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Uxn-Logisim

Implements the Uxn instruction set in digital hardware. Very WIP.

An animation showing different Uxn mode bits lighting up as stack control signals flow through logic gates

Contents

Known Bugs

  • The program counter doesn't reset to 0x0100
    • To fix this, hold down the Reset button attached to the program counter and press Ctrl-T twice to advance the clock. This should set it to 0x0100 and program execution can begin.
    • Alternatively, type a0 01 00 2c into the first four bytes of the zero-page to make the cpu jump to the start
    • If your ROM contains absolute addressing then you'll need to manualy zero-pad it to start at 0x0100 
      cat /dev/zero | head -c 256 > zero-page.rom
cat zero-page.rom someprogram.rom > padded-program.rom

Quickstart

  1. Open cpu.circ in Logisim

  2. ( Optional ) Build the latest microcode

    i. To assemble the microcode rom file run

    python microcode-asm.py microcode.mc microcode.tal
uxnasm microcode.tal microcode.rom

    ii. Right click on the ROM labelled Microcode_ROM

    iii. Load Image > Select microcode.rom > Select binary (big-endian)

  3. Load the Uxn ROM you wish to load.

    i. Right click on the 64K RAM module ii. Load Image > Select a UXN rom > Select binary (big-endian)

Microcode Format

TODO

Microcode Assembler

The microcode assembler is only a partial assembler and relies upon Uxntal assembly for the conversion to binary. It takes in a [format](Microcode Format) similar to tal, and outputs a valid .tal file (Including comments!). Requires uxnasm or asma.tal to assemble into the microcode rom.