Introduction to Sequential Logic Design. Latches. Terminology. A bistable memory device is the generic term for the elements we are studying. Latches and flip-flops (FFs) are the basic building blocks of sequential circuits.
Introduction to Sequential Logic Design
S sets the Q output to 1, R resets the Q output to 0.
If both R, S are negated, the latch remains in the state that it was forced to (like a bistable element).
QN is normally the complement of Q (but sometimes NOT).
Metastability is possibleif S and R are negatedsimultaneously.
When C is asserted, Q follows the D input, the latch is “open” and the path (D-->Q) is “transparent”.
When C is negated, the latch “closes” and Q retains its last value.