An SR latch can be implemented using NAND logic gates by performing the following steps:
- 1. Connect two NAND gates in a cross-coupled arrangement, with the output of each gate connected to the input of the other gate.
- 2. Connect SR inputs to the two NAND gates, where S is connected to one NAND gate's input and R is connected to the other NAND gate's input.
- 3. Connect the output of the NAND gate with S input to the input of the NAND gate with R input.
- 4. Connect the output of the NAND gate with R input to the input of the NAND gate with S input.
The resulting circuit will be an SR latch made up of NAND gates, and the output states will be as follows:
- When S=0 and R=0, the output of each NAND gate will be 1, and the latch will retain its previous state.
- When S=1 and R=0, the output of the first NAND gate will be 0, which will drive the second NAND gate's input to 1, setting the latch in the "set" state.
- When S=0 and R=1, the output of the second NAND gate will be 0, which will drive the first NAND gate's input to 1, resetting the latch to the "reset" state.
- When S=1 and R=1, both NAND gates' outputs will be 0, which will create an unstable condition where the output state is uncertain, and should be avoided.
The implemented SR latch using NAND gates can be used in memory circuits, in control circuits, and in other digital systems that require a stable memory element that can store the last input.