From Digital ICs to Computers
A computer is not a mysterious device beyond logic. It is a very large, carefully organized collection of the same ideas introduced in these pages: gates, multiplexers, registers, counters, arithmetic circuits, memory, clocks, and state machines.
Registers
Groups of flip-flops hold binary words. Registers store operands, addresses, instructions, status bits, and intermediate results.
Arithmetic
Adders and Boolean logic combine into an arithmetic logic unit. Wider arithmetic is created by connecting many one-bit or small multi-bit stages.
Control
Decoders and state machines interpret instruction bits and produce the control signals that move data through registers, memory, and arithmetic units.
Program counter
A counter-like register holds the address of the next instruction. Branch and jump logic can replace the normal incremented value with another address.
Memory
ROM or nonvolatile memory can hold instructions; RAM holds changing data and working state. Caches reduce the time required to reach frequently used data.
Clock
The clock coordinates state changes throughout synchronous parts of the processor. Modern processors use multiple clock domains, phase-locked loops, clock gating, and sophisticated timing distribution.
Microprocessor
A microprocessor integrates the CPU onto one or a small number of ICs. Early processors were only a few bits wide and contained thousands of transistors. Modern processors contain billions.
Microcontroller
A microcontroller combines a processor with memory and useful peripherals such as timers, serial interfaces, digital I/O, ADCs, PWM, and watchdog circuits. It is therefore a small computer intended to control equipment.
Why discrete logic still matters
A microcontroller can replace many packages, but simple hardware can be better when the job requires instant response, guaranteed timing, safety interlocks, level translation, pulse conditioning, or only one or two logic functions.