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A project log for 8-bit 74xx computer

Designing and building my own 8-bit computer from scratch with 74xx (TTL) logic chips

Ruud van FalierRuud van Falier 03/26/2019 at 12:340 Comments

It's been a while, but the project is still alive! Lately I found the motivation to work on it again and the result is that the computer is now 95% finished in Logisim.

It has been good to see that everything that was in my head is actually working for real, at least in simulation. Hopefully that is enough to keep me going!

Status as of March 26th, 2019:

Work done in chronological order:

General architecture has been worked out as high level schematic (see: Architecture.pdf).
Needs to be updated according to Logisim design!

Worked on instruction set, micro code, module documentation & general notes from time to time (see: Documentation). This is still heavily work in progress! I'm planning to write a short piece of documentation on each of the modules, like I did for the Sequencer / Instruction Decoder.
Needs to be updated according to Logisim design!

Circuit diagrams have been worked out in KiCad for all modules except for the Sequence / Instruction Decoder (see: Schematics-KiCad). These circuits were designed in KiCad and not tested.
Needs to be updated according to Logisim design!

The entire computer is being built in Logisim to verify all the circuits and the way I had everything in mind is actually going to work. I'd say it's 95% done as far as Logisim design goes, but it can't be fully tested until the entire instruction set and all microcode has been worked out.

While working on the Logisim design, I made several changes to the architecture and some to circuits. These changes still need to be applied to all previous work (architecture design, circuit diagrams, etc.)

TODO's / Plans:

Discussions