Embedded Systems Overview

Computer Organization & Embedded System — Hardware–Software Design Issues on Embedded System, NEC licence examination syllabus (Nepal Engineering Council).

Embedded Systems: computers you don't realize are computers

Your washing machine has a CPU. So does your car's brake system. Neither looks like a "computer."

Count the "computers" in your house right now: your laptop, obviously — but also your microwave, your washing machine, your car's brake system, maybe even your toothbrush. None of those look like a computer, yet every one of them has a CPU quietly running the exact same fetch-decode-execute cycle you've already learned.

🎯 What Makes a System "Embedded"

Dedicated functionUnlike a PC that runs whatever you install, it does ONE job, forever.

Resource constraintsTight limits on memory, power, and physical size.

Real-time requirementsOften must respond within a strict deadline.

Every embedded system is built from three layers: hardware (the physical processor/circuit), firmware/software (the code running on it), and the application logic that does the actual job (like controlling a motor).

Design metrics — the tradeoffs that drive every decision

Total cost = NRE cost + (unit cost × quantity) NRE (Non-Recurring Engineering) = one-time design cost, paid once Unit cost = per-item manufacturing cost, paid for every device made

Custom single-purpose hardware costs a lot upfront (high NRE) but is very cheap per unit at huge volumes. A general-purpose processor (GPP) has almost no NRE (it already exists) but each chip costs more. This is exactly why phones use custom chips (ASICs) at high volume — millions of units sold — but a one-off hobby project just uses an off-the-shelf microcontroller, since it'll only ever be built once.

💡 Numerical-style question: "At what quantity does a custom design become cheaper than a GPP design, given NRE and unit costs for both?" — set NRE₁+unit₁×Q = NRE₂+unit₂×Q and solve for Q (break-even quantity).

Syllabus points

Definition + characteristics
Components: hardware, firmware, application software
Design metrics (power, cost, size, performance, NRE)

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