Mind you that I have limited knowledge in the controllogix 1756-enbt, still I think that it can be configured as an EtherNet/IP Scanner (Master).
To configure the S7-200 as a EtherNet/IP adapter (slave) would be almost impossible, so I think that you need to solve it in a different way...
One way would be to use the serial interface of the S7-200, using Modbus RTU, connect a gateway (Modbus RTU to EtherNet/IP).
I have attached a simple picture that illustrates it.
I work for HMS and we have just the gateway needed: http://www.anybus.com/support/support.asp?PID=110&ProductType=Anybus Communicator
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