ControlLogix to Remote IO over 485?

Join Date
Feb 2008
Location
Walnuc Creek, CA
Posts
31
What would I need to use to communicate to remote IO over 485 from a ControlLogix? I saw the 1756-DHRIO module, but I believe this is DH+. If it's not obvious from my post, I don't know the AB networking interfaces very well. Also, what module would I need on the distributed IO side?

Thanks in advance.
 
What would I need to use to communicate to remote IO over 485 from a ControlLogix? I saw the 1756-DHRIO module, but I believe this is DH+. If it's not obvious from my post, I don't know the AB networking interfaces very well. Also, what module would I need on the distributed IO side?

Thanks in advance.

the 1756-DHRIO is also a RIO scanner. The I/O modules need a RIO adapter, such as 1794-ASB for Flex I/O. What is the I/O Flex, SLC or 1771 ?
 
Do any exist? I guess another possibility would be to get a DH+ to DH-485 converter? right?

DH+ protocol and DH485 protocol will not communicate with remote I/O equipment ( as listed above)
Maybe it would help if you tell the forum exactly what equipment you are trying to communicate with. Catalog numbers?
 
Thank you for the help Mickey.

I'm tied to a ControlLogix processor, but not any specific model. I have an old L2 network available and would like to make use of it. Those are my only two real constraints.

An L2 network, from my understanding, is 485 and is much like PROFIBUS.

From my limited understanding of AB communications protocols, I assumed that DH-485 would be the best approach to setting up remote IO over this existing L2 network.

Now I'm searching for the best way of communicating with RIO using DH-485. Am I mistaken that the 1756-DHRIO is specifically made for DH+ communication to distributed IO?
 
Thank you for the help Mickey.

I'm tied to a ControlLogix processor, but not any specific model. I have an old L2 network available and would like to make use of it. Those are my only two real constraints.

An L2 network, from my understanding, is 485 and is much like PROFIBUS.

From my limited understanding of AB communications protocols, I assumed that DH-485 would be the best approach to setting up remote IO over this existing L2 network.

Now I'm searching for the best way of communicating with RIO using DH-485. Am I mistaken that the 1756-DHRIO is specifically made for DH+ communication to distributed IO?

I don't know what your "L2"network is,never heard of it. So I'm still confused as to what you want to communicate with. Hopefully those that are will check in and help. I will post a link to the manual for the 1756-DHRIO if you don't already have it. ( see below)



http://literature.rockwellautomation.com/idc/groups/literature/documents/um/1756-um514_-en-p.pdf

And network info link

http://www.ab.com/networks/
 
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From how it was described to me, L2 is the predecessor to PROFIBUS and they can be thought of synonymously.

The more I look at this, the more I think that using the existing infrastructure isn't a good idea.

The existing cables have different electrical characteristics than those recommended for data highway, and AB sells specific cable for DH applications. I've heard that this could work, but as the transmission speed increases there's a higher probably for issues. This sounds pretty iffy, and I'd prefer not to suggest a potentially flawed solution.
 
From how it was described to me, L2 is the predecessor to PROFIBUS and they can be thought of synonymously.

The more I look at this, the more I think that using the existing infrastructure isn't a good idea.

The existing cables have different electrical characteristics than those recommended for data highway, and AB sells specific cable for DH applications. I've heard that this could work, but as the transmission speed increases there's a higher probably for issues. This sounds pretty iffy, and I'd prefer not to suggest a potentially flawed solution.

Profibus (which is RS-485) and AB DH-485 are two different beasts. DH-485 really is for processor to processor/HMI/PC communication. I've never seen it used for scanning remote I/O. Prosoft does make a few profibus cards which you can add to your rack if this "L2" network can communicate over Profibus DP or PA. I agree that the safe approach may be an overhaul if you are going to use a ControlLogix system.
 
What is it that you must achieve ?
Profibus or SINEC-L2 cabling are not the same as DH+, RIO or DH485 cabling.
And, DH+, RIO and DH485 are obsolete. Why base a new installation around an obsolete technology ? Dont just look at the cost for new cabling.
With ControlLogix, the natural contenders for an i/o bus network are DeviceNet and Ethernet/IP.
There IS a Profibus Scanner for ControlLogix, and it COULD reuse existing Profibus cables, but I would only select Profibus with ControlLogix if there is already some existing and expensive equipment with Profibus. Existing cables alone is not enough reason.

Sidenote alert:
SINEC-L2 is definitely not synonymous with Profibus.
At some time, Siemens called Profibus DP "SINEC-L2 DP", but Profibus/"L2-DP" was not compatible with the "SINEC-L2" (without the "DP" part). The similarites of the names causes much confusion even today.
 

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