ether_ip - EPICS EtherNet/IP support for ControlLogix Kay-Uwe Kasemir, LANL Nov. 2000

EtherNet/IP 4 IP = Industrial Protocol 4 Evolved from “ControlNet over EtherNet” SIG 4 Encapsulates CIP in TCP & UDP –(Ctrl. & Info. Protocol, shared by DeviceNet and ControlNet) 4 Part of ControlNet Specs: –Open DeviceNet Vendor Assoc.,

EtherNet/IP Spec. Details 4 ControlNet Spec.2 Errata 1, E.Net. still in red 4 Open portion of CIP (object & service codes): –How to route messages –How to read serial number and vendor code 4 Vendor specific: –Get data of real interest, e.g. PLC values 4 This driver: CIP Read/WriteData as used by Allen Bradley ControlLogix PLCs –Round-trip request/response mechanism –Subscription (ForwardOpen) with triggered updates via UDP not implemented/documented by AllenBradley

EPICS Driver/Device 4 No special hardware, neither for setup nor runtime 4 IOCs (pc486, PPC), command-line (Win32, Unix) 4 Can read & write any tag on PLC –DTYP=“EtherIP”, PS1RB2” –also: arraytag[21]”, struct.elem” –REAL, INT, DINT, BOOL, scalars, struct. elements, arrays –no need to “publish” tag in PLC’s LadderLogic or program ControlNet connection to allocate bandwidth –Records: ai, ao, bi, bo, mbbi, mbbo, mbbiDirect, mbboDirect 4 INP/OUT can be changed at runtime to use different tag on different PLC! 4 Handles disconnects/reconnects (e.g. PLC reboot)

Driver/Device Details 4 One communication thread per PLC 4 Combines requests to minimize transfers –(up to ~500 byte PLC buffer limit) 4 Arrays are transferred as a whole (default) 4 Output records: – Monitors PLC, updates rec. on change 4 Supports SCAN=I/O Event (also for e.g. 30Hz scans) 4 Provides statistics: min/max/last scan times, #errors,... 4 Performance: about 8ms per transfer Single REAL tag: 8ms BOOL[352]: 8ms 3xREAL[30]: ~20ms (combined requests)

Conclusion 4 Setup: –No additional hardware (neither for PC, IOC, nor communication setup) 4 Use: –No special LadderLogic required, though arrays might be preferred (performance) –Good IOC support (I/O Event, runtime change) 4 Performance: –8ms/transfer, susceptible to network delays –good enough for most applications?

Test Taken after about runs, PPC IOC, Hz, switched network. After 1 week: max. scan time 0.15 sec