DE Unit 7
Flip-Flops Introduction

Last semester we looked at the complexities of digital logic, and how the careful use of mathematics can make a variety of cool circuits possible.  Throughout last semester we used AOI, NAND, and NOR gate logic to build circuits that turned a variety of inputs (usually switches) into a variety of outputs (usually lights).

Here in this semester, we will continue with these ideas but limitour breadboarding to the use of those handy-dandy PLDs.  As we build more complex circuits in this next unit, we’ll look at some digital devices (IC chips) called Flip-Flops and how they can be used to make circuits that do neat new things.  For example, the use of Flip-Flops can help us make circuits that wait for events to happen before an output gets triggered. In other ways, we’ll be able to make circuits that can count for us in binary.  As we look at these new ideas we’ll cover the following topics:

  • What D-FlipFlops and a J/K-FlipFlops are and how they work
  • How Flip-Flops can be used to make Event Detectors
  • How Flip-Flops can be used to make Shift Registers
  • How Flip-Flops can be used to make Asynchronous Counters 

As we jump into this unit, it’ll be essential to take some detailed and careful notes.  In each of these sections we’ll be learning about new IC chips that take some serious effort to understand.  Taking detailed notes will be essential!

Part 1: Flip-Flops

Flip Flop Reference

 Download the Part 1 Rubric Only

 Flip Flop Assignment

 Event Detection Assignment

The first part of this unit is all about a device called a “Flip-Flop”.  In a way, the Flip-Flop is a chip that acts as a tiny memory unit that can keep track of (or ‘remember’) a single bit of information:  just one “1” or “0” at a time. This simple component might seem trivial, but it makes some really cool things possible. By being able to remember a single piece of information, your circuit will be able to remember it’s prior state. As an example, this will be essential when we try to keep track of previous values in a counter.


 Watch the videos on the Flip Flops and how they work.  As you watch them, take a full page of notes on how they work and what the different pins do.

 Add to your notes (so you have at least two full pages) by reviewing the pin diagram for the flip flops and adding what new information those pictures provide to your engineering notebook.

 Complete the Flip Flop Assignment

 Complete the Event Detection Assignment

 Have Mr. Benshoof confirm your working Multisim circuits for both assignments

Flip Flops

Flip Flops Explained!

Flip Flop Application: D Latch

Part 2: Shift Registers

Shift Register Logic

The second part of our unit looks at another cool application of flip-flops: Shift Registers.  In short, a “Shift Register” is a series of flip-flops that store a series of single bits in a row, moving (shifting) their values along that row.  This lets us keep track of larger, more complex things than single-bit values. WIth a single bit (a single 0 or 1), the largest value we can keep track of is 1.  By stringing together multiple bits in a shift-register, we can keep track of larger numbers like 4, 8,16, or 32.

In this part of the unit, you’ll build a simple shift register circuit.  After that, we’ll continue to develop those ideas as we build our first (of 4) Asynchronous Counter.


 Take a full page of notes on Shift Register from the videos below

 Complete the Shift Registers Assignment

 Take a full page of notes on the Asynchronous Counters presentation

 Complete the Asynchronous Counters (#1) Assignment

 Have Mr. Benshoof confirm your working shift register & counter



Shift Registers

Shift Registers (2)

Asynchronous Counter

Asynchronous Counter with MSI

Part 3: Asynchronous Counters

Event Detection With Flip Flops

The final part of this unit looks at other applications of flip flops for event detection and for other kinds of asynchronous counters.  We’ve seen the basic function of both D- and J/K-Flip Flops and how their inputs determine their outputs – now it’s time to put them to work as we build three different (and increasingly complex) asynchronous counters.


 Watch the Event Detection with Flip Flops presentation and think through those ideas.  Add to your notes on flip flops with any new concepts you come across.

 Complete the Asynchronous MOD Counter (#2) activity

 Complete the Asynchronous SUSPEND/RESET (#3) activity

 Complete the Now Serving Counter (#4) activity

 Have Mr. Benshoof confirm your three working asynchronous counters

DE Unit 7 Map
Looking for something?  Here you'll find a library of links to all the documents, images, and videos needed here in DE Unit 7.