1.What are the various registers in 8085?

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2 Νοε 2013 (πριν από 3 χρόνια και 5 μήνες)

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1.What are the various registers in 8085?


Accumulator register, Temporary register, Instruction register, Stack Pointer,
Program Counter are the various registers in 8085 .


2.What is Stack Pointer


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


3.What is Program counter?


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.


4.Which Stack is used in 8085?


LIF
O (Last In First Out) stack is used in 8085.In this type of Stack the last stored
information can be retrieved first.


5.What is meant by a bus?


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


6.What is Tri
-
state log
ic?


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.


7.Give an example o
f one address microprocessor?


8085 is a one address microprocessor.


8.In what way interrupts are classified in 8085?


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


9.examples of Software interrupts?


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


10.EXAMPLES of Hardware interrupts?


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


11.Which interrupt has the highest priority?


TRAP has the highest priority.


12.Name 5 different addressing modes?


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


13.How many interrupts are there in 8085?


There are 12 interrupts in 8085.


14.What is clock frequency for 8085?


3 MHz is the maximum clock frequency for 8085.


15.In 8085 which is called as High order / Low order Reg
ister?


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


16.Why crystal is a preferred clock source?


Because of high stability, large Q (Quality Factor) & the frequency that doesn’t drift
with aging. Crystal is used a
s a clock source most of the times.


17.What does Quality factor mean?


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.


1.What are the flags in 8086?


Carry fla
g, Parity flag, Auxiliary carry flag, Zero flag, Overflow flag, Trace flag,
Interrupt flag, Direction flag, and Sign flag.


2.
What are the various interrupts in 8086??


Maskable interrupts, Non
-
Maskable interrupts


3.What is meant by Maskable interrupts?



An interrupt that can be turned off by the programmer is known as Maskable
interrupt.


4.Which interrupts are generally used for critical events??


Non
-
Maskable interrupts are used in critical events Such as Power failure,
Emergency, Shut off etc.


5.What

is the Maximum clock frequency in 8086?


5 Mhz is the Maximum clock frequency in 8086.


6.What are the various segment registers in 8086?


Code, Data, Stack, Extra



7.Which Stack is used in 8086?


FIFO (First In First Out) stack is used in 8086.In this t
ype of Stack the first
stored information is retrieved first
.













Q1)Why a MOSFET is preferred over a transistor?

A)A MOSFET is very small in size as compared to a transistor and its biasing is easier as
compared to latter.


Q2)Please tell me why b
iasing is required in a transistor?

A)Biasing is required to get the load line and the operating point of a transistor. Moreover
different regions are achieved through different biasing types.


Q3)How different regions are got and what are those regions? E
xplain taking a Common Base
connection.

A)Well the transistor can be biased in 3 different types to get three different regions
-
Active
region, Saturation Region, Cut
-
off Region

Active Region
-
:Emitter is forward biased and collector is reverse biased

Cut
-
of
f Region
-
:Both emitter and collector are reverse biased

Saturation region: Both emitter and collector are forward biased


Q4)What is a tunnel diode ?

A)Tunnel diode was invented by Esaki and its different from the normal diode in terms of the
doping concen
tration as in 1part of doping is present in 10^3 atoms whereas in normal diode it is
1 part in 10^8 atoms. It is basically used for very fast switching response.



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--------



1)what is 555 and why is it named so

555 Timer is used to produce accurate and stable time delays ranging from microseconds to
hours.

inside the 555 timer, there are 3 resistors used in series

all the 3 resistors used are same and are 5k ohm res
istors..

so its called 555 timer..


2)Give Shannon's source coding and channel coding theorem

Source coding theorem

is stated as follows:

"Given a discrete memory less source of entropy H(p), the average code
-
word length L for any
source encoding is bounde
d as L >= H(p)"

This is basically used for Data Compression using different codes but following this rule.

Channel coding theorem

says "Let a discrete memory less source with an alphabet p have
entropy H(p) and produce symbols once every Ts seconds.
"Let a

memory less channel have
capacity C and be used once every Tc seconds. Then if

H(p)/Ts <= C/Tc there exists a coding scheme for which the source output can be transmitted
over the channel and reconstructed with very small error.
"

This is basically used f
or Error Detection.


3)what is Hoffman coding

Hoffman code is a source code whose average word length approaches the fundamental limit
set by the entropy of a discrete memory less source. It is optimum in the sense that it follows
Source coding very closel
y


4)Design AND/OR/NOT using transistors.
.

Refer books


5)What is Grey coding, XS
-
3 coding, K
-
Map?


6)Why are nand gates and NOR gates called Universal gates.....

Becoz using these 2 gates any other type of gates can be made


7)What is the Sampling theorem
?

A continuous time signal may be completely represented in its samples and recovered back if
sampling frequency is greater than equal to twice the maximum frequency present in the signal

Fs >= 2Fm


What is Convolution theorem

Time convolution theorem

Convolution in time domain = Multiplication in Frequency domain

x1(t) * x2(t) <
---
> X1(w) x X2(w)
--



Frequency Convolution theorem

Convolution in frequency domain = 2pi x Multiplication in time domain

X1(w) * X2(w) <
---
> 2pi x x1(t) x x2(t)


9)What are F
IR and IIR filters

Finite impulse response and infinite impulse response filters

finite

impulse response settles to zero in a finite number of sample intervals. This is in contrast to
infinite impulse response (IIR) filters, which have internal feedback an
d may continue to
respond indefinitely

FIR filters are always stable but IIR may or may not be stable


10)Why is a common collector called an emitter follower..?

In this configuration the voltage gain is equal to unity and hence a change in base voltage
a
ppears as an equal change across the load at the emitter. Thus the emitter follows the input
signal. The most common use of this circuit is to use as a buffer stage which functions as
resistance transformation from high to low resistance.



11)
What is DTM
F

Dual
-
tone multi
-
frequency signaling (DTMF) is used for telecommunication signaling over
analog telephone lines in the voice
-
frequency band between telephone handsets and other
communications devices and the switching center.


12
)

what are The venin and
Norton's theorems, Maximum power transfer theorem
?

Sometimes we need to calculate current or voltage in a particular branch of a circuit. In that
case we needn't calculate for all branches..so techniques like The venin and Norton are used.

In both theorems

we replace the 2
-
terminal linear device which may contain voltage source,
current source both independent and dependent with the following orientation:

If they are replaced with a
resistor in series with a Voltage source

then its
The venin

and if it is
re
placed with a
resistor in parallel with a Current source

then its
Norton
.

Maximum Power transfer theorem is basically a linear device when connected to its The venin
equivalent it receives Maximum power .

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1.what is the difference between SCR and diode rectifier?

ans: diode is a 2 terminal device, in scr gate controls the rectifing.SCR is used in High frequency
applicat
ions but diode is low frequency devices, SCR can be in high temperatures but not diode.


3.Distinguish between Angle modulation and Amplitude modulation.

ans: In amplitude Modulation as the amplitude of given signal varies, the amplitude of carrier
signal

also varies in the same way.

In angle modulation, the frequency or phase may vary according to the amplitude of given
signal


4.What is Biasing?

ans: biasing is a process of connecting dc voltage to a device by which we can select the
operating point of
the device. by biasing actually we select the operating point of the device.


5.What do you mean by ASCII, EBCDIC?

ans:ASCII (American Standard Code for Information Interchange), is a character encoding
based on the English alphabet.


EBCDIC (Extended Bina
ry Coded Decimal Interchange Code) is an 8
-
bit character encoding
used on IBM mainframe operating systems




6.
What is Race
-
around problem? How can you rectify it?

ans: A condition in logic network in which the difference in propagation times through two
or
more signal paths in the network can produce an erroneous output. in jk flip flop race around
problem will occur when both the inputs are high. it can be prevented by usi
ng master slave jk
flip flop


7
.What is the basic difference between Latches and Fl
ip flops?

ans: latch works without clock signal, but works with a control signal and it is level triggered
device. Whereas flip flop is a 1 bit storage element and works with a clock signal. its a edge
triggered device. normally latches are avoided an
d fli
p flops are preferred.


8.

what is Barkhausen Criterion?

ans:

1./AB/=1,i.e. the magnitude of loop gain must be unity

2.the total phase shift around the closed loop is zero or 360 degrees.














1.

What is meant by D
-
FF? D Flip Flop (or did you mean to
ask its working?)

2.

What is the basic difference between Latches and Flip flops? (Latches do not
store information, here, a bit)

3.

What is a multiplexer?

4.

How can you convert an SR Flip
-
flop to a JK Flip
-
flop?

5.

How can you convert an

JK Flip
-
flop to a D Flip
-
flop?

6.

What is Race
-
around problem? How can you rectify it?

7.

Which semiconductor device is used as a voltage regulator and why? (zener
diode in reverse bias, why because it allows for a large variation in current for a
negligible va
riation in voltage)

8.

What do you mean by an ideal voltage source? (Sources infinite current to any
load without any change in o/p voltage)

9.

What do you mean by zener breakdown and avalanche breakdown?

10.

What are the different types of filters? (low pass, high
pass, band pass, band
stop, resonant)

11.

What is the need of filtering ideal response of filters and actual response of
filters?

12.

What is sampling theorem? (minimum 2 samples per time period? not too sure of
this)

13.

What is impulse response?

14.

Explain the
advantages and disadvantages of FIR filters compared to IIR
counterparts.

15.

What is CMRR? Explain briefly. (explained by someone a few posts above)

16.

What do you mean by half
-
duplex and full
-
duplex communication? Explain
briefly. (half duplex
-

both sender & r
eceiver can communicate with each other,
but not simultaneously...full duplex
-

same but simultaneous communication
possible)

17.

Which range of signals are used for terrestrial transmission?

18.

What is the need for modulation? (transmitting over a distance, encr
yption?)

19.

Which type of modulation is used in TV transmission?

20.

Why we use vestigial side band (VSB
-
C3F) transmission for picture?

21.

When transmitting digital signals is it necessary to transmit some harmonics in
addition to fundamental frequency?

22.

For asynchro
nous transmission, is it necessary to supply some synchronizing
pulses additionally or to supply or to supply start and stop bit?

23.

BPFSK is more efficient than BFSK in presence of noise. Why?

24.

What is meant by pre
-
emphasis and de
-
emphasis?

25.

What do you mean b
y 3 dB cutoff frequency? Why is it 3 dB, not 1 dB? (3dB is the
half power value)

26.

What do you mean by ASCII, EBCDIC?








The basic difference in layman's terms is:


While both provide backup power during mains outage, with the UPS the switch is
instantan
eous whereas with the Inverter there is a gap of a second or two. This gap is
OK for household gadgets such as lights, fans, fridge, etc. but not OK for computers.


In technical terms:


UPS: The mains power comes to the UPS. The AC is converted to DC and t
his DC is
constantly charging the battery. The output of the battery is fed to the Sine wave
inverter and it converts DC to AC and this feeds the equipment. Since power out is
always drawn from the battery, there is no time lag when mains switches off; it
just
stops the battery from being charged and the UPS continues to supply power till the
battery runs out.


Inverter: The mains power comes to the Inverter. This is directly sent to the output but
the AC is also converted to DC and this DC is constantly ch
arging the battery. A sensor
and relay mechanism checks whether the mains is ON or OFF. When the main switches
OFF, the relay actuator triggers to switch from mains to inverter. Rest is same like the
UPS. Because of this sensor and relay, there is a gap be
tween triggering.


UPS involves more costly circuitry and is therefore more expensive to make and sell.