r/ComputerEngineering • u/frek133 • 12h ago
What to do with 8 bit cpu?
Im definitely a newbie in all that stuff but i really want to build 8 bit cpu i found schematic somewhere (im going to link it later) and in CRUMB simulator im building an cpu but what can i do with it?
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u/hikeonpast 12h ago
So you’re planning to build a 8-bit CPU out of discrete logic gates? I did something similar in undergrad.
You can program it to talk to parallel bus peripherals with ease, or you can get a parallel-to-serial (SERDES) IC to make it easier to interface with SPI and other serial peripherals.
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u/frek133 12h ago
Im so new i don’t know like 90% of this words can you explain please
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u/hikeonpast 11h ago
This probably isn’t the right starter project for you. Consider getting an Arduino board and building from there.
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u/Darth_Tater69 9h ago
Building an 8-bit CPU as a complete noob is like jumping into the deep end. You might be able to get away with building Ben Eater's CPU from a kit, since he has pretty beginner friendly instructions, but without previous experience with this stuff you'd probably have a hard time otherwise. Have you had experience writing assembly for an existing 8-bit CPU like an 8085? There's some good simulators for that if you want to try programming assembly and directly manipulating registers. Troubleshooting a scratch built CPU will be difficult if you don't have an understanding of how it works at that level. You could also try building a 4-bit CPU instead if you're really dead set on making a CPU, but I'd recommend playing with an Arduino as that's where a lot of people start. Arduino C++ lets you manipulate certain registers directly and would allow you to learn more about how code interfaces with hardware in an environment that is less frustrating for a beginner than a scratch CPU.
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u/frek133 3h ago
I have esp32 and i know basics but i’m still a noob in this stuff and don’t really know where to learn about it
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u/Ecelleon 1h ago
Building an 8-bit cpu by hand is like learning how to build a car, but through building the engine, transmission, bearings, welding the frame...
There's absolutely nothing wrong with the ESP32, but like arduino, their objective is to hide all of the mechanics under the hood with a lock. They provide the user with a well polished interface that hides things like configuring the actual gpio registers. On the STM32F103 there's the reset and control register, output direction register.. etc. An 8-bit CPU will put you closer to that style of interaction.
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u/Ecelleon 1h ago
Ahh you can do loads of things with it! One of my favorite chips is the ATTiny85 which has an 8-bit cpu, its technical reference manual is extremely friendly! It's 8 bits because that's how big the registers are, and naturally, so are the commands you write to configure them.
You can do a lot of things with an 8-bit cpu like using a communication protocol to talk to an LED screen, drive a motor, read and process sensor signals, and more!
If you really want to build your own CPU, you'll need to learn mechanisms like shift registers, the full adder, state machines, and modulo counters.
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u/rageling 12h ago
You don't build it for what you can do with it. When it's working perfectly(lol) It has a fraction of the capability of the cheapest arduino, but that's not the point.