# Implementing D Flip-Flops into a circuit

Discussion in 'Homework Help' started by kevob33, Oct 26, 2015.

1. ### kevob33 Thread Starter New Member

Oct 26, 2015
3
0
Hi,

I have just started learning about D Flip-Flops and believe that I understand how they function. However, I have an assignment where I have to create a circuit for a Tic Tac Toe game in the program Logisim, while implementing D Flip-Flops into the circuit. So for example, the circuit has to have a section where it has an "Illegal Move Indicator" - that is that an LED lights up if one of the players chooses a box that has already been used by the other player. I am very lost as to how to create this using D Flip-Flops.

We have already created a Tic Tac Toe game previously without using D Flip-Flops. Here is an example of my circuit with the Illegal Move Indicator:

Here is my D Flip-Flop circuit I have created in Logisim:

So I now need to implement one or more of these D Flip-Flop circuits within my Illegal Move circuit as so:

Here the blue dot is "D" in my D Flip-Flop circuit and the two red dots are Q and Q'. I need this to function so that if, for example, A1 is selected (A1=1) and then B1 is selected , the output from this circuit will to be equal to 1.

Do I need to edit my flip flop circuit so that it has two input, one of which acts as the clock, and then have just Q as the only output? I really am lost and don't know where to start.

Thank you for any help in adavnce

2. ### WBahn Moderator

Mar 31, 2012
18,087
4,917
If you don't need one of the outputs, then just don't connect it to anything. You still need the signal internally within the FF so there's no simplification to be had.

3. ### kevob33 Thread Starter New Member

Oct 26, 2015
3
0
Thank you for your reply, but I am still completely lost as to how I can have A1 and B1 as inputs into a DFF and an output of 1 when both A1=1 and B1=1.

4. ### WBahn Moderator

Mar 31, 2012
18,087
4,917
A FF is used to store state information. If you just want to have a circuit that outputs a 1 when A1 and B1 are both 1, then you used an AND gate.

What you are doing here is (or at least I think this is the intend) is to allow the use of momentary switches (perhaps even a single set of switches) and have each position remember if it is open or, if not, who selected it.