i8080-clj is a working Intel 8080 emulator in Clojure. Implementing a CPU emulator in Clojure is heroically inefficient, but is undeniably educational and even fun (for varying definitions of fun).
Since i8080-clj is a CPU emulator, it doesn't do much on its own. Like any processor, it needs a machine and an executable to do something interesting.
To really dive in and learn about the instruction set, check out the i8080 Programmer's Manual in this repository.
Otherwise, try running 👾 Space Invaders!
The i8080 is a relatively simple processor to emulate, since it's 8 bit and only has 256 instructions. We can store the entire machine state in a simple map, which makes debugging easy:
{; registers
:cpu/a 0 ; accumulator
:cpu/b 0 ;
:cpu/c 0 ;
:cpu/d 0 ;
:cpu/e 0 ;
:cpu/h 0 ; hi address byte
:cpu/l 0 ; lo address byte
:cpu/sp 0 ; stack pointer
:cpu/pc 0 ; program counter
:cpu/mem mem-64k ; memory
:cpu/int-enable? false ; enable interrupt
:cpu/nopc? false ; don't advance pc
; condition codes
:cpu/cc/z 0 ; zero
:cpu/cc/s 0 ; sign
:cpu/cc/p 0 ; parity
:cpu/cc/cy 0 ; carry
:cpu/cc/ac 0 ; aux carry
:cpu/last-mem nil ; addr and data of write from last op (or nil)
}This means executing an instruction is as simple as calling a function that takes a map of the current state as input and returns the next state as output.
To install, add the following to your project :dependencies:
[i8080-clj "0.4.0"]
Most instructions have an associated unit test. To run them all, just do:
lein test
Copyright © 2018-2020 Matt Grimm
Distributed under the Eclipse Public License either version 1.0 or (at your option) any later version.
- This project owes a lot to Emulator 101 for inspiration and guidance.