# Logisim exercise..

Discussion in 'Homework Help' started by alexandre199, Jan 2, 2015.

1. ### alexandre199 Thread Starter New Member

Jan 2, 2015
3
0
I've to do this with logisim:
input:
I have a sequence of 8 bit word.
Unique CK for the circuite.
Reset signal.
output:
The decoded 16 bit word

I have to decode the input word like the image attached (the mealy machine).

example :
Input word W: 10100010

Output word: 1101000111001101

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2. ### tshuck Well-Known Member

Oct 18, 2012
3,527
675
Your output does not look like a 16 bit word.

It looks like what you meant is that the output is a signal that denotes when the machine has recognized the 16 bit pattern.

Try making a state transition table (use your state transition diagram), I find they make it easier to describe the logic.

What have you done thus far?

We will not do your homework for you, so you will need to put some work in on your own.

Is there a question you have?

3. ### alexandre199 Thread Starter New Member

Jan 2, 2015
3
0
I try to do this exercise, i've done the transition diagram, but i can't find any solutions ( probably i don't understand well those passages).
Anyway i try to do it with a 8 bit pin, a bit selector ( to serialize the sequence), than i ve done the circuital "decoding" , after that i put a multiplexer to select the state where the circuit is.
But there is also another problem: How can i bring the circuit in the right state?
Here's my work..

4. ### tshuck Well-Known Member

Oct 18, 2012
3,527
675
You seen extremely confused. Don't use there simulator yet - design your state machine.

First, acknowledge whether or not what I said is accurate: your output is a single bit.

Second, make a state transition table.

5. ### alexandre199 Thread Starter New Member

Jan 2, 2015
3
0
Ok..now i re-study the univeristy slides and these arguments.. and i try to do that with your method.. thank you.. i will write for other questions!

6. ### tshuck Well-Known Member

Oct 18, 2012
3,527
675
You may also want to look at this thread I made to explain Mealy FSMs. It specifically addresses input sequence recognition.

Note: output states are usually on the bottom in a state diagram (you have yours on the top in the one you posted).