As the DCI Systems have progressed through introduction and various stages of enhancement, four controller products have been offered.
The DCU-1000 controller (DCI-4000 series) was the first DCI System controller introduced in 1979. It consisted of a CPU subsystem with up to 2 linked I/O subsystems. The I/O was non-redundant and the controller redundancy was one to one. The controller software was a modular function block style engine called Controlware.
In 1985, the PCU-2000 controller (DCI-5000 Series) was introduced with an updated microprocessor, greater memory capacity, and support for redundant Ethernet communications.
DCI System Six, introduced in 1992, included a new rack mountable controller called the DCU3200, which provided a simplified redundancy scheme and front access I/O boards. The DCU3200 supported redundant Ethernet communications and improved on its predecessors controller language with the more powerful Controlware II.
As part of a common architecture, the Harmony DCU took the place of its predecessor with added support for new I/O boards and ABB's flagship I/O, S800 and S900 I/O, through Profibus DP communications.