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OPC - Device Support

OPC - Device Support. Bernhard Kuner, Carsten Winkler BESSY, Berlin, Germany. Introduction to OPC. OPC: OLE (COM) for process control DCOM: Distributed Component Object Model Client/Server scalable and distributed over network “Data Access” specification read/write, time stamps, quality

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OPC - Device Support

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  1. OPC - Device Support Bernhard Kuner, Carsten Winkler BESSY, Berlin, Germany

  2. Introduction to OPC • OPC: OLE (COM) for process control DCOM: Distributed Component Object Model • Client/Server scalable and distributed over network • “Data Access” specification read/write, time stamps, quality polled or callback • “Alarm and Event” specification Existing OPC servers support only a subset of the defined OPC features

  3. Data Flow • Device - OPC server communication: proprietary, vendor dependant • OPC client - OPC server communication: via DCOM (Microsoft) • OPC libraries available for: all Windows, Unix, not vxWorks

  4. Client Data Access • Connect to server Client will start/stop the server • Add group Client defines groups with common parameters for all items within the group • Add items Client subscribes for several data objects

  5. Bessy Installation • Connect PLC controlled beamlines to EPICS - 30 PLCs: c. 6,000 PVs - 4 OPC servers • Currently 600 PVs with the new iocShell • In the future: 30,000 PVs • Data volume One PLC: 6 kB/s, polled with 50 ms - > 2 GB/d raw data over the network - > 200 kB Channel Access data

  6. Former Approaches • OPC_CAS • Doesn’t work reliably • Several crashes a day • VisualBasic program with Kepware OPC client and ActiveX_CAS • Proper handling of values, alarms and graphic limits • Crashes ALH and other clients • No access security • OPC can’t set STAT and SEVR • XCas • Another CAS based solution

  7. Device Support for EPICS 3.14 • For these record types: - ai, ao - bi, bo - mbbi, mbbo - mbbiDirect, mbboDirect - longin, longout - stringin, stringout - (waveform) • OPC client with - Softing OPC Toolbox 3.01 - Other client libraries possible

  8. opcDevSup Features • Data conversion for all integer and float data types • Timestamp generated by OPC server or EPICS determined by the record‘s TSE field • Map OPC quality to records STAT/SEVR fields • Out records may be written by the PLC and by EPICS in - records: read only records out - records: read/write records • Record processing: SCAN field: „I/O Intr“ or „.1 second“ to „10 second“ OUT records are not „Passive“, but „I/O Intr“

  9. Conclusions • Portable CAS solutions never satisfy EPICS clients. • For full range of EPICS functionality EPICS records are required.

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