The third step to troubleshoot ladder logic diagrams is to simulate the diagram using a software tool or a test mode. You can use a software tool such as RSLogix, Ladder Logic Simulator, or PLC ...

WPLSoft is a fully-featured free PLC simulation software. You will find all the ladder logic functions here, such as bit logics (NO, NC, set coil, normal coil, reset coil), mathematical operators ...