Interfacing EPICS IOCs With Allen Bradley PLCs

1
Interfacing EPICS IOCs With Allen Bradley PLCs

• Applications
• Recent enhancements
• Backwards compatibility
• Reliability

2
EPICS device and driver support for Allen Bradley
DF1 protocol

• Originally written for (and funded by) the KECK
  observatory
• Recently updated for APT high power RF and
  personnel safety subsystems

3
DF1 Driver Applications

• IOC host architecture neutral
• runs on PC, VME, and VXI IOCs
• Point to point serial communication
• Allen Bradley Data Highway communication
• Allen Bradley KF2 standalone
• Data Link DL PC low cost ISA card

4
Recent Enhancements

• Support for Allan Bradley PLC5 architecture
• Output tracking
• DF1 server
• Others

5
Support for Allan Bradley PLC5 architecture

• PLC5 addressing
• Thanks to Eric Bjorklund for improved ASCII
  address parser
• PLC5 protocol
• Data type safe R/W
• Elements in files
• Improved access control granularity

6
Output Tracking

• IOC initialization does not block for Initial
  output value query completion
• Output records in invalid / undefined alarm state
  until this query completes
• Output records track changes occurring in PLC
  (they are processed)
• Potential side effects when output records have
  forward links

7
DF1 server

• Allan Bradley PLCs see EPICS records as elements
  in files in a PLC5 on DH
• Reduced latency
• Occurs when record addresses data highway node
  number of IOC

8
Other Enhancements

• Specification of independent scan rate for each
  PLC5 file
• Each serial link or Data Highway may be assigned
  a different local node address
• drvSerial does not delete tasks when a link
  drops out

9
Backward compatibility

• Continue to support original addressing and
  protocol of older PLCs
• additional testing required for this version
• Driver no-longer aborts a write in the queue so
  that it can be combined with another subsequent
  write

10
Reliability

• This driver has been supporting the APT high
  level RF and window test systems since the
  beginning of the calendar year
• The driver has been very reliable on this very
  lightly loaded PLC5 system
• Now have operational experience with Allen
  Bradley Data Highway

11
Getting a copy of the DF1 protocol driver
described here

• KECK (Allan Honey) is the distribution point but
  I have not yet sent them a copy of this version

12
In Memory Communication with VME Resident Allen
Bradley PLC5?

• Contact Eric Bjorklund (LANL LANSCE-6) for his
  driver
• Both the DF1 driver (described here) and Erics
  VME driver use the same common PLC5 enhanced
  device support

13
Conclusions

• The Allen Bradley DF1 device / driver support has
  been upgraded to support PLC5s, output tracking,
  and DF1 server operation.
• It has been very reliable under continuous
  production, but lightly loaded, operation of the
  APT high power RF system.