Determining Rack Number...

rs14smith · Nov 15, 2012

This is a simple question, however, I am not sure I fully understand how to determine the rack number for different devices in a cabinet.

I have 1 cabinet that houses the main Compact Logix PLC which has 12 slots, and then in another cabinet, I have a SLC 5 PLC that has 6 slots.

The 1st cabinet communicates with the 2nd cabinet with DHRIO (located on slot 12).

So my question is, what is the correct "rack" number for the 2nd cabinet?

Ken Roach · Nov 15, 2012

It's a great question, because the RIO protocol does addressing using "Rack, Group, Slot" values.

So all the data from that second 1746 style chassis (I assume equipped with a 1747-ASB adapter) is in a "Rack Number" that you configure with DIP switches.

I don't think there is a single good answer for this.

You probably want to refer to the 1746 chassis with "slot numbers" that are associated in some way with the ControlLogix slots.

If you have the ability to call it "Rack 2" and assign Slot numbers beginning at 1 to the I/O modules, that's what I would do.

If the 1747-ASB and 1756-DHRIO are the only devices on the RIO network, you could even literally address the 1747-ASB as "RIO Rack 02".

rs14smith · Nov 15, 2012

Ken Roach said:
It's a great question, because the RIO protocol does addressing using "Rack, Group, Slot" values.

So all the data from that second 1746 style chassis (I assume equipped with a 1747-ASB adapter) is in a "Rack Number" that you configure with DIP switches.

I don't think there is a single good answer for this.

You probably want to refer to the 1746 chassis with "slot numbers" that are associated in some way with the ControlLogix slots.

If you have the ability to call it "Rack 2" and assign Slot numbers beginning at 1 to the I/O modules, that's what I would do.

If the 1747-ASB and 1756-DHRIO are the only devices on the RIO network, you could even literally address the 1747-ASB as "RIO Rack 02".

So in a nut shell, it's some what up to me what rack number to assign it when I set the Dip Switches correct? Right now they are set to Rack 3, even though I asked the guy who switched them, "why rack 3...", he was unable to answer. So I'm assuming, as long as the configuration I set in RS5000 under the properties menu, matches the same Rack/Group/Slot number for the RIO Adapter?

To me, it makes more sense to make it Rack 2 and not Rack 3. We have the group set to 0, and the Size at Full Rack (8 I/O Groups). Everything right now works fine, but before we make a label for the cabinet, I just need to know if I can make it Rack 2 instead.

Ken Roach · Nov 15, 2012

You can set the 1747-ASB for any Rack Number between 0 and 77 (they're Octal).

If there's just that one Adapter, set it for any Rack Number you want. The default would be zero, but there's no time or performance penalty for making it 1 or 2 or 3 or anything else.

All that matters is that it's in the Scanlist for the 1756-DHRIO module.

The fellow who set it up might have been remembering something from the 1747-SN (the SLC-family scanner, not the adapter). Those will only scan adapters at Rack 0, 1, 2, 3.

Determining Rack Number...

rs14smith

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Ken Roach

Lifetime Supporting Member + Moderator

rs14smith

Member

Ken Roach

Lifetime Supporting Member + Moderator

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