1.1 Core Definition and Components

An embedded system is a specialized computer hardware system with software embedded within it, designed to perform a specific task. It can function as an independent system or as part of a larger system. An embedded system is formally defined as a microcontroller-based, software-driven, reliable, real-time control system.

It is composed of three primary components:

1. Hardware: The physical electronic components, including the microprocessor or microcontroller.
2. Application Software: The code that performs the specific, dedicated function of the system.
3. Real Time Operating System (RTOS): Supervises the application software and manages the processor’s operations according to a scheduling plan to control latencies. An RTOS defines the system’s working rules during program execution, although a small-scale embedded system may not have one.

1.2 Defining Characteristics

Embedded systems are distinguished by a set of unique characteristics:

• Single-functioned: Typically performs one specialized operation repeatedly. For instance, a pager’s sole function is to operate as a pager.
• Tightly constrained: Design metrics such as cost, size, power, and performance are subject to severe limitations. The system must often fit on a single chip, perform fast enough for real-time data processing, and consume minimal power to maximize battery life.
• Reactive and Real-time: Must continually react to environmental changes and compute results without delay. A car’s cruise controller, for example, must repeatedly calculate acceleration or deceleration within a limited time to maintain control.
• Microprocessor-based: The system must be built around a microprocessor or microcontroller.
• Memory: Contains memory, with software typically embedded in ROM, eliminating the need for secondary storage.
• Connected: Includes connected peripherals for interfacing with input and output devices.
• HW-SW systems: Employs a combination of hardware for performance and security, and software for enhanced features and flexibility.

1.3 Advantages and Disadvantages

1.4 Basic System Structure

The fundamental structure of an embedded system involves a flow of information through several key components:

1. Sensor: Measures a physical quantity and converts it into an electrical signal.
2. A-D Converter (Analog-to-Digital): Converts the analog signal from the sensor into a digital signal that the processor can read.
3. Processor & ASICs: Processes the digital data, measures the output, and stores it in memory.
4. D-A Converter (Digital-to-Analog): Converts the processed digital data back into an analog signal.
5. Actuator: Compares the output from the D-A Converter with the expected output and stores the approved result.