Flex I/O and Ethernet I/P addressing

In the past we have always used Remote I/O with Flex I/O modules. We are getting ready to do a project that will have Control Logix in the main panel and several remote panels with 1794-AENT adapters. We will have analog and 24VDC I/O. Was just wondering if there is significant difference in the addressing format for real world I/O when using Ethernet I/P. I'm getting ready to dig into the manuals but was just looking for a little head start from anyone who is already doing Eth. I/P with Flex I/O. By the way, we have about 95 Analog Inputs and about 75 Discrete I/O in this project.

Its a breeze, just add the adaptors and io to the tree, call it a name that makes sense and it will all appear in your controller tags.
Regards Alan Case

Does sound easy. I will give it a try on Monday. Thanks!

Like Alan says, the addressing is no big deal. There are other things to consider though:
connections, transactions, bandwidth

If a bank of flex I/O contains only digital modules with 16 points or less each, then one connection is required for the entire bank. Configure for rack-optimized and only one transaction is required.
All 32-point modules and analogue modules require individual connections and transactions which can effect bandwidth.
The default RPI is too fast for most requirements and will use up bandwidth in a hurry.

Good grounding is required for reliable operation of flex I/O.
Mount it on steel din rail, not ali.

We don't do anything high speed. Mostly process variables on the analog side such as pressures, flows, and storage tank levels. On the digital side it's mostly solenoid valves, motor starters, and discrete alarms. Most if not all of our remote panels will be a combination of analog and digital. Do you configure connection type for each module or each adapter? Looking at the example in the EthernetI/P manual it looks like you would have to use direct connection if you have both analog and digital connected to the same adapter. Is there a fixed limit to how many connections you can have? Also what determines the best RPI to use?

The connection type is set on the adapter. If you're using only 32-point digital I/O then set the connection type to "none". The "rack optimized" setting can be used if you have a mixture of modules, but there's no advantage unless there's more than one 8 or 16 point module. Analogues and 32-point digitals still get direct connections if "rack optimized" is selected.

There is a limit to the number of connections. I can't remember the details just now but the number 128 comes to mind. Also can't recall if it's the ENBT or the processor that has the limit.

The ENBT has a theoretical bandwidth of 5000 transactions/second. Leaving the RPI's at the default will eat that up in a hurry, particularly if you have a lot of direct connections. From what you've said, I would set the digital RPI's no lower than 20 msec and the analogues to 50 or 100 msec. Try not to use more than about half of the 5000, or HMI and RSLogix access can get sluggish. Don't be surprised if you need an additional ENBT.

What about scaling of analog modules

I am using 1794-IE8 and 1794-IE12 Flex I/O modules in this project. I can't find any info about the raw data for the inputs. I am using 4-20 mA inputs. The last time I used Flex I/O I used a 1794-IE8, Remote I/O and RSLogix 500 (SLC 500) I looked at my program and I used 0 to 30840 for the raw input data. I don't have a clue where I got that from. Any help is appreciated.

See page C-2 of this manual, IE8 and IE12 use the same format

http://literature.rockwellautomation.com/idc/groups/literature/documents/um/1794-um002_-en-p.pdf

For the 1794-IE8 see PDF. (Not 100% sure about the 1794-IE12 but my guess its the same, might have to test to be sure. Just apply 4ma and see what you get, same for 20ma)

Contr_Conn said:

See page C-2 of this manual, IE8 and IE12 use the same format

Click to expand...

I was looking at this very page of the manual just before leaving work today. Now I see where the 30840 came from. If I had looked down a little further at the example I would have seen it earlier. This has been one of my frustrations with Rockwells' manuals. Maybe it's just me but sometimes it seems like I am hunting for buried treasure when looking for info that ought to be front and center. And what is the purpose of showing the values in hex? Anyway thanks to C_C and Mickey for the help.

Additional Resources

After beating my head against the wall several times, slow learner, I always download all the manuals listed in the Additional Resources section of any new module, or communication interface, that I'm trying to use.

You are right it is out there but not always in the first manual you read.

rta53 said:

And what is the purpose of showing the values in hex?

Click to expand...

Cost savings, not as much ink used. Must be a green thing.

Mickey said:

Cost savings, not as much ink used. Must be a green thing.

Click to expand...

Good one Mickey! I should have thought of that. Hey, maybe that's why they haven't updated the manual since May 1996.

What about configuring 1794-AENT

OK, right now I am feeling frustrated with Rockwell/AB again with their documentation or lack thereof. I had previously configured my I/O for this project in RSLogix 5000. When I was setting up the 1794-AENT I had a choice of 1794-AENT/A or 1794-AENT/B. Well since I did not yet have the adapter I assumed it would be the latest series, namely B. Well, yesterday we finally received all the hardware and it looks like to me it is Series A. When you choose Series B in RSLogix it automatically assigns it Rev. 4 Firmware. The only kind of info that comes with the adapter is the Installation Instructions and Release Notes. But hey, all is not lost, because these instructions refer to a User Manual, 1794-UM006. Great, this will show me how to configure the adapter. Guess what, this manual is no longer listed in the literature library. . But hey, all is not lost. They now have a manual which combines all the Ethernet I/P modules. But guess what, it tells me nothing specific about how to configure the 1794-AENT. It's mostly just general stuff. Why would they get rid of the 1794-UM006? I know it sounds like I'm making a big deal about nothing, but when you have limited time and resources it gets very frustrating. When you look at the generic EthernetI/P user manual it has one page that shows a picture of the adapter module properties and all it says is "Specify the general information about the module". Maybe specific info about the 1794-AENT is available elsewhere, if someone knows please point me to it.

When you look at the label on the module it has this info. Ser. A, REV. B01, F/W Rev. 3.1. The label on the box also has a Catalog Rev. M01, whatever that means. It seems to me now that I should have configured a 1794-AENT/A with Firmware of 3.1. Looks like there is no way to change this in RSLogix without deleting the adapters and adding them back in. I already have a lot of programming done that references the I/O. Am I going to be able to delete these I/O modules and add them back in? Thank for any advice/help.

Remain calm. All is well.

There's nothing to configure on the 1794-AENT outside RSLogix 5000 except the IP address of the module, which is done using the BOOTP/DHCP server that installs with RSLinx. The new Series B modules will have a last-octet set of wheelswitches like the 1734-AENT does.

The quick way to handle the 1794-AENT's being configured for the wrong Series is just to disable Electronic Keying. They'll run fine.

The less quick way is to delete and re-create the I/O modules with the same names. All the tags you have already created will attach themselves back to the I/O module names if they are the same when re-created.

I know that you can save the project as an *.L5K format and manually edit the I/O type but I'm not familiar enough with that to give advice.