CLX to ML1400 Messaging Question

[lostcontrol]

Hi,
I am configuring a message from a ControlLogix to a ML1400. I have no issues with setting this up, but have a question in how it reads from the SLC.

if I want to read from B3:0, & I specify the destination as a DINT, with the Number of Elements as 2, will it read B3:0 & B3:1 to the complete DINT, or will it split them over 2 separate elements?

 

[Ken Roach]

You might have to experiment with this one.

What I expect is that if the destination tag is a DINT, and the number of elements is 1, that the message will place B3:0 in the low 16 bits and B3:1 in the high 16 bits.

In general, the Length argument of a ControlLogix instruction is the number of destination elements.

I always use INT[x] arrays when messaging to and from PLC/SLC/MicroLogix controllers to avoid any ambiguity for future maintainers of my code.

Let us know the experimental result !

 

[lostcontrol]

Update.
The source is read based on the destination (I think..)
I configured the instruction to read a single element from B3:5 & write to a DINT. 32 bits were coped across as expected.

I always use INT[x] arrays when messaging to and from PLC/SLC/MicroLogix controllers to avoid any ambiguity for future maintainers of my code.

I hadn't thought of this since I was not sure how it exactly worked. I have commented each individual bit as to where it comes from in the source PLC.

 

[brstilson]

Hi,
I am configuring a message from a ControlLogix to a ML1400. I have no issues with setting this up, but have a question in how it reads from the SLC.

if I want to read from B3:0, & I specify the destination as a DINT, with the Number of Elements as 2, will it read B3:0 & B3:1 to the complete DINT, or will it split them over 2 separate elements?

When I ran into a situation similar to this (Reading a value in a ML1100 from an L35E), My MSG instruction would error out as a Data Type mismatch. I had to use the L File in the Micrologix Processor to message back and forth, although I bet if I specified the data type as INT in the CLX it also would have worked.