Digital One Shot

The following is another classic interview question.

This “one-shot” shall produce a single output pulse for any long pulse in the input. The length of the output pulse shall be one clock cycle. Assume that the input pulse is as you see in the following figure.

Figure 1: One Shot Timing Diagram

The answer is showed in Figure 2. It’s based on two flip-flops, which create a delay on the signal input. Then the result of the outputs (Q0, Q1) are logically AND, and output the result.

Figure 2: One Shot Schematics

Figure 3: One Shot Detailed Timing Diagram

This is a simplified design and thus has some problems (hint: asynchronous input). Please write us with your improvement ideas and we will update the entire solution with your inputs.

Home | Interview Quiz | Board Design | System Design | Lab Stuff | About