Bus segment or bus interface for connection of a subassembly of a programmable controller to a bus

摘要

In order, in the case of a programmable logic controller having a modular structure, to be able to insert and withdraw assemblies even in the course of operation, without disturbing the data traffic taking place via the bus of the programmable logic controller, provision is made for arranging an evaluation circuit in a bus segment or a bus access circuit. The evaluation circuit establishes whether an assembly is connected to the bus and accordingly controls a variable resistor, which is arranged in one of the supply lines for the assembly, to have a high resistance or a low resistance.