PLC5-Enet question

We currently have several PLC 5's networked together via DH+ (5/40,5/25,5/15).

The company would like to replace the 5/40 to a 5/40E to enable ethernet communications.

As I understand it I will not be able to access the other 5's on the DH+ network through the 5/40E. I just want to confirm this as one of my colleagues was under the impression that he could.

I believe I will need a control logix bridge to accomplis this correct?

True.


Even if you could gain access to the DH+ network via the PLC5/40E, you really wouldn't want to. If this PLC was offline for any reason, you would lose the ability to connect to the DH+ processors.

The best solution is a ControlLogix gateway.

here is the link

http://domino.automation.rockwell.com/applications/kb/RAKB.nsf/0/369E2B8093E4E23685256AFB006567F5

member.php?u=7334allscott,

We just changed all of our HMIs and instead of buying new KT cards we decided to use ControlLogix ENBT and DH-RIO modules to talk to our eight PLC5/40 processors. They work ok although I think the DH-RIO modules can be a bit of a bottleneck at times. We built two "bridges" with 4 available RIO modules so we can spread out the traffic (4 separate DH+ networks). We still use the DH+ for node to node comms on like dh+ netwroks. I have yet to try comms from one dh+ to another via the bridges.

Question for the rest of you...when you say "Gateway" are you talking about a single module or is it like I have, the ENBT and DH-RIO modules in a CLX chassis? If it's a single piece of harware could you please provide a link?

A "ControlLogix Gateway" is a general term for a ControlLogix chassis with one or more communication modules in it.

Before the ControlLogix controllers were available (a decade ago!), A-B sold just the Ethernet modules and DHRIO modules as a modular communications bridge.

Several DHRIO modules and one ENBT is a common configuration. I've also seen six 1756-CNB's connecting PLC-5C15 ControlNet networks together and adding a single 1756-ENBT for HMI access.

The DH+/DH+ message bridging can be complicated if you haven't worked with subnets before, but RSLinx makes navigation among networks point-and-click simple for HMI or RSLogix access.

To answer allscott's question directly:

You are correct: a PLC-5 controller cannot bridge between Ethernet and DH+ networks.

A lot of users have become so accustomed to the Logix bridging between networks that they forget it wasn't present in the PLC-5 architecture.