Microprocessor & Microcontroller Systems (1333202) - Summer 2024 Solution

Question 1(a) [3 marks]

List common features of 8051 microcontroller.

Answer:

Table: Common Features of 8051 Microcontroller

Mnemonic: "On Program Data I/O Timers Serial Interrupts SFRs"

Question 1(b) [4 marks]

Define T-State, Machine Cycle, Instruction Cycle and Opcode.

Answer:

Table: Microprocessor Timing Definitions

• T-State: Smallest unit of time in microprocessor operation
• Machine Cycle: Contains multiple T-states for memory access
• Instruction Cycle: Complete instruction execution time
• Opcode: Binary code identifying specific instruction

Mnemonic: "Time Machine Instruction Operation"

Question 1(c) [7 marks]

Compare Von-Neumann and Harvard Architecture.

Answer:

Table: Von-Neumann vs Harvard Architecture Comparison

Key Differences:

• Memory Access: Von-Neumann uses sequential access, Harvard allows simultaneous
• Performance: Harvard is faster for embedded applications
• Applications: Von-Neumann for general computing, Harvard for real-time systems

Mnemonic: "Von-Single Harvard-Dual"

Question 1(c) OR [7 marks]

Explain Microcomputer System with block diagram.

Answer:

Microcomputer System Components:

Table: Microcomputer System Components

• CPU: Executes instructions and controls system operation
• Memory: Stores programs and data for processing
• I/O: Provides communication with external devices
• Bus: Connects all components for data transfer

Mnemonic: "CPU Memory I/O Bus"

Question 2(a) [3 marks]

Draw Bus organization in 8085 Microprocessor.

Answer:

goat

Table: 8085 Bus Organization

Mnemonic: "Address Data Control"

Question 2(b) [4 marks]

List Flags used in 8085 and Explain working of each flags.

Answer:

Table: 8085 Flags Register

goat

• Sign Flag: Indicates negative result (MSB = 1)
• Zero Flag: Set when arithmetic result is zero
• Auxiliary Carry: Used for BCD arithmetic operations
• Parity Flag: Checks even number of 1's in result
• Carry Flag: Indicates overflow in arithmetic operations

Mnemonic: "Sign Zero Auxiliary Parity Carry"

Question 2(c) [7 marks]

Draw and Explain Block Diagram of 8085.

Answer:

Table: 8085 Block Components

• Data Flow: Instructions fetched via PC, decoded by CU, executed in ALU
• Register Operations: Accumulator works with ALU, other registers store data
• Address Generation: PC and SP provide 16-bit addresses
• Control Signals: CU generates timing and control signals

Mnemonic: "ALU Accumulator Registers Program Stack Control"

Question 2(a) OR [3 marks]

Explain Instruction Fetching, Decoding and Execution Operation in microprocessor.

Answer:

Table: Instruction Cycle Phases

Mnemonic: "Fetch Decode Execute"

Question 2(b) OR [4 marks]

What is Demultiplexing of Lower order Address and Data lines in 8085? Explain using neat sketch.

Answer:

goat

Demultiplexing Process:

• ALE Signal: Controls separation of address and data
• Latch IC: 74LS373 stores address when ALE is high
• Timing: Address appears first, then data on same lines

Table: Demultiplexing Components

Mnemonic: "Address Latch Enable Demultiplexes Lines"

Question 2(c) OR [7 marks]

Draw and Explain Pin Diagram of 8085.

Answer:

goat

Table: 8085 Pin Functions

• Address Lines: 16-bit addressing capability (64KB)
• Data Lines: 8-bit data transfer
• Control Lines: Memory and I/O operation control
• Interrupt Lines: Hardware interrupt handling

Mnemonic: "Address Data Control Interrupt Power Clock"

Question 3(a) [3 marks]

Draw IP SFR of 8051 and Explain function of each bit.

Answer:

goat

Table: IP Register Bit Functions

• Priority Levels: 1 = High priority, 0 = Low priority
• Default: All interrupts have low priority (00H)
• Usage: Set bit to 1 for high priority interrupt

Mnemonic: "Timer2 Serial Timer1 External1 External0"

Question 3(b) [4 marks]

Draw and explain Timer/Counter Logic diagram for 8051.

Answer:

Table: Timer Components

• Clock Source: Internal (system clock/12) or External (T0 pin)
• Operation: Counts up from loaded value to FFH
• Overflow: Sets TF0 flag and generates interrupt
• Modes: 4 different timer modes available

Mnemonic: "Timer High-Low Mode Control Flag"

Question 3(c) [7 marks]

Draw and Explain Block Diagram of 8051.

Answer:

Table: 8051 Block Components

• Architecture: Harvard architecture with separate program/data memory
• I/O Capability: 32 bidirectional I/O lines
• On-chip Features: Timers, serial port, interrupt system
• Memory: Von-Neumann for data, Harvard for program

Mnemonic: "CPU Program Data I/O Timer Serial Interrupt"

Question 3(a) OR [3 marks]

Draw PCON SFR of 8051 and Explain function of each bit.

Answer:

goat

Table: PCON Register Bit Functions

• SMOD: Doubles serial port baud rate when set
• GF1, GF0: User-defined flag bits
• PD: Activates power-down mode
• IDL: Activates idle mode

Mnemonic: "Serial General Power Idle"

Question 3(b) OR [4 marks]

In 8051 Serial communication Mode 1, For XTAL=11.0592 MHz, find TH1 value needed to have for 9600 and 4800 baud rate.

Answer:

Formula for Mode 1 Baud Rate:

Baud Rate = (2^SMOD/32) × (Timer1 Overflow Rate)
Timer1 Overflow Rate = XTAL/(12 × (256 - TH1))

For 9600 Baud Rate:

9600 = (1/32) × (11059200/(12 × (256 - TH1)))
9600 = 28800/(256 - TH1)
256 - TH1 = 3
TH1 = 253 = FDH

For 4800 Baud Rate:

4800 = (1/32) × (11059200/(12 × (256 - TH1)))
4800 = 28800/(256 - TH1)
256 - TH1 = 6
TH1 = 250 = FAH

Table: TH1 Values for Baud Rates

Mnemonic: "Higher Baud Higher TH1"

Question 4(a) [3 marks]

What are the differences in LCALL and LJMP instructions in 8051?

Answer:

Table: LCALL vs LJMP Comparison

• LCALL: Calls subroutine, saves return address on stack
• LJMP: Unconditional jump to specified address
• Stack Impact: LCALL uses 2 stack bytes, LJMP uses none
• Usage: LCALL for functions, LJMP for program flow control

Mnemonic: "Call Saves Jump Goes"

Question 4(b) [4 marks]

Write 8051 Assembly Language Program to generate square wave on port 1.0 using Timer0.

Answer:

Assembly

Program Explanation:

• Timer Setup: Mode 1 (16-bit timer)
• Count Value: -50000 for specific delay
• Square Wave: Toggle P1.0 on each overflow
• Continuous: Loop maintains square wave

Mnemonic: "Mode Load Start Wait Toggle Reload"

Question 4(c) [7 marks]

Explain any three Logical and any four Data Transfer Instruction of 8051 with example.

Answer:

Table: Logical Instructions

Table: Data Transfer Instructions

Detailed Examples:

Assembly

Mnemonic: "AND OR XOR Move External Push Pop"

Question 4(a) OR [3 marks]

Explain Instructions: (i) RRC A (ii) POP (iii) CLR PSW.7

Answer:

Table: Instruction Explanations

goat

• RRC A: Rotates accumulator right through carry flag
• POP: Removes top stack element into specified register
• CLR PSW.7: Clears carry flag (bit 7 of Program Status Word)

Mnemonic: "Rotate Pop Clear"

Question 4(b) OR [4 marks]

Write 8051 Assembly Language Program to Divide data stored in location 30H by data stored in location 31H and store remainder in 40h and quotient in 41h memory location.

Answer:

Assembly

Program Steps:

1. Load Data: Move dividend and divisor to A and B
2. Division: Use DIV AB instruction
3. Store Results: Quotient in A, remainder in B
4. Save: Store results in specified memory locations

Table: DIV AB Instruction

Mnemonic: "Load Divide Store"

Question 4(c) OR [7 marks]

List Addressing Modes of 8051 Microcontroller and Explain each with Example.

Answer:

Table: 8051 Addressing Modes

Detailed Examples:

Assembly

Mnemonic: "Immediate Register Direct Indirect Indexed Relative Bit"

Question 5(a) [3 marks]

Draw Interfacing of Relay with 8051 microcontroller.

Answer:

goat

Table: Interface Components

• Operation: Port pin HIGH → Transistor ON → Relay energized
• Protection: Diode prevents back EMF damage
• Isolation: Relay provides electrical isolation

Mnemonic: "Transistor Resistor Relay Diode"

Question 5(b) [4 marks]

Interface 7 Segment display with 8051 microcontroller and write a program to print "1" on it.

Answer:

goat

Program to Display "1":

Assembly

Table: 7-Segment Display Components

Mnemonic: "Current Limit Segment Pattern"

Question 5(c) [7 marks]

Interface DAC 0808 with 8051 microcontroller and write a program to generate Square wave.

Answer:

goat

Program to Generate Square Wave:

Assembly

Table: DAC Interface Specifications

Square Wave Generation:

• Low Level: 00H produces approximately 0V output
• High Level: FFH produces approximately 5V output
• Frequency: Determined by delay routine duration
• Output: Clean analog square wave at DAC output

Mnemonic: "Digital Analog Convert Square"

Question 5(a) OR [3 marks]

Interface of Push button Switch with 8051 microcontroller.

Answer:

goat

Table: Push Button Interface Components

Sample Program:

Assembly

Operation:

• Switch Open: Pull-up resistor makes pin HIGH (logic 1)
• Switch Pressed: Pin connected to GND, becomes LOW (logic 0)
• Debouncing: May require software debouncing for reliable operation

Mnemonic: "Pull-up Switch Ground"

Question 5(b) OR [4 marks]

Interface DC Motor with 8051 microcontroller.

Answer:

goat

Motor Control Program:

Assembly

Table: DC Motor Interface Components

Operation Principle:

• Motor ON: Port pin HIGH → Transistor saturated → Motor runs
• Motor OFF: Port pin LOW → Transistor cut-off → Motor stops
• Speed Control: PWM technique varies average power to motor
• Protection: Diode protects transistor from back EMF

Mnemonic: "Transistor Resistor Diode Motor"

Question 5(c) OR [7 marks]

Interface LCD with 8051 microcontroller and write a program to display "Hello".

Answer:

goat

Complete LCD Interface Program:

Assembly

Table: LCD Control Signals

Table: Important LCD Commands

LCD Display Process:

1. Initialization: Configure LCD parameters and clear display
2. Command Mode: Send commands with RS=0
3. Data Mode: Send characters with RS=1
4. Enable Pulse: Latch data/command with EN signal
5. String Display: Loop through message characters until null terminator

Character Display Steps:

• Set RS=1 for data mode
• Put character code on data bus
• Generate enable pulse (HIGH to LOW)
• Wait for LCD to process (1ms delay)
• Repeat for next character

Mnemonic: "Initialize Command Data Enable Display"