A 29.Write a program to add 2 8-bit numbers using 8051? MOV A,#30H ADD A,#50H 30.Write a program to swap two numbers using 8051? MOV A, #data SWAP A 31.Write a program to subtract 2 8-bit numbers &exchange the digits using 8051? MOV A,#9F

MOV R0,#40 SUBB A,R0 SWAP A 32.Write a program to subtract the contents of R1 of Bank 0from the contents of R0 of Bank 2 using 8051? MOV PSW,#10 MOV A,R0 MOV PSW,#00 SUBB A,R1

33. What is an Interrupt?

Interrupt is a signal send by an external device to the processor so as to

request the processor to perform a particular task or work

34. What is program counter? How is it useful in program execution?

The program counter keeps track of program execution. To execute a

program the starting address of the program is loaded in program counter.

The PC sends out an address to fetch a byte of instruction from memory

and increments its content automatically.

35. Define stack

Stack is a sequence of RAM memory locations defined by the programmer.

UNIT I

1. With neat sketch explain the architecture of 8085 Processor

Ø Block Diagram

Ø Registers Available

Ø Function Of Accumulator

Ø Explanation about all blocks in the block diagram

2.Draw the Pin Diagram of 8085 and explain the function of various

signals.

Ø Pin Diagram

Ø Explanation about all signals

3.List the various Instruction available in 8085 processor.

Ø Data Transfer Instructions

Ø Arithmetic Instructions

Ø Logical Instructions

Ø Branch Instructions

Ø Machine Control Instructions

4. Write a program to sort the numbers in ascending and descending order.

Ø Program

Ø Result Verification

5.Draw the timing diagram of the following Instructions

Ø PUSH

Ø IN Port A

Ø STA 5000

Ø MVI A, 08

Ø Explain the machine cycles needed for every Instructions and

draw the timing diagram

UNIT II

1.With neat sketch explain the architecture of 8086 processor.

Ø Block Diagram



signals.

Ø Pin Diagram


3.List the various Instruction available in 8086 processor.



Ø Bit Manipulation Instructions

Ø String Instructions

Ø Program Execution Transfer Instructions

Ø Processor Control Instructions

UNIT III

1.With neat sketch explain the architecture of 8086 in minimum mode.

Ø Block Diagram


2.With neat sketch explain the architecture of 8086 in maximum mode.

Ø Block Diagram


3. With neat sketch explain the architecture of 8087 coprocessor.

Ø Block Diagram


4.With neat sketch explain the architecture of 8089 I/O processor.

Ø Block Diagram


5.With neat sketch explain the multiprocessor configurations.

Ø Explanation about all Configurations

Ø Loosely Coupled and Tightly Coupled

UNIT IV

1.With neat sketch explain the functions of 8255 PPI.

Ø Block Diagram

Ø Explanation about all the ports available.

Ø Explanation about the modes of transfer

Ø Explain the control Word Register

2. With neat sketch explain the functions of 8251.

Ø Block Diagram

Ø Types of data transfer

Ø Explanation about all the blocks.

Ø Explain the control Word Register, Status Register

3. With neat sketch explain the function of DMA contoller.

Ø Block Diagram


4.With neat sketch explain the function of Programmable Interrupt

Controller.

Ø Block Diagram


5.With neat sketch explain the function of Keyboard and display

controller.

Ø Block Diagram

Ø Types of Display Available

Ø Types of keys available


6.With neat sketch explain the function of A/D converter.

Ø Fundamental steps

Ø Figure

Ø Explain the functions.

7.With neat sketch explain the function of D/A converter.

Ø Fundamental steps

Ø Figure

Ø Explain the functions.

UNIT V

1.With neat sketch explain the architecture of 8051 microcontroller.

Ø Block Diagram



signals.

Ø Pin Diagram


3.List the various Instruction available in 8051 microcontroller.



Ø Logical Instructions

Ø Boolean variable Manipulation Instructions

Ø Program and Machine Control Instructions

4. With neat sketch explain the architecture of 8096 microcontroller.

Ø Block Diagram



signals.

Ø Pin Diagram


Documents

CS1304-mp