# An excercise on decoders

Discussion in 'Homework Help' started by nerazzurri10, Jun 26, 2014.

1. ### nerazzurri10 Thread Starter New Member

Jun 26, 2014
2
0
I have the following exercise:

Design a circuit that takes a 2 bit binary and makes it x^3 (x cubed), using a decoder

I thoguht to do it with a 3 to 8 decoder, because I have 2 bits of input, and 4 bits of output, since the largest output is 11011 (which is 27 in decimal).

I have managed to get to a truth table. Input = x0x1x2. Output=a,b,c,d,e.

 x1 x1 x2 a b c d e 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 1 0 1 0 0 1 0 0 0 0 1 1 1 1 0 1 1

However, I am not quite sure what should I do now. I have to get to a function to represent it in gates? How can I make a karnaugh map from that table?

I am aware that I would have to add three more outputs to the 3 to 8 decoder, but they will be just "don't cares".

2. ### MrCarlos Active Member

Jan 2, 2010
400
134
Hello nerazzurri10

You say this statement:
Design a circuit That Takes a 2 bit binary and makes it x ^ 3 (x cubed), using a decoder of your choice.

I have to get to a function to Represent it in gates?
look at the blue underlined words in your statement
If you want to do with logic gates the Decoder, the answer is YES
but if not,
You can select a decoder chip

How can I make a Karnaugh map from That table?
It is relatively easy to use.

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3. ### nerazzurri10 Thread Starter New Member

Jun 26, 2014
2
0
Hello Mr. Carlos,