DE Unit 8: Flip Flops & Counters

New tools for building asynchronous counters


Last semester we were briefly introduced to the idea of a “Flip Flop”.  Here, we will get into the details of the D-FlipFlop and the J/K-FlipFlop and see what can be done with them.  These tools help us store a single piece of information and use that to create more complex systems like counters.  As you learn about Flip Flops, you’ll go through three major steps:

  1. Learn how D-Flip Flops and J/K-Flip Flops work and how to wire them into circuits
  2. Learn how Flip Flops are applied in both shift registers and event detection
  3. Simulate Asynchronous Counters in Multisim

When you’re done, Flip Flops will be a new tool for you to use when developing

PART 1: Flip Flops

(20 pts)  About 3 days

This unit begins with an introduction to the use of Flip Flops.  We saw flip flops last semester in some of our circuits, but here we get to actually learn what they do and how to use them.  We’ll also see how flip flops can be used for event detection in circuits and then we’ll build examples in Multisim.

PART 2: Shift Registers

(30 pts)  About 3 days

Next we’ll investigate another application of flip flops: shift registers.  Shift registers will help us keep track of longer strings of bits and data, and will help us work our way into the more complex problem of building an asynchronous counter.

PART 3: Asynchronous Counters

(20 pts)  About 3 days

Here we’ll put together more complex asynchronous counters.  First we’ll build a modulus counter that will allow us to set the starting and ending value of the counter.  Then we’ll build in the functionality to be able to suspend the counter and the ability to reset the counter.

 Download the part 1 rubric

 Download the part 2 rubric

 Download the part 3 rubric

PART 1: Flip Flops

Learning about D and J/K Flip Flops

Flip Flop Pin Diagrams

 Flip Flop Assignment

The first thing we get to work on in this unit is our understanding of the Flip Flop.  Flip Flops are a tool that we can use in a digital circuit that helps us store single bits of information (individual 0’s/1’s) for use later on in the circuit.  Flip Flops come in two flavors: “D Flip Flops” and “J/K Flip Flops” that both can be used to hold bits of information.  We’ve seen them used in previous circuits that we built to make counters and random number generators.  Here we will investigate Flip Flops further and start to look at how they can be used in more complex circuit design.


 Take notes on the function of both D-Flip Flops and J/K-Flip Flops

 Take notes on applying Flip Flops in the creation of the Transparent D Latch

 Complete the Flip Flop Assignment

Flip Flops

Flip Flop Application: D-Latch

Flip Flop Explained

What’s Due In Flip Flops & Counters Part 1: Flip Flops

  • Notes: Flip Flops
  • Notes: Applications
  • Flip Flop Assignment
  • Benshoof’s Check-Off

Here’s what’s due in Part 1: Flip Flops

  1.  Take notes on the two kinds of Flip Flops and how they function
  2.  Take notes on some of the applications of Flip Flops
  3.  Complete the Flip Flop Assignment
  4.  Have Benshoof check-off your assignment

PART 2: Shift Registers

Flip Flop Applications

Asynchronous Counters


Flip Flops are relatively simple tools that can have very cool and complex applications.  Earlier you should have looked at event detection and how the Flip Flop can be used to trigger other actions in a circuit.  Here we get to look at how Flip Flops can be used as “shift registers”.  A shift register is a circuit that simply passes single bits of information ‘left’ or ‘right’ along the circuit.  Flip Flops are perfect for this.  In this part of the unit we’ll learn a bit about shift registers and see them in action as we build our first simple asynchronous counter.


 Take notes on the Asynchronous Counter and its function

 Complete the Shift Registers Assignment

 Complete the Simple Counter Assignment

What’s Due In Flip Flops & Counters 2: Shift Registers

  • Asynchronous Notes
  • Shift Register Assignment
  • Simple Counter Assignment
  • Benshoof’s Check-Off

Here’s what’s due in Part 1: Wiring

  1.  Notes on Asynchronous Counters
  2. Shift Registers Assignment
  3.  Asynchronous Counters Assignment
  4.  Have Benshoof check-off your careful drawing

PART 3: Asynchronous Counters

Build a variety of asynchronous counters

Asynchronous counters take advantage of the functionality of Flip Flops to keep track of values and help units ‘carry over’ as they add up.  We can even use the different components of a Flip Flop – like the reset and preset pins – to make our counters stop at maximum values, or reset their overall count.  Here in this part of the unit you’ll investigate different types of asynchronous counters as you build them and get them working in Multisim and with the PLD.


 Complete the Asynchronous Counter: Mod Counter Assignment

 Complete the Asynchronous Counter: Suspend/Reset Counter Assignment

 Complete the Asynchronous Counter: Now Serving Counter Assignment

What’s Due In Flip Flops & Counters Part 3: Asynchronous Counters

  • Mod Counter
  • Suspend/Reset Counter
  • Now Serving Counter
  • Benshoof’s Check-Off

Here’s what’s due in Part 3: Build It!

  1.  Complete the Mod Counter Assignment
  2.  Complete the Suspend/Reset Counter Assignment
  3.  Complete the Now Serving Counter Assignment
  4.  Have Benshoof check-off your finished, working Bug Bot

Double Check: Unit Expectations

Check what you need to have completed by the unit deadline

The purpose of this unit is to give you lots of exposure to the D- and J/K-Flip Flops.  You should be able to identify what the different pins in the flip flop do, and be able to identify situations where a flip flop can help make a circuit more effective.  You should have investigated different applications of flip flops as well such as event detection and shift registers.  A lot of the time was spent in this unit creating counter circuits as well and getting them working on PLDs.  All together, the expectation is that you understand the big ideas of how flip flop works and when they are useful tools.

Engineering Notebook:

 (Part 1) Notes on Flip Flops and how they work

 (Part 1) Notes on applications of Flip Flops

 (Part 2) Notes on Asynchronous Counters

Building & Making:

 (Part 1) The Flip Flop Assignment should have been completed

 (Part 2) The Shift Register Assignment should have been completed

 (Part 2) The Asynchronous Counter (Number 1) Assignment should have been completed

 (Part 3) The Mod Counter Assignment should be complete

 (Part 3) The Suspend/Reset Counter Assignment should be complete

 (Part 3) The Now Serving Counter Assignment should be complete

Benshoof Checkpoints

 (Part 1) Benshoof should have seen your working wiring before you moved on

 (Part 2) Benshoof should have seen your careful drawing before you moved on

 (Part 3) Benshoof should have seen your working Bug Bot