1. Define Microprocessor?
Microprocessor is a multipurpose, programmable, clock-driven, register
based electronic device that reads binary instructions from a storage device
called memory, accepts binary data as input and processes data according to
those instructions, and provides as output.
2. What is Hardware and Software?
The physical components of the system i.e. computer are called
Hardware. Group of programs is called software.
3. Why the microprocessor is viewed as a programmable
Device?
Microprocessor is programmable because it can be instructed to perform
given tasks within its capability. Microprocessor is designed to understand and
execute many binary instructions.
4. What is Central processing Unit ( CPU ) ? And Write
the use of it.
CPU is a
heart of the computer. Central processing Unit controls the operation of the
computer. In a microcomputer the CPU is a microprocessor. The CPU fetches
binary coded instructions from memory, decodes the instructions into a series
of simple actions and carries out these actions in a sequence of steps.
5. What is a chip?
A chip is also called
an integrated circuit. Generally it is a small, thin piece of silicon onto
which the transistors making up the microprocessor have been etched. A chip
might be as large as an inch on a side and can contain tens of millions of
transistors. Simpler processors might consist of a few thousand transistors
etched onto a chip just a few millimeters square.
6. What is mini computer?
Scaled down
versions of mainframe computers are often called minicomputers. The main unit
of a minicomputer usually fits in a single rack or box. A mini computer runs
more slowly, works directly with smaller data words and does not have as much
memory as mainframe. computers of this type are used for business data
processing, industrial control and scientific research
7.
What is
System Bus?
The System bus is a communication path between the microprocessor and
peripherals. It is nothing but a group of wires to carry bits.
8. What is Address
Bus?
The address
bus consists of 16, 20, 24 or 32 parallel signal lines. On these lines the CPU
sends out the address of the memory location that is to be written to or read
from. The number of memory locations
that the CPU can address is determined by the number of address lines. If the
CPU has N address lines, then it can directly address 2N memory
locations. Simply, we can say that
Address Bus is used to carry the address.
9. What is Data Bus?
The data
bus consists of 8, 16, or 32 parallel signal lines. The data bus lines are
bidirectional. This means that the CPU can read data in from memory or from a
port on these lines, or it can send data out to memory or to a port on these
lines. Simply we can say that data bus is used to carry the data .
10.
What is Assembly Language?
A medium of
communication with a computer in which programs are written in mnemonics.
Binary instructions are given abbreviated names called mnemonics, which form
the assembly language for a given processor.
11.
What is Machine Language?
The binary
medium of communication with a computer through a designed set of instructions
specific to each computer.
12. Define Embedded Systems:
Embedded
systems are those used to control specialized hardware in which the computer
system is installed.
Microprocessor
is the final product and is not available for reprogramming to the end user.
E.g. Copying machine
13. What is Bit-Slice processor?
For some Applications , general purpose CPUs such as the 8080 and 6800
are not fast enough or do not have suitable instruction sets. For these
applications ,several manufacturers produce devices which can be used to build
the custom CPU. This family includes 4 bit ALUs, multiplexers, sequencers and
other parts needed for custom building a CPU. The term slice comes from the
fact that these parts can be connected in parallel to work with 8 bit words,
16- bit words, or 32 bit words.
14. What is microcontroller?
Microcontroller is a Device that includes microprocessor, memory
and I/O signal lines on a single chip, fabricated using VLSI technology.
15. Write about the importance of instruction set of Z80 8bit microprocessor?
Instruction set 158 basic instructions . Instruction set is the most
powerful set among the 8 bit microprocessors. It does not include two serial
I/O instructions. It includes block I/O instructions
16. List the main
applications of 8 bit microprocessors?
8 bit
microprocessors is used in a variety of applications such as appliances ,
automobiles ,industrial process and control applications.
17. Write the uses of microprocessors in Medical
Instrumentation field?
Patient
Monitoring in Intensive Care Unit, Pathological Analysis and the measurement of
parameters like blood pressure and temperature.
18. Define Real
Time Systems :
Real Time
Systems are those in which timeliness is as important as the correctness of the
outputs, although this does not mean that they have to be “fast systems”.
19. List the limitations of 8 bit microprocessor:
Lower
Execution Speed
It can
address less memory size
Few
instructions are available
20. What do you mean ‘ Data Width’?
Data Width
is the width of the ALU. An 8 bit ALU can add / subtract/ multiply etc.. two 8
bit numbers . In many cases, the
external data bus is the same width as the ALU, but not always. The 8088 had a
16 bit ALU and 8 bit bus , while the modern Pentiums fetch data 64 bits at a
time for their 32 bit ALUs.
21. Draw and specify the complete bit configuration of
8085 flag Register?
D7
D6 D5 D4
D3 D2 D1
D0
|
S
|
Z
|
|
AC
|
|
P
|
|
CY
|
S- Sign
Flag .
If D7 =1 , then sign flag is set, otherwise rest.
Z-Zero flag. If
ALU operation results in zero, then this flag is set, Otherwise it is reset.
AC-Auxilliary flag. In an arithmetic operation ,when a
carry is generated by digit D3 and passed on to digit D4, the AC flag is set.
Otherwise it is reset.
P-Parity Flag. If the result of an arithmetic or logic
operation has an even number of 1’s then this flag is set. Otherwise it is
reset.
CY-Carry Flag. If an arithmetic operation results in a
carry, the carry flag is set. Otherwise it is reset.
22. What is compiler?
Compiler is
a program that translates English like words of a high level language into the
machine language of a computer. A compiler read a given program ,called a
source code, in its entirely and then translates the program into the machine
language, which is called an Object Code.
23. List the four operations commonly performed by MPU(
Micro processing Unit)?
Memory Read
: Reads data (or instructions) from memory.
Memory
Write: Writes Data (or instructions) into memory.
I/O Read:
Accepts data from input devices.
I/O Write:
Sends data to output devices.
24. Write about RST pins in 8085?
In 8085 ,three RST pins are
available, such as RST 7.5 ,RST 6.5 , RST 5.5
RST
represents Restart Interrupts. These are vectored interrupts that transfer the
program control to specific memory locations. They have higher priorities than
the INTR interrupt. Among these three, the priority order is 7.5,6.5,5.5.
25. List the control and status signals available in 8085.
----- ------ ----
ALE , RD,
WR, IO/M, S1, S2
ALE-Address
Latch Enable
-----
RD – Read
Control Signal
----
WR – Write
Control Signal
---
IO/M - To specify I/O or memory operation
S1 , S2 –
Status signals
26. What are the limitations of 8085 MPU?
(i) The lower order address bus of the 8085 microprocessor
is multiplexed (time shared) with the data bus. The buses need to be demultiplexed.
(ii) Appropriate
control signals need to be generated to interface memory and I/O with the 8085.
27. Compare the 8
bit microprocessors 8080A and 8085.
8080A is the predecessor of 8085. 8085 has the instruction set of 8080A
plus some additional ones. Program written for 8080A will be executed by 8085.
8085 and 8080A are not pin compatible. Both require a +5V power supply.
28.
Define Register Relative
Addressing Mode.
Register Relative Addressing Mode : The Effective Address is
Calculated by the sum of 8- or 16 bit displacement and the contents of a base
Register or an index Register.
E.A. =
content of(BX or BP or SI or DI) + (8
bit displacement (sign extended ) or 16 bit displacement
Physical
Address = E.A +(DS)*1610
29. Define Immediate Addressing.
An
8 bit or 16 bit immediate data follows the instruction. For e.g MOV
AX,5020H instruction transfers a word
5020H to the AX register .
30. Define Direct Addressing mode :
A
16 bit offset address of the data memory location is specified with reference
to the DS segment starting address.
For.E.g MOV [1020H],5020H instruction transfers a word
5020H to the data memory location at 11020H if DS=1000H.
31. Define Relative based indexed addressing mode:
Relative Based Indexed Addressing Mode : Effective Address is
calculated by the sum of 8- or 16 bit displacement and a based indexed address.
E.A.=
(BX or BP) + (SI or DI) +( 8 bit displacement (sign extended ) or 16 bit
displacement)
Physical
Address= E.A + (DS)*1610
32. List the branch related addressing mode:
Intra
segment Direct
Intra
segment Indirect
Inter
segment Direct
Inter
Segment Indirect
33.
List the functions of Bus Interface Unit in 8086.
Sends
out addresses
Fetches
instructions from memory
Reads
data from ports and memory
Writes
data to port and memory
34.
Write any two advantages of segment registers in 8086
a. It allows the memory capacity to be
1MB even though the address associated with individual instructions are 16 bits
wide.
b. It allows the instruction,data, or
stack portion of a program to be more
than 64KB long by using more than one code, data, or stack segment
35.
What is the use of Instruction pointer in 8086 ?
Instruction pointer holds the 16 bit address of the next code
byte within the code segment. The value contained in the IP is called effective
address or offset. It contains the distance from the base address to the next
instruction byte to be fetched.
36.
Write about the auxiliary carry flag used in 8086 ?
It is set if there is a
carry out of bit 3 during an addition or a borrow by bit 3 during a
subtraction. This flag is used exclusively for BCD arithmetic.
37.
When the Overflow flag is set ?
For
addition of 16 bits, this flag is set when there is a carry into the MSB and no
carry out of the MSB.
38.
Define Register addressing mode:
Datum is in the register
that is specified by the instruction
E.g : MOV CX,AX (16 bit operand)
MOV CL,AL ( 8 bit operand)
39.
Define Register Indirect Addressing mode:
Effective address of the
datum is in the base register BX or an index register that is specified by the
instruction.
40.
Define Register relative addressing mode:
The effective address is
the sum of an 8- or 16 bit displacement and the contents of a base register or
an index register.
41.
Define Based Indexed addressing mode:
The effective address is
the sum of a base register and an index register , both of which are specified
by the instruction.It is also called as Base related Indexed addressing.
42.
Define Intra segment direct addressing mode:
The effective branch
address is the sum of an 8- or 16 bit displacement and the current contents of
IP.
43.
Define Intra segment Indirect addressing mode:
The
effective branch address is the contents of a register or memory location that
is accessed using any of the data related addressing modes except the immediate
mode. The contents of IP are replaced by the effective branch address.
44.
Define Inter segment addressing mode:
It replaces the contents
of IP with part of the instruction and the contents of CS with another part of
the instruction.
45.
Define Inter segment Indirect addressing mode:
It replaces the contents
of IP and CS with the contents of two consecutive words in memory that are
referenced by using any of the data related addressing modes except immediate
and register modes.
46.
What is the use of PUSHF instruction used in 8086 ?
It pushes the flag
register contents to the top of the stack. No flags are affected.
47.
Define XLAT instruction used in 8086.
It translates a byte in AL AL AL
48.
What is the use of ‘W’ bit in opcode ?.
W bit in op-code : If an instruction in 8086 can operate on
either a byte or a word , the op-code includes a W-bit which indicates whether
a byte ( W =0 ) or a word (W =1) is being accessed.
49.
What is DAS instruction ?
DAS :
Decimal Adjust After Subtraction
This
instruction converts the binary result of a SUB or SBB instructi
on in AL
50.
What is Packed BCD Format ?
Packed BCD Format : Packed BCD Numbers are stored in two digits
to a byte , in 4 bit groups referred to as nibbles. ALU is capable of
performing only binary addition and subtraction , but by adjusting the sum or
difference the correct result in packed BCD format.
51.
What is the value of ‘AX’ after
executing following instructions.
MOV AH,00
MOV AL
ADD AL
AAA
Ans : AX= 0100 H
52.
What is difference between DIV and IDIV instruction in 8086 ?
DIV :
It operates only on unsigned number.
IDIV : It operates only
on signed numbers.
53.
Write about the following instruction :
MOV CS:[BX], DL
MOV CS:[BX],DL - It copies a byte from DL Register. Effective Address
for the memory location is contained in the BX Register. Normally an effective
address in BX will be added to the data segment base in DS to produce the
physical memory address. In this instruction CS: indicates that we want the BIU to add the
effective address to the code segment base in CS to produce the physical
address.
content of(BX+(CS) * 1610) = (DL)
54.
What is Programmed I/O ?
Programmed I/O : It
consists of continually examining the status of an Interface and performing an
I/O operation with the Interface when its status indicates that it has data to
be input or its data- out buffer register is ready to receive data from the
CPU.
55.
What is the use of Directives in 8086 ?
Directives in 8086 give
directions to the assembler during the assembly process but are not translated
into machine instruction.
56.
What is AAS
instruction in 8086 ?
AAS : Adjust Result of ASCII Subtraction
This
instruction adjust the binary result of SUB or SBB instruction.
57.
What is
Unpacked BCD Format ?
Unpacked BCD Format : In
Unpacked BCD, there is only one digit per byte and because of this,unpacked
multiplication and division can be done. Binary operations act on signle bytes
and the results are adjusted. For Division , the adjustment is done before the
binary division.
58. What is the value of AL
MOV AL,35H
ADD AL,49H
DAA
Ans : AL
59. Define Segment Override Prefix.
Segment Override Prefix :
To permit exceptions to the Segment Register usage, a special one byte
instruction called a segment override prefix is available . It is of the form :
|
X X X
|
X X
|
X X X
|
|
Mod
|
REG
|
R/M
|
60. Write the difference between CBW and CWD instruction
in 8086.
CBW : Convert a byte to a
word, sign extend AL Register into a AH Register.
CWD : Convert a word to a double word ,sign
extend the AX Register into the DX Register.
61.
Write about
the following instruction : LES CX, [3483H]
Copy the contents of memory at the
displacement of 3483H in DS to CL, contents of 3484H in DS to CH, and copy the contents of memory
at displacement of 3485H and 3486H in DS to ES Register.
62. What is the use of D bit in opcode?
D
bit: It is used in double operand
instruction. It is used to indicate whether the register specified by REG is
the source operand (D=0) or the
destination operand (D=1).
63. What is the use of V bit in opcode ?
It
is used by shift and rotate instructions to determine the number of shifts. V
bit is set to 0 if the shift count is to be 1. V bit is set to 1 if the CL
register contains the shift count.
64. Write the use of Z bit in opcode?
It
is used by REP instruction. Z bit helps to control the loop. It will be
repeated the number of items indicated by the CX register or until Z bit dose
not match the Zero flag whichever occurs first.
65. How the execution
time of an instruction is calculated?
Execution
time of an instruction can be determined by multiplying the number of clock
pulses needed to execute the instruction by the clock period.
66. Define EQU directive in 8086 assembly language?
It
is used to assign a name to constants used in the programs. Consider the
statement ‘corr EQU 07H’ , this would
tell the assembler to insert the value 07H everytime that it finds the name
corr in the program statement.
67. Write the use of Assume directive in 8086 assembly
language using one example?
Assume
CS: code_here, DS:data_here
It tells the assembler
that the logical segment code_here
contains the instruction statements for the program and should be treated
as a code segment. It also tells the assembler that it should treat the logical
segment data_here as the data segment for this program.
68. Define EXTRN directive in in 8086 assembly language?
The
EXTRN directive is used to inform the assembler that the names or labels
following the directive are in some other assembly module.
69. What is Emulator?
Emulator
is a mixture of hardware and software .It is used to test and debug the
hardware and software of an external system such as the prototype of a microprocessor
based instrument.
70. What is the use of TEST instruction in 8086?
Test instruction is the same as the AND instruction
except that ite does not put the result anywhere. Like the CMP instruction , it
is used only to set the flags.
71. Define LAHF and SAHF instructions in 8086.
LAHF : Load the 8085 equivalent flags into the AH
register.
SAHF: Store the AH register into the low order byte of
the flag register.
72. While handling the interrupt instructions in 8086,
What are the internal operations may be carried out by the stack?
(i)SP
=SP-2 , stack ß Push flag reg. Contents, IF =0
, TF =0
(ii)
SP=SP-2, Stackß CS Reg. Contents, Address of Interrupt pointer = Interrupt type * 4 ,
CS Register Contents ß Second word of Interrupt pointer
(iii)
SP=SP-2, Stackß IP, IPß First word of Interrupt pointer
73. Write an ALP program in 8086 to add two 16 bit
numbers.
MOV AX,1236H
MOV BX,8765H
ADD AX,BX
HLT
74. Write about EVEN directive in 8086 ALP.
It
forces the address of the next byte to be even. 8086 words can be accessed in
less time if they begin at even address.
75. Write about the following instruction :
Call WORD PTR [BX]
Offset
of the first instruction of procedure is in two memory addresses in DS. It
replaces the contents of IP with contents of word memory locations in DS
pointed to by BX.
76. Write an ALP program in 8086 to subtract numbers.
MOV AX,1236H
MOV BX,8765H
SUB AX,BX
HLT
77. When the 8086 processor is in minimum mode?
___
The
processor 8086 is in minimum mode when its MN/MX pin is strapped to +5 V
78. When the 8086 processor is in maximum mode?
___
The
processor 8086 is in maximum mode when its MN/MX pin is grounded.
79. Define latch.
A
bistable circuit that is set and reset by appropriate input signals . An
electronic circuit that records the status of a signal until it is reset.
80. Define clock pulse.
A
synchronization signal provided by a clock . A periodic signal used for
synchronization and for measuring intervals of time.
81. What is the use of s1 , s2 ,s3 signals when 8086 is in maximum mode?
It
indicates the type of transfer to take place during the current bus cycle.
82.
Define Machine cycle.
A
group of states required for a basic bus operation is called a machine cycle.
83.
Write any three differences between 8086 and 8088?
a.
8086 – 20 address
lines , 16 data lines
8088
– 20 address lines, 8 data lines
__
b.
( Maximum Mode)
8086 – M/IO
__
8088 – IO/M
c.
8086 uses a
maximum supply current of 360 mA
8088
uses a maximum supply of 340mA
84. Define Instruction cycle?
The total time takes the
8086 to fetch an instruction is called an instruction cycle. Instruction cycle
consists of one or more machine cycles. Each machine cycle is made up of states.
85. What is polling?
In
programmed I/O , testing of ready bits or signals is known as polling.
86. Define Interrupt I/O?
Interrupt
is an event that causes the CPU to initiate a fixed sequence known as an
interrupt sequence.
87. What do you mean by wait states in system bus timing?
Wait
states are inserted between T3 and T4, when a memory or I/O interface is not
able to quickly enough during a transfer.
88. What is block transfer?
To
execute a sequence of instructions that causes a special system component
associated with the interface to transfer a sequence of bytes or words to or
from a predesignated block of memory locations . It is called a block transfer.
89. What is the use of A1,A2 pins 8255A ?
A1
and A0 determine which register is to be selected. It determines the port
address. If A1 A0 = 11, the control port is accessed.
90. Write about mode 1 in 8255A?
Mode
1 is intended for handshaking and
interrupt –driven I/O interfaces. In this mode ports A and B are programmed as
data ports and port C is programmed to carry status signals. In this mode , the
data transfers can take place without direct CPU intervention.
91. Define Stop bit.
Bit
or group of bits that identifies the end of a data word and defines the space
between data words. Bit indicating the end of an asynchronous serial
transmission.
92. Define Baud Rate:
The
data rate can be expressed as bits/sec or characters/sec . The term bits/sec is
called baud rate.
93. Define Modem.
Acronym
for modulator/Demodulator. A device that translates digital pulses from a
computer into analog signals for telephone transmission and analog signals from
the telephone into digital pulses the computer can understand.
94.
Define synchronous Communication.
It means regular time
relationship. Pertaining two or more processes that depend upon the occurence
of specific events such as common timing signals.
95.
What is overrun error ?
Loss of data because a
receiving device is unable to accept data at the rate it is transmitted.
96.
What is the use of ADSTB signal in 8237?
ADSTB is Address Strobe.
Same as address latch enable signal. It is used by DMA controller to latch the
address bits A15-A8 during DMA transfer.
97.
What is the use of Current Byte count register?
It programs a channel for
the number of bytes transferred during a DMA action. The number loaded into
this register is one less than the number of bytes transferred.
98.
Define Asynchronous Communication.
Without regular time
relationship. Transmission of a
character or a block of characters can begin at any time , but in which the
bits that represent the character or block have equal time duration.
99.
Write about 80486 processor?
It is an enhanced
version of 80386. It executes instructions in one clocking period. It also
contains 8k byte cache memory. Pentium and Pentium pro also contain improved numeric
co-processors that operate 5 times faster than 80486 numeric co-processor.
100.
What is the difference between 80186 and 80188?
Difference between
these two is width of their data buses. 80186 has 16 bit data bus and 80188 has
8 bit data bus.
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