I had a chance to review the CIP Library Volume 7: Integration of Modbus Devices into the CIP Architecture that was issued in Nov 2007. This spec defines a translation from a CIP client to a Modbus device. The user of the CIP client sees the Modbus device as a set of CIP parameters and objects. The CIP client or a CIP router then converts these objects to Modbus TCP or Modbus serial Modbus request messages. The translator then converts Modbus response messages back to the CIP format.

Very cool especially since EtherNet/IP and Modbus TCP represent about 50% of industrial ethernet in some market surveys.

The opposite translation, a Modbus client talking to a DeviceNet or EtherNet/IP device, is not specified or supported. This would be difficult since CIP objects are much more complex and flexible than Modbus coils, discrete inputs and registers.

What we were also hoping to see was an effort by ODVA to add source and data authentication to the protocol like the DNP3 Users Group has, but this does not appear to be a priority yet.