# Complex Combinational System Design

Discussion in 'Electronics Homework Help' started by vick5821, Oct 30, 2012.

1. ### vick5821

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0
Jan 22, 2012

As in the image, how can I implement them ? What type of ICs should I use ?

Hope someone can help me with this.

Thank you

Last edited: Oct 30, 2012
2. ### Harald KappModeratorModerator

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2,984
Nov 17, 2011
A good start would be to follow the lectures you're given, study the topic and give the assignment a try by yourself. It is obviously no use coming to this forum for ready made solutions.
Look at the list of information that you'll have to supply. This list is pretty much the sequence you have to go along to solve the assignment:
1) create the truth table according to the specifications
2) simplify the equations using the Quine McClusky technique (you do know what this is and how to use it, do you?)
etc., etc. ...

Please note that the idea here is to guide you into finding the solution yourself - that's what you will be facing for the rest of your future career. If we were to supply the solution, you'd be finished with this assignment in a wink - but you'd be stuck with the next one.

Once you have found the minimized equations use logic ICs that represent the functions as needed (AND, OR, NAND, NOR, INVERTER etc.)

A personal note (although I'm inclined to think that I'm not alone):
Time and again we've been trying to help you. Most of your threads end with posts by other forum members containing everything from tips to guide you into the right direction to upright complete solutions. We almost never hear back from you whether our help was useful, whether you could complete the assignment or whether an issue still is open and mybe you need more help.
The maps we supply, the equations we setup for you etc.: this all takes our time. We'd love to have some feedback from you so we can see if it was worth the effort.
My personal wish: Please close your threads once the issue is solved and let us know the outcome of the topic at hand.
That way no one will bother posting answers that are not read and we can put our effort in current threads.

Regards,

Harald

3. ### davennModerator

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2,018
Sep 5, 2009
hey vic

Harald has given some excellent advice
surely if you are getting these sorts of questions in assignments, you must have covered the topic in class to some degree ??

its not a topic I could personally guide you with, heck I would have to google Quine McClusky technique for a start to find out what that is haha

work through the assign. systematically, your class text references must also have info for these questions

Dave

4. ### (*steve*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

25,505
2,852
Jan 21, 2010
I'll "third" it.

And let us know what grades we're getting in your course! (Just kidding, I don't think we've been doing the work for you)

These assignments are not there to trick you. The assignment tells you what to do in a pretty step by step manner. Part of the skill involved in completing these things is figuring out where the question is trying to help you.

edit: We also *really* appreciate feedback. If our help managed to get you a good result, let us know. If we missed something out, tell us that too.

Last edited: Oct 31, 2012
5. ### vick5821

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Jan 22, 2012
Actually I really appreciate all of your help. Your help really do improve myself in completing my assignment and to improve my understanding in electronic's world.

I think I would need to be more hardworking in doing some research so that I could understand what you all are explaining about.

Heehehe.. Thank you all !!

6. ### vick5821

700
0
Jan 22, 2012
So basically I need to design a logic circuit where I have one input to determine whether the circuit is in adder mode or multiplier mode right ? But how ? and how can i control the input to be 0 to 2 ?

7. ### Harald KappModeratorModerator

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2,984
Nov 17, 2011
1) input 0...2 requires 2 bits: 00, 01, 10
2) the mode selector is just a 3rd bit: mode=0 = adder, mode=1 = multiplier.
3) since 2*2 = 4 your output signal has 3 bits.
4) for displaying the result on a 7-segment display, you need an additional binary-to-7-segment decoder.
Or you can integrate the binary-to-7-segment decoder into your logic optimization using the quiny McClusky technique.

8. ### vick5821

700
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Jan 22, 2012
so if 00 means I connect both input to 0V right ? Hahaha..I do not learn about the techniques yet ><

9. ### vick5821

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Jan 22, 2012
where is the 5 variables ? LOL

10. ### Harald KappModeratorModerator

12,455
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Nov 17, 2011
input A = 2 variables: a1 and a0
input B = 2 variables: b1 and b0
mode = 1 variable
Sum of variables = 5

By now you should be familiar with binary numbers and the corresponding mathematics.

For the sake of simplicity: yes.
For standard CMOS "0"=0V and "1"=5V can be assumed.
But it depends on the definition of the logic and on the type of logic family what voltage (or current) represents a logical "1" or a logical "0". Without going into details (I don't want to irritate you) there is such a thing as negative logic where a "1" is represented by 0V and there are types of logic where negative voltages are involved or even multiple levels, not just 2.
Forget about these, concentrate on standard CMOS logic!

Then it is time you learn. Obviously the teacher who gave you the assignment assumes that you are or should be familiar with basic digital electronics. If not, go back to your textbooks or Google. Read the first hits in the search results.