AAsm

A modified implementation of the textbook architecture introduced in CS 110 at the University of Auckland. This project provides a simple assembler and emulator for a 16-bit architecture.

Architecture Overview

The architecture uses 16-bit instructions:

• OpCode: 4 bits
• Address: 12 bits (supporting 4096 addresses)

Registers

• Accumulator (R): Primary data register.
• Logic Register (C): Stores comparison results for branching.
• Program Counter (PC): Points to the next instruction in memory.

Instruction Set

Name	OpCode	Description
LOAD	0x0000	Load memory value at address into R
STORE	0x1000	Store R value into memory at address
CLEAR	0x2000	Store 0 into memory at address
ADD	0x3000	R = R + value at address
INC	0x4000	Increment value in R and store at address
SUB	0x5000	R = R - value at address
DEC	0x6000	Decrement value in R and store at address
COMP	0x7000	Compare R with value at address (sets C register)
JMP	0x8000	Jump to address
JMPGT	0x9000	Jump if value > R (from last COMP)
JMPEQ	0xA000	Jump if value == R (from last COMP)
JMPLT	0xB000	Jump if value < R (from last COMP)
JMPNE	0xC000	Jump if value != R (from last COMP)
IN	0xD000	Read integer from stdin into address
OUT	0xE000	Print value at address to stdout
HALT	0xF000	Stop execution

Example Program (Fibonacci)

        IN    MAX
START:  OUT   A
        LOAD  B
        STORE TEMP
        ADD   A
        STORE B

        LOAD  TEMP
        STORE A

        COMP  MAX
        JMPLT END

        JMP   START

END:    HALT

MAX:    .DATA 0
TEMP:   .DATA 0
A:      .DATA 0
B:      .DATA 1

Usage

Assembling an .aaexe file

To assemble one or more .aasm files into a single .aaexe executable:

java -jar AAsm.jar ASSEMBLE <output_path> <aasm_file1> <aasm_file2> ...

• <output_path>: The path to the output .aaexe file.
• <aasm_file>: The names of the source .aasm files, located in the same directory as the output path.

Example:

java -jar AAsm.jar ASSEMBLE output.aaexe fib.aasm link_fib_stack.aasm stack.aasm

Executing an .aaexe file

To run an assembled .aaexe file:

java -jar AAsm.jar EXECUTE <aaexe_path> [Debug]

• <aaexe_path>: The path to the .aaexe file to execute.
• Debug: Optional. Prints each instruction's opcode, address, and register value while executing.

Example:

java -jar AAsm.jar EXECUTE output.aaexe

Debug example:

java -jar AAsm.jar EXECUTE output.aaexe Debug

Disassembling an .aaexe file

To disassemble an .aaexe file back into an .aasm file:

java -jar AAsm.jar DISASSEMBLE <aaexe_path>

• <aaexe_path>: The path to the .aaexe file to disassemble.

The output .aasm file is written to the same directory as the input file and uses the same file name.

Example:

java -jar AAsm.jar DISASSEMBLE output.aaexe