Can a Siemens TP1200 Comfort use string8 tags with AB L8 PLC

[dev67]

I've got a whole bunch of L8's and a whole bunch of UDTs that use custom string lengths, but can't seem to figure out how to get these to communicate with this Siemens panel. My only option right now seems to be moving all of my string data into default 82 char strings and talk with the panel that way. Is there really no way to use custom strings with these panels?

 

[mk42]

In Siemens, in the String properties, you can define a string length. It defaults to 10, but the help file says it supports anything from 1 to 82. I don't know if that changes the actual data type though for the comms, or just how the string is stored/displayed.



It's been a while since I looked at custom strings. My recollection from diving into a L5X file long ago is that custom string lengths in AB end up implemented as a UDT with a Length tag and an array of characters or something like that, and the HMI only supports arrays of numbers (int/real/etc).



Might be worth calling Siemens tech support to ask, if no one else has a better idea.

 

[JeremyM]

There's an underlying attribute of all Logix UDTs that indicate whether it represents a string family type. The Siemens panel might be looking for the de-facto Logix string (i.e. STRING) with type code 0xAFCE. A packet capture may reveal this. In this case, mk42 is right, and it expects STRING only.

 

[JeremyM]

It's been a while since I looked at custom strings. My recollection from diving into a L5X file long ago is that custom string lengths in AB end up implemented as a UDT with a Length tag and an array of characters or something like that, and the HMI only supports arrays of numbers (int/real/etc).

All strings in Logix are UDTs with attribute FamilyType == 1. All others are 0.

This is why you can create UDTs that are structurally STRING, but code won't compile if you treat it as a string.

 

[plvlce]

fwiw

Not too long ago I was trying to read a custom string length in a Logix into an AD C-More.

I was unable to get it to work with the PLC memory type set as String. Fortunately the C-More allows you to read into a string tag with the memory type set as SINT and by directly addressing the .DATA array I got it working.

I don't know if something similar is possible in your panel, but I can say that simply changing the string length to match did *not* work for me; it definitely seems like custom lengths are handled differently by Logix in some fashion.