4. Computer Organization and Embedded System (ACtE04)

4.1 Control and Central Processing Units (CPU) (ACtE0401)

Control Memory and Addressing Sequencing

• Control Memory: Stores microinstructions used by the control unit.
• Addressing Sequencing: Determines how instructions are fetched and executed in sequence.

Computer Configuration and CPU Structure

• Components:
  • Control Unit (CU): Directs data flow.
  • Arithmetic Logic Unit (ALU): Performs calculations.
  • Registers: Temporary storage locations.
  • Bus System: Transfers data.

Microinstruction Format & Control Unit Design

• Microinstructions: Instructions stored in control memory.
• Control Unit Types:
  • Hardwired Control: Uses fixed logic circuits.
  • Microprogrammed Control: Uses control memory for instruction execution.

Arithmetic and Logic Unit (ALU)

• Performs:
  • Arithmetic operations: Addition, subtraction, multiplication, division.
  • Logical operations: AND, OR, NOT, XOR.

Instruction Formats and Addressing Modes

• Instruction Formats: Define how an instruction is structured (Opcode + Operands).
• Addressing Modes:
  • Immediate: Operand is part of instruction.
  • Direct: Address of operand is in instruction.
  • Indirect: Instruction contains a pointer to the address.

RISC and CISC Architectures

• RISC (Reduced Instruction Set Computing):
  • Fewer, simpler instructions.
  • High-speed execution.
• CISC (Complex Instruction Set Computing):
  • More complex instructions.
  • Uses microprogramming.

Pipelining and Parallel Processing

• Pipelining: Execution of multiple instructions in parallel stages.
• Parallel Processing: Use of multiple processors to speed up execution.

4.2 Computer Arithmetic and Memory System (ACtE0402)

Arithmetic and Logical Operations

• Binary Addition/Subtraction
• Multiplication (Booth’s Algorithm)
• Division (Restoring & Non-Restoring)

Memory Hierarchy

• Registers → Cache → RAM → Hard Drive

Internal and External Memory

• Internal Memory: Cache, RAM.
• External Memory: Hard Disk, SSD, USB.

Cache Memory Principles

• Purpose: Stores frequently accessed data for faster access.
• Elements of Cache Design:
  • Cache Size: Determines speed.
  • Mapping Functions: Direct, Associative, Set-Associative.
  • Replacement Algorithm: FIFO, LRU, Random.
  • Write Policy: Write-through, Write-back.

Memory Write Ability and Storage Permanence

• Volatile Memory: RAM (data lost when power is off).
• Non-Volatile Memory: Hard Drive, SSD, Flash Memory.

4.3 Input-Output Organization and Multiprocessor (ACtE0403)

Peripheral Devices and I/O Modules

• Peripheral Devices: Keyboard, Mouse, Printer, Storage.
• I/O Modules: Interface between CPU and peripherals.

I/O Interface and Modes of Transfer

• Programmed I/O: CPU manually checks for data transfer.
• Interrupt-Driven I/O: CPU is interrupted when I/O is ready.
• Direct Memory Access (DMA): Data transfers directly without CPU intervention.

Multiprocessors

• Characteristics: Multiple CPUs working together.
• Interconnection Structures: Shared memory, Bus-based, Point-to-Point.
• Inter-Processor Communication & Synchronization: Message passing, Shared memory.

4.4 Hardware-Software Design Issues on Embedded Systems (ACtE0404)

Overview of Embedded Systems

• Definition: A dedicated computing system for specific tasks.
• Examples: Washing machines, ATMs, Smart TVs.

Classification of Embedded Systems

• Real-time: Used in time-sensitive applications.
• Stand-alone: Independent systems.
• Networked: Connected via networks.

Custom Single-Purpose Processor Design

• Optimized for specific tasks.
• Example: Signal processing chips, Car engine controllers.

Basic Architecture and Programmer’s View

• Architecture Components: CPU, Memory, I/O, Timers.
• Programmer’s View: Registers, Memory access, Instruction Set.

Application-Specific Instruction-Set Processors (ASIP)

• Customized instruction sets for specific applications.
• Example: DSP Processors, Image Processing Units.

4.5 Real-Time Operating and Control Systems (ACtE0405)

Operating System Basics

• Types of OS:
  • Batch OS: Jobs executed in batches.
  • Multitasking OS: Runs multiple processes.
  • Real-Time OS (RTOS): Time-sensitive operations.

Task, Process, and Threads

• Task: Basic unit of work.
• Process: Independent execution unit.
• Thread: Smallest executable unit within a process.

Multiprocessing and Multitasking

• Multiprocessing: Multiple CPUs working together.
• Multitasking: Running multiple tasks simultaneously.

Task Scheduling and Synchronization

• Task Scheduling: Determines execution order of tasks.
  • Preemptive Scheduling
  • Non-Preemptive Scheduling
• Synchronization: Prevents data conflicts (Mutex, Semaphore).

Device Drivers

• Software that enables hardware communication.

Control Systems

• Open-Loop: No feedback (e.g., Microwave timer).
• Closed-Loop: Uses feedback (e.g., Air Conditioner).

4.6 Hardware Description Language (HDL) and IC Technology (ACtE0406)

VHDL Overview

• VHDL (Very High-Speed Integrated Circuit Hardware Description Language) is used to model digital circuits.

Data Representation Using VHDL

• Binary, Octal, Hexadecimal formats.
• Bitwise operations (AND, OR, XOR).

Design of Combinational and Sequential Logic Using VHDL

• Combinational Circuits: Logic gates, MUX, DEMUX.
• Sequential Circuits: Flip-Flops, Counters.

Pipelining Using VHDL

• Used to improve performance by executing multiple instructions simultaneously.
• Example: Processor instruction pipelining.