16-bit CPU built in Logisim

[Redesign]: A 16 bit RISC processor built with a logic simulator

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I started this project wanting to better understand how computers work at the logic level. I originally bit off more than I could chew, attempting to implement what I called RISC, which was really more CISC, and a pipeline (the pipeline was the biggest oops). That being said, I am building a simpler design that is still quite functional.

The processor deals with data in 16-bit words. All scalar values are represented in 16 bits.

My instruction word is 16 bits, 4 of which are opcode, the next two define whether or not the operands are immediate values. The final 9 bits are divided into two or three parts. When the operation is unary, the upper 6 bits of the twelve are used as a cache address or immediate value (depending on the opcode), and the other 3 a register address. When the operation is binary, the 9 bits are divided into 3 chunks of 3 bits, the first being operand1, the second operand2, and the third a register address for the result.

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Peabody1929 wrote 11/26/2022 at 18:31 point

I realize this work was done a while ago, but it caught my interest.  Do you have anymore GUI images?  A page with the ALU and registers and a page showing the instruction bit allocation would be great to see.


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Richard Milward wrote 06/17/2017 at 20:04 point

Reed, I think prijazendom is asking for the Logisim .circ file of the design. I'd be interested in it too.

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Reed Foster wrote 09/16/2015 at 04:48 point

Hi @prijazendom,

Because the cpu was built in a graphical user interface, there isn't necessarily any code. Also, since the project isn't actually complete (I've stopped working on it), I don't have any file that you could load into the simulator.

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prijazendom wrote 09/15/2015 at 21:18 point

Probabl stupid question - can I get code somewhere ?

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jay_zee102188 wrote 12/27/2014 at 21:39 point

Logisim, that is the name of the application.

Here is a download link:

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Hacker404 wrote 12/13/2014 at 22:06 point
What logic simulator are you using?

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