“Difference Between Preset And Clear” is a very useful and basic concept in digital electronic circuit design. But most learners are not able to understand what is the exact meaning of Preset and Clear, How it is useful from a digital design perspective, and when “clear” and “preset” should be applyed.
| Preset | Clear |
|---|---|
| 1. It is a direct input or overriding input or asynchronous input. | 1. It is also a direct input or overriding input or asynchronous input. |
| 2. Preset or Set generally refers to forcing an output stage to logic 1. | 2. Clear or Reset generally refers to forcing an output stage to logic 0. |
| 3. It is an active low input. | 3. It is also an active low input. |
| 4. When Preset = 0 , it forces the output on the flip flop Qn=1 irrespective of the synchronous input value (S,R,J,K,D,T,CLK). Hence it sets the flip-flop. | 4. When Clear = 0 , it forces the output on the flip flop Qn=0 irrespective of the synchronous input value (S,R,J,K,D,T,CLK). Hence it resets the flip-flop. |
| 5. When Preset = 1 , it has no impact on the flip flop. Flip flop will perform its normal operations. | 5. When Clear = 1 , it has no impact on the flip flop. Flip flop will perform its normal operations. |
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