Patent ID: 6199129
Filing Date: 2001-03-06
Classification: G06F

Abstract:
A bus segment for connecting an assembly of a programmable logic controller to a bus, comprising:a first supply line;a second supply line;a signal line; anda plug-in location for inserting the assembly, the plug-in location including a first supply contact, a second supply contact, a signal contact and at least one test contact, the at least one test contact connected to the first supply line via a pull-up resistor and being connectable to the second supply line via the assembly, the first supply line being connected to the first supply contact of the plug-in location via a first spur line, the second supply line being connected to the second supply contact of the plug-in location via a second spur line, and the signal line being connected to the signal contact via a third spur line, the first spur line including a variable resistor; andan evaluation circuit connected to the plug-in location, the first supply line, the second supply line and the first supply contact of the plug-in location, the evaluation circuit evaluating a potential at the at least one test contact and controlling the variable resistor to have a high resistance if the potential at the at least one test contact approximately corresponds to a potential of the first supply line, the evaluation circuit further controlling the variable resistor to have a low resistance only when the potential at the test contact approximately corresponds to the potential of the second supply line and a potential of a supply contact of a bus connection in an uninterrupted manner during a predetermined waiting time, the evaluation circuit further controlling the variable resistor to have the high resistance, if, after a predetermined stabilization time, the potential of the first supply contact of the plug-in location is outside a predetermined value range.