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One shot is interesting and invaluable programming tool. At first sight, difficult to figure out why we have such an instruction. Once we understand what this command does and how to use them, but will have to clarify.

One-shot is used to make something happen just 1 WCD. (You name it, scan, right?) Most manufacturers have one-shots that address the transition and another type that corresponds to the transition path. Some names for instructions Difu / difd (modulate up / down), spot / sotd (a production of up / down), OSR (one-shot rising) and others. Everyone, however, ends with the same result regardless of the name.

One-shot instructions
Above is the symbol for Difu (one-shot) instructions. Difd looks the same, but within the symbol says, “difd. Some producers in the form of the box, but regardless of the symbol, all functions in the same way. For manufacturers, the distinction no instructions are, you get the same effect by NC (normally closed) instructions from him instead of NO (normally open) inquiry. (ie inverted logic Difu instructions)

Let us set the application to see how it actually works in the education ladder. This instruction is typically used some of the advanced instruction, we have a number of things that happen only once. However, because we are so much further, let the flip / flop circuit. Simply put, flip / flop around slightly changed each time the action occurs. Here we use a single button switch. For the first time the operator pushes it out we want to run. It will remain “inclined” the next time the operator presses a button. If it does, the output.

Here is a ladder diagram, which does exactly this:

Now seems a mistake! Actually this is not that we are a step by step.

Place 1 to NO (normally open) input 0000 which is 1000 Difu is true.
Crossing 2 - NO it is true, 1000, No. 1001 remains false, it remains true, NC 1001, NC 1000 proves to be false. As we correctly (NO 1000 & 1001) of 1001 is true.
Place 3 to 1001 is true, so right turns OUT 500.
Next Scan

Place 1 - NO 0000 remains true. Difu 1000 is false. This is because the doctrine applies only to a test Difu. (ie the edge of the logic, then the sport)
Crossing 2 - No 1000, is false, NO 1001 remains true, 1001 is incorrect, NC 1000 turns right. Because we are still the right way, (NO 1001 & NC 1000) of 1001 remains true.
Place 3 to 1001 is true, therefore OUT 500 remains true.
After 100 shots, NE from 0000 (is false). The logic remains the same status as the “next scan” described above. (Difu response remains the same logic to the sports 2 and 3)

0000 NE 101, the scan again. (is true)

Place 1 to NO (normally open) input 0000 which is 1000 Difu is true.
Crossing 2 - NO it is true, 1000, No. 1001 remains true, 1001 is false, NC 1000 is also false. Because we no longer the correct path, OUT 1001 is false.
Place 3 - NE in 1001 OUT 500 is false is false.

Running program 1 instruction at a time and any programs easy to follow. In fact, larger program that bouncing around can be difficult to control, but pencil drawing from the registers, if it helps!

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