*Hello great people, its been so wonderful here on steemit with everyone and i will bring to you a clear study of a specific kind of microprocessor known as 8086 microprocessor.*

![images(41).jpg](https://steemitimages.com/DQmXv7q2GH2dHgGuw9yB2WBZfiLxAQyK4csmFguqwFhjCPe/images(41).jpg)
[8086 microprocessor](https://en.m.wikipedia.org/wiki/Intel_8086)

Assembly languages require a thorough knowledge of the architecture of the computer of which it is available, since unlike high-level languages that are machine independent. We are going to briefly review the architecture of 8086 microcomputers. We shall take the review from a programming point of view. Notice that by architecture, we mean the general layout of the major components or the organization of its major components. Let's go there!;

**THE SYSTEM**
In microcomputers, the CPU is a microprocessor and it’s often called **microprocessor unit** (MPU).  The CPU which is labeled as the brain of the computer, is where all processing activities within the computer system are done and also controlled. These include instruction decoding, arithmetic and logical operations. 

Where do you think the instruction decoding, arithmetic and the logical operations are done?alright let study...The former is done in the decoding circuitry within the control unit (CU) of the CPU while the later are performed by the arithmetic and logic units (ALU). 
>Now within the system, all these are achieved through the timing signals or pulses generated by timing circuitry maybe a clock within the CU of the CPU. These processes are used to synchronize the activities done.

![images(39).jpg](https://steemitimages.com/DQmR9Lq9zufhku7hipSGPCGwBAt7GpNpySedbyBJnM4zHsh/images(39).jpg)
[credit: a typical 8086 microprocessor](http://www.eazynotes.com/pages/microprocessor/notes/block-diagram-of-intel-8086.html)

Now we are making progress. The illustration above represents the architectural diagram of a typical 8086 microprocessor. As you can see from it, it shows that a typical microprocessor-based microcomputer system consists of two functional units; the Bus interface nit(BIU) and the execution unit(EU). 

 The BIU is responsible for all data and address transfers on the buses for execution unit. It fetches instructions from the memory, reads data from the ports and memory and also writes data to ports and memory. The BIU makes se of the input and output interfaces to read and write data. It’s a very sensitive area which is made up of segment registers, instruction pointer and the instruction stream queue. 

On the other hand, EU informs the BIU where to fetch instructions and data, then it decodes and executes the instructions fetched by the BIU. The EU comprises of the general-purpose registers, pointer and index registers, control units, the arithmetic and logic units (ALU), and the flag registers.

It is important to note that the main components in the microcomputer system (CPU, RAM, ROM, and I/O interfaces) are connected together by number of signal lines called **BUSES**. *I know one day I will be opportune to be where its been assembled, positive minds*….so Buses are set of conductors or signal lines used in transmitting information within the computer system, and especially between the CPU and the other units or components. 

The data bus is the set of signal lines for transmitting data, the address bus is for transmitting the memory address of the data transmitted to the data bus, while the control bus is for transmitting the control signal instructions that regulate activities in the bus. The data bus, address bus and the control bus are generally known as the system bus.

**CPU REGISTERS**
The CPU registers are a special group of fast access memory locations within the CPU itself. The registers are all 16 bit in size and have the names as shown in the image below.
![memory-segment-8086.jpg](https://steemitimages.com/DQmYu2JddWkbpZBcABYhsYsRCZSYuLBibZPAbXvQ58VS4nd/memory-segment-8086.jpg)
[Credit](http://www.eazynotes.com/pages/microprocessor/notes/block-diagram-of-intel-8086.html)

The 8086 CPU registers are classified into a number of groups. The major groups being the **general purpose registers** and **special purpose registers**. Within the general purpose registers we have the data registers, the index registers, and a part of the pointer registers.
Similarly the group of special purpose registers has the pointer registers,flag register and segment registers.

**8086 MICROPROCESSOR ADDRESSING MODES**
Let’s just briefly discuss the addressing modes in 8086 microprocessor.  Now this processor uses different ways to access data on which it operates.  *it is very crucial to understand clearly those different ways; otherwise you won’t be able to program the microprocessor effectively. These different ways are called the addressing mode. Addressing modes refers mainly to memory and *registers*.

![images(42).jpg](https://steemitimages.com/DQmSjK2cnATYAiyFc3pj2VKqhCEVJZhBXVm8WuqzTkz8YPZ/images(42).jpg)
[Credit](http://iitestudent.blogspot.com/2012/02/pin-configuration-8086-and-8088.html?m=1)

Anyways lets consider the following instruction; MOV destination, *source*. When these instruction is executed, it copies a word or rather a byte from the specified source location to the specified destination location. The source can be either  a number written directly in the instruction or a memory location specified in any of its different ways.
Addressing modes can be one of the following – implicit, direct, indirect, immediate, relative, based or index addressing. Let me try and brief them a bit;
- In **immediate addressing mode**, the source is specified as an immediate value in the instruction. 
- In **implicit addressing mode**, one or both operands are not specified in the instruction. However the omitted operands are implied.
- **Direct addressing mode** relates mostly to accessing data from memory address specified directly in an instruction.
-In **Indirect addressing**mode unlike the direct addressing mode which uses the memory as the source operands, however the memory address is not directly specified in an instruction. The source memory is usually computed from a value contained in a register.
- In **register addressing mode**, a register is always the source of an operand in an instruction.
- **Relative or base addressing mode** uses the base register with an offset to access data in memory.
- In **Index addressing mode**, an index or subscript is used to determine the address of an operand in memory. 

I believe you have learnt a lot on the wonderful study, I appreciate your time. I still remain your humble friend,@setapart.     

REFERENCES


https://www.pcworld.com/article/146957/components/article.html- Birth of a Standard: The Intel 8086 Microprocessor. Thirty years ago, Intel released the 8086 processor, introducing the x86 architecture that underlies every PC — Windows, Mac, or Linux — produced today

New 8086 family products boost processor performance  by 50 percent, Intel Preview Special Issue: 16-Bit Solutions, Intel Corporation, May/June 1980, page 17.

Microprocessor 8086 overview, Tutorial points- https://www.tutorialspoint.com/microprocessor/microprocessor_8086_overview.html

Intel 8086- Wikipedia. 
https://en.m.wikipedia.org/wiki/Intel_8086

https://www.amazon.in/pantech-solutions-8085-PS2-LAB-KIT-Microprocessor-Trainer/dp/B014HCUORA

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Much LOVE @steemstem