8086 Microprocessor is an enhanced version of 8085 Microprocessor that was designed by Intel in 1976. It is a 16-bit Microprocessor having 20 address lines and 16 data lines that provides up to 1MB storage. In April 1978, intel introduced this microprocessor and it was officially released on June 8.

1. Architecture of
8086 microprocessor
MICROPROCESSOR AND EMBEDDED SYSTEMS

2. Group Member:
❏ ANIRBAN SAHA ANIK (18-36207-1)
❏ BISHOWJIT DATTA (18-37372-1)
❏ JOYDEEP KARMOKER (16-33028-3)
❏ LUTFA NOOR LABONY (18-36187-1)

3. Overview
In April 1978, Intel introduced
its first 16 bit microprocessor.
Production started in May,
eventually, the 8086 was
officially released on June 8.

4. INTERNAL
ARCHITECTURE
❖ 8086 has two blocks BIU and
EU.
❖ BIU contains Instruction queue,
Segment registers, Instruction
pointer, Address adder, the
Address Summing block (Σ)
❖ EU contains Control circuitry,
Instruction decoder, ALU,
Pointer and Index register, Flag
register.

5. Bus Interface Unit (BIU)
❖ The bus control logic of the BIU generates
all the bus control signals such as read and
write signals for memory and I/O.
❖ This unit handles all transfer of data and
addresses on the buses for the
EU(execution unit).

6. Bus Interface Unit (BIU)
Main Components are-
❖ Instruction Queue
❖ Segment Registers
❖ Instruction Pointer

7. Bus Interface Unit (BIU)
The function of BIU is to :
❖ Fetch the instruction or data from memory.
❖ Generate physical address.
❖ Write the data to the memory and port.
❖ Supports pipelining in instruction queue.

8. Execution Unit (EU)
❖ Execution Unit also called a
functional unit
❖ An execution unit is a part of the
central processing unit (CPU) that
performs the operations and
calculations as instructed by the
computer program

9. Execution Unit (EU)
Main components are-
❖ Instruction Decoder
❖ Control System
❖ Arithmetic Logic Unit
❖ General Purpose Registers
❖ Flag Register
❖ Pointer & Index registers

10. Execution Unit (EU)
The functions of execution unit are :
❖ To tell BIU where to fetch the instructions or data from.
❖ To decode the instructions.
❖ To execute the instructions.

11. Features of 8086 Microprocessor
❖ It was the first 16-bit microprocessor.
❖ This microprocessor had major improvement over the
execution speed of 8085.
❖ It is available as 40-pin Dual-Inline-Package (DIP).
❖ It is available in three versions:
➢ 8086 (5 MHz)
➢ 8086-2 (8 MHz)
➢ 8086-1 (10 MHz)
❖ It consists of 29,000 transistors.

12. Features of 8086 Microprocessor
❖ 8086 is designed to operate in two modes, Minimum and
Maximum.
❖ It can pre-fetches up to 6 instruction bytes from memory and
queues them in order to speed up instruction execution.
❖ It requires +5V power supply.
❖ A 40 pin dual in line package.
❖ Address ranges from 00000H to FFFFFH

13. General Purpose Registers
We have discussed general purpose registers as being discrete memory
locations within the CPU used to hold temporary data and instructions.
However there are also special purpose registers. A special purpose
register is one that has a specific control or data handling task to carry
out.

14. Type Of General
Purpose
Registers
❖ AX - the accumulator
➢ register Arithmetic, logic and data
transfer
➢ Multiplication & Division
➢ Input & Output
❖ BX - the base address register
➢ BX register is an address register.
➢ It usually contain a data pointer
used for based, based indexed

15. Type Of General
Purpose
Registers
❖ CX - the count register
➢ Iterative code segments using the
LOOP instruction Repetitive
operations on strings with the REP
command
❖ DX - the data register
➢ Data register can be used as a
port number in I/O operations. It
is also used in multiplication and
division.

16. Pointers and index
registers
The pointers contain within the particular segments. The pointers IP, BP, SP
usually contain offsets within the code, data and stack segments respectively
❖ SI - Source index register
❖ DI - Destination index register
❖ BP – Base pointer
❖ SP - Stack pointer

17. Pointers and index
registers
❖ Used to keep offset addresses.
❖ Used in various forms of memory addressing.
❖ In the case of SP and BP the default reference to form a physical address is
the Stack Segment (SS-will be discussed under the BIU)
❖ The index registers (SI & DI) and the BX generally default to the Data
segment register (DS).

18. Flag Register
❖ 8086 has a 16-bit flag register
❖ Contains 9 active flags
❖ There are two types of flags in 8086
➢ Conditional flags – six flags, set or reset by EU on the basis of results of some
arithmetic operations
➢ Control flags – three flags, used to control certain operations of the processor

19. Conditional Flags Control Flags
➔ Trap Flag (TP)
➔ Interrupt Flag (IF)
➔ Direction Flag (DF)
➔ Carry Flag (CF)
➔ Parity Flag (PF)
➔ Auxiliary Flag (AF)
➔ Sign Flag (SF)
➔ Overflow Flag (OF)
➔ Zero Flag (ZF)

20. Memory Segmentation
8086 has a 20-bit address bus So it can address a maximum of 1MB of
memory. 8086 can work with only four 64KB segments at a time within this
1MB range. These four memory segments are called
❖ Code segment (CS)
❖ Stack segment (SS)
❖ Data segment (DS)
❖ Extra segment (ES)

21. Segment
Code Segment
That part of memory from where BIU is
currently fetching instruction code
bytes
Stack Segment
A section of memory set aside to store
addresses and data while a subprogram
executes
Data & Extra Segments
Used for storing data values to be used
in the program

22. Instruction Pointer (IP) Register
A 16-bit register Holds 16-bit offset, of the next instruction byte in
the code segment . BIU uses IP and CS registers to generate the 20-
bit address of the instruction to be fetched from memory. The CS
register contains the segment number of the next instruction and IP
contains the offset.

23. Applications of 8086
microprocessor
❖ Gaming devices.
❖ Mobile phones.
❖ Laptops and some electronic gadgets.
❖ Traffic Lights Controller.
❖ Washing Machines.
❖ Microwave ovens.
❖ Frequency counters and synthesizers.
❖ Digital Clocks.

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