(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

HI

This 4 bit ALU requires 8 functions in a bit slice, and satisfies following criteria

Also, it can only be constructed via basic logic gate..and,or,not,xor....

No filp-flop...etc.

S1 S2 S3 OUTPUT

0 0 0 Shift A Through (X = A)

0 0 1 Shift input A Left (X = A Shifted right by 1 bit)

0 1 0 Shift Input A Right (X = A Shifted left by 1 bit)

0 1 1 Logical AND (X = A AND B)

1 0 0 Logical XOR (X = A XOR B)

1 0 1 Logical NOR (X = A NOR B)

1 1 0 Full adder (X = A + B)

1 1 1 Subtraction (using the Full Adder) (X = A - B)

2. Relevant equations

Designing a 4 bit ALU

https://www.physicsforums.com/showthread.php?t=265676

3. The attempt at a solution

I've complete the other six tasks(but subtractors doesn't work properly?!)

However,shifting right&left really beat me up...

this is what i got in one bit ALU...and then got stuck

http://tinyurl.com/ybhqex2

unable to build a shifter to fill in the blank

0 0 1 Shift input A Left (X = A Shifted right by 1 bit) =D1

0 1 0 Shift Input A Right (X = A Shifted left by 1 bit) =D2

somehow i hav rough ideas to build a shifter but seems cant satisfy the requirement or not this case

2 bit shifter

http://tinyurl.com/yjvdx34

4 bit shifter

http://tinyurl.com/ye9enhd

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# Homework Help: Shift LR in 4 bit ALU?

Can you offer guidance or do you also need help?

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