Description (from Recipaedia)
Logic SR latch. Can be used as a memory element holding a single bit. Has three inputs (S, R, and clock), and one output. A signal on S input sets the state to 1. A signal on R input resets the state to 0. Output always indicates the current state of the latch. Can work in synchronous or asynchronous mode, depending on whether clock input is connected. In synchronous mode the states of S and R inputs are read only during a rising esge on the clock input. Can be placed on any surface and rotated to desired orientation.
Crafting
Crafting requires 5 Germanium Crystals and 2 Copper Ingots. You get 4 latches.
Hooking It Up
Modes
SR Latch has two modes, asynchronous (clock is not connected) and synchronous (clock is connected).
- Asynchronous mode
- The Latch outputs a 1 when the SET input changes to 1. It will stay at 1 even when the S input returns to 0. The output will only return to 0 when Reset changes to 1 AND the Set is at 0.
- Synchronous mode
- This latch is considered dominant Set. That means that if both S and R inputs are active, the Set will override the Reset and the latch will NOT reset until the Set returns to 0.
- The Latch will only change its output when the clock input changes to 1. Then the output will be 1 if Set is 1. It will only be 0 if Reset is 1 AND Set is 0.
Connections
The output is at the 'top' - the single dot without a letter by it. The S and R inputs are where the letters are. The clock input is where the arrow or dart is (the 'bottom'). All signals are digital.
Truth Table
Truth table shows all input combinations and the output signal for each combination.
| Input | Output | |
|---|---|---|
| S | R | |
| 0 | 0 | 0 |
| 1 | 0 | 1 |
| 1 | 1 | 1 |
| 0 | 1 | 0 |
See modes above, for the difference between sync and async modes. The table is no different for either mode.
Uses
- It is used where you want to turn something on at one place but turn it off from another place.
- The latch can be used to simulate a lever switch when only a button can be used. It needs a little extra circuitry (to make it a T latch).
- It will remember if you turned something on.
- It is mostly used in bigger circuits and is very flexible and useful device.
- It can be used to extend the range of an electric signal, beyond the view distance limit.