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After watching the video explanation (https://www.youtube.com/watch?v=mXoQ4WAQ0qk) regarding PRESET and CLEAR . I have made following conclusions .

Considering Active Low / bubbled case as shown below image

enter image description here

  • Whenever CLEAR is 0 implies output Q is 0
  • Whenever PRESET is 0 implies output Q is 1

So Is it correct to conclude that

  • Whenver not(PRESET) is 1 implies output Q is 0
  • Whenever not(CLEAR) is 1 implies output Q is 1

[![enter image description here][3]][3]

Or in other words is it correct to conclude

  • PRESET is 0 implies output Q is 1 , not(PRESET) is not(0) i.e 1(WHENEVER ACTIVE LOW/BUBBLED)
  • not(PRESET) is 0 implies PRESET is not(0) i.e 1 , Q is 1 (WHENEVER ACTIVE HIGH/not BUBBLED)
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2 Answers 2

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PRESET and CLEAR work like this:

If PRESET is LOW and CLEAR is HIGH, Q is HIGH regardless of what happens on J,K, and CLK.

IF PRESET is HIGH and CLEAR is LOW, Q is LOW regardless of what happens on J,K, and CLK.

IF PRESET is LOW and CLEAR is LOW, Q is undefined. (The two inputs are fighting each other.)

IF PRESET is HIGH and CLEAR is HIGH, the rules concerning the J,K and CLK inputs for a JK flip-flop apply.

In other words, if neither PRESET nor CLEAR is asserted, the flip-flop operates normally, However, asserting either will override the state of the flip-flop. And if both are asserted, the result is unknown.

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Set will set the Q output HIGH

Reset will reset the Q output LOW

Set, Reset means that it is activated by a HIGH (normally input is pulled LOW)

Not Set, Not Reset means that it is activated by a LOW (normally input is pulled HIGH)

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