Duo BASIC – 8 Bit Microcomputer

It’s implemented across 7400 series logic. It’s pretty cool.

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I had to assemble the whole thing. About 500 solder connections. Took about 3.5 hours. So doing the math that’s 142.86 soldered connections per hour, 2.4 a minute. That’s because you have to prep the components by taping them to the opposite side, then soldering the pins, trimming leads etc.

I’ve applied power and done the smoke test. One LED doesn’t work. I may have killed it with the heat. But I can replace it, just gotta make sure I put a 1K resistor on it. But otherwise everything works. I’m able to watch the PC LED’s count upward. So it’s executing code.

It only has two instructions – MNZ or Move Not Zero and ADD. It has 3 registers, A, B, and PC. PC is Program Counter btw.

The logic is all discrete. You have buffers, inverters, schmidt triggers, adders, etc. And I want to see if I can write to the EEPROM. If I can I could add command like JMP, JNZ, etc. A half dozen more commands would make this a kick ass machine.

And you could potentially tap the LED outputs and run it through say an Arduino with LCD attached and have a rudimentary display for it.

I’m just learning how to flip the switches and commit things to memory. Lots of fun!

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2 thoughts on “Duo BASIC – 8 Bit Microcomputer

    1. Oh you don’t know how much fun. It’s called an educational kit. You actually get to see the bits fly as it was. And I’m already thinking of modifications, like maybe using a 555 timer chip to serve as clock driver. And maybe tapping outputs and using it to drive an Arduino and onto a visual text display.

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