8086/80386/Pentium Microprocessor with Assembly Programming

Explore the evolution of Intel microprocessors from 4004 to modern core i3 through i7, and learn why understanding 8085 and 8086 foundations remains essential.

Explore what a computer is, with the processor as its heart—the ALU, resistor array, and control unit—fetching, decoding, and executing instructions, and memory storing programs and data.

Compare microprocessors and microcontrollers: microprocessors lack built-in memory, IO, and timers, while microcontrollers integrate CPU, memory, IO, and timers on one chip.

Learn how to load programs into 8085 memory by interfacing external memory and converting code to machine code via a compiler or assembler, covering 64 KB address space 0000h–ffffh.

Explore how a microprocessor with no internal storage executes programs by loading them into external memory, fetching, decoding, and executing each instruction via the program counter in the instruction cycle.

Count memory size by identifying address lines and data lines using binary and hex, determining 2^n address spaces and scales such as kilo and mega.

Explore machine language, assembly language, and higher level languages, and learn how mnemonics, compiler, and assembler translate code for 8085 microprocessors, enabling C/C++ programming in embedded systems.

Explore how compiler, assembler, interpreter, and linker transform higher level and assembly language source files into machine code, object files, and dot exe executables for simulation and hardware.

Explore how daisy chain, polling, and independent request methods manage bus contention and arbitration on the system bus, detailing bus busy, bus request, and bus grant signals.

Compare risc and cisc architectures, tracing their history from early 8086/8088 designs to modern processors, and contrast instruction formats, addressing modes, pipelining, and memory usage.

Explore how the 8086 supports mixed language programming by combining assembly language with C/C++, using compiler, assembler, and linker to generate machine code and executable files.

Examine the 8086 features, including a 16-bit ALU and data bus. Compare its 20-bit address space, memory segmentation, and pipelining to 8085.

Explore how 8086 pipelining overlaps fetch and execute to boost throughput, and how branch prediction with 99.2% accuracy, data bus, clock, ALU, memory upgrades accelerate performance.

Explore memory banking with the 8086 to transfer two bytes in one cycle by using even and odd banks, lower and higher bytes, and little endian byte ordering.

Explore the 16-bit 8086 flag register, covering carry, parity, zero, sign, auxiliary carry, and overflow flags, plus trap, interrupt, and direction control flags for string operations.

Explore memory segmentation in the 8086, splitting memory into code, stack, data, and extra segments, using segment registers and offsets to convert virtual addresses to physical addresses.

Explore the 8086 programming model by examining general purpose registers in 16- and 8-bit forms and segment registers with code, data, extra, and stack segments.

Explain how the 8284a clock generator provides clock, reset, and ready for 8086, dividing crystal by three for CPU and by six for peripherals to yield a 33% duty cycle.

Compare memory mapped I/O and I/O mapped I/O on the 8086, focusing on address lines, decoding complexity, and the use of memory versus I/O instructions.

Explore the architecture of the 8086, detailing the bus interface unit and execution unit, their prefetch instruction queue, segment registers, and physical addressing via segment and offset.

Explains the 8086 pin diagram, detailing the 40 pins, multiplexed address/data bus, address status lines, min/max mode, and essential control signals like ready, reset, NMI, and BHE.

Explore address data demultiplexing in the 8086, detailing minimum mode operation, the role of address latch enable, and how 8282 latches and 8286 transceivers separate AD0-AD15 from bus signals.

Learn how to generate memory and I/O control signals for the 8086 using a 3-to-8 decoder, enabling memory read, memory write, IO read, and IO write operations.

Explore the 8086 minimum mode operation, control signal generation for memory read, memory write, input/output read, and input/output write, and address data separation using ALE and latches.

Explore how the 8086 in maximum mode grants and takes bus master control using bus request and bus grant signals, prioritizing coprocessors like 8089 and 8087.

Demonstrate how the 8086 lock prefix, active low lock bar, and maximum mode prevent bus grants to a coprocessor, ensuring a single instruction completes before sharing the bus.

Explains the maximum mode of 8086, including address/data generation and bus control signals. Covers interfacing up to two coprocessors with bus requests and grants, and 8 to 84 clocking.

Explore 8086 interrupt types, including hardware interrupts, NMI and intr, with vectored and non-vectored forms. Edge triggering, interrupt service routines, software interrupts via int 0–255, vector table, and divide-by-zero exceptions.

Learn how the 8086 handles an interrupt by saving flags and next instruction address (cs:ip) on the stack, loading the ISR from the interrupt vector table, and restoring program state.

Explore how the 8086 interrupt vector table maps 256 interrupts to four-byte IP and CS addresses for defined memory locations. Note type 0–4 dedicated, 5–31 Intel reserved, 32–255 user defined.

Learn how 8086 uses two hardware pins, nmi and intr, to manage vectored and non-vectored interrupts, including vector addresses and interrupt priorities.

Explore how to use the dos interrupt int 21h in 8086 assembly to access 39 dos functions, including input character, display character, input string, display string, and program termination.

Design memory interfacing for the 8086 in minimum mode, teaching address and data line counts, chip select, and memory mapping. Explains even and odd addressing with EEPROM and RAM configurations.

Explore how the 8086 uses immediate, register, direct, and indirect addressing modes to specify operands, including memory pointer and displacement.

Explore the 8086 assembler directives, including segments, data definitions (db/dw/dd/equ), procedures and macros, org and offset, dup, near/far, and modal directives.

Explore macro and procedure in 8086 assembly, two assembler directives that repeat functions; compare call-based subroutines versus in-place macros, highlighting speed, memory, and pipelining trade-offs.

Learn push and pop on the 8086, using the stack segment to store 16-bit registers with last-in, first-out; observe SP decrement on push and increment on pop, in little endian.

Explore the xlat instruction, translating al data via a bx-based lookup table for code conversion, such as ascii to display data on a seven-segment display.

Explore 8086 in and out instructions, learn direct and indirect I/O addressing with eight-bit and sixteen-bit modes, and master Rd resistor addressing for interfacing input and output devices.

Explore the 8086 da and das instructions, performing decimal adjustment after addition and subtraction in the al register. Understand conditional adjustments that convert hex results to decimal with examples.

Explore 8086 data transfer instructions, including move, exchange, la and sah, load effective address, push and pop, and in and out operations, with size rules.

Master arithmetic instructions for 8086 assembly, including add/adc, sub/sbb, inc/dec, mul/imul, div/idiv, neg, cmp, cbw/cd, and ascii/bcd adjustments such as aaa, aas, aad, aam, and am.

Explore 8086 logical instructions (not, and, or, xor, test) with destination and source syntax and bit-by-bit operations; learn how parity, sign, and zero flags behave.

Explore 8086 shift instructions, including shift left and right (shl/sal and shr/sar), with and without sign conservation, and using cl for multi-bit shifts.

Master 8086 rotate instructions, including rol and ror and rcl and rcr, with and without carry, using cl for multi-bit counts to rotate the destination register left or right.

Compare jump and call instructions in 8086 microprocessor, noting that jump transfers control to a label, while call pushes the return address on the stack and executes a subroutine.

Discover 8086 branch instructions, including unconditional and conditional jumps, and learn how call saves return addresses on the stack to subroutines, and how loop reduces instruction execution.

Explore 8086 string instructions, including movsb/movsw, lodsb/lodsw, stosb/stosw, cmpsb/cmpsw, and scasb/scasw, using cx, di, si, and the direction flag to transfer and compare data across 64 KB efficiently.

Explore 8086 instruction prefixes in max mode: e prefix identifies 8087, lock prefix ensures complete instruction before co-processor access, and rep prefix repeats string instructions using cx.