One push button connected to input E0.0 should activate output A3.7; a second push button connected to input E0.1 should deactivate it.

The exercise is exactly the same as the previous one but on this occasion the solution uses set and reset coils.

If we run the program, we can see that pressing the two buttons at the same time sets the output to zero. Effectively, in both languages, when both test conditions are valid at the same time, the operand A3.7 is activated first, in path 1 or with the first two statements, and then deactivated, in path 2 or with the third and fourth statement. But remember that A3.7 does not really represent the physical output of the PLC, only that corresponding to the bit in the interior of the memory of the process image. This memory bit is effectively moved to 1 and then to 0 but it is only once the program used has been fully loaded that the assigned value is transferred to the physical channel of the corresponding output which is maintained constant at the low value when both inputs are closed.
This means that by writing the program in this way we have given the reset action (deactivation) priority over the set action (activation). If we want to achieve the opposite effect, we simply invert the position of the first two paths (rungs) of the ladder diagram or interchange the first and second groups of statements in the AWL program.

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