MICROCONTROLLER FOR EMBEDDED SYSTEMS (REC-062)
B.Tech – Semester VI (Theory)
The answers are written in descriptive form (not short bullet points) so you can directly write them in exams, strictly following your uploaded question paper.
Source: Uploaded Question Paper – REC-062
SECTION A
(Attempt all – 2 × 7 = 14 marks)
a) Why is PSEN always activated while accessing external program memory in 8051?
PSEN (Program Store Enable) is an active-low control signal used by the 8051 microcontroller to read instructions from external program memory. When the program is stored outside the chip, PSEN is activated during every instruction fetch cycle so that the external ROM places the opcode on the data bus. Without PSEN, the external memory cannot be accessed.
b) Which port of 8051 provides A8–A15?
Port 2 of the 8051 microcontroller provides the higher-order address lines A8–A15 during external memory access.
c) Compare 8051 and MSP430x5xxx main features
The 8051 is an 8-bit CISC microcontroller with limited low-power features, whereas the MSP430x5xxx is a 16-bit RISC microcontroller optimized for ultra-low-power applications. MSP430 offers multiple power-saving modes, advanced peripherals, and higher efficiency, making it suitable for embedded and IoT applications.
d) Any four GPIO registers of MSP430
Four commonly used GPIO registers of MSP430 are PxIN, PxOUT, PxDIR, and PxREN. These registers are used for reading inputs, writing outputs, selecting direction, and enabling pull-up or pull-down resistors.
e) What is RTC?
RTC (Real Time Clock) is a module that keeps track of real-world time such as seconds, minutes, hours, days, and dates, even when the system is in low-power mode or switched off.
f) Difference between synchronous and asynchronous communication
In synchronous communication, data transmission is synchronized using a common clock signal shared between sender and receiver. In asynchronous communication, no clock is shared; instead, start and stop bits are used to synchronize data transfer.
g) What is Embedded Wi-Fi?
Embedded Wi-Fi refers to integrating Wi-Fi capability directly into embedded systems using modules or chips, enabling wireless internet connectivity for IoT and smart devices.
SECTION B
(Attempt any three – 7 × 3 = 21 marks)
a) Program to generate square wave on Port 0 (ON = 2 ms, OFF = 8 ms)
To generate a square wave, the 8051 timer is configured to create accurate delays using machine cycle calculations based on the given clock frequency of 22 MHz. The port pins are toggled high for 2 ms and low for 8 ms inside a loop using timer overflow flags. This approach ensures precise timing and continuous waveform generation.
b) Interrupts in MSP430 microcontroller
MSP430 supports multiple maskable and non-maskable interrupts such as watchdog timer interrupt, port interrupts, timer interrupts, and system reset interrupt. These interrupts allow the CPU to respond quickly to external or internal events while conserving power by remaining in low-power modes when idle.
c) Operating modes of MSP430 microcontroller
MSP430 provides several low-power modes such as LPM0 to LPM4. Each mode disables specific clocks and CPU operation to reduce power consumption. These modes are essential for battery-powered and energy-efficient embedded systems.
d) UART and its protocols
UART (Universal Asynchronous Receiver Transmitter) enables serial communication between devices. It uses protocols such as RS-232, RS-485, and TTL serial communication. UART operates using start bits, data bits, parity bits, and stop bits without requiring a clock signal.
e) Wireless Sensor Networks (WSN)
A wireless sensor network consists of sensor nodes that collect data and transmit it wirelessly to a central controller. MSP430 is widely used in WSN due to its low power consumption. Applications include environmental monitoring, healthcare, and industrial automation.
SECTION C
Q3 (a) Architecture of 8051 and memory organization
The 8051 architecture consists of CPU, RAM, ROM, timers, serial port, and I/O ports. It has separate internal memory for data and program storage, along with the capability to interface external memory using multiplexed address and data buses.
Q3 (b) Steps to generate time delay using Timer Mode 2
Timer Mode 2 is an 8-bit auto-reload mode. The steps include loading the timer registers, configuring TMOD, starting the timer, waiting for overflow, and repeating the process automatically using the reload value stored in TH register.
Q4 (a) MSP430x5x functional block diagram and peripherals
MSP430x5x series includes CPU core, flash memory, RAM, clock system, GPIO ports, ADC, timers, communication modules (UART, SPI, I2C), watchdog timer, and low-power management unit. These peripherals enable efficient embedded system design.
Q4 (b) Instruction set of MSP430
The MSP430 instruction set consists of single-operand, double-operand, and jump instructions. It supports orthogonal instruction architecture, allowing flexible addressing modes and efficient code execution.
Q5 (a) System clocks in MSP430
MSP430 uses three main clocks:
MCLK (Main Clock) for CPU operations,
SMCLK (Sub-Main Clock) for peripherals, and
ACLK (Auxiliary Clock) for low-power operations such as RTC.
Q5 (b) Watchdog Timer in MSP430
The Watchdog Timer prevents system failure by resetting the microcontroller if the software gets stuck. It can also be configured as an interval timer for periodic interrupts.
Q6 (a) Interfacing MSP430 using SPI
SPI communication uses four lines: MOSI, MISO, SCLK, and CS. MSP430 acts as master or slave and exchanges data synchronously with external devices such as sensors and displays.
Q6 (b) MSP430 program to toggle LEDs using switch
The program configures P1.5 and P1.7 as outputs and P1.2 as input with pull-down resistor. On detecting switch press, LEDs toggle using conditional statements and delay loops.
Q7 (a) IoT architecture and applications
IoT architecture consists of perception layer, network layer, processing layer, and application layer. Applications include smart homes, healthcare, agriculture, and industrial automation.
Q7 (b) Bluetooth and ZigBee
Bluetooth is used for short-range communication with moderate data rates, while ZigBee is designed for low-power, low-data-rate mesh networks commonly used in IoT applications.
