Tutorials
Programming the SIMCO in Assembly Language
What Is A Computer? Computer Programming, The Purpose of All Computers
Building Simple Machines That Make Decisions
Getting Started Using Programmable Logic Devices
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How to build a simple digital computer - Getting Started
1. Learn Digital Logic
Computers are made up of smaller machines called logic gates. Two or more
logic gates connected together comprise a digital logic circuit, and digital
logic consists of the rules governing the behavior of individual logic
gates and logic gates connected together to form circuits.
If you do not understand how digital logic and logic gates work, you
will not be able to understand how a digital computer works, either.
The good news is that all digital logic circuits are made up of only
a handful of logic gates, and the operation of the gates are very
simple to understand.
Below are links to online tutorials and books on learning the basics:
PlayHookey.com Good introduction to digital logic
2. Make a laminated map of the Simple Digital Computer(called the SIMCO) digital logic circuit
Print out the schematic diagrams of the SIMCO and make a 2' X 4' map of the SIMCO digital
logic circuit. Get the 2' X 4' map laminated, and follow the operation of
the SIMCO's digital logic gates using dry erase markers.
The easiest way to gain a solid, conceptual understanding of how a simple
digital computer works is to trace through the operation of the computer,
on paper, logic gate by logic gate. Because the state of the gates are
constantly changing over time, laminating your 2' X 4' map will let you
follow the operation of the SIMCO using dry erase markers. As the gates
change state over time, you will be able to erase the old states. This
will let you easilly follow the operation of the simple digital computer.
3. Read the Gettting Started with Programmable Logic Devices tutorial by Al Williams
A programmable logic device(PLD) allows you to build actual, working digital logic
circuits. The XC2C256 Cool Runner 2 PLD from XILINX is used to build the
simple digital computer on this website.
To follow along in the Getting Started with Programmable Logic Devices tutorial,
you will need to purchase a CPLD(Complex Programmable Logic Device) Design Kit from XILINX.
This kit contains everything you need to build the both the digital
logic circuit described in the tutorial and the Simple Digital Computer you made a schematic
diagram of in step 2.
4. Download the PLD source code for the SIMCO.
Using the instructions for programming a CPLD from step 3, program
the xilinx XC2C256 with the source code.
Presto, you've just built a working computer.
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