CPU-16

This is a 16 bit logisim CPU, complete with a simple assembler. The instruction set is detailed in IS.md.

Assembler

The assembler is written in javascript, and requires node.js to be installed.

./assembler.js <infile> [outfile]
./assembler.js --help

If infile is -, read from stdin. If outfile is -, write to stdout. If outfile is omitted, write to img.raw.

After assembling, right click the block labeled Program ROM, click load image..., and select the .raw file you just made.

The assembly language, masm

Registers:

• A: Register for ALU A input.
• B: Register for ALU B input.
• RAM: Register which can be used as a RAM address.
• FLAG: Flag register, for conditional jumps.

Instructions

From assembler.js -h:

<val>:
	'*'        : Value from RAM
	'$<number>': Number
	':<name>'  : Instruction with label <name>
	':current' : Current instruction
	'INPUT'    : External input (only load-a and load-b

<opr>: A, GT, EQ, LT, NEQ, NOT_A, ADD, SUB, MUL, DIV, MOD, LSHIFT, RSHIFT, XOR, AND, OR

Instructions:
	load-a <val>: Load A
		Load <val> to reg A.
	load-b <val>: Load B
		Load <val> to reg B.
	load-ram <val>: Load RAM register
		Load <val> to reg RAM.
	write <opr>: Write RAM
		Write A <opr> B to RAM.
	write-flag <opr>: Write FLAG register
		Write A <opr> B to FLAG.
	write-extern <opr>: Write externally
		Write A <opr> B externally.
	cjmp <opr>: Conditional jump
		Jump to A <opr> B if FLAG.
	jmp <opr>: Unconditional jump
		Unconditionally jump to A <opr> B.

Preprocessor

• #define name val: Define a name. Any occurrence of that name later will be replaced.
• #define name {: Define a name, multiple lines. All lines until the next } will be included.
• #include "path": Include a file, if it hasn't been included yet. Path is relative to the directory of the current file.
• #include <path>: Include a file like above. Path is relative to the directory the assembler was ran from.