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Lessons · Industrial control · one-shots

True for exactly one scan

Rising edge: input true now AND a memory of last scan false. Falling edge: the reverse. Write the memory after.

Hone is a place to practise programming. This is one of its lessons, written out in full and free to read without an account.

What it is for

Counting parts, starting a cycle once per press, toggling.

How to think about it

What was the input last scan? Pulse = [In] [/Was]. Then, below, Was = [In]. The order makes Was one scan behind.

Worked example

[Btn] [/BtnWas] (Press)
True only on the scan Btn first goes true.
[Btn] (BtnWas)
Memory, written after it was read.

Your turn

Falling edge.

[Btn] [BtnWas] (Release)
[Btn] (BtnWas)

The trap

Writing the memory rung ABOVE the pulse rung. Then they are equal every scan and the pulse never fires.

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