The integration of two control systems

During the past year the Continuous Electron Beam Accelerator Facility (CEBAF) has installed a new machine control system, based on the Experimental Physics and Industrial Control System (EPICS). The migration from CEBAF´s old control system, Thaumaturgic Automated Control Logic (TACL), had to be done concurrently with commissioning of the CEBAF accelerator. The smooth transition to EPICS was made possible by the similarity of the control systems´ topological design and network communication protocol. Both systems have operator display computer nodes which are decoupled from the data acquisition and control nodes. The communication between display and control nodes of both control systems is based on making named requests for data, with data being passed on change of value. Due to TACL´s use of a central communications process, it was possible to integrate both control systems´ network communications in that process. This in turn meant that CEBAF did not require changes to any other software in order to support network communication between TACL and EPICS. CEBAF implemented the machine´s control under EPICS in an evolutionary, controlled manner