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Implementated instructions 0x4000 to 0xC000
- Moved commonly used variables in runSystem() above the main match statement
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1 changed files with 97 additions and 6 deletions
103
scripts/Chip8.gd
103
scripts/Chip8.gd
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@ -77,6 +77,11 @@ func runSystem():
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var jump = false
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opcode = (memory[pc] << 8) | memory[pc + 1]
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var vx = (opcode & 0x0F00) >> 8
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var vy = (opcode & 0x00F0) >> 4
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var address = opcode & 0x0FFF
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var byte = (opcode & 0x00FF)
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# Instructions
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match (opcode & 0xF000):
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@ -87,36 +92,122 @@ func runSystem():
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gfx[i] = 0
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isRedraw = true
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0x00EE: # RET
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sp -= 1
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pc = stack[sp] + 2
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jump = true
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_:
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var address = opcode & 0x0FFF
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pc = address
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jump = true
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0x1000: # JP
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var address = opcode & 0x0FFF
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pc = address
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jump = true
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0x2000: # CALL
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var address = opcode & 0x0FFF
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stack[sp] = pc
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sp += 1
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pc = address
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0x3000: # SNE Vx, byte
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var vx = (opcode & 0x0F00) > 8
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var byte = (opcode & 0x00FF)
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if (registers[vx] != byte):
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pc += 2
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if (registers[vx] != byte):
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pc += 2
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0x4000: # SE Vx, byte
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if (registers[vx] != byte):
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pc += 2
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0x5000: # SE Vx, Vy
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if (registers[vx] != registers[vy]):
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pc += 2
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0x6000: # LD Vx, byte
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registers[vx] = byte
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0x7000: # ADD Vx, byte
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registers[vx] = (registers[vx] + byte) & 0xFF
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0x8000:
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var result = registers[vx] - registers[vy]
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match (opcode & 0x000F):
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0x0000: # LD Vx, Vy
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registers[vx] = registers[vy]
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0x0001: # OR Vx, Vy
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registers[vx] = (registers[vx] | registers[vy]) & 0xFF
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0x0002: # AND Vx, Vy
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registers[vx] = (registers[vx] | registers[vy]) & 0xFF
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0x0003: # XOR Vx, Vy
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registers[vx] = (registers[vx] ^ registers[vy]) & 0xFF
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0x0004: # XOR Vx, Vy
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if (result > 255):
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registers[0xF] = 1
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registers[vx] = result & 0xFF
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0x0005: # SUB Vx, Vy
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if (registers[vx] > registers[vy]):
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registers[0xF] = 1
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else:
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registers[0xF] = 0
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registers[vx] = result & 0xFF
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0x0006: # SHR Vx {, Vy}
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var shr_result = registers[vx] & 0x1
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if (shr_result == 1):
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registers[0xF] = 1
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else:
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registers[0xF] = 0
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registers[vx] = registers[vx] >> 1
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0x0007: # SUBN Vx, Vy
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if (registers[vy] > registers[vx]):
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registers[0xF] = 1
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else:
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registers[0xF] = 0
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registers[vx] = result & 0xFF
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0x000E: # SHL Vx {, Vy}
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if (result == 1):
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registers[0xF] = 1
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else:
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registers[0xF] = 0
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registers[vx] = registers[vx] << 1
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_:
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print("Unsupported opcode at 0x8000: %X" ,opcode)
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0x9000: # SNE Vx, Vy
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if (registers[vx] != registers[vy]):
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pc += 2
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0xA000: # LD I, address
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index = address
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0xB000: # JP V0, address
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pc = address + (registers[0x0] & 0xFF)
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jump = true
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0xC000: # RND Vx, byte
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var rnd_result = (randi() % 256) & byte
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registers[vx] = rnd_result
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_:
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print("Unsopported opcode: %X", opcode)
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