Chapter 9 Notes: Embedded Systems Design

Embedded Systems

  • Definition of Embedded Systems: Embedded systems are real computer systems designed to support the operation of a device or machine that is typically not perceived as a computer.

  • User Awareness: Users of these systems are rarely aware of the computer's existence within the device itself.

  • Ubiquity: These systems are found in a vast array of "intelligent" devices that react to humans or their environment, including:

    • Watches

    • Automobiles

    • Coffeepots

    • Televisions

    • Telephones

    • Aircraft

Key Differences from General-Purpose Systems

  • Resource Constraints: Embedded systems are characterized by limited resources. The efficient utilization of memory and power is critical. Hardware and software economy is often the primary concern and significantly impacts design decisions.

  • Hardware and Software Partitioning: The boundary between what is implemented in hardware versus software is fluid and subject to change during the design process.

  • Hardware Detail: Programmers of embedded systems must possess an intimate understanding of every detail of the underlying hardware.

  • Timing and Events: Signal timing and the handling of asynchronous events are crucial factors in the operation of embedded systems.

Taxonomy of Embedded Hardware

  • Embedded hardware is classified based on the extent to which it can be adapted by the people programming or installing the system. There are three primary categories in this taxonomy:

    • Off-the-shelf

    • Configurable

    • Fully customized

Off-the-Shelf Hardware and Microcontrollers

  • Customization: Minimal hardware customization is possible with off-the-shelf components. While memory or peripherals might be added, the internal wiring of the chip remains static.

  • Microcontrollers: This is the most common form of off-the-shelf hardware.

    • They are often derivatives of older PC technology.

    • They are inexpensive because their original development costs were recouped over long production cycles.

    • There are thousands of different microcontroller varieties available.

  • Examples of Microcontrollers:

    • Motorola 68HC1268HC12

    • Intel 80518051

    • Microchip 16F84A16F84A

    • The PIC family

  • Microcontroller Components: Standard blocks include a CPU, Memory, and I/O. A specific component often included is the Watchdog Timer.

    • Watchdog Timer: A hardware component that helps prevent system hangs by continually checking for