This is all much simpler than you could possibly imagine !!
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A Very Important Note (Please read this):
On the main menu this page was How A Microprocessor works and I changed it to Please Read This because I realised that even those words would stop many from coming to this page because they think this is very complicated and perhaps beyond their comprehension !
It is not. It is actually VERY SIMPLE… This is essentially what it is all about:
(1) “The Microprocessor is a simple but very fast machine that manipulates and performs simple Arithmetic 1 on Real Numbers 2 combined with Boolean Algebra (logic) in order for a simple machine to be able to make logical decisions…“
What I have said above is what Real Code actually is (and that is all it is)
Everything else is just a very sophisticated, wonderful, clever Illusion 3 (a form of Virtual Reality)…
And that is it !! Truly. I know - I’ve been doing software for over 40 years !! And this is ALL BASED upon principles established over 100 years ago. Boolean Logic was devised in 1847 !! The Greeks were performing Arithmetic 2,000 years ago !! Binary numbers were used by the Chinese in the 9th century BC
Albert Einstein said: “If you can’t explain it simply, you do not understand it well enough…“
(2) In “The Annotated Turing” (Wiley 2008), Page 127, Charles Petzold says: “In this digital age of ours we have grown used to representing all forms of information as numbers. Text, drawings, photographs, sound, music, movies – everything goes into the digitisation mill and gets stored on our computers and other devices in ever more complex arrangements of 0s and 1s…” 4
(3) Petzold highlights that we use numbers (as symbols) to represent data and information
Learn more about Data & Information
And you do not have to do this electronically…
What I have outlined above in (1) is based upon some very basic and simple principles
Doing it electronically is purely implementation detail…
You can do it with Marbles…
… Water …
… Dominoes
So let’s start at the very beginning… (with the Z80)
- The Z80 is the Master-of-Ceremonies (“MC”) • All the other devices are slaves
- When the Z80 system is “powered-up” it resets/initialises its internals
- It then reads a byte (8-bits) from memory at address 0000
- It is expecting the fetched byte of data to be an instruction 5
What is the Z80 ?
“The Z80 is an 8-bit microprocessor introduced by Zilog as the startup company’s first product … in July 1976. With the revenue from the Z80, the company built its own chip factories and grew to over a thousand employees over the following two years” Source: Wikipedia (My emphasis)
1976 ?!! What on earth are you on about?
This is a 45-year-old microprocessor !! Why/How is this still relevant?
Indeed !! So surely NOBODY could still be using it? WRONG! VERY WRONG !!
My tried-and-tested Digikey/Mouser sanity/reality test
The Z80 is a very simple microprocessor… 6
… and ideal to show the essense of “how it works” and it is much simpler than you may believe !!!
A very simple Z80 System…
To be exact, Binary Arithmetic “Arithmetic in binary is much like arithmetic in other numeral systems. Addition, subtraction, multiplication, and division can be performed on binary numerals - Wikipedia” ↩
And all the numbers must be “chopped-up” into little pieces… In the case of an 8-bit machine, these are 8-bit chunks - integers between 0 and 255 ↩
Arthur C Clarke’s 3rd “Law”: “Any sufficiently advanced technology is indistinguishable from magic” We live in a world full of magic & death… ↩
Petzold goes on to say: “In the 1930’s, however, only numbers were numbers, and if somebody was turning text into numbers, it was for the purposes of deception and intrigue…“ ↩
It MUST be an instruction !! If it is not an instruction, the Z80 will treat it as an instruction, try to internally decode it and the results of this will be VERY UNPREDICTABLE ↩
Compared to today’s complexity - but the essential principles and concepts HAVE NOT CHANGED !! ↩