# Sequential Logic & JK Flip Flops

• rofln
In summary, the conversation is about completing a truth table for a logic circuit and understanding the characteristic tables for JK and D flip flops. The issue is with an AND gate involving variables A and X, which always results in a zero except for two specific entries. The person is seeking help and clarification before their final exam.
rofln

## Homework Statement

Complete the truth table for the following

## Homework Equations

JK Flip Flop Characteristic Table
D Flip Flop Characteristic Table

## The Attempt at a Solution

I understand how to make truth tables for logic circuits and I know the characteristic tables. But what is really stumping me is the AND gate that go to the JK Flip flop. It seems to me that whenever x and A are put together in the AND gate, it will always be zero except for the two entries where A and X are equal to one. I have the solutions manual and my answer is incorrect. It has 1's in row 2 and 4 but I have absolutely no idea how.
Here is what I have down just for the A column.
A B X A(t+1) B(t+1)
0 0 0 0
0 0 1 0
0 1 0 0
0 1 1 0
1 0 0 0
1 0 1 1
1 1 0 0
1 1 1 1

Any help and/or explanation would be very much appreciated, my final is on Wednesday and I want to get this topic rock solid in my head.

Last edited by a moderator:
If the circuit powers up with A=0, B=0 as far as I can see it's game over and nothing ever changes no matter what you do to X. JK is allways 00 = "no change" so A(t+1) = 0. D is allways 0 so B(t+1)=0.

So I can't see how they get a different answer to you for row two.

I make A(t+1) and B(t+1) both = 0 for rows 2 and 4.

## 1. What is sequential logic?

Sequential logic is a type of digital logic that uses a clock signal to store and process data in a sequential manner. It involves the use of flip flops, which are basic building blocks of sequential circuits.

## 2. How does a JK flip flop work?

A JK flip flop is a type of sequential logic circuit that has two inputs (J and K) and two outputs (Q and Q'). It works by storing a single bit of data and changing its output based on the inputs and the clock signal. The inputs control when the output changes, and the clock signal controls when the inputs are read.

## 3. What is the difference between a JK flip flop and other types of flip flops?

The main difference between a JK flip flop and other types of flip flops (such as D, T, and SR flip flops) is that it has the ability to toggle its output when both J and K inputs are high. This makes it more versatile and useful in certain applications.

## 4. What are the applications of JK flip flops?

JK flip flops are commonly used in digital circuits for applications such as frequency division, shift registers, and counters. They can also be used for storing data in memory and controlling the sequencing of operations in a system.

## 5. What are the advantages of using sequential logic and JK flip flops?

Sequential logic and JK flip flops offer several advantages over combinational logic. They allow for the storage of data, which is necessary for sequential operations, and can be used to create more complex circuits. They also have the ability to synchronize operations with a clock signal, making them more reliable and predictable.

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