4 bit processor

I need information about 4 bit processor
1)4 bit ALU
2)3:8 decoder



for 4 Bit ALU
4 bit ALU
4 bit input A
4 bit input B

S2  S1  S0              F
0     0    0            F= A and B
0     0    1            F= A or B
0     1    0            F= A Nand B
0     1    1            F= A nor B
1     0    0            F= A Xor B
1     0    1            F=A X nor B
1     1    0            F= A addition B
1     1    1            F= A subtraction B

truth table

Code:

S2  S1  S0             A     B     F
0     0    0           0     0      0         AND
                       0     1      0
                       1     0      0
                       1     1      1

0     0    1           0     0      0        or
                       0     1      1
                       1     0      1
                       1     1      1

0     1    0            0     0      1          NAND
                        0     1      1
                        1     0      1
                        1     1      0

0     1    1            0     0      1        NOR
                        0    1     0
                        1    0      0
                        1     1      0

1     0    0            0     0      0          Xor
                         0    1     1
                         1    0      1
                         1     1      0

1     0    1            0     0      1          X nor
                         0    1     0
                         1    0      0
                         1     1      1

1     1    0           0     0      0          addition
                        0    1     1
                        1    0      1
                        1     1      0

1     1    1            0     0      0        subtraction
                        0    1     1
                       1     0     1
                        1    1     0

and I have uploaded truth table for decoder

 

I made truth table I want to make verilog code for processor

ALU perform following function
AND logic

OR logic

NAND logic

NOR logic

X or logic

X nor logic

addition

subtraction

I am not going to design for specific purpose

don't mind I made some simple specification for 4 bit processor
specification for 4 bit processor

1)4 bit ALU
2)3:8 decoder
3) 4 bit A register ( data register )
4) 4 bit B register (data register )
5) 4 bit Instruction register
6)4 bit address register