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Hermit DCPU-16 Toolchain


Hermit is a DCPU-16 Toolchain written in Clojure.


The DCPU-16 processor is an imaginary processor designed for 0x10c – Notch’s new project.


This project includes the following

  • Disassembler
  • Assembler (with Clojure-y ‘syntax’)
  • Emulator
  • User Interface


There’s no external interface to this part of the toolchain. And, honestly, it’s probably not very useful to you. It was written to support the emulator. Although, it helps with testing, too.


No command line interface for this, yet…but soon. You have some options from a REPL, however. The main entry point to the assembler is the hermit.assembler/asm macro.

Here’s an example:

 (set x 5)
 (set y 0x30)
 (add y x)
 (set (ptr x 0x8000) y)
 (sub x 1)
 (ifn x 0)
 (set pc :loop)
 (sub pc 1))

Each form within the asm call is either an (op a b) operation triple or a keyword denoting a label that can be referenced within a or b in instructions.

There are some helper functions in hermit.core to help read files containing these types of forms and to write the resulting assembled words out to a file.

Note that there is some code in hermit.core to support writing out the unsigned word values that the dcpu-16 exclusively deals with. Of course, Java doesn’t have the concept of unsigned values. So there’s some code to handle that in there.


The code for this is in hermit.cpu. Since this is Clojure, you’ll be working with immutable machine s. To get an initialized machine, use the init-machine def. Now you can do some stuff with your new machine.


To get the value of a register use hermit.cpu/reg-val.

(reg-val init-machine :a)  ;=> 0

To set a register hermit.cpu/machine-with-reg-set.

(machine-with-reg-set init-machine :a 0xbeef) ;=> <machine map>

This returns a new machine with the A register set to 0xBEEF.

(reg-val (machine-with-reg-set init-machine :a 1) :a) ;=> 1


Similarly you can get and set the value of a memory location.

(mem-val (machine-with-mem-set init-machine 0x8000 48) 0x8000) ;=> 48

Also, you can load the machine with the data from a file starting at a specific memory location using hermit.cpu/load-data-file.

(def some-machine (load-data-file init-machine 0 "~/some.bin"))


Once you loaded some instructions into the machine you’ll naturally want to run the machine. The function for that is hermit.cpu/step.

;run from the hermit.test.integrated ns since it :use's everything else
(-> init-machine (load-data 0 (asm (set x 7))) step (reg-val :x))

The above pretty much exersices the whole toolchain (aside from the UI). It starts with a new machine, loads the result of assembling (set x 7) into memory location 0, steps the machine one instruction, then pulls out the value of register X to ensure it was set properly.

So, step just reads the instruction at PC, executes that instruction and returns a new machine representing the result.

User Interface

Currently this is really rough. It currently supports:

  • load up a binary file into memory location zero.
  • run the machine (calls step over and over as fast as possible…which isn’t very fast at all…maybe 120khz)
  • step the machine one step
  • view register values
  • view memory contents (click refresh XXXX button)
  • a text display of the video memory area (0x8000) with no color support
  • ability to enter text into the 16 word keyboard ring buffer at 0x9000

I wouldn’t say it’s really in a useable state right now. I do plan on focusing on this part of the system now. It is the reason I wrote this thing, after all!


Copyright (C) 2012 Wayne Rittimann, Jr.

Distributed under the Eclipse Public License, the same as Clojure.

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