School of Engineering & Technology

SEE 215 Microprocessor principles


Inside a Microprocessor
To understand how a microprocessor works, it is helpful to look inside and learn about the logic used to create one. In the process you can also learn about assembly language - the native language of a microprocessor - and many of the things that engineers can do to boost the speed of a processor.

A microprocessor executes a collection of machine instructions that tell the processor what to do. Based on the instructions, a microprocessor does three basic things:

There may be very sophisticated things that a microprocessor does, but those are its three basic activities. The following diagram shows an extremely simple microprocessor capable of doing those three things:

This is about as simple as a microprocessor gets. This microprocessor has:

Let's assume that both the address and data buses are 8 bits wide in this example.

Here are the components of this simple microprocessor:

  Motorola 68HC11

         Though they are not shown in this diagram, there would

          be control lines from the instruction decoder that would:

Coming into the instruction decoder are the bits from the test register and the clock line, as well as the bits from the instruction register.

68HC11 link data instruction set