THEORY EXAMINATION (SEM–VI) 2016-17 MICROCONTROLLER

MICROCONTROLLER AND ITS APPLICATIONS (NEC022)

SECTION – A

(Attempt All | 10 × 2 = 20 Marks)

(a) CISC

CISC (Complex Instruction Set Computer) uses a large set of complex instructions that can perform multiple operations in a single instruction.
Example: Intel x86 family.

(b) RISC

RISC (Reduced Instruction Set Computer) uses a small set of simple instructions, resulting in faster execution and easier pipelining.
Example: ARM processors.

(c) Registers

Registers are high-speed storage locations inside the CPU used to store data, addresses, or instructions temporarily during execution.

(d) Addressing Modes

Addressing modes specify how the operand of an instruction is accessed.
Examples: Immediate, Direct, Indirect, Register, Indexed.

(e) Microcontroller

A microcontroller is a single-chip embedded system containing CPU, memory (RAM/ROM), I/O ports, timers, and peripherals for control applications.

(f) External and Software Interrupts

External interrupts: Generated by hardware signals (e.g., INT0, INT1 in 8051)

Software interrupts: Generated by instructions in the program

(g) Delay

Delay is a time gap introduced intentionally in a program, usually created using loops or timers.

(h) RAM and ROM

RAM: Volatile memory used for temporary data storage

ROM: Non-volatile memory used to store program code

(i) Interfacing

Interfacing is the process of connecting external devices (LCD, motors, sensors) to a microcontroller for data exchange.

(j) Serial Port Programming

Serial port programming enables serial data communication between microcontroller and external devices using protocols like UART.

SECTION – B

(Attempt Any Five | 5 × 10 = 50 Marks)

(a) Block Diagram of a Microcontroller             A typical microcontroller consists of:

CPU                                                                   Program memory (ROM/Flash)

Data memory (RAM)                                         I/O ports

Timers/Counters                                                Serial communication unit

Interrupt control                                                Oscillator & clock circuitry

Each block works together to sense inputs, process data, and control outputs.

(b) Working of 8051 Oscillator and Clock

The 8051 uses an external crystal oscillator (typically 11.0592 MHz or 12 MHz).

One machine cycle = 12 oscillator periods

Clock controls instruction execution timing
Stable clock ensures accurate timing and serial communication.

(c) Hardware and Software Attributes of Vectored Interrupts

Vectored interrupts have predefined memory locations.

Hardware attributes:                                       Interrupt pins

Priority logic                                                       Vector addresses

Software attributes:                                         ISR (Interrupt Service Routine)

Enable/disable control                                        Priority setting

(d) Current Program Status Register (CPSR – ARM)

CPSR stores processor status information.

Fields include:                                                   Condition flags (N, Z, C, V)

Interrupt enable bits                                           Processor mode bits

It controls execution state of ARM core.

(e) Memory Types in 8051                                  8051 memory organization includes:

Internal ROM: Program storage                        Internal RAM: Data storage

External ROM: Program expansion                   External RAM: Data expansion

Special Function Registers (SFRs): Control registers

(f) Modes of 8051 Timers

8051 has two timers (T0, T1) with modes:

Mode 0: 13-bit timer                                       Mode 1: 16-bit timer

Mode 2: 8-bit auto-reload                              Mode 3: Split timer mode

Used for delay generation, event counting, and baud rate control.

(g) Stack and Stack Pointer

The stack is a memory area used for temporary data storage during function calls and interrupts.

Stack Pointer (SP): Points to top of stack

In 8051, stack grows upward in RAM

(h) LCD Interfacing with 8051                            LCD is connected using:

Data lines (D0–D7)                                             Control lines (RS, RW, EN)

Functioning:                                                     Commands sent via RS=0

Data sent via RS=1                                             LCD displays characters based on ASCII codes

SECTION – C

(Attempt Any Two | 2 × 15 = 30 Marks)

8031 with External ROM and 8255

(a) 8031 Connection

8031 has no internal ROM, so external program ROM is required.

Port-0 used as multiplexed address/data bus

ALE used for address latching

8255 provides programmable I/O

(b) Block Access

Address decoding logic selects ROM and 8255 using chip-select signals.

(c) Programming Model of 8051

Includes:

Accumulator

B register

General purpose registers (R0–R7)

PSW

PC and DPTR

Special Function Registers & Serial Communication

(a) Special Function Registers (SFRs)

SFRs control internal operations.

(b) 8051 Flags and PSW

PSW contains:                                                   Carry (CY)

Auxiliary carry (AC)                                            Overflow (OV)

Parity (P)                                                             Register bank select bits

(c) Serial Communication Using Interrupts

Steps:                                                                  Configure serial mode

Enable serial interrupt                                         Load data into SBUF

ISR handles transmission/reception                    Interrupts improve efficiency by avoiding polling.

Interfacing Motors with 8051

DC Motor                                                            Uses driver IC (L293D)

Controls speed and direction                             Stepper Motor

Driven in steps                                                    Controlled using sequence of pulses

Servo Motor                                                        Controlled by PWM signals

Precise angular positioning                                Applications: robotics, automation, CNC machines.