Question

A basic S-R flip-flop can be constructed by cross-coupling of which basic logic gates?

• A. AND or OR gates
• B. XOR or XNOR gates
• C. NOR or NAND gates
• D. AND or NOR gates

Hint:

SR Latch Construction. Built using two cross-coupled NOR gates or two cross-coupled NAND gates.

Answer 1

The Correct Option is C

The fundamental building block for sequential logic circuits like flip-flops is the latch
A basic Set-Reset (S-R) latch, the simplest form of flip-flop (though often asynchronous), is created by cross-coupling two basic logic gates with feedback
This bistable circuit can be constructed using either: - Two cross-coupled NOR gates
- Two cross-coupled NAND gates (this implementation typically has active-low inputs \(\overline{S}\) and \(\overline{R}\))
Using AND or OR gates in a simple cross-coupled manner does not create the required bistable latching behavior
XOR/XNOR gates are used in more complex flip-flops or logic functions