Sequential Logic - An Overview Digital Electronics TM 1.3 Introduction to Digital Sequential Logic Post-Activity Discussion: An Overview Digital Electronics © 2014 Project Lead The Way, Inc. Project Lead The Way, Inc. Copyright 2009

Sequential Logic - An Overview Digital Electronics TM 1.3 Introduction to Digital This presentation will Introduce the basics of combinational and sequential logic. Present the logic symbol and function table for the “D” flip-flop. Review the design for a simple sequential logic circuit. Introductory Slide / Overview of Presentation Project Lead The Way, Inc. Copyright 2009

Combinational & Sequential Logic Sequential Logic - An Overview Digital Electronics TM 1.3 Introduction to Digital Combinational Logic Gates Inputs Outputs . Combinational Logic Sequential Logic Combinational Logic Gates . Inputs Outputs Memory Elements (Flip-Flops) Clock Combinational Logic has one or more inputs and one or more outputs. The outputs are a function of the present value of the inputs. Sequential logic can also have one or more inputs and one or more outputs. However, the outputs are a function of both the present value of the inputs and also the previous output values. Thus, sequential logic requires memory to store previous outputs values. Project Lead The Way, Inc. Copyright 2009

Sequential Logic - An Overview The “D” Flip-Flop Sequential Logic - An Overview Digital Electronics TM 1.3 Introduction to Digital Q Preset Data-In Clock Clear Inputs Outputs Preset Clear Clock Data-In 1  : Rising Edge of Clock The output will stay the same. X ILLEGAL CONDITION The basics of the D flip-flop. Project Lead The Way, Inc. Copyright 2009

Sequential Logic - An Overview Digital Electronics TM 1.3 Introduction to Digital The “D” flip-flop is just one of several types of flip-flops that can be used to implement sequential logic designs. This presentation will look at the Divide-by-Two circuit. This sample flip-flop application can be implemented with “D” flip-flops. Unit 3 of this course will spend a significant amount of time exploring other flip-flops and their applications. The purpose of this introduction is to provide a basis of understanding for the sequential logic subsection of the Board Game Counter design. A brief overview of sequential logic and why it is being introduced at this point. Project Lead The Way, Inc. Copyright 2009

Divide-by-Two Circuit: 1st Clock Sequential Logic - An Overview Digital Electronics TM 1.3 Introduction to Digital Preset = 1 Pulse-Out Pulse-In Logic ‘0’ Logic ‘1’ Clear = 1 Analysis of a Divide-by-Two circuit (1st Clock Pulse). Pulse-Out Pulse-In Preset = 1 Clear = 1 Project Lead The Way, Inc. Copyright 2009

Divide-by-Two Circuit: 2nd Clock Sequential Logic - An Overview Digital Electronics TM 1.3 Introduction to Digital Preset = 1 Pulse-Out Pulse-In Logic ‘0’ Logic ‘1’ Clear = 1 Analysis of a Divide-by-Two circuit (2nd Clock Pulse). Pulse-Out Pulse-In Preset = 1 Clear = 1 Project Lead The Way, Inc. Copyright 2009

Divide-by-Two Circuit: 3rd Clock Sequential Logic - An Overview Divide-by-Two Circuit: 3rd Clock Digital Electronics TM 1.3 Introduction to Digital Preset = 1 Pulse-Out Pulse-In Logic ‘0’ Logic ‘1’ Clear = 1 Analysis of a Divide-by-Two circuit (3rd Clock Pulse). Pulse-Out Pulse-In The 3rd pulse is a repeat of the 1st, the 4th will be a repeat of the 2nd, etc. Preset = 1 Clear = 1 Project Lead The Way, Inc. Copyright 2009

Divide-by-Two Circuit Period & Frequency - Overview Sequential Logic - An Overview Digital Electronics TM 1.3 Introduction to Digital The period of Pulse-Out is twice the period of Pulse-In. Since the period is twice, the frequency is divided in half. Thus, this is a Divide-by-Two circuit. Preset Pulse-In Clear Pulse-Out Complete waveform for the Divide-by-Two Circuit. Pulse-Out Pulse-In Preset Clear Project Lead The Way, Inc. Copyright 2009

Divide-by-Two Circuit Period & Frequency – The Numbers Sequential Logic - An Overview Digital Electronics TM 1.3 Introduction to Digital Pulse-Out Pulse-In T1 T2 Detailed view of the period & frequency of the input/output signals for the Divide-by-Two circuit. Pulse-Out Pulse-In Preset Clear Project Lead The Way, Inc. Copyright 2009

Divide-by-Two Circuit Preset & Clear Sequential Logic - An Overview Digital Electronics TM 1.3 Introduction to Digital Preset Pulse-In Clear Pulse-Out Detailed view of the CLEAR & PRESET inputs and their effect on the output waveform. Pulse-Out Pulse-In Preset & Clear are active low signals. Preset preset holds the output high Clear clear holds the output low Project Lead The Way, Inc. Copyright 2009

Sequential Logic Design Example Sequential Logic - An Overview Sequential Logic Design Example Digital Electronics TM 1.3 Introduction to Digital The following is a review of the design and operation of a sequential logic circuit using “D” flip-flops. This design is a simple two-bit binary counter that counts from zero (010=002) to three (310=112) and then repeats. Specifications for an simple sequential logic design. Project Lead The Way, Inc. Copyright 2009

Design Example: Circuit Design Sequential Logic - An Overview Digital Electronics TM 1.3 Introduction to Digital Zero-to-Three Counter circuit diagram or schematic. Note: This is the first time the students will have seen the CLOCK_VOLTAGE component. Be sure to explain what it is. Project Lead The Way, Inc. Copyright 2009

Design Example: Functional Test (1 of 3) Sequential Logic - An Overview Digital Electronics TM 1.3 Introduction to Digital THE FIRST FLIP-FLOP IS CLOCKED BY CLOCK-IN. Step-by-step analysis (functional test) of the Zero-to-Three Counter. B IS HALF THE FREQUENCY OF CLOCK-IN. A B Clock-In Project Lead The Way, Inc. Copyright 2009

Design Example: Functional Test (2 of 3) Sequential Logic - An Overview Digital Electronics TM 1.3 Introduction to Digital The second flip-flop is clocked by the of the first flip-flop. A is half the frequency of B. Note: A toggles on the falling edge of B, which is the rising edge of . Step-by-step analysis (functional test) of the Zero-to-Three Counter. A B Clock-In Project Lead The Way, Inc. Copyright 2009

Design Example: Functional Test (3 of 3) Sequential Logic - An Overview Digital Electronics TM 1.3 Introduction to Digital “0” “1” 1 “2” 1 “3” 1 “0” Step-by-step analysis (functional test) of the Zero-to-Three Counter. A B Clock-In Project Lead The Way, Inc. Copyright 2009

Design Example: IC Component View Sequential Logic - An Overview Digital Electronics TM 1.3 Introduction to Digital This slide shows how the gates are actually part of integrated circuits. This connection diagram was taken directly from a manufacturer datasheet for the flip-flop. In this case both flip-flops happen to be in the same IC package. 3 2 1 4 5 6 11 12 13 10 9 8 Project Lead The Way, Inc. Copyright 2009