Please explain :-
I need to connect tw control logics chassis together.
and :-
what I need to talk to both of these chassis
Do both of these chassis contain a controllogix processor and you need to pass data between the controllers ?
or are you simply trying to set-up a remote chassis for additinal I/O ?
How far apart are the two chassis ?
Do you have an existing Ethernet connection to either chassis for HMI or SCADA ?
I used to think ControlNet was the "bees-knees", but having used ethernet/ip on 100 Mbs, and, coupled with the advantage of not needing to schedule the connection, I would go for ethernet. If you
definately don't need an external ethernet connection into the system, you
COULD use an ethernet cross-over cable between the two ENBT or EN2T (ethernet bridge modules), but I would recommend using an ethernet switch, that would give you an ethernet programming connection, much much faster than serial.
Tell us more about what the two chassis are doing.