PLC Programming

Controlling a Traffic Signal Unit...
The steps (from top to bottom) receive the names Switch1, Green2, Switch2, Green1, whereby Init of
course keeps its Name. "Switch" should include a yellow phase, at Green1 TRAFFICSIGNAL1 will be
green, at Green2 TRAFFICSIGNAL2 will be green. Finally change the return address of Init after
Switch1. If you have done everything right, then the diagram should look like in the following image:
Program SEQUENCE, First Expansion Level, Instruction Part
Now we have to finish the programming of the individual steps. If you doubleclick on the field of a
step, then you get a dialog for opening a new action. In our case we will use IL (Instruction List).
Actions and transition conditions
In the action of the step Init the variables are initialized, the STATUS of TRAFFICSIGNAL1 should be
1 (green). The state of TRAFFICSIGNAL2 should be 3 (red). The action Init then looks like in the
following image:
3-6 CoDeSys V2.3