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EPICS support for ControlLogix via EtherNet/IP

EPICS support for ControlLogix via EtherNet/IP. Kay-Uwe Kasemir, LANL May 2001. PS. CNet. PLC. Allen-Bradley ControlLogix. SNS: HPRF, Vac., RCCS, Facility, … Up to 7MB, multithreaded, … Symbolic ‘tag’ names, no ‘I10:12’ Accepts DeviceNet, ControlNet, EtherNet/IP, … like any I/O module.

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EPICS support for ControlLogix via EtherNet/IP

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  1. EPICS support for ControlLogix via EtherNet/IP Kay-Uwe Kasemir, LANL May 2001

  2. PS CNet PLC Allen-Bradley ControlLogix • SNS: HPRF, Vac., RCCS, Facility, … • Up to 7MB, multithreaded, … • Symbolic ‘tag’ names, no ‘I10:12’ • Accepts DeviceNet, ControlNet, EtherNet/IP, … like any I/O module

  3. IP = Industrial Protocol • Evolved from “ControlNet over EtherNet” SIG • Encapsulates CIP in TCP & UDP • (Ctrl. & Info. Protocol, shared by DeviceNet and ControlNet) • Specs. used to be part of ControlNet,now available as separate “EtherNet/IP”: • Open DeviceNet Vendor Assoc.,http://www.odva.org

  4. EtherNet/IP Spec. Details • Open portion of CIP (object & service codes): • How to route messages • How to read serial number and vendor code • Vendor specific: • Get data of real interest, e.g. PLC values • This driver:CIP Read/WriteData as used byAllen Bradley ControlLogix PLCs • Round-trip request/response mechanism • Subscription (ForwardOpen) with triggered updates via UDP not implemented/documented by AllenBradley

  5. EPICS Driver/Device • No special hardware, neither for setup nor runtime • IOCs (pc486, PPC), command-line (Win32, Unix) • Can read & write any tag on PLC • Records: ai, ao, bi, bo, mbbi, mbbo, mbbiDirect, mbboDirect • DTYP=“EtherIP”, INP=“@plc1 PS1RB2” • also: INP=“@plc2 arraytag[21]”, “@plc2 struct.elem” • REAL, INT, DINT, BOOL,scalars, struct. elements, arrays • no need to “publish” tag in PLC’s LadderLogicor program ControlNet connection to allocate bandwidth • INP/OUT can be changed at runtime to use different tag on different PLC! • Handles disconnects/reconnects (e.g. PLC reboot)

  6. Driver/Device Details • One communication thread per PLC • Combines requests to minimize transfers • (up to ~500 byte PLC buffer limit) • Arrays are transferred as a whole (default) • Output records: • Monitors PLC, updates rec. on change • Supports SCAN=I/O Event (also for e.g. 30Hz scans) • Provides statistics:min/max/last scan times, #errors, ... • Performance: (default “System Overhead Time Slice”) • Single REAL tag: 11ms (7ms with 50% SOTS) • BOOL[352] + 3xREAL[30]: 15ms + 25ms (combined requests)

  7. 352 BI @ 10Hz, 3 x REAL[40] @ 2 Hz Transfer Time Histogram

  8. Conclusion • Setup: • No additional hardware (neither for PC, IOC, nor communication setup) • Use: • No special LadderLogic required, though arrays might be preferred (performance) • Good IOC support (I/O Event, runtime change) • Performance: • 11ms/transfer, susceptible to network delays • good enough for most applications?

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