1769-L18ER-BB1B-Dynamic Expansion I/O

Hello!

Further to a previous post that Ken helped me out with but thought it should be a new string.

On our L32E project I had an IF4 module programmed in the I/O config and set it to NOT "Major Fault On Controller...." This allowed me to have the program be identical every time and our software could then config the Local.xxx tags dynamically for scaling when we had the IF4 present. When our clients did not want a pH/Conductivity etc. we would not include the module. All we would get is a green blinking I/O light and all was good.

The config for this 1734-232ASC and the 1734-IE4C has the same "Major Fault On Controller..." selection but that does not seem to matter. Under the GENERAL tab of the PLC config you need to define the number of expansion I/O modules. If this does not match the number physically present it will fault the CPU.

I liked that I could complete the program and "anyone" could load up our PLC's in the shop with the program and not know anything about RSLogix. Is there a way to "trick" the system in the way we did with the L32E?

Thanks again in advance for any help!

In my humble opinion it will be easier to simply create a project file with the specific I/O configuration for each variant of the machine.

The idea of "one general purpose program for all variants" is great in theory but in practice it never really pays off.

You could try to use MSG instructions to programmatically modify the POINT I/O configuration in your project. There's a Knowledgebase document (AID#28877) that describes doing that for a 1734-AENT or 1734-ACNR but I don't know if it will work for the local POINT scanner of the 1769-L18ER controller.

I have been the guy trying to figure out why there is logic for absent I/O modules before... it's unpleasant at best.

The easiest solution would be to get a 1734-ARM (Address Reserve Module) for those situations where you don't have the IE4C. That way, every rack you make has the same number of modules and your I/O mapping all stays the same. Plus, if a customer ever wants to add that functionality, all you need to do apart from installing the actual probes is replace the ARM with the IE4C and you're good to go.

Oh, hey, excellent point ! I was too focused on the POINT chassis object.

It's easy to use an SSV to inhibit a POINT I/O module connection, so you would not even get a blinking I/O status LED.