Chapter 3

ARM Architecture


  • Understanding the basic terms
  • Understanding a processor
  • ARM processor internals
  • Understanding program flow and interruption
  • The different technologies

It doesn’t matter if you are talking about an ARM processor, a 68k or even an x86 processor; they all have some common subsystems. There are slight differences in the way some subsystems are accessed, or the amount of subsystems present, but all processors retain the same basic principle, no matter what architecture. Following is a brief explanation of the core technology found in all modern processors, before going deeper into the specific details that make ARM processors what they are.


Everything in a computer is a number — text, images, sounds — everything is written down as a collection of numbers. A computer’s job is to take some data and run operations on it; put simply, take some numbers, and do some mathematical computations.

The Colossus was the first programmable digital electronic computer, used in Britain during World War II to help in the cryptanalysis of the Lorenz cipher code, a cryptocode used by the German High Command to communicate with its armies. Colossus didn’t actually completely decrypt messages; it was used to break Lorenz key settings using specialized code. Colossus could outperform humans both in terms of speed and reliability, and by the end of the war ten Colossus computers were in service.

While the Colossus was programmable, ...

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