N Bit ALU

[vead]

how to make N bit ALU
ALU has two input word A, B
N bit ALU
An input
Bn input
F input
example
1 bit alu
0+1=1

2 bit ALU
01+10=11

4 bit ALU
0101+1010=1111

example -
1 bit ALU
1 bit input A
1 bit input B
1 bit output F

s         ALU performance
0        F= addition
1        F= A and B

same for 2 bit ALU
2 bit ALU
2 bit input A
2 bit input B
2 bit output F

S0  S1          F
0    0         F= addition
0    1         F= subtraction
1    0         F= A and B
1    1         F= A or B

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

S2  S1  S0              F
0     0    0            F= addition
0     0    1            F= subtraction
0     1    0            F= shift right
0     1    1            F=shift right
1     0    0            F= A and B
1     0    1            F=A or B
1     1    0            F= A not B
1     1    1            F= A and B

 

[Harald Kapp]

You need a funvtional unit where the function can be controlled by the S-inputs. Tis is described e.g.here.

Check your function codes: S= 100 and S=111 both are F=A and B. Is this what you want? Also you should clarif S=110. I do not understand what F=A not B means.because "not" is a unary operator, not a biary one (not works with one input only, it does not calculate an output from two inputs).

 

[vead]

I am not sure what function are you talking ?
lets see for 2 bit ALU
same for 2 bit ALU
2 bit ALU
2 bit input A
2 bit input B
2 bit output F

S0  S1          F
0    0         F= addition
0    1         F= subtraction
1    0         F= A and B
1    1         F= A or B

function F= A&b (A and B logic )
A B F
0 0 0
0 1 0
1 0 0
1 1 1

 

[Harald Kapp]

Did you read the ínformation I linked in post #2?

 

[vead]

Did you read the ínformation I linked in post #2?

yes I read and I made following for example

function F= A&b (A and B logic )
A B F
0 0 0
0 1 0
1 0 0
1 1 1

 

[Harald Kapp]

O.K. Now where' the question?

This is just one function (A & B). You want to make the function being controlled by the function code inputs (S0, S1, S2). How would you do that? (hint: it's in the linked text).

 

[vead]

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

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

 

[vead]

please some one check out this table. and tell me its correct or wrong ?
I read in every blog that processor made with ALU and control unit. so after some reading I made this table. i am not going to make for company. I am just going to make specific one for my basic understanding

 

[(*steve*)]

I think the problem is that you don't understand what an ALU is or does.

The big hint is that it doesn't perform just a single function.

 

[Harald Kapp]

Maybe a video is beter than reading stuff?
Sorry, I don't have the time to check the full function table. As these are basic functions, you should be able to verify by yourself.

 

[vead]

I think the problem is that you don't understand what an ALU is or does.

The big hint is that it doesn't perform just a single function.

I already mention function for ALU in my previous post

ok look at this

ALU perform following function

AND logic
OR logic
NAND logic
NOR logic
X or logic
X nor logic
addition
subtraction

 

[Harald Kapp]

If you design so, yes.

You don't necessarily have to design an ALU this way. ALU stands for Arithmetic Logic Unit. Which means it is a unit that can perform arithmetic and logic operations on its inputs and generate an output accordingly. You can use the functions as indicated by your table, bt as a designer you are free to chose any set of functions that is suitable for the purpose which can be very different from your table. This is your own design decision.

 

[vead]

Maybe a video is beter than reading stuff?
Sorry, I don't have the time to check the full function table. As these are basic functions, you should be able to verify by yourself.

thanks for looking

Maybe a video is beter than reading stuff?
Sorry, I don't have the time to check the full function table. As these are basic functions, you should be able to verify by yourself.

thanks for looking this post

4 bit processor
component for 4 bit processor
1)4 bit ALU
2)3:8 decoder

now If I want to make 8 bit processor then I think I need following things ( I am not sure ?
1)8 bit ALU
2)3:8 decoder