MICROPROCESSOR AND MICROCONTROLLER QUESTION WITH ANSWER 8085
PROVIDED BY ASST. PROF,SATYANARAYAN PRADHAN
GANDHI ENGINEERING COLLEGE, BHUBANESWAR
ELECTRONICS AND COMMUNICATION ENGINEERING DEPT. |
1. What is Microprocessor? Give the power supply & clock
frequency of 8085
Ans:-A microprocessor is a multipurpose, programmable logic
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 result as
output. The power supply of 8085 is +5V and clock frequency
in 3MHz.
2. List few applications of microprocessor-based system.
Ans:-
It is used:
i. For measurements, display and control of current,
voltage, temperature, pressure, etc.
ii. For traffic control and industrial
tool control.
iii. For speed control of machines.
3. What are the functions of an accumulator?
The accumulator is the register associated with the ALU
operations and
sometimes I/O operations. It is an integral part of ALU. It
holds one of data to be
processed by ALU. It also temporarily stores the result of
the operation performed
by the ALU.
4. List the 16 – bit registers of 8085 microprocessor.
Stack pointer (SP) and Program counter (PC).
5. List the allowed register pairs of 8085.
- B-C register pair
- D-E register pair
- H-L register pair
6. Mention the purpose of SID and SOD lines
SID (Serial input data line):
It is an input line through which the microprocessor accepts
serial
data.
SOD (Serial output data line):
It is an output line through which the microprocessor sends
output
serial data.
7. What is an Opcode?
The part of the instruction that specifies the operation to
be performed is
called the operation code or opcode
8. What is the function of IO/M signal in the 8085?
It is a status signal. It is used to differentiate between
memory locations
and I/O operations. When this signal is low (IO/M = 0) it
denotes the
memory related operations. When this signal is high (IO/M =
1) it denotes
an I/O operation.
9. What is an Operand?
The data on which the operation is to be performed is called
as an
Operand.
10. Control signals used for DMA operation are
HOLD & HLDA.
11. What is meant by interrupt?
Interrupt is an external signal that causes a microprocessor
to jump to a
specific subroutine.
12. Explain priority interrupts of 8085.
The 8085 microprocessor has five interrupt inputs. They are
TRAP, RST
7.5, RST 6.5, RST 5.5, and INTR. These interrupts have a
fixed priority of
interrupt service. If two or more interrupts go high at the
same time, the 8085 will service
them on priority basis. The TRAP has the highest priority
followed bye RST 7.5,
RST 6.5, RST 5.5. The priority of interrupts in 8085 is
shown in the table.
| Interrupts |
Priority |
| TRAP |
1 |
| RST 7.5 |
2 |
| RST 6.5 |
3 |
| RST 5.5 |
4 |
| INTR |
5 |
13. What is a microcomputer?
A computer that is designed using a microprocessor as its
CPU is called
microcomputer
14. What is the signal classification of 8085
All the signals of 8085 can be classified into 6 groups
- Address bus
- Data bus
- Control and status signals
- Power supply and frequency signals
- Externally initiated signals
- Serial I/O ports
15. What are operations performed on data in 8085
The various operations performed are
Store 8-bit data
Perform arithmetic and logical operations
Test for conditions
Sequence the execution of instructions
Store data temporarily during execution in the defined R/W
memory locations called the stack
16. Steps involved to fetch a byte in 8085
i. The PC places the 16-bit memory address on the address
bus
ii. The control unit sends the control signal RD to enable
the memory
chip
iii. The byte from the memory location is placed on the data
bus
iv. The byte is placed in the instruction decoder of the
microprocessor and
the task is carried out according to the instruction
17. How many interrupts does 8085 have, mention them
The 8085 has 5 interrupt signals; they are INTR, RST7.5,
RST6.5, RST5.5
and TRAP.
18. What is an instruction?
An instruction is a binary pattern entered through an input
device to
command the microprocessor to perform that specific
function.
19. What is the use of ALE
The ALE is used to latch the lower order address so that it
can be available
in T2 and T3 and used for identifying the memory address.
During T1 the ALE
goes high, the latch is transparent ie, the output changes
according to the input
data, so the output of the latch is the lower order address.
When ALE goes low the
lower order address is latched until the next ALE.
20. Explain the signals HOLD, READY and SID
HOLD indicates that a peripheral such as DMA controller is
requesting the
use of address bus, data bus and control bus. READY is used
to delay the
microprocessor read or write cycles until a slow responding
peripheral is ready to
send or accept data. SID is used to accept serial data bit
by bit.
21. Explain the different
instruction formats with examples
The instruction set is grouped into the following formats
One byte instruction
Two byte instruction
Three byte instruction
MOV C,A
MVI A,39H
JMP 2345H
GANDHI ENGINEERING COLLEGE, BHUBANESWAR
ELECTRONICS AND COMMUNICATION ENGINEERING DEPT.
1. On which model is based the basic architecture of a digital computer?
ANS;
The basic architecture of a digital computer is based on Von Neumann model.
2. What is meant by distributed processing?
ANS:
Distributed processing involves the use of several microprocessors in a single
computer system. For example, for such a system, the first microprocessor may control
keyboard activities, the second controls storage devices like disk drives, the third controls
input/ output operations, while the fourth may act as the main system processor.
3. What is the technology used in microprocessor?
ANS:
NMOS technology is used in microprocessors.
4. How does the microprocessor communicate with the memory and input / output
devices?
ANS:
The microprocessor communicates with the memory and input / output
devices via three buses, viz., data bus, address bus and control bus.
5. What are the different jobs that the CPU is expected to do at any given point of time?
ANS:
The CPU may perform a memory read or write operation, an I/O read or write
operation or an internal activity.
6. What is mnemonic?
ANS:
It is very difficult to understand a program if it is written in either binary or
hex code. Thus the manufactures have devised a symbolic code for each instruction,
called a mnemonic.
7. What is machine language programming?
ANS:
Programming a computer by utilizing hex or binary code is known as machine
language programming.
8. How many different instructions microprocessor 8085 has? What is an instruction set?
ANS:
8085 microprocessor has a total 74 different instructions for performing
different operations or tasks.
The entire different instructions that a particular microprocessor can handle is
called its instruction set.
9. What an instruction consists of?
ANS:
An instruction consists of an operation code (called opcode) and the address of
the data (called operand), on which the opcode operates.
| Operation code(op code) |
Address of data (operand) |
| Field1 |
field 2 |
10. In how many groups can the signals of 8085 be classified?
ANS:
The signals of 8085 can be classified into seven groups according to their
functions. These are:
(a) Power supply and frequency signals
(b) Data and Address buses
(c) Control bus
(d) Interrupt signals
(e) Serial I/O signals
(f) DMA signals
(g) Reset signals
11. What is the operating frequency of 8085?
ANS;
8085 operates at a frequency of 3 MHZ, and the maximum frequency of
operation is 500 KHz.
The versions 8085 A-2 operates at a maximum frequency of 5 MHz
12. What is the purpose of CLK signal of 8085?
ANS;
The CLK (out) signal obtained from pin 37 of 8085 is used for synchronizing
external devices.
13. What are the temporary registers of 8085?
ANS:
The temporary registers of 8085 are temporary data register W and Z registers.
These registers are not available to the programmer, but 8085 uses them internally to
hold temporary data during execution of some instructions.
14. In what other way HL pair can be used?
ANS:
HL register pair can be used as a data pointer or memory pointer.
15. Describe the Status Register of 8085?
ANS:
Explain the Flag registers and the structure.
16. What is the purpose of increment/decrement address latch register?
ANS:
These 16-bit registers increment/decrement the contents PC or SP when
instructions related to them are executed.
17. What is an instruction?
ANS:
An instruction is a command which asks the microprocessor to perform a
specific task or job.
18. What is meant by instruction set?
ANS:
The entire different instructions that a particular microprocessor can handle is
called its instruction set.
19. What are the different types of data transfer operations possible?
ANS:
The different types of data transfer operations possible are cited below;
Between two registers.
Between a register and a memory location.
A data byte can be transferred between a register and a memory location.
Between an I/O device and the accumulator.
Between a register pair and the stack.
The term ‘data transfer’ is a misnomer – actually data is not transferred, but copied from
source to destination.
20. Explain the two instructions (a) LDAX and (b) STAX
ANS;
The instruction LDAX indicates that the contents of the designated register
pair point to a memory location and copies the content of the memory location into the
accumulator.
As an Example: let D=40H, E= 50H and memory location 4050H =AB H. Then LDAX D
transfers the contents of memory location 4050H to the accumulator. Thus, after the
execution of instruction, ACC = AB H.
Register contents Memory Register contents after
Before execution location instruction
Posts
