# Any idea about how to build a bit rotation circuit

Discussion in 'Digital Circuit Design' started by Denner Paganoti, Mar 5, 2017.

1. ### Denner Paganoti Thread Starter New Member

Mar 5, 2017
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Hey guys,
I'm trying to build with a friend a bit rotation circuit (circular shift) for an ALU of 4 bits, but we didn't get anything until now. May you help us with any idea? (we're a kind of desperate about it and this is our first project in the area), we're accepting any advice to build it. We can make it with logic gates, flip flops, IC's, registers etc.... Anything about it is good for us now!.

Thanks for all.

2. ### djsfantasi AAC Fanatic!

Apr 11, 2010
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What technology are you using CMOS? Have you looked up "shift registers"?

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3. ### Denner Paganoti Thread Starter New Member

Mar 5, 2017
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We've trying to adapt an arithmetic shift register to do that, but that's our problem, we didn't get to change it from a linear shift register to a circular shift register.

Thanks.

4. ### djsfantasi AAC Fanatic!

Apr 11, 2010
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So, what is the difference between a linear shift register and a circular shift register. All shift register shift a bit one position to the right or left. What does a circular shift register do differently in certain cases?

What do you mean, "we didn't get to change it"?

5. ### Denner Paganoti Thread Starter New Member

Mar 5, 2017
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The basic difference is the linear shift register loses a bit for example: a 3 bit sequence 001, in a linear shift register after a shit it becomes 000, but in a circular shift register it becomes 100 (if you're rotating it to the right, of course), it's like the circular one would have a carry system to storage this bit.

When I said "we didn't get to change it", we were trying to adapt a linear into a circular.

6. ### hp1729 Well-Known Member

Nov 23, 2015
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Shift register with presettable inputs. 4 Quad 4 to 1 data selector on each presettable input.

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7. ### djsfantasi AAC Fanatic!

Apr 11, 2010
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So, why don't you feed the first bit from the last bit?

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8. ### EM Fields Active Member

Jun 8, 2016
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Here's one way to do it: