ControlLogix ControlNet I/O

Hi

I have to add some I/O cards to a ControlLogix PLC.
Here's the configuration:

1st chassis - 17 slot with CNB card (no spare slots)
2nd chassis - 17 slot with CNB card (1 spare slot)
3rd chassis - 7 slot with CNB card (6 spare slots)

I need to add the cards in the third chassis and somehow re-schedule the ControlNet network. Is it possible to do this without a 1784-PCC? Tho only comms options are DH+ (via DHRIO card in the 1st chassis) or DF1 (via the processor serial port).

I've done a search on this forum and found a post from a couple of years ago which suggests it may be possible to re-schedule the network using DF1 passthru to the ControNet network, but I,m not totally convinced. The CNB manual suggests that Ethernet or 1784-PCC is the only way.

Whilst on site yesterday, I attempted to gain access to the ControlNet network using DF1 and RSNetworx for ControlNet, but I was unsuccessful (error message "cannot find the active keeper ..." The PLC was in run mode - does it need to be stopped?

Any help is appreciated as I really don't want to spend hundreds of pounds for a 1784-PCC just for this.

Whilst a 1784-PCC will certainly do what you want and will also vastly increase the speed of downloads and other online work you should also bear in mind that CLX modules can be inserted and removed under power. I keep a "spare" ENET module which I can add into any rack with a spare slot when I need to connect to a CLX system locally. The DF1 alternative is so slow that I would not normally consider it for anything except an absolute emergency.

Keith,

I have always done my scheduling via Ethernet or direct CNET access.

I would hesitate to try it on Serial myself. I think it would take a decade, if it even works.

I would attempt to do it accross DH+ and see what happens. It might work? It is not recommended for sure!

Keep in mind, fooling around with your scheduled network could crash it leaving you helpless until the proper hardware can be gathered. If that is not a good thing, I would buy a 1756-ENBT card or the PCMCIA card for your laptop.

If I was responsible for the system in question, I would get an Ethernet card for the CLX rack. It would make me nervous having no way to service my CNET.

Scheduling the network for the first time can be confusing too. If you have not done it before, I would allow plenty of downtime for the learning curve.

Sorry I don't have any better advice.

RSL

Absolutely second RSL's sound advice.

Hi

Thanks for your replies.
I have scheduled ControlNet I/O from scratch before using Ethernet, so I have a basic understanding of scheduling an I/O network.

If I go the Ethernet route, does the ENBT card need to be in the primary chassis? If it was in any other chassis surely it would need to go through the existing ControlNet to get to the processor chassis. As I have no spare slots in the 1st chassis, would this prevent me from scheduling the network this way?

Keith,

You can place your ENBT in any of the racks which are part of your ControlNet network. It does not matter which. The path will cross the backplane and access the ControlNet. It will work.

There is a little chance that you will be able to schedule via DHRIO card. I know CH0 DF1 will not work for sure.
Thechnically only 100% guarantee way is to use ControlNet card.
In most of cases ENBT bridge will work, except some situations:
- CPU load of CNB in a bridge rack is close to 100% or
- his CNB is a keeper and faulted for some reason.

What card you are adding?
If this is a descrete module and rack 3 CNB set for rack opt. you may not need to reschedule - some times it works, some times not.