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Added draw instruction

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- Renamed byte and address to vbyte and vaddr, respectfully, to avoid conflicts
This commit is contained in:
Tony Bark 2021-03-09 06:08:20 -05:00
parent 3c4404f072
commit a75bc3ca56
1 changed files with 37 additions and 15 deletions
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52
scripts/Chip8.gd
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@ -80,8 +80,8 @@ func runSystem():
var vx = (opcode & 0x0F00) >> 8
var vy = (opcode & 0x00F0) >> 4
var address = opcode & 0x0FFF
var byte = (opcode & 0x00FF)
var vaddr = opcode & 0x0FFF
var vbyte = (opcode & 0x00FF)
# Instructions
match (opcode & 0xF000):
@ -99,28 +99,25 @@ func runSystem():
jump = true
_:
pc = address
pc = vaddr
jump = true
0x1000: # JP
pc = address
pc = vaddr
jump = true
0x2000: # CALL
stack[sp] = pc
sp += 1
pc = address
pc = vaddr
0x3000: # SNE Vx, byte
if (registers[vx] != byte):
pc += 2
if (registers[vx] != byte):
if (registers[vx] == vbyte):
pc += 2
0x4000: # SE Vx, byte
if (registers[vx] != byte):
if (registers[vx] != vbyte):
pc += 2
0x5000: # SE Vx, Vy
@ -129,10 +126,10 @@ func runSystem():
0x6000: # LD Vx, byte
registers[vx] = byte
registers[vx] = vbyte
0x7000: # ADD Vx, byte
registers[vx] = (registers[vx] + byte) & 0xFF
registers[vx] = (registers[vx] + vbyte) & 0xFF
0x8000:
var result = registers[vx] - registers[vy]
@ -198,16 +195,41 @@ func runSystem():
pc += 2
0xA000: # LD I, address
index = address
index = vaddr
0xB000: # JP V0, address
pc = address + (registers[0x0] & 0xFF)
pc = vaddr + (registers[0x0] & 0xFF)
jump = true
0xC000: # RND Vx, byte
var rnd_result = (randi() % 256) & byte
var rnd_result = (randi() % 256) & vbyte
registers[vx] = rnd_result
0xD000: # DRW Vx, Vy, nibble
var nibble = (opcode & 0x000F)
var yPos = registers[vx]
var xPos = registers[vy]
registers[0xF] = 0
for yLine in range(nibble):
var line = memory[index + yLine]
for xLine in range(8):
var pixel = line & (0x80 >> xLine)
if (pixel != 0):
var totalX = (xPos + xLine) % 64
var totalY = (yPos + yLine) % 32
var px_index = (totalY * 64) + totalX
if (gfx[px_index] == 1):
registers[0xF] = 1
gfx[px_index] = gfx[px_index] ^ 1
isRedraw = true
_:
print("Unsopported opcode: %X", opcode)