Sequential (21) level trigger

https://wodewangzhishime.blogspot.com/2022/10/httpswodewangzhishime.html

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Ref: https://kamchihau.blogspot.com/2023/02/blog-post.html

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Me: This article mention "level" triggering . https://wodewangzhishime.blogspot.com/2023/02/if-ipaddress133133-nathon-road.html .

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Serial input = edge trigger. . Left or right shift.

Parallel input = level trigger. . No left or right shift. . The output is ouput to the output line.