On Logix5000 system, why there are two or more Ethernet cards on the same rack?

[wendaiyu 0]

 

Hi, folks, how’s going?

 

We just get one new production line with Logix5000 system. But I cannot understand why there are 4 Ethernet cards and 1 Controlnet card over PLC rack.

 

For my understanding, we can use 1 Ethernet card to connect to a hub, then connect to few modules with that hub. So why we need 4 Ethernet cards on the same rack?

 

Thanks for your help.

[TimWilborne 108]

Posting you program will probably give the specific reason, but lots of time you will see one Ethernet card used for HMI and programming access and the other used for connections to Ethernet devices.  Also while they may be on the same physical network they could be on two separate IP networks...192.168.1 vs 100.99.88.  Sometimes I would say it is overkill but it could have to do with the number of connections. Each Ethernet module is only capable of so many connections so adding multiple modules can increase the maximum number of connections

[Michael Lloyd 85]

Same here- SCADA, HMI, and programming on one Ethernet card and remote io on the other Ethernet card

 

My guess is that you have a redundant system for remote io comm and a second pair of cards for redundant HMI comm

 

but without the program it's just a guess

[kaiser_will 65]

Your new machine builder, I hope, provided a set of electrical schematics.  There should be a network design drawing to explain the multiple Ethernet and single ControlNet cards.  I would say the multiple Ethernet cards are for communicating to a high number of remote I/O nodes with the fastest loop response time.  

Yes, you may be able to connect all Ethernet devices to a single Ethernet module, but loop response time may not be within spec for the machine design.