VHDL fundamentals — primitive JK flip-flop interface In synthesizable VHDL describing a primitive JK flip-flop, how many primary inputs does the device have (considering J, K, and clock as the essential inputs; ignore optional asynchronous set/clear)?

Introduction / Context:
Hardware description languages such as VHDL capture the behavior of fundamental storage elements. A JK flip-flop is a classic device with two data-type inputs (J and K) and a clock input that governs when the stored state may change. Clarifying the count of the essential inputs avoids confusion when writing entity/architecture declarations and testbenches.

Given Data / Assumptions:

• We focus on the basic, clocked JK flip-flop behavior.
• Asynchronous preset/clear lines, if present, are not counted for this question.
• We consider the inputs required to define the synchronous operation.

Concept / Approach:
At minimum, a JK flip-flop needs the J input, the K input, and the clock that determines the exact instant of sampling. Additional lines (like asynchronous set or clear) modify state outside the clocked path but are not part of the primitive synchronous interface under discussion here.

Step-by-Step Solution:

Verification / Alternative check:
Examine a typical VHDL entity for a synchronous JK FF: entity ports usually include J, K, and CLK as required; PRE/CLR lines are optional extras.

Why Other Options Are Wrong:

• 2: omits the clock, which is mandatory for a flip-flop.
• 4 or 5: would imply inclusion of extra asynchronous controls that the prompt asked us to ignore.

Common Pitfalls:
Confusing a JK latch (level-sensitive enable) with a clocked flip-flop; the clock is essential in the flip-flop case.

Final Answer:
3