A Latch to Start and Stop the Light Do you remember the SR…
““A Latch to Start and Stop the Light Do you remember the SR latch from “Saving One Bit at a Time” on page 240? The start/stop circuit for this game is a similar SR latch but built with two NAND gates. (The SR latch in Chapter 11 used NOR gates.) The SR latch is a circuit that can remember a single bit. Its output is either 0 or 1, and it keeps that number until it gets set or reset with a new input. You can create a circuit that tells the latch what to output with two buttons: one for setting the output to 1 and one for setting the output to 0. Using NAND gates instead of NOR gates means the buttons must make the inputs low to output a 1. In this circuit, it doesn’t matter whether you click the buttons quickly or slowly. The 1-button always sets the output to 1, and the 0-button always sets the output to 0. That’s perfect for the reaction game! Connecting the output to the start/stop pin, or pin 13, on the decade counter gives you a button for starting and stopping the LEDs.””
About This Quote
This interpretation was drafted with AI assistance. It is one reading of the quote, not the author's own explanation.
An SR latch built with NAND gates stores a single bit, toggled by two buttons, enabling start/stop control for a reaction game.
In simple terms: A NAND‑gate latch remembers a bit and can be set or reset with buttons.
Key Takeaway
Use the latch to toggle game LEDs.
Themes
digital logic
state memory
control systems
Mood
technical
practical
Type
explanatory
instructional
When to use this quote
- electronics hobby
- Arduino projects
- reaction game design
Key Concepts
SR latch
NAND gates
binary storage
Questions to Reflect On
- How can you extend this to more states?
- What are the timing constraints?
A Different Perspective
Only works for binary on; not suitable for multi‑state control.