ANAND INSTITUTE OF HIGHER TECHNOLOGY
KAZHIPATTUR-603103
DEPARTMENT OF EIE
QUESTION BANK
Staff Name: Dr. S. Solai manohar/ J.Anitha
Year/Sem: III /V
Sub/Code: Microprocessors & Microcontrollers/ EC2312
Unit I -8085&8086 PROCESSOR
PART A
1. What is Microprocessor? Give the power supply & clock frequency of 8085?
[May 2014]
A microprocessor is amultipurpose, 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. What are the various flags used in 8085? [Nov/Dec 2013 , Nov/Dec 2012]
The 8085 includes five flip-flops, also called flags, which are set or reset after an operation
according to data conditions of the result in the accumulator and other registers. They are
called Zero (Z); carry (CY), Sign(S), Parity (P) and Auxiliary Carry (AC) flags. And the
most commonly used flags are Zero, Carry, and Sign.
3. What are the different addressing modes of 8085. [Nov/Dec 2013]
The 8085 has the 5 different types of addressing. They are
1.
2.
3.
4.
5.
Immediate Addressing
Direct Addressing
Register Addressing
Register Indirect Addressing
Implied Addressing
4. What is ALE? [Nov/Dec 2013]
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.
5. What is the function of program counter in 8085 microprocessor? [May 2013]
The function of the program counter is to point to the memory address from which the next
byte is to be fetched. When a byte (machine code) is being fetched, the program counter is
incremented by one to point to the next memory location.
6. How many address and data lines are used in 8086 microprocessor? [May 2014]
The 8086 is a 16-bitmicroprocessor . It has 20 address lines i.e AD0- AD15,A16-A19 and 16
Data lines.
7. What is meant by minimum and maximum modes used in 8086? [Nov/Dec 2012]
When the Minimum mode operation is selected, the 8086 provides all control signals
needed to implement the memory and I/O interface.The minimum mode signal can be
divided into the following basic groups : address/data bus, status, control,
interrupt and DMA
When the 8086 is set for the maximum-mode configuration, it provides signals for
implementing a multiprocessor / coprocessor system environment.
8. What is program counter? [Nov/Dec 2012, May 2014]
The function of the program counter is to point to the memory address from which the next
byte is to be fetched. When a byte (machine code) is being fetched, the program counter is
incremented by one to point to the next memory location.
9. What is Microprocessor ?[Nov/Dec 2011]
It is a program controlled semiconductor device (IC}, which fetches, decodes and executes
instructions.
10. What is assembly language?[April 2009]
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.
11. What is the drawback in machine language and assembly language, programs?[April
2009]
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.
12. Why address bus is unidirectional?[May/Jun 2010]
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.
13. Explain the function of M/IO in 8086.[Apr/May 2010]
The signal M/IO is used to differentiate memory address and 1/0 address When the
processor is accessing memory locations MI 10 is asserted high and when it is accessing
1/0 mapped devices it is asserted low.
14. Define flag and write the flags of 8086.[Apr/May 2011]
The flags are used to reflect the data conditions in the accumulator.
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)
15. What are the interrupts of 8086?[Nov/Dec 2009]
The interrupts of 8085 are INTR and NMI. The INTR is general maskable interrupt and
NMI is non-maskable interrupt.
16. How clock signal is generated in 8086? What is the maximum internal clock
frequency of 8086?[Nov/Dec 2009]
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.
17. Differentiate between software and hardware interrupts? [Apr/May 2010]
The Software interrupt is initiated by the main program, but the Hardware interrupt is
initiated by an external device. In 8085, the Software interrupt cannot be disabled or
masked but the Hardware interrupt except TRAP can be disabled or masked.
18. What is interrupt? [Apr/May 2010]
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.
19. What do you mean by masking the interrupt? How it is activated in8085? [Apr/May
2012]
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.
20. List the main applications of 8 bit microprocessors? [May/Jun 20012]

LCD

Microcomputer

Keyboard display.
21. What is Address Bus and System Bus? [Apr/May 2010]
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. System Bus is a group of conducting lines that carries data,
address and control Signals.
22. What is a flag? [Apr/May 2010]
The data conditions, after arithmetic or logical operations, are indicated by setting or
resetting the flip-flops called flags.
23. What is an Interrupt? Haw the interrupt are classified ?[Nov 2008]
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
22. Give the power supply & clock frequency of 8085[NOV/DEC 2011]
The power supply of 8085 is +5V and clock frequency in 3MHz.
23. List the four instructions which control the interrupt structure of the 8085
[NOV/DEC 2006, APR/MAY 2011]
• DI (Disable Interrupts)
• EI (Enable Interrupts)
• RIM (Read Interrupt Masks)
• SIM (Set Interrupt Masks)
24. Define instruction cycle, machine cycle and T-state [May/Jun 2006, APR/MAY2011]
Instruction cycle is defined, as the time required completing the execution of an instruction.
Machine cycle is defined as the time required completing one operation of
accessing
memory, I/O or acknowledging an external request. T-cycle is defined as of subdivision of
the operation performed in one clock period.
25. Steps involved to fetch a byte in 8085[Apr 2012]
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
PART B
1. (i) Interface a 8KX8 EPROM IC and 2KX8 RAM IC with 8085 such that the starting
address assigned to them are 0000H and 4000H respectively using address decoder having
NAND gate and inverters (8)[May 2014]
(ii) Draw the timing diagram of I/O read cycle in 8085 and explain it (8)[May 2014]
2. Draw and Explain the Architecture of 8085(16) [ Nov 2013]
3. Explain with a neat block diagram the architecture of 8086 microprocessor (16)[ Nov 2013]
4. (i) Compare the features of 8085 and 8086 microprocessor (6) [ Nov 2013]
(ii) Describe the interrupt structures of 8086 microprocessor (10) [Nov 2013]
5. Describe the functional pin diagram of 8085. (16)[Nov 2011, 2012]
6. Describe the functional block diagram of 8085. (16)[May 2006,2010]
7. Explain the 8085 interrupt structure in detail. (16)[Apr 2005, 2008, Nov 2013]
8. Explain with neat diagram architecture of 8086. (16)[ Nov 2012]
9. (i) Draw the timing diagram of OUT instruction.(8) [ Nov 2012]
(ii) What are interrupts? Explain the interrupts in 8085. (8) [Nov 2012]
10. (i) Explain in detail about the addressing modes in 8085. (6) [ Nov 2012]
(ii) Write an assembly language program with algorithm in 8085 to implement a counter
from FF-00 (Down counter) in Hex. Use a subroutine to generate a delay of one second
between the counts. (8) [Nov 2012]
11. i) write an assembly language program to generate the square wave form using DAC .
Assume the Ton = 70 % (10) [ Nov 2012
12. (ii) Write an assembly language program with algorithm in 8085 to convert a given ASCII
number to binary Equivalemt. (8) [ Nov 2012]
13. Explain various machine cycles supported by 8085. (16)[Nov 2009]
14. (i) With suitable examples explain how I/O devices are connected using memory mapped
I/O and peripheral I/O. (10)[Apr 2008]
(ii) Design a microprocessor system to interface an 8K × 8 EPROM and 8K × 8 RAM.
(6)[Apr 2010]
15. Draw timing diagrams for the following instruction with appropriate control and status
signal. Explain in brief. CALL 2000 (16)[Nov 2009]
16. Draw and explain the timing diagram of the following instructions of 8085
Microprocessor.[Nov 2010]
(i)
LDA 2050H
(ii)
RET (16)
17. With necessary diagrams, write short notes on the following [May 2011]
(i)
RAM memory interfacing
(ii)
ROM memory interfacing
(iii)
Interrupt structure of 8085 (16)[Apr 2007]
18. (i) Using peripheral mapped I/O, design a seven segment LED output port with device
address of F2h using necessary control ICs. Draw the schematic and write 8085 ALP for
displaying digit 8. (8)[Apr 2006]
(ii) Distinguish peripheral mapped I/O and memory mapped I/O technique (8)[May 2005]
19. (i) Write short notes on vectored interrupts of 8085. (8)[Nov 2011]
(ii) Draw the microprocessor Bus timing for the instruction STA 4500h and Explain. (8)
Nov 2011]
UNIT II -8085 PROGRAMMING & INSTRUCTION
PART A
1.
What is the difference between MOV and MVI instructions? [ Nov 2012]
In the
The MOV instruction copies data between two registers, or between a register and
memory. The MVI instruction differs only in that the source data is contained in the byte
immediately following the opcode byte.hat the s
2.
Show the different instruction formats used in 8085.[Nov 2013]
(i)One byte instruction
(ii) Two byte instruction
(iii) Three byte instruction
3.
What is the type of stack used in 8085? [Nov 2009]
First in First out
4.
Define addressing modes. How many addressing modes are available in 8085?[Apr
2003]
The different ways that a microprocessor can access data are referred to as addressing
modes.5 addressing modes are available in 8085.
5.
Explain the following instruction.[Apr 2007]
i) LHLD 8020 (1)
This instrtion copies the contents of the memory location given within the instruction into
the L reg and the contents of the next memory location into the H reg.
ii) XTHL (1)
This instruction exchanges the contents of the memory location pointed by thewith the
contents of the L Reg and the contents of the next memory location into the H reg.
6.
What do you mean by Looping, Counting and Indexing? [Nov 2006]
Looping: In this tech the program is instructed to execute certain set of instructions
repeatedly to execute a particular task number of times.
Counting: This tech allows programmer to count how many times the ins of instruction are
executed.
Indexing: This tech allows programmer to point or refer the data stored in sequential
memory location one by one.
7.
What is the subroutine? How it is useful? [Dec 2012]
When interrupt line is high, the microprocessor executes the current operation and goes to
the specific vector location.
8.
Explain the need of software timers. [Nov 2010]
A timer can be used to control the sequence of an event or process.
9.
Differentiate cascade stack and memory stack? [Apr 2012]
Cascade stack- stack to store the return address memory stack- meaning that only 1 MB of
memory can be addressed
10. What is the significance of ‘XCHG’ and ‘SPHL’ instructions? [Nov 2008]
‘XCHG’-Exchange the contents of HL register pair
SPHL-store the contents of HL register pair
11. Define two-byte instruction with one example?[May 2008]
In a 2-byte instruction, the first byte specifies the Opcode; the second byte specifies the
operand.
Example: Opcode operand binary code hex code
MVI A, Data 0011 1110 3E First byte
DATA Data second byte
12. Write instructions to load the hexadecimal numbers 65H in register C, and 92h in the
accumulator A .Display the number 65H at PORT0 and 92H at PORT1? [Apr 2011]
MVI C, 65H
MVI A, 92H
OUT PORT1 ; DISPLAY 92H
MOV A, C ; COPY C INTO A FOR DISPLAY
OUT PORT0 ; DISPLAY 65H
HLT
13. What operation can be performed by using the instruction ADD A? [Apr 2005]
The instruction ADD a will add the content of the accumulator to itself; this is equivalent to
multiplying by 2.
14. What is the machine control operations used in 8085 microprocessor? [Apr 2011]
HLT: Halt
NOP: No Operation
16. Give the difference between JZ and JNZ? [Apr 2010]
JZ change the program sequence to the location specified by the 16-bit address if the zero
flag is set
JNZ change the program sequence to the location specified by the 16-bit address if the zero
flag is reset.
20. What operation can be performed by using the instruction SUB A? Specify the status
of Z and CY? [Apr 2008]
The instruction SUB a will clear the accumulator. The flag status will be CY = 0 and Z =
1.
21. Define Opcode and operand? [Apr 2010]
The operation to be performed is called Opcode. The data to be operated is called operand.
22. Define the types of branching operations?[May 2011]
Jump: to test the conditions
Call, Return, And Restart: Change the sequence of the program
29. Write 8085 assembly language instructions to store the contents of the flag register in
memory location 2000H.[Nov 2010]
PUSH PSW
POP B
MOV A,C
STA 2000H.
HLT
30. Write an 8085 program to generate a time delay of 0.4sec given crystal frequency
5MHZ.[May 2009]
Operating frequency = 5/2 = 2.5MHZ.
Time for one T-state = 1/ 2.5MHZ = 0.4sec.
Number of T-states required = Required Time/Time for 1T-state
= 0.4sec/ 0.4sec
= 1 x 106
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
31. What is assembler? [APRIL/MAY2008 NOV/DEC 2011,APR/MAY2011]
The assembler translates the assembly language program text which is given as input to
assembler to their binary equivalents known as object code. The time required to
the
translate
the assembly code to object code is called access time. The assembler checks for syntax errors
& displays them before giving the object code.
33. What are Macros?[NOV/DEC 2007,2011]
Macro is a group of instruction. The macro assembler generates the code in the program. Each
time where the macro is called. Macros are defined by MACRO & ENDM directives.
Creating macro is similar to creating new opcode that can be used in the program
INIT MACRO
MOV AX, data
MOV DS
MOV ES, AX
ENDM
35. List the Software and Hardware interrupts of 8085? [Apr 2011]
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.
37. Differentiate Register addressing mode and register indirect addressing mode with an
example. (April/May 2011)
A. Register addressing mode
A.Register indirect addressing mode
B .When a microprocessor wants to store a
B. When a microprocessor wants to retrieve a
byte of information in memory, or retrieve a
byte of information from memory, it needs to
byte of information from memory, it needs to
refer to the address of the byte in the
refer to the address of the byte in the
instruction with the help of a memory
instruction. Ex: MOV A,B
location. Ex: MOV A,M Where M is the
address of memory stored in HL pair.
38. Define look up table. (April/May 2011)
A look up table, is what it say, a list of data that is used in programming ofmicrocontrollers,
it is a table that the program use to look up data that it need to do the job, it is a list of data and
each data item is associated with a index, in other words where in the table it is, look at the
examples at this link.
39. What is a Stack? (NOV 2011)
The stack is an area of memory identified by the programmer for temporary storage of
information. In other words, the programmer defines the bottom of the stack and the stack
grows up into reducing address range.
40. What is indirect addressing? (NOV 2011)
Indirect addressing mode in an 8085 is when the address of the operand is contained within a
register, rather than directly within the instruction itself. Instructions that do this are LDAX,
STAX, and any of the move, arithmetic, logical, or compare instructions that use M as the
source or destination.
PART-B
1. Write an assembly language program with its output to add two 16 bit numbers using 8085
(16) [Nov 13]
2. Discuss in detail about the 8085 instruction set, explaining about the various typesof
operations (16) [ Nov 13]
3. (i) Describe with suitable examples the data transfer instructions in 8085 microprocessor(8)
[Nov 13]
(ii) Write an 8085 assembly language program to sort numbers ascending orders (8)
[Nov 13]
4. (i) Describe the categories of instructions used for data manipulations in 8085
microprocessor (8) [Nov 13]
(ii) Describe with a suitable 8085 assembly language program the use of subroutine
instructions. (8) [Nov 13]
5. . Explain the addressing modes of 8085 with example. (16)[Nov 2010]
6. 2. Explain the Different types of instruction in 8085. (16)]May 2009]
7. 3. i) Write a program to arrange n numbers in ascending order. (8)[Apr 2008]
ii) Write a program to unpack a two digit BCD number stored at memory location 1C00H. (8)
10. Explain the BCD to Decimal code conversion technique and write 8085 assembly language
program for the same. (16)[Apr 2008]
11. Explain the BCD to Seven Segment code conversion technique and write 8085 assembly
language program for the same. (16)[May 2010]
12. i) Write a program to calculate the factorial of a number between 0 to 8. (8)[Nov 2005]
ii) Write a program to find the number of negative, zero and positive numbers. (8)
13. Explain the operations carried out when 8085 executes the instructions (16)[Apr
2007,2009]
(i) MOV A, M
(ii) XCHG
(iii) DAD H
(iv) DAA
(v) POP PSW
14. Write 8085 assembly language program to find the seven segment codes for the lower and
upper nibble of the given 8 – bit binary number using look up table technique and store the
result in memory. (16)[May 2010]
15.Write 8085 Assembly language program to perform the following ab + ac, where a, b
and c are 8 bit binary numbers. Explain with algorithm and flowchart. (16)[Nov 2012]
16 (i) Write 8085 ALP to perform 16 bit addition of 2 numbers from location 4100h
and 4102h using 16 bit move and arithmetic instructions and save the result from the next
memory location. (8)[Apr 2006]
(ii) With suitable example explain the various addressing modes used in the instruction set of
8085 microprocessor. (8)[Apr2005]
17. (i) Explain the operation of stack in 8085 microprocessor (8)[Nov 2008,2005]
(ii) Explain the sequence of events in the execution of CALL and RET instructions. (8)
UNIT -III PHERIPHERAL INTERFACING FOR 8085
PART A
1. What are the basic modes of operation of 8255. [ Nov 2013]
There are two basic modes of operation of 8255, They are:
1. I/O mode. 2. BSR mode.
In I/O mode, the 8255 ports work as programmable I/O ports, while In BSR mode only
port C (PC0-PC7) can be used to set or reset its individual port bits. Under the IO mode
of operation, further there are three modes of operation of 8255, So as to support
different types of applications, viz. mode 0, mode 1 and mode 2.
1) Mode 0 - Basic I/O mode
2) Mode 1 - Strobed I/O mode
3) Mode 2 - Strobed bi-directional I/O
2. What is the need for 8259 PIC?
[ Nov 2013]
The 8259A/82C59A-2 is a programmable interrupt controller (PIC). It is designed to
allow prioritizing and handling of Fahardware interrupt requests from peripheral
devices, mainly in a PC environment.
3. Write down the function of OBF in 8255. [Nov 2005]
Output Buffer Full function determines whether the bidirectional data transfer is allowed or
not.
4. Define PPI. [Nov 2008]
The 8255A is a widely used, programmable, parallel I/O device. It can be programmed
to transfer data under various conditions, from simple I/O to interrupt I/O.
5. Bring about the features of 8259. [Apr 2006]
It manage eight interrupt request
The interrupt vector addresses are programmable.
The priorities of interrupts are programmable.
The interrupt can be masked or unmasked individually.
6. Explain the advantages of PIC chips in microprocessor based systems.[Apr 2009]
To increase the interrupt handling capacity of the microprocessor.
7. Explain the working of receiver part of USART. [May 2003]
It manages all receiver related activities.Along with data reception, it does false start bit
detection,parity error detection,framing error detection,sync detection and break
detection.
8. What is key debouncing? [Nov 2006]
Key bouncing may cause multiple entries made for the same key.To overcome this
problem after a key press is sensed the device is made to wait for few milliseconds
Then the key is checked again to ensure it is still pressed. If it is still pressed it is taken
as a valid key press. This process is called keyboard debouncing.
9. How much current is needed to drive an LED? Draw a typical driver circuit for
it?[Nov 2008]
A current of between 5 and 30mA to light.
10. What is the count value needed to program the 8254 to generate a delay of 1
ms?[Apr 2004]
Count-1000,frequency-1khz
11. Name any two type of ADCS.[Apr 2010]
The different types of ADC are successive approximation ADC, Counter type ADC
flash type ADC, integrator converters and voltageto-frequency converters.
12. For a A/D converter circuit why Vref should be stabilized supply.[Apr 2010]
To regulate the supply.
13. Which is the fastest ADC and why? [May 2005]
Flash type ADC.
14. What do you mean by Quantization error? [May 2005]
The difference between an analog wave and its digital representation. Also known as
"quantization noise.".
15. What is the necessity of the programmable interval timer? [Nov 2002]
To generate the accurate time delay.
16. List the features of 8279.[Apr 2011]
It has built in hardware to provide key debounce.
It provides two output modes for display interface.
It provides three input modes for keyboard interface.
17. Compare parallel and serial type of data transfer. [May 2007]
In parallel communication number of lines required to transfer data depend on the
number of bits to be transferred.
In serial communication one bit is transferred at a time over asingle line.
18. Why the number of out ports in the peripheral-mapped I/O is restricted to 256
ports?[Apr 2005]
The number of output ports in the peripheral I/O is restricted to 256 ports because the
operand of the OUT instruction is 8-bits; it can have only 256 combinations
19. What are the control signals necessary in the memory mapped I/O? [May 2007]
MEMR, MEMW
20. What happens when the 8085 execute the out instruction? Nov 2009]
When the 8085 executes the out instruction, in the third machine cycle, it places the
output port address on the low-order address bus, duplicates the same port address on
the high-order bus, places the contents of the accumulator on the data bus and asserts
the control signal WR.
21. What are modes of operation supported by 8255? (Nov 2005 ECE)
The operating modes are:
Mode 0
-
buffered i/p or fetched o/p
Mode 1 strobe i/p-causes port A or B to function as latching i/p devices
Mode 1 strobe o/p-used in handshaking mode
Mode 2-only for group A, which is operated in bi-directional
22. What is the internal operating frequency of the 8279? How can you derive it from
any available clock signal? (Nov 2005 )
The 8279 require an internal clock frequency of 100KHz this can be obtained by
dividing the input clock by an internal prescaler. The prescaler can take the value from
2 to 31, which is programmable.
23. List the functions performed by 8279. (Apr 2005 )
The functions performed by 8279
Keyboard Scanning, Key Deboncing, Key code Generation, Informing the key entry to
CPU, Storing display codes, output display codes to LEDs and Display refreshing
24. How a keyboard matrix is formed in keyboard interface using 8279? (Apr 2004 )
The Return lines RL0 to RL7 of 8279 are used to form the columns of keyboard matrix.
In decoded scan the scan lines SL0 to SL3 of 8279 are used to form the rows of the
keyboard matrix. In encoded scan lines are connected to input of the decoder and the
output lines of the decoder are used as rows of keyboard matrix.
25. What is the resolution and conversion time in ADC? (Apr 2004 )
The resolution in ADC is minimum analog value that can be represented by the digital
data. If the ADC gives n bit digital output and the analog reference voltage is Vref, then
the resolution is (1/2n)*Vref volts .the conversion time in ADC is defined as the total
time required to convert an analog signal into its digital equivalent.
26. What is the difference between two key lockout and N-key rollover modes in 8279?
(Apr 2005 )
In keyboard interface there are two methods of handling keys. If one key is pressed and
generates its code that is called as two key lockout and on the other hand it detects all
the keys pressed in the order of entry and generates corresponding keycode.
27. State the functions of the control register in INTEL 8255? (Apr 2004 )
The content of this register called control word specify an input/output function for
each port.
28. What do you mean by BSR mode of 8255 PPI? (Nov 2003 )
The BSR mode is concerned only with the eight bits of port C, which can set or reset by
using an appropriate control word in the control register with D7 =0 is recognized as a
BSR control word and it does not alter any previously transmitted control word bit D7
=0
29. Mention any two functions performed by INTEL 8251. (Nov 2004 )
It is used for converting parallel data to serial or vice versa. The data transmission or
reception can be either asynchronous or synchronous. It is also used to interface
MODEM and established serial communication through MODEM over telephone lines
30. Specify the two types of serial communication. (Nov 2003 )
The two types are: i) synchronous and ii)asynchronous communication
31. What are the internal devices of 8255 ?[Apr 2005]
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.
32. What are the operating modes of port -A 8255?[May 2010]
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
33. What are the functions performed by port-C of8255?[Nov 2009]
The port-C pins are used for handshake signals.
Port-C can be used as an 8-bit parallel 1/0 port in mode-0.
It can be used as two numbers of 4-bit parallel port in mode-0.
The individual pins of port-C can be set or reset for various control
applications.
34. What are the different scan modes of of8279?[Apr 2012]
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.
35. What is USART ? What are the functions performed by INTEL 8251A?[May
2009, May 2013]
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.
36. What are the control words of 8251A and what are its functions ?[Dec 2011]
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 sending to enable the data transmission and reception.
37. What is key debouncing ?[May 2012]
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.
38. What is the difference in programming the 8279 for encoded scan and decoded
scan?[Nov 2010]
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.
39. Calculate full scale output for an 8 bit DAC for (0-10V) range. (NOV-2010)
Output = (Vfs /2n)[20+21+22+23+24+25+26+27] Where Vfs=10;n=8; =9.96 V
40. Distinguish between half duplex & full duplex transmission. (NOV-2012)
Half duplex---- no simultaneous both side transmission i.e though transmission
&reception can be done through the same channel they can‟t be done simultaneously.
Full duplex---- no simultaneous both side transmission i.e though transmission
&reception can be done through the same channel they can‟t be done simultaneously.
41. What are the features of 8051 microcontroller? (April/May 2011)
Inbuilt memory
Inbuilt ADC and DAC
Programmable with ALP and high level languages such as C
42. Distinguish between timers and counters. (April/May 2011)
A counter accumulates an unknown quantity of external events over a known interval
of
time. The measurement of interest is typically frequency when the events are
periodic. If
time. A timer
the events are random, the measurement involves event density over
accumulates a series events of a known interval over an interval that
is being measured. The measurement of interest is typically the time elapsed between
two events. If the start and stop events recur periodically, multiple measurements can
be made and averaged, allowing for increased resolution. Counter/timers in MPU's are
typically just counters that count external events in counter mode and processor cycles
in timer mode.
43. What are the modes in which 8255 can be operate? (NOV-2011)
The two basic modes of PPI are,
Bit set / reset mode,
I/O mode.
The I/O mode is further divided into 3 modes, 1.Mode 0 – simple I/O, 2.Mode 1 –
Handshake mode, 3.Mode 2 – Bi-directional I/O.
PART-B
1. (i) Draw and explain the functional block diagram of 8251 PPI (8) [ Nov 13]
(ii) Draw and explain the functional block diagram of 8251 USART(8) [Nov 13]
2. (i) Draw and explain the functional block diagram of 8279 keyboard display controller
(8) [ May 13]
(ii) Draw and explain the functional block diagram of 8253 timer (8) [ May 13]
3. Explain any one of the modes of 8255 in detail. (16)[Nov 2012]
4. With neat block diagram explain PPI. (16)[Apr 2005]
5. i) Using model, write a program to communicate between two microprocessors using
8255. (10)[May 2004]
ii) Show the control word format of 8255 and explain how each bit is programmed.
(6)[Nov 2010]
6. With neat block diagram explain the functions of 8259. (16)[Nov 2003]
7. i) Bring about the features of 8251. (6)[May 2006]
ii) Discuss how 8251 is used for serial communication of data. (6)[Apr 2007]
iii) Explain the advantages of using the USART chips in microprocessor based systems.
(4)[Apr 2007]
8. Design an interface circuit needed to connect DIP switch as an input device and display the
value of the key pressed using a 7 segment LED display. Using 8085 system, write a program
to implement the same. (16)[Nov 2005]
9. Explain the 7 segment LED interface with microprocessor.[Apr 2009]
10 i) Explain the advantages of using the keyboard and display controller chips in
microprocessor based system. (6)[May 2009]
ii) Write a program using RST 5.5 interrupt to get an input from keyboard and display it on the
display system. (6)
iii) Use RST 5.5 instead of RST 7.5 and change mask pattern accordingly. (4)
11i) Explain the working of 8254 timer and write a program using it to generate a square
waveform of period 3 msec. (10)[Nov 2007]
ii) Describe with any one of the mode configurations of 8254 timer in detail (6)[Nov 2010]
12. Explain how to convert an analog signal into digital signal. (16)[Apr 2010]
13. Interface an 8-bit DAC with 8085 microprocessor using 8255 and write assembly language
programs to generate square wave of 1 KHZ and triangular wave of 100 Hz.
The crystal frequency connected to 8085 is 6 MHz (16)[May 2011]
14. With necessary diagrams explain the interfacing of Analog to Digital converter with
microprocessor 8085. (16)[Nov2011]
UNIT- IV 8051 MICROCONTROLLER
PART A
1. What is the purpose of over flag in 8051 microcontroller? [ Nov 2013]
The OV, the overflow flag is set whenever the result of a signed number operation is
too large, causing the high-order bit to overflow into the sign bit. In general, the carry
flag is used to detect errors in unsigned arithmetic operations. The overflow flag is only
used to detect errors in signed arithmetic operations.
2. What is Microcontroller? [Nov 2012,2006]
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.
3. What are the addressing modes of 8051 microcontroller? [ Nov 2013]

Immediate Addressing Mode

Direct Addressing mode



Register direct addressing mode
Register indirect addressing mode
Indexed addressing mode
4. Write the vector address and priority sequence of 8051 interrupts.[May 2014]
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
5. List the features of 8051 microcontroller. [May 2005,2008]
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
6. Name any four additional hardware features available in microcontrollers when
compared to microprocessors. [Nov 2003]
Two multible mode,16 bit timers/counters,Four register banks,integrated Boolean
processor.
7. Explain software and hardware methods to start and stop timers in 8051.[Nov
2008]
When a timer is used to measure time it is also called an "interval timer" since it is
measuring the time of the interval between two events.
8. What is the purpose for the 8255 PPI? [May 2008,2012]
The 8255A is a widely used, programmable, parallel I/O device.It can be programmed to
transfer data under various conditions, from simple I/O to interrupt I/O.
9. List the operating modes of 8255A PPI? [Apr 2005,2009]
Two 8-bit ports (A and B)
Two 4-bit ports (Cu and CL)
Data bus buffer
Control logic
10. Specify the bit of a control word for the 8255, which differentiates between the I/O
mode and the BSR mode? [Nov 2009]
BSR mode D7= 0, and I/O mode D5 = 1
11. Write the control word format in the BSR mode? [Nov 2006]
D7 D6 D5 D4 D3 D2 D1 D0
0 X X X Bit Select S/R
BSR mode Not used Set = 1
Generally Set= 0 Reset = 0
12. What is USART? [May 2014]
USART is an integrated circuit. It is a programmable device ;its function and specifications
for serial I/O can be determined by writing instructions in its internal registers.
13. List the major components of 8251A programmable communication inteface?
[Apr 2009]
Read/Write control logic

¨ Three buffer registers

¨ Data register

¨ Control registertransmission receiver

¨ Data bus buffer

¨ Modem control
14. What is the purpose for scan section in Keyboard interface? [May 2011,2006]
The scan section has a scan counter and four scan lines. These scan lines can be decoded
using a 4-to-16 decoder to generate 16 lines for scanning.
15. What is the need of Coprocessor?[Nov 2004]
The general-purpose processors such as 8086 or 8085 are not optimized to do arithmetic
manipulations, CRT display manipulation and word processing. Hence we go for a
coprocessor, which is capable of doing dedicated functions (Special Operations) to increase
the overall execution speed of larger systems.
16. What is transmitter section in USART? [Apr 2011]
The transmitter section accepts parallel data from the MPU and converts them in to serial
data. It has two registers. A buffer register and an output register
17. Give the various modes of 8253 timer? [Apr 2005]
Mode 0: interrupt or terminal count
Mode 1: Rate generator
Mode 3:square wave generator
Mode 4: software triggered strobe
Mode 5:hardware triggered strobe
18. Write the steps necessary to initialize a counter in write operations? [Nov 2007]
Write a control word into the control register
Load the low-order address byte
Load the high order byte
19. List
the
major
components
of
8251A
programmable
communication
inteface?[May 2010]
Read/Write control logic
Three buffer registers
Data register
Control registertransmission receiver
Data bus buffer
Modem control
20. What are alternate functions of port 3 in 8051 microcontroller? [Nov 2006 , May
2014]
The alternate functions of port 3 are
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.
21. Compare the 8051,8031 and 8751 microcontroller? (Nov 2005 )
In 8031 there is no ROM
In 8051there is internal 128bytes EPROM
In 8751 there is internal 128bytes Flash ROM
22. What is function of DPTR register? (Apr 2005 )
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.
23. Name the interrupt of 8051 micro controllers. (Apr 2005 )
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
24. What is the special function registers available in 8051 micro controller? (Nov
2004)
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.
25. What is job of TMOD register? (Nov 2004 )
The TMOD register is used to select the operating mode and timer/counter operation of the
timers
26. What is the interrupt priority control register in 8051 micro controller? (Apr
2004)

External interrupt 0

Timer interrupt 0

External interrupt 1

Timer Interrupt 1

Serial Interrupt
27. List the merits of Memory Segmentation. (Apr 2004 )
It is easier to access the memory 256 bytes has been separated into two parts one is RAM
and other one is SFR .Due to memory segmentation we can program the SFR by
mentioning its address and moreover we can do bit wise as well as byte programming
28. Distinguish between Microprocessor and Micro controller. (Nov 2003 )
Sl.
Microprocessor
Microcontroller
No
1
Microprocessor
contains Microcontroller contains the circuitry of
ALU,general
purpose microprocessor and in addition it has
registers,stack pointer, program built- in ROM, RAM, I/O devices, timers
counter, clock timing circuit and and counters.
interrupt circuit.
2
It has many instructions to move It has one or two instructions to move
data between memory and CPU.
3
data between memory and CPU.
It has one or two bit handling It has many bit handling instructions.
instructions.
4
Access times for memory and I/O Less access times for built-in memory
devices are more.
5
Microprocessor
and I/O devices.
based
system Microcontroller based system requires
requires more hardware.
less hardware reducing PCB size and
increasing the reliability.
29. List any two application of micro controller. (Nov2003 )
Standalone devices
Automotive applications
30. State the function of RS1 and RS0 bits in the flag register of Intel 8031/8051. (Apr
2004 )
RS1 , RS0 – Register bank select bits
RS1
RS0
Bank Selection
0
0
Bank 0
0
1
Bank 1
1
0
Bank 2
1
1
Bank 3
31. Write a short note on bit wise instruction of 8051 micro controllers. (Nov 2003 )
Some of the SFR are both bit wise as well as byte wise programming some of them are B
register, ACC, IP, P0-P3, SCON, TCON, IE, PSW
32. Explain the function of the pins PSEN and EA of 8051.[May 2012]
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 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.
33. Write down the different operating modes for serial communication of 8051.[May
2008]
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
8-bit data, 9th programmable bit,1 stop bit, 1
2
start bit, Baud rate fixed.
1
3 8-bit data, 9th programmable bit,1 stop bit, 1
1
start bit, Baud rate variable
34. Explain the register IE format of 8051.[Apr 2003]
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.
35. What is the use of timing and control unit?[Apr 2009,2005]
Timing and control unit is used to deliver all the necessary timing and control signals
required for the internal operation of the circuit. It also derives control signals that are
required for controlling external system bus
36. List the features of 8051 microcontroller?[May 2009]
The features are
1.single_supply +5 volt operation using HMOS technology.
2.4096 bytes program memory on chip(not on 8031)
3.128 data memory on chip.
4.Four register banks.
5.Two multiple mode,16-bit timer/counter.
6.Extensive boolean processing capabilities.
7. 64 KB external RAM size
8. 32 bidirectional individually addressible I/O lines.
9.8 bit CPU optimized for control applications.
37. What are the distinct address spaces supported by 8051(Nov 2011)
The 8051 architecture supports several distinct physical address spaces. a) On - chip
program memory b) On - chip data memory c) External program memory, d). External
data memory, e).On-Chip special function registers.
38. What is the need for D/A converter?. (April/May 2011)
D/A converter (Digital to Analog Converter) is used to interface the microprocessor
output with the external device.
39. Specify the purpose of overflow flag in 8051 Microcontroller. (NOV-2010)
CY AC F0 RS1 RS0 OV - P0 0 - Select register bank 00 1 - Select register bank 11 0 Select register bank 21 1 - Select register bank 37 6 5 4 3 2 1 0.
PART-B
1. (i) Explain the different addressing modes in 8051 in detail (8) [May 2014]
(ii) Describe the different modes of operation of timers in 8051. (8)[May 2014]
2. Discuss the addressing modes of 8051 microcontroller with suitable examples (16)
[Nov 2013]
3. Write an 8051 C program that continuously gets a single bit of data from p 1.7 and
sends it to p1.0 , while simultaneously creating a square wave of 200 us period on pin
p2.5 . Use timer 0 to create the square wave . Assume that XTAL = 11.0592 MHZ (
Nov 2013]
4. Draw and explain the block diagram of 8051 microcontroller, also draw the diagram to
connect the 4K external EPROM [ Nov 2012]
5. What are the function of Timer in 8051? Explain the three modes of the same. [ Nov
2012]
6. Describe the architecture of 8051 with neat diagram. (16)[May 2009,2011]
7. i) Discuss the peripheral interface of 8051. (8)[Apr 2009]
ii) Explain the interrupt structure of 8051 microcontroller Explain how interrupts are
prioritized. (8)[Nov 2005]
8. i) What is the difference between the Microprocessors and Microcontrollers? (8)[Nov
2005]
ii) Explain the I/O port structure of 8051. (8)[May 2005]
9. I)Explain the different serial communication modes in 8051. (8)[Nov 2007]
ii) Explain the memory structure of 8051. (8)[Apr 2008]
10. States various modes available for timer in 8051. (8)[Nov 2011]
11. 6. Explain the functional pin diagram of 8051 Microcontroller. (8)[Apr 2004]
12. Explain the Timer/Counter functional unit of Microcontroller 8051 with relevant
diagrams. (16)[Nov 2011,2005]
13. Write 8051 ALP to read data from port 1 when negative edge triggered at INT0 and
supply the data to port 2 by masking the upper 4 bits. (8)[May 2010]
14. Explain the different serial communication modes in 8051. (8)[Apr 2006]
15. Write 8051 ALP to transmit ‘Hello World’ to PC at 9600 baud for external crystal
frequency of 11.0592 MHz. (8)[Apr 2010]
16. List out the steps involved in programming Timer 0 is model.(6) (NOV 2010)
17. i. With a neat sketch, explain the working of the 8051 microcontroller. (16) (Apr
2011)
ii. Explain in detail about the 8081 I/O ports and their functions. (16) (April/May
2011)
18. Explain in detail how serial communication is implemented in 8051 microcontroller.
(16) (April/May 2011).
19. With suitable block diagram, explain the architecture of 8051 microcontroller. Also
explain the function of each block. (16) (Nov 2011)
20. Explain the different modes of operation by serial port in 8051 in detail with its
associated registers. (16) (Nov 2011)
UNIT- V MICROCONTROLLER PROGRAMMING &
APPLICATIONS
PART A
1. Write about the jump statement? [May 2014]
There are three forms of jump. They are
LJMP(Long jump)-address 16
AJMP(Absolute Jump)-address 11
SJMP(Short Jump)-relative address
2. How the 8051 instructions are classified?[May 2014]
The 8051instructions are classified as five groups

Data transfer instructions

Arithmetic instruction

Logical instruction

Branching instruction

Boolean instruction
3. LED is connected to pin p0.7 , Write an assembly program to toggle the LED forever.[
Nov 2013]
4. Write an ALP to receive input from port p1.5 and if it is high an output 35 H is sent to
port 0? What are I/O instructions in 8051 microcontroller? .[ May2013]
5. What is the jump range? [Apr 2010]
There are three forms of jump. They are
LJMP(Long jump)-address 16
AJMP(Absolute Jump)-address 11
SJMP(Short Jump)-relative address
3. Explain the addressing modes of 8051. [May 2010]
(i)register addressing
(ii)Direct byte addressing
(iii)Register indirect addressing
(iv)Immediate addressing
(v)register specific addressing
(vi)Index addressing
4. Identify the addressing mode used by each of the following instruction.[Nov 2011]
i) MOV A, R4
register addressing
ii) MOVC A, @A+DPTR
Index addressing
iii) SWAP A
register specific addressing
iv) MOV A, #30H
Immediate addressing
5. Explain PUSH and POP instructions in 8051. [Apr 2005]
PUSH-The stack pointer is incremented by one. The contents of the indicated variable is
then copied into the internal RA M location addressed by the stack pointer.
POP-Reverse of PUSH operation
6. What are the instructions used to access external RAM. [Apr 2009]
MOVC A,@A+DPTR
MOVC A,@A+PC
7. What is key bounce? How it is achieved? [Nov 2009]
Mechanical switches are used as keys in most of the keyboards. When a key is pressed the
contacts bounce back and forth and settle down only after a small time delay (about 20 ms).
Even through a key is actuated once, it will appear to have been actuated several times.
This problem is called key bouncing .
11.How can you perform multiplication in 8051? [Nov 2008]
MUL AB multiplies the unsigned eight bit integers in the Accumulator and REG B .The
low order byte of the 16 Bit product is left in the accumulator,and the high order byte in B.
12.If the product is 12. How can you perform addition in 8051? [Apr 2012]
MOV A,#30H
ADD A,#50H
13 .Name any four bit manipulation instructions in 8051? [Apr 2012]
ANL A,ORL A,XRL A,CLR A
14. Write a program to subtract the contents of R1 of Bank 0from the contents of R0 of
Bank 2 using 8051? [May 2006]
MOV PSW,#10
MOV A,R0
MOV PSW,#00
SUBB A,R1
15. Write a program to subtract 2 8-bit numbers &exchange the digits using 8051? [May
2009]
MOV A,#9F
MOV R0,#40
SUBB A,R0
SWAP A
16. Write a program to swap two numbers using 8051? [Nov 2006,2003]
MOV A, #data
SWAP A
17. Write a program to add 2 8-bit numbers using 8051? [Nov 2005]
MOV A,#30H
ADD A,#50H
18. Write a program to find the 2’s complement using 8051? [Apr 2003,2009]
MOV A,R0
CPL A
INC A
21. Write about CALL statement in 8051? [Nov 2007]
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.
22. List the addressing modes of 8051?[May 2012,2006]
Direct addressing
Register addressing
Register indirect addressing.
Implicit addressing
Immediate addressing
Index addressing
Bit addressing
23. Write a program to mask the 0th &7th bit using 8051? [Apr 2007]
MOV A,#data
ANL A,#81
MOV DPTR,#4500
MOVX @DPTR,A
LOOP SJMP LOOP
24. Write A program to perfom multiplication of 2 nos using 8051? [May 2007]
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
25. Explain the interrupts of 8051 microcontroller? [Nov 2009]
INT0,TF0,INT1,TF1,R1&T1
26. Write a program using 8051 assembly language to change the data 55H stored in the
lower byte of the data pointer register to AAH using rotate instruction. (Apr 2004 )
MOV DPL,#55H
MOV A, DPL
RL A
Label :SJMP label
27. Explain the contents of the accumulator after the execution of the following program
segments:[Apr 2003]
MOV A,#3CH
MOV R4,#66H
ANL A,R4
A
3C
R4
66
A
24
28. Explain DJNZ instructions of Intel 8051 microcontroller?[Nov 2002]
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
29. Specify the single instruction, which clears the most significant bit of B register of
8051, without affecting the remaining bits.[Apr 2010]
Single instruction, which clears the most significant bit of B register of 8051, without
affecting the remaining bits is CLR B.7.
31. Write a program to load accumulator A, DPH and DPL with 30H.[Nov 2012]
MOV A,#30
MOV DPH,A
MOV DPL,A
34. What are the operations performed by Boolean variable instructions of 8051?[Apr
2007,2008]
The Boolean variable instructions can clear or complement or move a particular bit
addressable
RAM /SFR or carry flag.
35. Write a program to mask the 0th and 7th bit using 8051?[May 2009]
MOV A,#DATA
ANL A,#81
MOV DPTR ,#4500
MOVX @DPTR,A
LOOPSJMP LOOP
36. Write a program to subtract 2 8-bitnumbers and exchange the digits using 8051?[Nov
2004]
MOV A,#9F
MOV R0,#40
SUBB A,R0
SWAP A
37. List the instructions that affect all flags of 8051?[Nov 2005]
ADD,ADDC and SUBB
38. Which mode & Timer is used to set the baud rate?[Jun 2008]
Mode 2 and Timer 1 is used to set baud rate for serial communication.
39. Find the baud rate if TH1=-2,SMOD=1 and XTAL=11.0592 MHz. is this baud rate
support by IBM PCs?[May 2010]
With XTAL=11.0592 and SMOD =1,we have the timer 1 frequency =57600Hz.the baud
rate is 57600/2= 28800. This baud rate is not supported by the BIOS of the PC. However,
the PC can be programmed to do data transfer at such high speed . The software of many
modems can do this.
40. Discuss what happens if interrupt INT0, TF0 and INT1 are activated at the same
time. Assume priority levels were set by power up reset and that the external hardware
interrupts are edge triggered?[May 2008]
If these three interrupts are activated at same time, they are latched and kept internally.
Then the 8051 check all five interrupts according to their priority. If any is activated, it
services it in sequence. So above interrupts are services in the order of IE0, TF0 and IE1.
41. Give the number of times the four step sequence must be applied to a stepper motor
to make an angle 80 degree move if the motor has a 2 degree step angle?[Nov 2003,2009]
A motor with a 2- degree step angle has the following characteristics:
Step angle : 2 degrees Step per revolution :180Number of rotor teeth :45 Movement per 4step sequence : 8 degrees
So to move the rotor 80 degrees, we need to send 10 four-step sequence sight from each
other, 10*4*2=80 degrees
42. Write a program to send data to the DAC to generate a stair step ramp?[May 2010]
CLR A
AGAIN: MOV Pl, A
INC A
ACALL DELAY
SJMP AGAIN
43. Differentiate among SJMP, AJMP & LJMP instructions of 8051 microcontroller.
(NOV-2010)
SJMP short jump, two byte instruction, offset -127 to +128 AJMP Absolute jump, two
byte instruction, offset within 2Kbytes LJMP Long jump, three byte instruction, offset
within 64 Kbytes
24. Why do we put a driver in between the microcontroller and the stepper motor?
(April/May 2011)
A driver is the major interfacing device used between the stepper motor and the
Microcontroller. It is used to transfer the excitation signal from the microcontroller to the
stepper motor.
25. What are the registers involved in the serial data communication circuit of an 8051
microcontroller. (April/May 2011)
The 8051 has a serial data communication circuit that uses register SBUF to hold data.
Register SCON controls data communication; register PCON controls data rates and pins
RXD (P3.0) and TXD (P3.1) connect to the serial data network.
43. Write an 8051 assembly language to copy 10 bytes from RAM starting at 35H to RAM
starting at 60H. (NOV-2010)
ORG 0030H
MOV R0,#35H
MOV R1,#60H
MOV R2,#10
REPT:MOV A, @RO
MOV @R1,A
INC R0
INC R1
DJNZ R2,REPT
HERE:SJMP HERE
PART-B
1. What is 7 segment LED display? How to connect the same to the microcontroller?
Generate the Hex codes and Write and assembly language program to display the
numbers 1,2,3 and 4 in the LED display? (16) [ Nov 2012]
2. (i) Draw the diagram of Key matrix interfaced with 8051.(8) [ Nov 2012]
(ii) How the keyboard can interfaced with 8051? (8) [Nov 2012]
3. A switch is connected to pin p 2.7 . Write a ALP to monitor the status of SW and
perform the following [ Nov 2012]
i.
If SW = 0, the stepper motor moves clockwise.
ii.
If Sw = 1, the stepper motor moves counter clockwise.
(16)
4. Describe with a neat diagram the stepper motor control using microcontroller[May
2013]
5. Explain with a neat diagram the closed loop control of servo motor using
microcontroller(16) [ May2013]
6. With a neat circuit diagram explain how a 4 x 4 keypad is interfaced with 8051
microcontroller and write 8051 ALP for keypad scanning. (16)[Nov 2009]
7. Draw the schematic for interfacing a stepper motor with 8051 microcontroller and write
8051 ALP for changing speed and direction of motor. (16)[May 2005]
8. Draw the schematic for interfacing a servo motor with 8051 microcontroller and write
8051 ALP for servo motor control. (16)[Apr 2009]
9. i) Explain addition and subtraction instructions of 8051. (8)[Apr 2008]
ii) Explain various types of jump instructions according to range. (8)[Apr 2008]
10. i)Write a 8051 ALP to find Fibonacci series of N given numbers. (8)[Nov 2012]
ii) Write a 8051 ALP to find the average of given N numbers. (8)
11. Explain the operations carried out when the following instructions are executed by
8051.[May 2011]
(i) MOVX @R0,A
(ii) MOVC A, @A + PC
(iii) RLC A
(iv) CJNE A, 50H, L2
(v) JBC 20H, L3
(vi) XCH A, 30H where L2 and L3 are labels. (16)[Apr 2010]
12. Interface a 20 x 2 LCD with 8051 micro controller and write assembly language
program to display the following message in it at the middle.
HELLO ! ALL ARE WELCOME (16)[May 2009,2012]
13. Explain the 4 X 4 Keyboard interfacing with Microcontroller 8051. (16)[Nov 2006]
14. Explain the Microcontroller 8051 based Stepper motor control. (16)[Apr 2007]
15. Explain how you can control servo motor using IC8051.(16)(NOV 2010)
16. Write an 8085 ALP to transfer a message “YES” serially at 9600 band,8 bit data,1 bit
stop. Do this continuously.(16)(NOV 2010).
17. Explain in detail the procedure for interfacing the keyboard to the 8051 microcontroller.
(16) (April/May 2011)
18. I) Assuming that XTAL = 11.0592 Mhz, write a program to generate a square wave of
2 Khz frequency. (10) (April/May 2011)
ii. Explain the data transfer instructions used in the 8051 microcontroller.(6)
(April/May 2011)
19. Explain how stepper motor is interfaced to 8051 to enable the motor to rotate in the
clockwise direction. (16) (Nov 2011).
20. Describe how washing machine actions are designed using a microcontroller. (16)
(Nov 2011).