EU and BIU in microprocessor

The Execution Unit (EU): 
-->  The execution unit of the 8086 tells the BIU where to fetch instructions or data from,             decodes instructions, and the executes instruction.                    
-->The EU contains control circuitry, which directs internal operations.  
-->A decoder in the EU translates instructions fetched from memory into a series of actions,       which the EU carries out.  
-->The EU has a 16-bit arithmetic logic unit (ALU) which can add, subtract, AND, OR,             XOR, increment, decrement, complement or shift binary numbers.    
-->The main functions of EU are: o) Decoding  of Instructions  (o)Execution of instructions.


Some important points:-
> EU extracts instructions from top of queue in BIU 
> Decode the instructions 
> Generates operands if necessary 
> Passes operands to BIU & requests it to perform read or write bus cycles to memory or          I/O 
> Perform the operation specified by the instruction on operands.

Bus Interface Unit (BIU): 
-->The BIU sends out addresses, fetches instructions from memory, reads data from ports and memory, and writes data to ports and memory. 
-->In simple words, the BIU handles all transfers of data and addresses on the buses for the execution unit. 

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