When a PT instruction bit variable turns ON, only the first scan turns ON. Subsequent scans are OFF even though the bit variable may be in the ON state. You can use the PT instruction for counting the number of ON states.
You cannot use a NO instruction without including another instruction just to the left of the right power bar. The other instruction can be an output instruction or any instruction other than an input.
Program Example
Point A
The variable (Start) turns ON, and then the variable motor turns ON.
Point B
After a scan is executed once, the variable motor will be turned OFF.
Point C
The variable (Motor) remains OFF because the upward transition of the variable (Start) is not detected.