Bit16 is a 16-bit CPU, emulator, assembler, circuit with fully custom architecture
The Bit16 CPU is a custom 16-bit architecture designed with the following specifications:
-
A (0x0): General Purpose Register
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B (0x0): General Purpose Register
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C (0x2): General Purpose Register
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SR (0x3) Settings Register: left-to-right i/o, MB/(M)emory (B)ank (0x6) 0x0 for General Purpose RAM or 1 for VRAM
i/o flag specifies usage of PORT or RAM for LW and SW instructions, can be used as a replacement for dedicated instructions like INB reg, red/immg : reg <- PORT[reg/imm8] OUTB reg/imm8, reg : PORT[reg/imm8] <- reg 0 -> use current RAM 1 -> use PORT
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HL (0x4): HL 16-bit Register
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Flag (0x5): Flag register with the following flags (left-to-right):
- Zero
- Negative
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SP (0x6) Stack Pointer Register
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PC (0x7) Program Counter Register
The Bit16 CPU supports the following instructions, each encoded with a 4-bit opcode:
| Opcode | Instruction | Description |
|---|---|---|
| 0x0 | NOP | No operation, increments the program counter |
| 0x1 | HALT | Stops the CPU, program execution is finished |
| 0x2 | MW reg, reg/imm8 | Move data from a register or immediate value to a register |
| 0x3 | MWL imm8 | Move an immediate 8-bit value to the lower byte of HL |
| 0x4 | MWH imm8 | Move an immediate 8-bit value to the upper byte of HL |
| 0x5 | LW reg, [HL/imm8] | Load data from memory (RAM) to a register |
| 0x6 | SW [HL/imm8], reg | Store data from a register to memory (RAM) |
| 0x7 | ADD reg, reg/imm8 | Add data from a register or immediate value to a register |
| 0x8 | SUB reg, reg/imm8 | Subtract data from a register or immediate value from a register |
| 0x9 | AND reg, reg/imm8 | Perform a bitwise AND operation between a register and a register or immediate value |
| 0xA | OR reg, reg/imm8 | Perform a bitwise OR operation between a register and a register or immediate value |
| 0xB | NOT reg, reg/imm8 | Perform a bitwise NOT operation on a register or immediate value |
| 0xC | JMPZ reg/imm8 | Conditional jump based on the value in a register or immediate value |
| 0xD | JMPN | Conditional jump based on the Negative flag |
| 0xE | PUSH imm8/reg | Push a value from a register or immediate value onto the stack |
| 0xF | POP reg | Pop a value from the stack into a register |
The memory layout of the Bit16 CPU is as follows:
- 0x0000..0x7FFF: GENERAL PURPOSE ROM 32768*16bit
- 0x8000..0xBFFF: GENERAL PURPOSE RAM (BANKED/VRAM) 16384*16bit
- 0xC000..0xFDFF: GENERAL PURPOSE RAM 15872*16bit
- 0xFF00..0xFFFF: STACK (RECOMMENDED), else GP RAM 256*16bit
This memory layout provides a framework for storing program code, data, and stack information.
- Clone this repository to your local machine.
git clone https://github.com/guptaanurag2106/Bit16.git- Build the emulator using your C++ compiler.
g++ -o Bit16 emulator.cpp