sequential (20) toggle

 https://kamchihau.blogspot.com/2023/02/sequential-7.html

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Ref: https://wodewangzhishime.blogspot.com/2023/02/httpswodewangzhishime.html

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There're 5 conditions on which left or right shift doesn't work.

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1) The latch is being preset and clear.

2) The latch is feedbacking.

3) The latch is being level-trigger.

4) The flip flops is at the stage of toggling.

5) The commutator is idle (no up , no down)

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John: We mention condition_4. . .If you input 1-1 to J-K, Q and -Q toggle.

Me: In this case, no left shift, no right shift.