Teto

A minimal 32-bit CPU emulator that implements a simplified fixed-width x86-like instruction set.

Architecture (currently)

• Memory: 64KB addressable memory space
• Registers: 8 general-purpose 32-bit registers (similar to x86):
  • eax, ebx, ecx, edx, esi, edi, esp, ebp
• Memory Segments:
  • Text Segment: 16KB
  • Data Segment: 16KB
  • Heap Segment: 16KB
  • Stack Segment: 16KB
• Program Counter: Starts at 0x0000
• Stack: Grows downwards from 0xFFFF
• Heap: Grows upwards from 0x8000

Instruction Format

Each instruction is 32 bits (4 bytes) with the following layout:

0            8       12     16                32 (BIT)
+------------+-------+------+--------------------+
|   Opcode   |  Reg  | Mode |      Operand       |
+------------+-------+------+--------------------+

Opcode  = 8 bits  (Operation to execute)  
Reg     = 4 bits  (Target register)  
Mode    = 4 bits  (Addressing mode)
Operand = 16 bits (Immediate value or register address)

Addressing Modes

Binary	Decimal	Mode Name	Description
0000	0	Immediate	Operand is an immediate 16-bit WORD
0001	1	Memory Direct	Operand is a 16-bit address in memory
0010	2	Register Direct	Operand is a register (EAX, EBX, etc.)
0011	3	Heap Relative	Operand is an offset from the heap base
0100-1011	4-11	Register Relative	Operand is an offset from the register value