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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.
| Register | Function | Address |
|---|---|---|
| ACC | Arithmetic operations | E0H |
| B | Multiplication/division | F0H |
| PSW | Flag control | D0H |
| TMOD | Timer mode | 89H |
| SCON | Serial control | 98H |
(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.