Here is the python code of my initial CHIP-8 disassembler. I believe most things are there, but you never know! Here is a small script that I used to test it using the “Breakout.ch8” binary :
# Rob Russell
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#
from disassembler import DisassembleChip8Op
fil=open("Breakout.ch8",'rb')
dat = fil.read()
sz = len(dat)
fil.close()
pc = 0
while(pc < sz):
DisassembleChip8Op(dat,pc)
pc += 2
print ("Finished...")
Here is the actual disassembler code:
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#
def oc0x0(val,pc):
# either E0 or EE op codes
h = val[pc]
l = val[pc+1]
if h==0 and l != 0:
if (l == 224 ): # 00E0 - CLS
print("%-10s" % ("CLS "))
elif (l == 238 ): # 00EE - RTS Return from subroutine
print("%-10s" % ("RTS "))
else:
print("UNKNOWN 0")
return -1
else:
print("UNKNOWN 0")
return -1
return 0
def oc0x1(val,pc):
print("%-10s $%01x%02x" % ("JUMP", val[pc]&0xf,val[pc+1]), end=" ")
print(" Jump to $%01x%02x" % (val[pc]&0xf,val[pc+1]) )
return 0
def oc0x2(val,pc):
print("%-10s $%01x%02x" % ("CALL", val[pc]&0xf, val[pc+1]))
return 0
def oc0x3(val,pc):
print("%-10s V%01X,#$%02x" % ("SKIP.EQ", val[pc]&0xf, val[pc+1]), end = " ")
print(" Skip next op if V%01X equals #$%02x (%d)" % (val[pc]&0xf,val[pc+1], val[pc+1]))
return 0
def oc0x4(val,pc):
print("%-10s V%01X,#$%02x" % ("SKIP.NE", val[pc]&0xf, val[pc+1]), end=" ")
print(" Skip next op if V%01X doesn't equal #$%02x (%d)" % (val[pc]&0xf,val[pc+1], val[pc+1]))
return 0
def oc0x5(val,pc):
print("%-10s V%01X,V%01X" % ("SKIP.EQ", val[pc]&0xf, val[pc+1]>>4), end=" ")
print(" Skip next op if V%01X equals V%01X" & (val[pc]&0xf, val[pc+1]>>4))
return 0
def oc0x6(val,pc):
reg = val[pc] & 0x0f
print("%-10s V%01X,#$%02x" % ("MVI", reg, val[pc+1]) + " Move " + str(val[pc+1]) + " to V" + str(reg))
return 0
def oc0x7(val,pc):
print("%-10s V%01X,#$%02x"% ("ADI", val[pc]&0xf, val[pc+1]), end=" ")
print(" Add " + str(val[pc+1]) + " to V" + str(val[pc]&0xf))
return 0
def oc0x8(val,pc):
lastnib = val[pc+1]>>4
val1=val[pc]&0xf
val2=val[pc+1]>>4
if lastnib==0:
print("%-10s V%01X,V%01X" % ("MOV.", val1, val2), end = " ")
print(" Set V%01X = V%01X" % (val1, val2))
elif lastnib == 1:
print("%-10s V%01X,V%01X" % ("OR.", val1, val2), end = " ")
print(" Set V%01X = V%01X OR V%01X " % (val1,val1,val2))
elif lastnib == 2:
print("%-10s V%01X,V%01X" % ("AND.", val1, val2), end = " ")
print(" Set V%01X = V%01X AND V%01X" % (val1,val1,val2))
elif lastnib == 3:
print("%-10s V%01X,V%01X" % ("XOR.", val1, val2), end = " ")
print(" Set V%01X = V%01X XOR V%01X " % (val1,val1,val2))
elif lastnib == 4:
print("%-10s V%01X,V%01X" % ("ADD.", val1, val2), end = " ")
print(" V%01X = V%01X + V%01X, VF carry set to 1 or 0" % (val1,val1,val2))
elif lastnib == 5:
print("%-10s V%01X,V%01X,V%01X" % ("SUB.", val1, val1, val2), end = " ")
print(" V%01X = V%01X - V%01X, VF=1 for borrow" % (val1,val1,val2))
elif lastnib == 6:
print("%-10s V%01X,V%01X" % ("SHR.", val1, val2), end = " ")
print(" LSB of V%01X in VF, then V%01X >> 1" % (val1,val1))
elif lastnib == 7:
print("%-10s V%01X,V%01X,V%01X" % ("SUB.", val1, val2, val2), end = " ")
print(" V%01X = V%01X - V%01X, VF=1 for borrow" % (val1,val2,val1))
elif lastnib == 0xe : # double check this!
print("%-10s V%01X,V%01X" % ("SHL.", val1, val2), end = " ")
print(" MSB of V%01X in VF, then V%01X << 1" % (val1,val1))
else:
print("UNKNOWN 8")
return -1
return 0
def oc0x9(val,pc):
print("%-10s V%01X,V%01X" % ("SKIP.NE", val[pc]&0xf, val[pc+1]>>4), end=" ")
print(" Skip next op if V%01X doesn't equal V%01X" % (val[pc]&0xf, val[pc+1]>>4))
return 0
def oc0xa(val,pc):
addresshi = val[pc] & 0x0f
print("%-10s I,#$%01x%02x" % ("MVI", addresshi, val[pc+1]) + " Move " + str(val[pc+1]) + " to Index Register")
return 0
def oc0xb(val,pc):
print("%-10s $%01x%02x(V0)" % ("JUMP", val[pc]&0xf, val[pc+1]), end=" ")
print(" Jump to $%01x%02x plus V0" % (val[pc]&0xf, val[pc+1]))
return 0
def oc0xc(val,pc):
print("%-10s V%01X,#$%02X" % ("RNDMSK", val[pc]&0xf, val[pc+1]), end= " ")
print(" Set V%01X to a random number AND'd with #$%02X (%d)" % (val[pc]&0xf,val[pc+1],val[pc+1]) )
return 0
def oc0xd(val,pc):
print("%-10s V%01X,V%01X,#$%01x" % ("SPRITE", val[pc]&0xf, val[pc+1]>>4, val[pc+1]&0xf), end=" ")
print(" Draw sprite @ V%01X,V%01X #$%01x pixels high (%d)" % (val[pc]&0xf, val[pc+1]>>4, val[pc+1]&0xf,val[pc+1]&0xf) )
return 0
def oc0xe(val,pc):
if val[pc+1]==158: # 9E for SKIPKEY.Y
print("%-10s V%01X" % ("SKIPKEY.Y", val[pc]&0xf), end=" ")
print(" Skip next OP if V%01X is pressed" % (val[pc]&0xf) )
elif val[pc+1]==161: # A1 for SKIPKEY.N
print("%-10s V%01X" % ("SKIPKEY.N", val[pc]&0xf), end=" ")
print(" Skip next OP if V%01X ISN'T pressed" % (val[pc]&0xf) )
else:
print("UNKNOWN E")
return -1
return 0
def oc0xf(val,pc):
val1=val[pc]&0xf
val2 = val[pc+1]
if val2 == 0x07:
print("%-10s V%01X,DELAY" % ("MOV", val1), end=" ")
print(" Sets V%01X to value of delay timer" % (val1))
elif val2==0x0a:
print("%-10s V%01X" % ("KEY", val1), end=" ")
print(" Block for keypress stored into V%01X" % (val1))
elif val2 == 0x15:
print("%-10s DELAY,V%01X" % ( "MOV", val1), end=" ")
print(" Sets delay timer to V%01X" % (val1))
elif val2 == 0x18:
print("%-10s SOUND,V%01X" % ("MOV", val1), end=" ")
print(" Sets sound timer to V%01X" % (val1))
elif val2 == 0x1e:
print("%-10s I,V%01X" % ("ADI", val1), end=" ")
print(" I = I + V%01X" % (val1))
elif val2 == 0x29:
print("%-10s I,V%01X" % ("SPRITECHAR", val1), end=" ")
print(" Sets I to loc of sprite for character in V%01X" % (val1))
elif val2 == 0x33:
print("%-10s (I),V%01X" % ("MOVBCD", val1), end=" ")
print(" BCD rep of V%01X" % (val1))
elif val2 == 0x55:
print("%-10s (I),V0-V%01X" ("MOVM", val1), end=" ")
print(" Store V0-V%01X in mem starting at I" % (val1))
elif val2 == 0x65:
print("%-10s V0-V%01X,(I)" % ( "MOVM", val1), end=" ")
print(" Fill V0-V%01X in mem starting at I" % (val1))
else:
print("UNKNOWN F")
return -1
return 0
def DisassembleChip8Op(codebuffer, pc):
firstnib = hex(codebuffer[pc] >> 4)
case='oc'+firstnib + "(val,pc)" # oc prefix means 'opcode', passing 'val' and 'pc' to fcn
print("%04x %02x %02x " % (pc+0x200, codebuffer[pc], codebuffer[pc + 1] ), end=" ")
val=codebuffer
result=eval(case) # run switch statement replacement