DE: 1.2 Circuit Design

DE: 1.2.4 Introduction to Sequential Logic Design: Counters

Multiple Choice

Sequential logic is _______?

• where the output is a function of only the present input.

• a fundamental building block of digital electronics.

• difficult to predict the output.

Multiple Choice

How many probes would I need to represent a 2-Bit counter?

• 2

• 6

• 1

• 4

What is a D flip flop?

• one of many different types of flip-flops that can to build a sequential logic circuit.

• ​simplistic design

​Examples

​Vending Machines

Security Alarms

Thermostats

Electronic Games

Anything requiring memory

​Oscilloscope

• ​Be sure to set the oscilloscope’s time-base to 20 ms/div and the vertical bases of the four channels to 10 volts/div.

• Also, adjust the Y position of the three channels such that the three signals are all clearly visible.

Frequency and period are inversely related. The frequency gets cut in half each time a flip-flop is added to the design.​

Write in your engineering notebook.​

Multiple Choice

This dependency is aided with a clock signal to _______ and ______ to retain previous outputs.

• open gate and light switch

• toggle and define

• flip and flop

• control sequencing and memory

Multiple Choice

The output values of sequential logic depend ______________.

• when the switch is on.

• The output values depend not only on the current input values, but also on previous output values.

• on the amount of inputs.

• the value of the resistor.

Multiple Choice

How many probes would I need to represent a 4-Bit counter?

• 2

• 6

• 1

• 4

Open Ended

If you added a fifth bit, what would you guess is the highest number

you could count to? (engineering notebook)

Multiple Choice

Counters are one of the most common applications of flip-flops. Now create a simple binary counter using two D flip-flops. 

• Dual D Flip-Flop 

• J/K Flip-Flop

Multiple Choice

The circuit that you will build is a two-bit binary counter. It will count from zero to three. What are these number values in binary?

• Zero is represented as 00 and two represented as 02 and three is represented as 11.

• Zero is represented as 00 and two represented as 01 and three is represented as 11.

• Zero is represented as 00 and two represented as 01 and three is represented as 101.

​In this activity, you use a D flip Flop specifically because of its simplicity.

​With such a fast clock speed (1kHz), it is very difficult to see the binary count. Change the clock frequency to something that allows you to see the four probes transition more slowly in the simulation.

Open Ended

Exit Ticket: The 2-Bit and 4-Bit counters you explored in this activity are referred to as “divide-by-two” counters. Explain the relationship between each consecutive flip-flop and the order in which they are laid out in the design from right to left that creates a binary count. (engineering notebook)

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