Microprocessor and Microcontroller (4341101) - Summer 2024 Solution
Solution guide for Microprocessor and Microcontroller (4341101) Summer 2024 exam
Question 1(a) [3 marks]
Describe any one Port Configuration of 8051 Microcontroller.
Answer:
| Configuration | Description |
|---|---|
| Port 0 | Dual-purpose port - 8-bit open drain bidirectional I/O port and multiplexed low address/data bus. External pull-up resistors required for I/O functions. |
Diagram:
goat
Mnemonic: "PORT 0-PLAD" (Port 0 needs Pull-ups, works as Latch/Address/Data)
Question 1(b) [4 marks]
Illustrate Microprocessor Architecture.
Answer:
| Component | Function |
|---|---|
| ALU | Performs arithmetic and logical operations |
| Registers | Temporary storage for data and addresses |
| Control Unit | Directs operation of processor and data flow |
| Buses | Pathways for data transfer (address, data, control) |
Diagram:
goat
Mnemonic: "RABC" - "Registers, ALU, Buses, Control"
Question 1(c) [7 marks]
Compare Von Neumann & Harvard architecture.
Answer:
| Feature | Von Neumann Architecture | Harvard Architecture |
|---|---|---|
| Memory Buses | Single memory bus for instructions and data | Separate buses for program and data memory |
| Execution | Sequential execution | Parallel fetch and execute possible |
| Speed | Slower due to bus bottleneck | Faster due to simultaneous access |
| Memory Access | Single memory space | Separate memory spaces |
| Complexity | Simpler design | More complex design |
| Applications | General-purpose computing | DSP, microcontrollers, embedded systems |
| Examples | Most PCs, 8085, 8086 | 8051, PIC, ARM Cortex-M |
Diagram:
goat
Mnemonic: "Harvard Has Separate Streets" (Harvard Has Separate memory paths)
Question 1(c OR) [7 marks]
Define RISC, CISC, Opcode, Operand, Instruction Cycle, Machine Cycle, and T State.
Answer:
| Term | Definition |
|---|---|
| RISC | Reduced Instruction Set Computer - architecture with simple instructions optimized for speed |
| CISC | Complex Instruction Set Computer - architecture with complex, powerful instructions |
| Opcode | Operation Code - part of instruction that specifies operation to be performed |
| Operand | Data value or address used in operation |
| Instruction Cycle | Complete process to fetch, decode and execute an instruction |
| Machine Cycle | Basic operation like memory read/write (subset of instruction cycle) |
| T-State | Time state - smallest unit of time in processor operation (clock period) |
Diagram:
goat
Mnemonic: "RICO ITEM" (RISC, CISC, Opcode, Instruction cycle, T-state, Execute, Machine cycle)
Question 2(a) [3 marks]
Define Data bus, Address bus and Control bus.
Answer:
| Bus Type | Definition |
|---|---|
| Data Bus | Bidirectional pathway that transfers actual data between microprocessor and peripheral devices |
| Address Bus | Unidirectional pathway that carries memory/IO device locations to be accessed |
| Control Bus | Group of signal lines that coordinate and synchronize all system operations |
Diagram:
goat
Mnemonic: "ADC" - "Address finds location, Data carries information, Control coordinates operations"
Question 2(b) [4 marks]
Compare Microprocessor and Microcontroller.
Answer:
| Feature | Microprocessor | Microcontroller |
|---|---|---|
| Definition | CPU on a single chip | Complete computer system on a chip |
| Memory | External RAM/ROM needed | Built-in RAM/ROM |
| I/O Ports | Limited or none on-chip | Multiple I/O ports on-chip |
| Peripherals | External peripherals needed | Built-in peripherals (timers, ADC, etc.) |
| Applications | General computing, PCs | Embedded systems, IoT devices |
| Cost | Higher for complete system | Lower (all-in-one solution) |
| Power Consumption | Higher | Lower |
Mnemonic: "MEMI-CAP" (Memory external/internal, Cost, Applications, Peripherals)
Question 2(c) [7 marks]
Sketch and explain 8085 block diagram.
Answer:
Diagram:
goat
Main Components:
- Register Array: A (Accumulator), Flags, B-L, SP, PC, temp registers
- ALU: Performs arithmetic and logical operations
- Timing & Control: Generates control signals, handles interrupts
- Bus Interface: Connects CPU to external devices
- Internal Data Bus: Links internal components
Mnemonic: "RATBI" - "Registers, ALU, Timing, Buses, Interface"
Question 2(a OR) [3 marks]
Explain Accumulator, Program Counter and Stack Pointer.
Answer:
| Register | Function |
|---|---|
| Accumulator (A) | 8-bit register that stores results of arithmetic and logical operations |
| Program Counter (PC) | 16-bit register that holds address of next instruction to be executed |
| Stack Pointer (SP) | 16-bit register that points to current top of stack in memory |
Diagram:
goat
Mnemonic: "APS" - "Accumulator Processes, PC Predicts, SP Stacks"
Question 2(b OR) [4 marks]
Sketch and explain Demultiplexing of Address bus and data bus.
Answer:
Diagram:
goat
Process:
- Multiplexing: AD0-AD7 pins share address and data signals to reduce pin count
- Demultiplexing Steps:
- CPU places address on AD0-AD7 pins
- ALE (Address Latch Enable) signal goes HIGH
- External latch (74LS373) captures lower address bits
- ALE goes LOW, latching the address
- AD0-AD7 pins now carry data
Mnemonic: "ALAD" - "ALE Active, Latch Address, After Data"
Question 2(c OR) [7 marks]
List any seven features of 8085.
Answer:
| Feature | Description |
|---|---|
| 8-bit Data Bus | Transfers 8 bits of data in parallel |
| 16-bit Address Bus | Can address up to 64KB of memory (2^16) |
| Hardware Interrupts | 5 hardware interrupts (TRAP, RST 7.5, 6.5, 5.5, INTR) |
| Serial I/O | SID and SOD pins for serial communication |
| Clock Generation | On-chip clock generator with crystal |
| Instruction Set | 74 operation codes generating 246 instructions |
| Register Set | Six 8-bit registers (B,C,D,E,H,L), accumulator, flags, SP, PC |
Diagram:
goat
Mnemonic: "CHAIRS" - "Clock, Hardware interrupts, Address bus, Instruction set, Registers, Serial I/O"
Question 3(a) [3 marks]
Illustrate any one Timer Mode of 8051.
Answer:
Mode 1: 16-bit Timer/Counter
| Feature | Description |
|---|---|
| Timer Structure | 16-bit timer using THx and TLx registers |
| Operation | Counts from 0000H to FFFFH, then sets TF flag |
| Counter Size | Full 16-bit counter (2^16 = 65,536 counts) |
| Registers | THx (high byte) and TLx (low byte) |
Diagram:
goat
Mnemonic: "MOGC" - "Mode 1 uses Overflow detection, Gate control, Complete 16-bits"
Question 3(b) [4 marks]
State function of ALE, PSEN, RESET and TXD pin for 8051.
Answer:
| Pin | Function |
|---|---|
| ALE | Address Latch Enable - Provides control signal to latch low byte of address from port 0 |
| PSEN | Program Store Enable - Read strobe for external program memory access |
| RESET | Reset input - Forces CPU to initial state when held HIGH for 2 machine cycles |
| TXD | Transmit Data - Serial port output pin for serial data transmission |
Diagram:
goat
Mnemonic: "APTR" - "Address latch, Program store, Total reset, tRansmit data"
Question 3(c) [7 marks]
Explain functions of each block of 8051 Microcontroller.
Answer:
| Block | Function |
|---|---|
| CPU | 8-bit processor that fetches and executes instructions |
| Memory | 4KB internal ROM and 128 bytes of internal RAM |
| I/O Ports | Four 8-bit bidirectional I/O ports (P0-P3) |
| Timers/Counters | Two 16-bit timers/counters for timing and counting |
| Serial Port | Full-duplex UART for serial communication |
| Interrupts | Five interrupt sources with two priority levels |
| Clock Circuit | Provides timing for all operations |
Diagram:
goat
Mnemonic: "CRIMSON" - "CPU, RAM/ROM, I/O, Memory, Serial port, Oscillator, iNterrupts"
Question 3(a OR) [3 marks]
Illustrate any one Serial Communication Mode of 8051.
Answer:
Mode 1: 8-bit UART
| Feature | Description |
|---|---|
| Format | 10 bits (start bit, 8 data bits, stop bit) |
| Baud Rate | Variable, determined by Timer 1 |
| Data Direction | Full-duplex (simultaneous transmit and receive) |
| Pins Used | TXD (P3.1) for transmit, RXD (P3.0) for receive |
Diagram:
goat
Mnemonic: "FADS" - "Format 10-bit, Auto baud from Timer 1, Duplex mode, Standard UART"
Question 3(b OR) [4 marks]
State function of RXD, INT0, T0 and PROG pin for 8051.
Answer:
| Pin | Function |
|---|---|
| RXD (P3.0) | Receive Data - Serial port input pin for serial data reception |
| INT0 (P3.2) | External Interrupt 0 - Input that can trigger external interrupt |
| T0 (P3.4) | Timer 0 - External count input for Timer/Counter 0 |
| PROG (EA) | Program Enable - When LOW, forces CPU to fetch code from external memory |
Diagram:
goat
Mnemonic: "RIPE" - "Receive data, Interrupt trigger, Pulse counting, External memory"
Question 3(c OR) [7 marks]
Describe ALU, PC, DPTR, RS0, RS1, Internal RAM and Internal ROM of 8051.
Answer:
| Component | Description |
|---|---|
| ALU | Arithmetic Logic Unit - Performs math and logical operations |
| PC | Program Counter - 16-bit register that points to next instruction |
| DPTR | Data Pointer - 16-bit register (DPH+DPL) for external memory addressing |
| RS0, RS1 | Register Bank Select bits in PSW - Select one of four register banks |
| Internal RAM | 128 bytes on-chip RAM (00H-7FH) for variables and stack |
| Internal ROM | 4KB on-chip ROM (0000H-0FFFH) for program storage |
Diagram:
goat
Mnemonic: "APRID" - "ALU Processes, PC Remembers, Register bank select, Internal memory, DPTR points"
Question 4(a) [3 marks]
Develop an Assembly language program to divide 08H by 02H.
Answer:
Assembly
Diagram:
goat
Mnemonic: "LDDS" - "Load dividend, Divisor in B, Divide, Store results"
Question 4(b) [4 marks]
Develop an Assembly language program to add 76H and 32H.
Answer:
Assembly
Diagram:
goat
Mnemonic: "LASER" - "Load A, Store second number, Execute addition, Result stored"
Question 4(c) [7 marks]
What is Addressing mode? Classify it for 8051.
Answer:
Addressing Mode: Method to specify the location of operand/data for an instruction.
| Addressing Mode | Description | Example |
|---|---|---|
| Register | Operand in register | MOV A, R0 (Move R0 to A) |
| Direct | Operand at specific memory location | MOV A, 30H (Move data from 30H to A) |
| Register Indirect | Register contains address of operand | MOV A, @R0 (Move data from address in R0 to A) |
| Immediate | Operand is part of instruction | MOV A, #55H (Load A with 55H) |
| Indexed | Base address + offset | MOVC A, @A+DPTR (Get code byte at A+DPTR) |
| Bit | Individual bit addressable | SETB P1.0 (Set bit 0 of Port 1) |
| Implied/Inherent | Operand implied by instruction | RRC A (Rotate A right with carry) |
Diagram:
goat
Mnemonic: "RIDDIB" - "Register, Immediate, Direct, Data indirect, Indexed, Bit"
Question 4(a OR) [3 marks]
Develop an Assembly language program to multiply 08H and 02H.
Answer:
Assembly
Diagram:
goat
Mnemonic: "LMSR" - "Load numbers, Multiply, Store Result"
Question 4(b) [4 marks]
Develop an Assembly language program to subtract 76H from 32H.
Answer:
Assembly
Diagram:
goat
Mnemonic: "LESS" - "Load first number, Enable borrow (CLR C), Subtract, Store"
Question 4(c) [7 marks]
List types of instruction set. Explain any three with one example.
Answer:
| Instruction Group | Description | Example |
|---|---|---|
| Arithmetic | Mathematical operations | ADD A, R0 (Add R0 to A) |
| Logical | Logical operations | ANL A, #0FH (AND A with 0FH) |
| Data Transfer | Move data between locations | MOV A, R7 (Move R7 to A) |
| Branch | Change program flow | JNZ LOOP (Jump if A not zero) |
| Bit Manipulation | Operate on individual bits | SETB P1.0 (Set bit 0 of Port 1) |
| Machine Control | Control processor operation | NOP (No operation) |
Explained Instructions:
-
Data Transfer Instructions:
- Move data between registers, memory, or I/O ports
- Example:
MOV A, 30H- Moves data from memory location 30H to accumulator - Operation:
A ← [30H]
-
Arithmetic Instructions:
- Perform mathematical operations like addition, subtraction, etc.
- Example:
ADD A, R0- Adds content of R0 to accumulator - Operation:
A ← A + R0
-
Logical Instructions:
- Perform logical operations like AND, OR, XOR, NOT
- Example:
ANL A, #0FH- Masks upper nibble (keeps only lower nibble) - Operation:
A ← A AND 0FH
Diagram:
goat
Mnemonic: "BALDM" - "Branch, Arithmetic, Logical, Data transfer, Machine control"
Question 5(a) [3 marks]
Sketch interfacing of four LEDs with 8051 Microcontroller.
Answer:
Diagram:
goat
Components:
- 8051 microcontroller
- Four LEDs
- Four current limiting resistors (220Ω)
- Power supply
Mnemonic: "PALS" - "Port pins, Active-low control, LEDs, Simple circuit"
Question 5(b) [4 marks]
Sketch interfacing of 7 segment LED with 8051 Microcontroller.
Answer:
Diagram:
goat
Components:
- 8051 microcontroller
- 7-segment LED display (common cathode)
- Seven current limiting resistors (not shown)
- Power supply
Code Example:
Assembly
Mnemonic: "SPACE-7" - "Seven Pins, Active segments, Common ground, Easy display"
Question 5(c) [7 marks]
Explain interfacing of DAC with 8051 Microcontroller and write necessary program.
Answer:
Diagram:
goat
Components:
- 8051 microcontroller
- DAC0808 (8-bit digital-to-analog converter)
- Operational amplifier for output buffering
- RC filter for smoothing
- Power supply
Connections:
- P1.0-P1.7 → D0-D7 (8-bit digital input)
- P3.0 → CS (Chip Select)
Program for generating a sawtooth wave:
Assembly
Working Principle:
- Digital value is output on Port 1
- DAC converts 8-bit digital value to proportional analog voltage
- Filter smooths the output signal
- Program creates a sawtooth wave by incrementing output value
Mnemonic: "DICAF" - "Digital input, Increment, Convert to analog, Amplify, Filter"
Question 5(a OR) [3 marks]
Sketch interfacing of four Switches with 8051 Microcontroller.
Answer:
Diagram:
goat
Components:
- 8051 microcontroller
- Four push buttons (normally open)
- Pull-up resistors (10KΩ)
- Power supply
Working Principle:
- Switches connect to ground when pressed
- Port pins read HIGH (1) when switch open
- Port pins read LOW (0) when switch pressed
Mnemonic: "PIPS" - "Pull-ups, Input pins, Press for zero, Switches"
Question 5(b) [4 marks]
Sketch interfacing of Stepper motor with 8051 Microcontroller.
Answer:
Diagram:
goat
Components:
- 8051 microcontroller
- ULN2003 driver IC
- Stepper motor (4-phase)
- Power supply
Excitation Sequence:
| Step | P1.3 (D) | P1.2 (C) | P1.1 (B) | P1.0 (A) | Hex Value |
|---|---|---|---|---|---|
| 1 | 0 | 0 | 0 | 1 | 01H |
| 2 | 0 | 0 | 1 | 0 | 02H |
| 3 | 0 | 1 | 0 | 0 | 04H |
| 4 | 1 | 0 | 0 | 0 | 08H |
Mnemonic: "CUPS" - "Controller outputs sequence, ULN2003 amplifies, Phases energized, Stepping motion"
Question 5(c) [7 marks]
Explain interfacing of ADC with 8051 Microcontroller and write necessary program.
Answer:
Diagram:
goat
Components:
- 8051 microcontroller
- ADC0804 (8-bit analog-to-digital converter)
- Reference voltage source
- Input conditioning circuit (not shown)
Connections:
- P1.0-P1.7 ← D0-D7 (8-bit digital output from ADC)
- P3.0 → CS (Chip Select)
- P3.1 → RD (Read)
- P3.2 → WR (Write)
Program for reading analog input:
Assembly
Working Principle:
- Controller sends start conversion signal
- ADC converts analog input to 8-bit digital value
- Controller reads digital value after conversion complete
- Program processes the digital value as required
Mnemonic: "CARSW" - "Convert Analog, Read Digital, Start conversion, Wait for completion"