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Microprocessors are used in many digital devices.

Depending on their use are divided into categories:
General purpose, are the microprocessors used in personal computers. They have high performance and very flexible.
Special purpose, they are microprocessors that havespecific tasks. They are found in video cards.
Embedded microprocessors that are designed solely torun a single application.

In addition to the processors in a modern processing system is a hierarchical memory system and a set of I / O, which can interconnect other systems or other devices.

Execution Unit

The EU provides the decoding and execution of the instruction. It processes the received instructions from the BIU. After decoding the operation, generates operand addresses and passes them to the BIU. The BIU will deliver at a later time the values of the operands, so that the EU to execute the instruction request and updates the flags.


Bus Interface Unit

The BIU is responsable for managing all operations to or form the processor. It works in parallel with the EU and deals:

  • phase-fetch instructions
  • reading and writing of the operands
  • reading and writing the results of the instructions
  • the physical address generation
  • management of the queue of instructions

The BIU manages the statements using a FIFO queue.

The tail is filled every time that there is a free word and the bus is not busy. The instrucitons are loaded or immediately after the CS. In the case where a jump instruction is executed the queue is cleared and recharged again.

This technical advance to load the queue of instruction is called prefetching.

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