Latch

A latch is a basic storage element. It’s one type of storage element in digital circuits.

Latches are level sensitive, meaning that they operate:

when a Control Signal is at either logic level 0 or 1
NOT at logic transitions from 0→1 or 1→0
On the other hand, Flip-Flop are edge-triggered

They are:

useful for Asynchronous Sequential Circuits
helps to understand the behavior of flip-flops (another type of storage element which is useful for clocked sequential circuits).

Active High vs. Active Low

Types of Latches

SR Latches

2 Inputs:

R - Reset
S - Set (sets Q to either 1 or 0), i.e.

If S = 1, Q = 1
If S = 0, Q = 0

There are several limitations with the SR Latch. Because we can set this at anytime, we can possibly accidentally reset stuff. Case #1: S = 1, R= 0 Case #2: S = 0, R = 1 Case #3: S =1 , R= 1 does not work

Afterwards, you go to S=0, R=0, to make sure that the memory is stored.

NAND SR-Latch We can also use NAND instead of NOR. A NAND implementation works similar to the NOR implementation, but the input values are reversed for each of the different cases. content…