RS Latch & Memory
An RS latch is the simplest redstone memory: a set input turns the output on, a reset input turns it off, and it holds that state on its own after the input is released.
What is an RS latch?
An RS latch (also called an SR latch) is a circuit that remembers. It has two inputs — Set and Reset — and one output. Pulse Set and the output turns on and stays on even after you release the button. Pulse Reset and the output turns off and stays off. The latch holds its last instruction, which is exactly what computer memory does at the smallest scale.
The classic build is the RS NOR latch: two NOR gates (a NOR is an OR followed by an inverter) cross-wired so each feeds back into the other.
How does the feedback hold the state?
The trick is the cross-connection. Each NOR gate's output loops back into the other gate's input. Once Set drives the output on, that output feeds back and keeps itself on — the loop sustains the state. Reset breaks the loop and lets it settle into the off state. Releasing both inputs leaves whatever was last latched untouched. (Driving Set and Reset at the same time is the one input you avoid — it's ambiguous.)
What is a T flip-flop?
A T (toggle) flip-flop takes the latch idea one step further: it has a single input, and every pulse flips the output to the opposite of what it was. Press once to turn on, press again to turn off — like a push-button light switch. This is how you make a lever-free toggle, driven by a button, a pressure plate, or any one-shot pulse.
Key facts
- Two inputs: Set (turn on, hold) and Reset (turn off, hold).
- Holds its last state with no power to the inputs — it remembers.
- Built from two cross-wired NOR gates (the RS NOR latch).
- Pulsing Set and Reset simultaneously is the one ambiguous input to avoid.
- A T flip-flop uses one input to toggle the output with each pulse — a push-button switch.
Bedrock note
Latches rely on torches and feedback, so the Bedrock strong-power rule applies: inputs must strongly power their target blocks to flip the torches. Bedrock's slightly different update timing can also matter for T flip-flops driven by very short pulses — if a toggle double-fires, stretch the input pulse with a repeater first. This simulator follows Bedrock rules.