how to realize the following logic function

[Guohua Jing]

I want to realize the following logic function

a line keeps for logic 'true' for some time, then
changes to logic 'false' for some time, then iteration
again and again.

GH

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[Gorka Larrea]

You can try using a shift register into the loop, place a wait into it, and use logical NOT in the shift register. The line will change from true to false in every iteration, timed by the wait function.
Hope this helps