Summary of How does an SR flip flop actually work? How did they come up with this?

Main Ideas and Concepts

• Introduction to SR flip-flops

  The video discusses the SR flip-flop, a fundamental sequential circuit in digital electronics that stores one bit of information. The speaker emphasizes the confusion often surrounding the concept and functionality of flip-flops.

• Building the Circuit from Scratch

  The speaker, a professor from the University of Cambridge, proposes to reinvent the SR flip-flop to better understand its operation. The goal is to create a circuit using basic logic gates (AND, OR, NOT) that can store a bit of data.

• Initial Attempts and Challenges

  The speaker explores various configurations using AND and OR gates, noting that while some setups can store bits, they lack the ability to set specific values (0 or 1) easily. The need for control inputs to set or reset the stored value is highlighted.

• Combining Circuits

  The solution involves combining the two configurations (one using an OR gate and the other using an AND gate) into a single loop. This combined circuit allows for writing either a 0 or a 1 into the memory.

• Final Configuration and Explanation

  The final design consists of two NAND gates, which can be configured to function as an SR flip-flop. The speaker explains how the inputs are set to be active low, meaning they perform their functions when set to 0.

• Comparison to Traditional Textbook Diagrams

  The speaker critiques traditional textbooks for presenting flip-flops in a way that can be confusing, advocating for a more intuitive understanding. A transformation of the circuit is shown to illustrate how the NAND gate configuration relates to the more complex traditional representations.

• Encouragement for Viewer Engagement

  The speaker encourages viewers to engage with the content, ask questions, and share their understanding in the comments.

Methodology / Instructions

1. Start with basic logic gates (AND, OR, NOT).
2. Create a circuit that can loop back its output to remember a bit.
3. Use an OR gate with one input set to 0 to allow the current value to circulate.
4. Introduce an AND gate in a similar fashion, with one input set to 1.
5. Combine both gates in a loop to allow writing of both 0 and 1 values.
6. Define control inputs for setting (1) and resetting (0) the stored value.
7. Transform the circuit into a NAND gate configuration for a more efficient design.
8. Ensure that control inputs are active low for consistent operation.

Speakers / Sources Featured

• Professor from the University of Cambridge: The main speaker and educator in the video, providing insights into the workings of digital electronics and flip-flops.

Notable Quotes

— 06:54 — « In my opinion digital electronic textbooks would be much clearer if they started with this or something like this as the first example of a sequential circuit. »

— 07:08 — « Here at least we understand perfectly what's happening and we have a pretty clear idea about the purpose and function of every part that we put in. »

— 11:40 — « It's not difficult, it's satisfactory when you figure it out. »

Category

Educational

Video