CODAC STANDARDISATION OF PLC COMMUNICATION

As defined by the CODAC (COntrol, Data Access and Communication) Architecture of ITER, a Plant System Host (PSH) and one or more Slow Controllers are connected over Switched Ethernet network. Siemens PLCs (Programmable Logic Controller) are standardized by CODAC as the Slow Controllers. An important part of Software Engineering for Slow Controllers is the standardization of communication between PSH and PLCs. Siemens PLCs offer various communication services such as OpenIE, Send/Receive and S7 Communication which are supported over transports such as TCP, ISO-On-TCP (RFC1006). Based on prototyping and performance evaluation, OpenIE communication over TCP was selected as it offers best performance and is also easy to use and configure. OpenIE Communication is used to implement the communication on PLCs to support the CODAC data model. The implementation is packaged with the Standard PLC Software Structure (SPSS) which is a part of official CODAC Core System release. SPSS can be easily configured by the SDD (Self-Description Data) Tools supporting PLC integration with EPICS IOCs. However, OpenIE is restricted to the PROFINET interface of PLC-CPUs and is not available on PLC-CPs (Communication Processor). Thus OpenIE can’t be used for redundant PLCs and when the PROFINET connection is needed for remote IOs. So another version of SPSS developed with Send/Receive communication is used to support communication over CPs. The S7plc EPICS driver is extended to support CODAC requirements and to support redundant PLCs. This paper describes PLC communication standardization in the context of CODAC environment. Future developments of EPICS driver to support the ISO-On-TCP and S7 communication are presented briefly.