Microprocessor and Microcontroller (4341101) - Winter 2023 Solution

Question 1(a) [3 marks]

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Compare RISC and CISC.

Answer:

Mnemonic: “RISCs Complete Instructions Simply”

Question 1(b) [4 marks]

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Compare Von-Neumann and Harvard architecture.

Answer:

Diagram:

Mnemonic: “Harvard Has Separate Spaces”

Question 1(c) [7 marks]

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Explain: 8085 Instruction Format, Control Unit, Machine Cycle, ALU

Answer:

Instruction Format:

• Instruction Format: Contains opcode (3-8 bits) and 0-2 operands
• Control Unit: Heart of processor that coordinates all operations
• Machine Cycle: Consists of fetch, decode, execute phases
• ALU: Handles ADD/SUB/AND/OR/XOR operations on data

Diagram:

Mnemonic: “CIMA: Control Interprets, Machine Acts”

Question 1(c OR) [7 marks]

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Compare Microprocessor and Microcontroller.

Answer:

Diagram:

Mnemonic: “Micro-P Processes, Micro-C Controls”

Question 2(a) [3 marks]

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Explain Instruction Fetching, Decoding and Execution Operation in microprocessor.

Answer:

Diagram:

Mnemonic: “FDE: First Get, Then Understand, Finally Do”

Question 2(b) [4 marks]

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Explain Bus Organization of 8085 microprocessor.

Answer:

Diagram:

Mnemonic: “ADC: Address points, Data flows, Control directs”

Question 2(c) [7 marks]

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Describe architecture of 8085 microprocessor with the help of neat diagram.

Answer:

Diagram:

• ALU: Performs arithmetic & logical operations
• Control Unit: Fetches & decodes instructions
• Registers: Store data temporarily during processing
• Buses: Carry address, data and control signals

Mnemonic: “ARCBD: Architecture Registers Control Buses Data”

Question 2(a OR) [3 marks]

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Explain De-multiplexing of Address and Data buses for 8085 Microprocessor.

Answer:

Diagram:

Mnemonic: “ALAD: ALE Latches Address before Data”

Question 2(b OR) [4 marks]

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Draw Flag Register of 8085 microprocessor & explain it.

Answer:

Mnemonic: “SuZie AC’s Perfect CarrY”

Question 2(c OR) [7 marks]

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Describe Pin diagram of 8085 microprocessor with the help of neat diagram.

Answer:

Diagram:

• Address/Data Pins: Multiplexed pins save physical pins
• Control Pins: Coordinate memory and I/O operations
• Interrupt Pins: Allow external device interrupts
• Serial Pins: Provide basic serial communication

Mnemonic: “ACID-PS: Address-Control-Interrupt-DMA-Power-Serial”

Question 3(a) [3 marks]

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Explain Stack, Stack Pointer and Stack operation.

Answer:

Diagram:

Mnemonic: “SP Points to LIFO Lane”

Question 3(b) [4 marks]

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Draw Pin diagram of 8051 microcontroller.

Answer:

Mnemonic: “PORT 0123: Data-General-Address-Special”

Question 3(c) [7 marks]

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Draw Timers/Counters logic diagram of 8051 microcontroller and explain its operation in various modes.

Answer:

Timer/Counter Diagram:

• Timer: Uses internal clock, counts machine cycles
• Counter: Uses external input, counts external events
• Control Bits: TMOD register sets mode, TCON controls operation
• Modes: Different configurations for different timing needs

Mnemonic: “MARC: Mode Auto-Reload Count”

Question 3(a OR) [3 marks]

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List Common features of Microcontrollers.

Answer:

Mnemonic: “CRITICS: CPU ROM I/O Timers Interrupts Comm Serial”

Question 3(b OR) [4 marks]

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Explain Internal RAM Organization of 8051 microcontroller.

Answer:

Diagram:

Mnemonic: “RBBS: Registers Bits Buffer Scratch”

Question 3(c OR) [7 marks]

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Explain architecture of 8051 microcontroller with the help of neat diagram.

Answer:

Diagram:

• Harvard Architecture: Separate program and data memory
• CISC Design: Rich instruction set (over 100 instructions)
• In-built Peripherals: No need for external components
• Single-chip Solution: Complete system on one chip

Mnemonic: “CAPITALS: CPU Architecture Ports I/O Timer ALU LS-Interface Serial”

Question 4(a) [3 marks]

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Write an 8051 Assembly Language Program to Copy the data from external RAM Location 0123h to TL0 and Data from external RAM location 0234h to TH0.

Answer:

      MOV  DPTR, #0123H   ; Load DPTR with source address 0123H
      MOVX A, @DPTR       ; Read data from external RAM
      MOV  TL0, A         ; Copy to Timer 0 low byte
      
      MOV  DPTR, #0234H   ; Load DPTR with source address 0234H
      MOVX A, @DPTR       ; Read data from external RAM
      MOV  TH0, A         ; Copy to Timer 0 high byte

Key Steps:

• Use DPTR to address external RAM
• MOVX instruction for external memory access
• Direct transfer to timer registers

Mnemonic: “DRAM: DPTR Read Address Move”

Question 4(b) [4 marks]

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Write an 8051 Assembly Language Program to blink LED interfaced at port P1.3 at time interval of 1ms.

Answer:

AGAIN:  SETB P1.3         ; Turn ON LED at P1.3
        ACALL DELAY       ; Call delay subroutine
        CLR  P1.3         ; Turn OFF LED at P1.3
        ACALL DELAY       ; Call delay subroutine
        SJMP AGAIN        ; Repeat forever

DELAY:  MOV  R7, #250     ; Load R7 for outer loop
OUTER:  MOV  R6, #1       ; Load R6 for inner loop
INNER:  DJNZ R6, INNER    ; Decrement R6 until zero
        DJNZ R7, OUTER    ; Decrement R7 until zero
        RET               ; Return from subroutine

Key Steps:

• Toggle P1.3 pin to blink LED
• Nested delay loop for timing
• Infinite loop for continuous blinking

Mnemonic: “STACI: Set-Timer-And-Clear-Infinitely”

Question 4(c) [7 marks]

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List Addressing Modes of 8051 Microcontroller and explain all of them with the help of example.

Answer:

Examples:

• Immediate: MOV A, #55H (Load A with 55H)
• Register: ADD A, R3 (Add R3 to A)
• Direct: MOV 40H, A (Store A at address 40H)
• Indirect: MOV @R0, #5 (Store 5 at address in R0)
• Indexed: MOVC A, @A+DPTR (Read code memory)
• Bit: CLR C (Clear carry flag)
• Relative: JZ LOOP (Jump if A is zero)

Mnemonic: “I’M DIRBI: Immediate Register Direct Bit Indexed”

Question 4(a OR) [3 marks]

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Write an 8051 Assembly Language Program to Subtract the content of RAM location 11h from RAM location 14h; put result in RAM location 3Ch.

Answer:

      MOV  A, 14H       ; Load content of RAM location 14H to A
      CLR  C            ; Clear carry flag
      SUBB A, 11H       ; Subtract content of 11H with borrow
      MOV  3CH, A       ; Store result in RAM location 3CH

Key Steps:

• Load minuend into accumulator
• Clear carry for correct subtraction
• Use SUBB for subtraction with borrow
• Store result in destination

Mnemonic: “LCSS: Load-Clear-Subtract-Store”

Question 4(b OR) [4 marks]

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Write an 8051 Assembly Language Program to generate a square wave of 50% duty cycle on bit 3 of Port 1 using Timer 0 in Mode 1.

Answer:

      MOV  TMOD, #01H   ; Timer 0, Mode 1 (16-bit)
AGAIN: MOV  TH0, #0FCH   ; Load high byte
      MOV  TL0, #18H    ; Load low byte (-1000 in 16-bit)
      SETB TR0          ; Start timer
      JNB  TF0, $       ; Wait for overflow
      CLR  TR0          ; Stop timer
      CLR  TF0          ; Clear timer flag
      CPL  P1.3         ; Toggle P1.3
      SJMP AGAIN        ; Repeat

Key Steps:

• Configure Timer 0 in Mode 1
• Preload timer with value for 1ms delay
• Wait for timer overflow
• Toggle output bit for square wave

Mnemonic: “MSTCCS: Mode-Set-Timer-Check-Clear-Switch”

Question 4(c OR) [7 marks]

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Explain any seven Logical Instructions with example for 8051 Microcontroller.

Answer:

Examples:

• ANL: ANL A, #0FH (A = A AND 0FH, masks high nibble)
• ORL: ORL 20H, A (20H = 20H OR A, sets bits)
• XRL: XRL A, #55H (A = A XOR 55H, toggles bits)
• CLR: CLR C (Clear carry flag, C = 0)
• CPL: CPL A (Complement A, A = NOT A)
• RL: RL A (Rotate A left one bit)
• RR: RR A (Rotate A right one bit)

Mnemonic: “A-OX-CCR: AND OR XOR Clear Complement Rotate”

Question 5(a) [3 marks]

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Draw Interfacing of Push button Switch with 8051 microcontroller.

Answer:

Key Points:

• Active-low configuration (button press gives 0)
• Pull-up resistor prevents floating input
• Can connect to any I/O pin

Mnemonic: “PIP: Pull-up-Input-Press”

Question 5(b) [4 marks]

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Interface Relay with 8051 microcontroller.

Answer:

Key Steps:

• Port pin drives transistor base
• Transistor switches relay coil
• Diode protects against back EMF
• Relay contacts switch high-power load

Mnemonic: “TRIP: Transistor-Relay-Interface-Protection”

Question 5(c) [7 marks]

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Interface ADC0804 with 8051 microcontroller.

Answer:

Circuit Diagram:

• ADC0804: 8-bit A/D converter with 0-5V input range
• Interface: Connect data pins to Port 1, control to Port 3
• Operation: Write to ADC to start conversion, wait for INTR, read result
• Resolution: 8-bit (256 steps) for 0-5V gives ~19.5mV per step

Mnemonic: “CRIW: Control-Read-Interrupt-Write”

Question 5(a OR) [3 marks]

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List Applications of microcontroller in various fields.

Answer:

Mnemonic: “I-MACS: Industrial-Medical-Automotive-Consumer-Security”

Question 5(b OR) [4 marks]

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Interface Stepper motor with 8051 microcontroller.

Answer:

Circuit Diagram:

Code Structure:

; Clockwise Rotation Sequence
STEP_SEQ: DB 0000_1000B  ; Step 1
          DB 0000_1100B  ; Step 2
          DB 0000_0100B  ; Step 3
          DB 0000_0110B  ; Step 4

Mnemonic: “PDCS: Port-Driver-Current-Sequence”

Question 5(c OR) [7 marks]

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Interface LCD with 8051 microcontroller.

Answer:

Circuit Diagram:

Basic Commands:

0x01 - Clear Display
0x02 - Return Home
0x0C - Display ON, Cursor OFF
0x38 - 8-bit, 2 line, 5x7 dots

• Initialization: Configure LCD for 8-bit mode, 2 lines
• Writing: Send data with RS=1, control with RS=0
• Timing: E pulse must meet timing requirements
• Contrast: Adjust with potentiometer on VEE pin

Mnemonic: “DICE: Data-Instruction-Control-Enable”