PLC-to-EPICS interface

In order to interface the application which at lower level use Allen-Bradley ControlLogix PLC control system we use ether_ip EPICS river/device support module. This allows us to interface EPICS records to PLC tags using Ethernet connection. On the PLC side the connection is provided by EN2T modules which communicate using through PLC's EtherNet/IP protocol. Overall this method seems to be working, but requires some coordination in the programming and notations to avoid complications when creating EPICS/PLC interfaced applications.

• Create CSV-file using RS5000 program and run script to generate EPICS database.
  1. The EPICS database is generated by a Perl script, similar to the script we used for solenoid magnet test. The script needs to know what type of variables each PLC hardware module correspond to. This needs to be coordinated between PLC programmer and whoever is building the EPICS database.
  2. It would be good to develop a standard set of notations for PLC modules so that the Perl-script can figure out the type of the variable based on the name of PLC module.
  3. When generating the CSV-file we should make sure that the tags imported from EPICS applications using EtherIP are not included.
  4. Only use DINT and REAL arrays. Other type of arrays are not guaranteed to work at this point, and we should avoid using them when interface PLC and EPICS.
  5. The alarm tag naming convention should be established.
  6. The Perl-script will not import the alarm tags into EPICS. They need to be included through a separate application/database for alarms manually using developed EPICS templates for PLC alarms.
  7. The Perl-script will also ignore function block tags and other composite tags.
  8. Use a separate set of PLC tags for input and output to EPICS. Using two-way communication using a single pair PV/tag for communication may turn into a problem.