Microprocessors & Microcontrollers

The 8086 forms a 20-bit physical address from a 16-bit segment and 16-bit offset (segment × 16 + offset), giving 1 MB of memory; its BIU prefetches instructions while the EU executes for a simple pipeline.

Assembly programming moves data between registers and memory (MOV), performs arithmetic that updates flags, and controls flow with loops and conditional jumps; CX is the built-in loop counter.

Peripheral interfacing uses programmable chips — the 8255 for parallel I/O, the 8253/8254 for timing, the 8259 for interrupts — configured by writing control words; the timer count = input clock / desired output frequency.

Interrupts let a peripheral suspend the CPU to run a service routine; the 8086 finds the routine via a vector table where each type’s address is at type × 4, while DMA transfers blocks without CPU involvement.

A microcontroller integrates CPU, memory and I/O on one chip; the 8051 uses a Harvard architecture, and its on-chip timers generate delays or baud rates set by the loaded count and the crystal frequency.