# Draw the logic diagram of the circuit.

Discussion in 'Homework Help' started by ITNetAngel, Jul 8, 2011.

1. ### ITNetAngel Thread Starter New Member

Jul 8, 2011
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0
A sequential circuit has two D flip-flops A and B, two inputs x and y, and one output z. The flip-flop equations and circuit are as follows:
DA = Bx + Ay
DB = Bx + Ay
z = AB
Draw the logic diagram of the circuit.

2. ### guitarguy12387 Active Member

Apr 10, 2008
359
12
Hey and welcome to the forums.

But you should know... while we're happy to help, we won't just do your homework for you. You need to post your attempted solution with specific questions. At which point, we can help you.

3. ### Georacer Moderator

Nov 25, 2009
5,151
1,266
Remember that in an expression, the $\cdot$ sign is an AND gate, the + sign is an OR gate and the ' sign is a NOT gate.

4. ### ITNetAngel Thread Starter New Member

Jul 8, 2011
4
0
Im really stuggling with this and I know what the adn, or, not gates and all are I just cant put it all together to complete the logic diagram.

5. ### guitarguy12387 Active Member

Apr 10, 2008
359
12
Ohh okay!

Well, as georacer suggested, each symbol represents a logic gate, more or less.

When I was learning, I would draw a line or wire representing each input. Then from there, i would draw different branches and connect them to different gates according to the equation.

Does that help at all?

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6. ### ITNetAngel Thread Starter New Member

Jul 8, 2011
4
0
This is what I submitted professor said not complete

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7. ### Georacer Moderator

Nov 25, 2009
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He's right, components are missing.

You must understand what the problem says first.
Your circuit has two inputs X and Y. These are not the outputs of the Flip Flops A and B, but actual wires going into your circuit from an outside source with names X and Y. Similarly, Z is a wire that goes out from your circuit and is the output signal.
The outputs of your FFs are called Qa (or A), Qa', Qb (or B) and Qb'.

Now, your first equation says that Da=BX+AY or more formally Da=B*X+A*Y. As I wrote you above, that can be transformed to Da=(Qb AND X) OR (Qa AND Y).
Can you transform that to a circuit with gates? Can you do the same with the other two equations?
Remember that X' is NOT(X).

<edit: Thanks for the heads-up djsfantasi>

Last edited: Jul 12, 2011
8. ### djsfantasi AAC Fanatic!

Apr 11, 2010
3,486
1,245
Typo alert! Da=(Qb AND X) OR (Qa AND Y)

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