Embedded Technosolutionsembeddedtechnosolutions.com/wp-content/uploads/...The Intel 8051 is an 8-bit microcontroller which means that most available operations are ... x List Out Addressing

Embedded Technosolutions

Venture of IIT Bombay & VJTI Alumni

We Are India’s one of the Leading Jobs & Training

Providing Organization

Government of India Registered & ISO

Certified Organization



8051 Microcontroller Revision

Introduction Of 8051 Microcontroller Architecture?

Answer :

In 1981, Intel Corporation introduced an 8-bit microcontroller called the 8051. The 8051

became widely popular after Intel allowed other manufacturers to make and market any

flavors of the 8051. They please with the condition that they remain code-compatible

with the 8051. This has led to many, versions of the 8051 with different speeds and

amounts of on-chip ROM marketed by more than half a dozen manufacturers. It is

important to note that although there are different flavors of the 8051 in terms of speed

and amount of on-chip ROM, they are all compatible with the original 8051 as far as the

instructions are concerned. This means that if you write your program for one, it will run

on any of them regardless of the manufacturer.

Intel 8051 Follows Which Architecture?

Answer :

Intel 8051 is Harvard Architecture.



What Is The Difference Between Harvard Architecture And Von

Neumann Architecture?

Answer :

The name Harvard Architecture comes from the Harvard Mark. The most obvious

characteristic of the Harvard Architecture is that it has physically separate signals and

storage for code and data memory. It is possible to access program memory and data

memory simultaneously. Typically, code (or program) memory is read-only and data

memory is read-write. Therefore, it is impossible for program contents to be modified by

the program itself.

The von Neumann Architecture is named after the mathematician and early computer

scientist John von Neumann. Von Neumann machines have shared signals and memory

for code and data. Thus, the program can be easily modified by itself since it is stored in

read-write memory.

8051 Was Developed Using Which Technology?

Answer :

Intel’s original MCS-51 family was developed using NMOS technology, but later

versions, identified by a letter C in their name (e.g., 80C51) used CMOS technology and

consume less power than their NMOS predecessors. This made them more suitable for

battery-powered devices.



Why 8051 Is Called 8 Bit Microcontroller?

Answer :

The Intel 8051 is an 8-bit microcontroller which means that most available operations are

limited to 8 bits.

What Is The Width Of Data Bus?

Answer :

8-bit data bus

What Is The Width Of Address Bus?

Answer :

16-bit address bus

List Out The Features Of 8051 Microcontroller?

Answer :

o 40 Pin IC.

o 128 bytes of RAM.

o 4K ROM.

o 2 Timers (Timer 0 and Timer 1).

o 32 Input/ Output pins.



o 1 serial port.

o 6 Interrupts (Including Reset).

What Location Code Memory Space And Data Memory Space

Begins?

Answer :

At location 0x00 for internal or external memory

How Much On Chip Ram Is Available?

Answer :

128 bytes of RAM (from 0x00 to 0x7F) and can be used to store data

List Out Addressing Modes In Mcs-51?

Answer :

o Direct Addressing

o Register Addressing

o Register Indirect Addressing

o Implicit Addressing

o Immediate Addressing

o Index Addressing



How Much Total External Data Memory That Can Be

Interfaced To The 8051?

Answer :

64K data memory

What Is Special Function Registers (sfr)?

Answer :

The memory addresses from 80H to 0FFH are called SFR. These are 128 bytes registers

specially designed for interrupts and few other operations.

Give Example Of Bit Address And Byte Address?

Answer :

Example: bit address 87h –> byte address 80h, bit #7

What Are The Types Of Interrupts In 8051?

Answer :

o External interrupt 0 (IE0) has highest priority among interrupts.

o Timer interrupt 0 (TF0)

o External interrupt 1 (IE1)



o Timer interrupt 1 (TF1) has lowest priority among other interrupts.

o Serial port Interrupt

o Reset.

What Are The Four Distinct Types Of Memory In 8051?

Answer :

o Internal RAM

o Special function registers

o Program memory

o External data memory

Tell The Addresses Which Are Bit Addressable?

Answer :

The bit addressable memory in 8051 is compose from 210 bits: bit address space: 20H –

2FH bytes RAM = 00H – 7FH bits address, SFR registers.

What Is Lst File?

Answer :

o This file is also called as list file.

o It lists the opcodes, addresses and errors detected by the assembler.



o List file is produced only when indicated by the user.

o It can be accessed by an editor and displayed on monitor screen or printed.

Programmer uses this file to find the syntax errors and later fix them.

Explain Db.?

Answer :

o DB is called as define byte used as a directive in the assembler.

o It is used to define the 8 bit data in binary, hexadecimal or decimal formats.

o It is the only directive that can be used to define ASCII strings larger than two

characters.

o DB is also used to allocate memory in byte sized chunks.

o The assembler always converts the numbers into hexadecimal.

What Is Equ?

Answer :

o EQU is the equate assembler directive used to define a constant without

occupying a memory location.

o It associates a constant value with data label.

o Whenever the label appears in the program, constant value is substituted for label.



o Advantage: The constant value occurring at various positions in a program can be

changed at once using this directive.

o Syntax: label EQU constant value

How Are Labels Named In Assembly Language?

Answer :

o Label name should be unique and must contain alphabetic letters in both

uppercase and lowercase.

o 1st letter should always be an alphabetic letter.

o It can also use digits and special characters?,.,@,_,$.

o Label should not be one of the reserved words in assembly language.

o These labels make the program much easier to read and maintain.

Are All The Bits Of Flag Register Used In 8051?

Answer :

o The flag register also called as the program status word uses only 6 bits.

o The two unused bits are user definable flags.

o Carry, auxiliary carry, parity and overflow flags are the conditional flags used in

it.

o 1 is a user definable bit and PSW.5 can be used as general purpose bit.

o Rest all flags indicate some or the other condition of an arithmetic operation.



Which Bit Of The Flag Register Is Set When Output Overflows

To The Sign Bit?

Answer :

The 2nd bit of the flag register is set when output flows to the sign bit. This flag is also

called as the overflow flag. Here the output of the signed number operation is too large to

be accommodated in 7 bits. For signed numbers the MSB is used to indicate the whether

the number is positive or negative. It is only used to detect errors in signed number

operations.

What Are Issues Related To Stack And Bank 1.?

Answer :

o Bank 1 uses the same RAM space as the stack.

o Stack pointer is incremented or decremented according to the push or pop

instruction.

o If the stack pointer is decremented it uses locations 7, 6, 5… which belong to

register bank 0.

o If a given program uses R1 then stack is provided new memory location.

o The push instruction may also take stack to location 0 i.e.it will run out of space.



Explain Jnc.?

Answer :

It is a command used to jump if no carry occurs after an arithmetic operation. It is called

as jump if no carry (conditional jump instruction). Here the carry flag bit in PSW register

is used to make decision. The processor looks at the carry flag to see if it is raised or not.

If carry flag is 0, CPU fetches instructions from the address of the label.

Can Port 0 Be Used As Input Output Port?

Answer :

Yes, port 0 can be used as input output port. Port 0 is an open drain unlike ports 2, 3, 4.

To use it as input or output the 10k ohm pull-up resisters are connected to it externally.

To make port 0 as input port it must be programmed by writing 1 to all bits.

Example:

o MOV A,#0FFH

o MOV P0,A

Which 2 Ports Combine To Form The 16 Bit Address For

External Memory Access?

Answer :

o Port0 and port2 together form the 16 bit address for external memory.



o Port0 uses pins 32 to 39 of 8051 to give the lower address bits(AD0-AD7)

o Port2 uses pins 21 to 28 of 8051 to give the higher address bits(A8-A15)

o This 16 bit address is used to access external memory if attached.

o When connected to external memory they cannot be used as input output ports.

Can Single Bit of A Port Be Accessed In 8051?

Answer :

o Yes, 8051 has the capability of accessing only single bit of a port.

o Here only single bit is accessed and rest is unaltered.

o SYNTAX: “SETB X. Y”.

o Here X is the port number and y is the desired bit.

o Example: SETB P1.2 Here the second bit of port 1 is set to 1.

Other Than Setb, Clr Are There Any Single Bit Instructions?

Answer :

o There are in total 6 single-bit instructions.

o CPL bit: complement the bit (bit= NOT bit).

o JB bit, target: Jump to target if bit equal to 1.

o JNB bit, target: Jump to target if bit is equal to 0.

o JCB bit, target: Jump to target if bit is equal to 1 and then clear bit.



8085 Microprocessor Revision

What Are The Various Registers In 8085?

Answer :

Accumulator register, Temporary register, Instruction register, Stack Pointer, Program

Counter are the various registers in 8085.

What Are The Various Flags Used In 8085?

Answer :

Sign flag, Zero flag, Auxillary flag, Parity flag, Carry flag.

What Is Stack Pointer?

Answer :

Stack pointer is a special purpose 16-bit register in the Microprocessor, which holds the

address of the top of the stack.

What Is Program Counter?



Answer :

Program counter holds the address of either the first byte of the next instruction to be

fetched for execution or the address of the next byte of a multi byte instruction, which

has not been completely fetched.

In both the cases it gets incremented automatically one by one as the instruction bytes

get fetched. Also Program register keeps the address of the next instruction.

Which Stack Is Used In 8085?

Answer :

LIFO (Last In First Out) stack is used in 8085.In this type of Stack the last stored

information can be retrieved first.

What Happens When Hlt Instruction Is Executed In Processor

Answer :

The Micro Processor enters into Halt-State and the buses are tri-stated.

What Is Meant By A Bus?

Answer :

A bus is a group of conducting lines that carriers data, address, & control signals.



What Is Tri-state Logic?

Answer :

Three Logic Levels are used and they are High, Low, High impedance state. The high

and low are normal logic levels & high impedance state is electrical open circuit

conditions. Tri-state logic has a third line called enable line.

Give An Example Of One Address Microprocessor?

Answer :

8085 is a one address microprocessor.

In What Way Interrupts Are Classified In 8085?

Answer :

In 8085 the interrupts are classified as Hardware and Software interrupts.

What Are Hardware Interrupts?

Answer :

TRAP, RST7.5, RST6.5, RST5.5, INTR.



What Are Software Interrupts?

Answer :

RST0, RST1, RST2, RST3, RST4, RST5, RST6, RST7.

Which Interrupt Has The Highest Priority?

Answer :

TRAP has the highest priority.

Name 5 Different Addressing Modes?

Answer :

Immediate, Direct, Register, Register indirect, Implied addressing modes.

How Many Interrupts Are There In 8085?

Answer :

There are 12 interrupts in 8085.



In 8085 Which Is Called As High Order / Low Order Register?

Answer :

Flag is called as Low order register & Accumulator is called as High order Register.

What Are Input & Output Devices?

Answer :

Keyboards, Floppy disk are the examples of input devices. Printer, LED / LCD display,

CRT Monitor are the examples of output devices.

Can An Rc Circuit Be Used As Clock Source For 8085?

Answer :

Yes, it can be used, if an accurate clock frequency is not required. Also, the component

cost is low compared to LC or Crystal.

Why Crystal Is A Preferred Clock Source?

Answer :



Because of high stability, large Q (Quality Factor) & the frequency that doesn’t drift

with aging. Crystal is used as a clock source most of the times.

What Does Quality Factor Mean?

Answer :

The Quality factor is also defined, as Q. So it is a number, which reflects the lossness of

a circuit. Higher the Q, the lower are the losses.

What Are Level-triggering Interrupt?

Answer :

RST 6.5 & RST 5.5 are level-triggering interrupts

How Can Signals Be Classified For The 8085 Microprocessor?

Answer :

The signals of the 8085 microprocessor based on their functions can be classified into 7

categories namely:

o Frequency and power signals

o Address and data buses



o The control bus

o Interrupt Signals

o Serial Input / Output signals

o DMA signals

o Reset Signals

Mention The Various Functional Blocks Of The 8085

Microprocessor.?

Answer :

The various functional blocks of the 8085 microprocessor are:

o Registers

o Arithmetic logic unit

o Address buffer

o Increment / decrement address latch

o Interrupt control

o Serial I/O control

o Timing and control circuitry

o Instructions decoder and machine cycle encoder.



Mention The Different Types Of Data Transfers Possible In The

8085.?

Answer :

The various types of data transfer operations possible are:

o Data transfer is possible between two registers.

o It is also possible between a memory location and a register.

o Also it can occur between an input/output device and an accumulator.

o In reality data is never transferred it can only be copied from one location to

another.

What Is A Stack Pointer Register, Describe Briefly.?

Answer :

o The Stack pointer is a sixteen bit register used to point at the stack.

o In read write memory the locations at which temporary data and return addresses

are stored is known as the stack.

o In simple words stack acts like an auto decrement facility in the system.

o The initialization of the stack top is done with the help of an instruction LXI SP.

o In order to avoid program crashes a program should always be written at one end

and initialized at the other.



Digital Electronics Revision

What Is Difference Between Latch And Flip-flop?

Answer :

The main difference between latch and FF is that latches are level sensitive while FF is

edge sensitive. They both require the use of clock signal and are used in sequential logic.

For a latch, the output tracks the input when the clock signal is high, so as long as the

clock is logic 1, the output can change if the input also changes.

FF on the other hand, will store the input only when there is a rising/falling edge of the

clock. Latch is sensitive to glitches on enable pin, whereas flip-flop is immune to

glitches. Latches take fewer gates (also less power) to implement than flip-flops. Latches

are faster than flip-flops

Given Only Two Xor Gates One Must Function As Buffer And

Another As Inverter?

Answer :



Tie one of xor gates input to 1 it will act as inverter.Tie one of xor gates input to 0 it

will act as buffer.

Difference Between One Hot And Binary Encoding?

Answer :

Common classifications used to describe the state encoding of an FSM are Binary (or

highly encoded) and One hot.

A binary-encoded FSM design only requires as many flip-flops as are needed to

uniquely encode the number of states in the state machine. The actual number of flip-

flops required is equal to the ceiling of the log-base-2 of the number of states in the

FSM.A one hot FSM design requires a flip-flop for each state in the design and only

one flip-flop (the flip-flop representing the current or "hot" state) is set at a time in a

one hot FSM design.

For a state machine with 9- 16 states, a binary FSM only requires 4 flip-flops while a

one hot FSM requires a flip-flop for each state in the design FPGA vendors frequently

recommend using a one hot state encoding style because flip-flops are plentiful in an

FPGA and the combinational logic required to implement a one hot FSM design is

typically smaller than most binary encoding styles.



Since FPGA performance is typically related to the combinational logic size of the

FPGA design, one hot FSMs typically run faster than a binary encoded FSM with larger

combinational logic blocks

How To Achieve 180 Degree Exact Phase Shift?

Answer :

Never tell using inverter

a) DCM an inbuilt resource in most of FPGA can be configured to get 180 degree phase

shift.

b) BUFGDS that is differential signaling buffers which are also inbuilt resource of most

of FPGA can be used.

What Is Significance Of Ras And Cas In Sdram?

Answer :

SDRAM receives its address command in two address words. It uses a multiplex

scheme to save input pins. The first address word is latched into the DRAM chip with

the row address strobe (RAS).

Following the RAS command is the column address strobe (CAS) for latching the

second address word. Shortly after the RAS and CAS strobes, the stored data is valid

for reading.



Tell Some of Applications of Buffer?

Answer :

a)They are used to introduce small delays.

b) They are used to eliminate cross talk caused due to inter electrode capacitance due to

close routing.

c) They are used to support high fan-out, e.g.: bufg

Give Two Ways Of Converting A Two Input Nand Gate To An

Inverter?

Answer :

a)Short the 2 inputs of the nand gate and apply the single input to it.

b) Connect the output to one of the input and the other to the input signal.

Why Is Most Interrupts Active Low?

Answer :

This answers why most signals are active low if you consider the transistor level of a

module, active low means the capacitor in the output terminal gets charged or

discharged based on low to high and high to low transition respectively. When it goes

from high to low it depends on the pull down resistor that pulls it down and it is



relatively easy for the output capacitance to discharge rather than charging. Hence

people prefer using active low signals.

Design A Four-input NAND Gate Using Only Two-input NAND

Gates.

Answer :

Basically, you can tie the inputs of a NAND gate together to get an inverter.

What Will Happen If Contents Of Register Are Shifter Left,

Right?

Answer :

It is well known that in left shift all bits will be shifted left and LSB will be appended

with 0 and in right shift all bits will be shifted right and MSB will be appended with 0

this is a straightforward answer What is expected is in a left shift value gets Multiplied

by 2 e.g.: consider 0000_1110=14 a left shift will make it 0001_110=28, it the same

fashion right shift will Divide the value by 2.

Given The Following Fifo And Rules, How Deep Does The Fifo

Need To Be To Prevent Underflow Or Overflow?



Answer :

RULES:

1)frequency(clk_A) = frequency(clk_B) / 4

2) period(en_B) = period(clk_A) * 100

3) duty cycle(en_B) = 25%

Assume clk_B = 100MHz (10ns)

From (1), clk_A = 25MHz (40ns)

From (2), period(en_B) = 40ns * 400 = 4000ns, but we only output for 1000ns,due to

(3), so 3000ns of the enable we are doing no output work. Therefore, FIFO size =

3000ns/40ns = 75 entries

Differences Between D-latch And D Flip-flop?

Answer :

D-latch is level sensitive where as flip-flop is edge sensitive. Flip-flops are made up of

latches.

What Is A Multiplexer?

Answer :



Is a combinational circuit that selects binary information from one of many input lines

and directs it to a single output line.

(2n =>n). Where n is selection line.

What Are Set Up Time & Hold Time Constraints? What Do

They Signify? Which One Is Critical For Estimating Maximum

Clock Frequency Of A Circuit?

Answer :

Set up time is the amount of time the data should be stable before the application of the

clock signal, where as the hold time is the amount of time the data should be stable after

the application of the clock. Setup time signifies maximum delay constraints; hold time

is for minimum delay constraints. Setup time is critical for establishing the maximum

clock frequency.

How Can You Convert An Sr Flip-flop To A Jk Flip-flop?

Answer :

By giving the feedback we can convert, i.e. !Q=>S and Q=>R.Hence the S and R inputs

will act as J and K respectively.



How Can You Convert The Jk Flip-flop To A D Flip-flop?

Answer :

By connecting the J input to the K through the inverter.

How Do You Detect If Two 8-bit Signals Are Same?

Answer :

XOR each bits of A with B (for e.g. A [0] xor B [0]) and so on. The o/p of 8 xor gates is

then given as i/p to an 8-i/p nor gate.

if o/p is 1 then A=B.

Embedded Technosolutionsembeddedtechnosolutions.com/wp-content/uploads/...The Intel 8051 is an 8-bit microcontroller which means that most available operations are ... x List Out Addressing

Documents