Opcode

1. (2)

3. 6- Then R/M = 100
0000001100000100
MACHINE CODE = 0304h
X X X X
ADD AX,[SI]
1- OPCODE = 000000
2- W=1 (16-BIT)
3- The REG is dest. i.e: D=1
4- then REG = 000 for AX
5- MOD =00
D
0
1
REG = code for Source reg
REG = code for Dest. reg
MODE

4. 6- Then R/M = 011
100010001100
000011
MACHINE CODE = 88C3h
X X X X
MOV BL,AL
1- OPCODE = 100010
2- W=0 (8-BIT)
3- Let REG be the source
i.e: D=0
4- then REG = 000 for AL
5- MOD =11
D
0
1
REG = code for Source reg
REG = code for Dest. reg
MODE
OR= 8AD8h (if D=1,REG=011&R/M=000)

5. 6- Then R/M = 110
0011001000001110
MACHINE CODE = 320E3412h
0011 01000001 0010
X X
XOR CL,[1234h]
1- OPCODE = 001100
2- W=0 (8-BIT)
3- The REG is dest. i.e:
D=1
4- then REG = 001 for CL
5- MOD =00
D
0
1
REG = code for Source reg
REG = code for Dest. reg
MODE

6. 6- Then R/M = 001
0000000110000001
MACHINE CODE = 01813412h
0011 01000001 0010
X X
ADD [BX][DI][1234],AX
1- OPCODE = 000000
2- W=1 (16-BIT)
3- The REG is source
i.e. D=0
4- then REG = 000 for AL
5- MOD =10
D
0
1
REG = code for Source reg
REG = code for Dest. reg
MODE

7. 6- Then R/M = 011
1100011110000011
MACHINE CODE = C7833412CDABh
0011 01000001 00101100 11011010 1011
MOV WORD PTR [BP][DI][1234],0ABCDh
1- OPCODE = 110001
2- W=1 (16-BIT)
3- D=1 from table
4- then REG = 000 from
table
5- MOD =10
MODE

8. 4- Then R/M = 011
1000110010011011
MACHINE CODE = 8CC9B3412h
0011 01000001 0010
X X
MOV [BP][DI][1234],DS
1- OPCODE = 10001100
2- then REG = 011 from
table
3- MOD =10
MODE

10. D
0
1
REG = code for Source reg
REG = code for Dest. reg
MODE