L35E Byte swap an Array

[Conor 4]

Hi guys, I am doing a new project were I am connecting an L35E to a Siemens controller. I have the Profibus connected and working, but I have found that there is byte swapping when sending INT data from Siemens to L35E. I have been able to use the SWPB instruction to reverse the byte swap, but this instruction only is for a length of one INT. I have an Array of data coming over, about 100 INT's. Can someone tell me the best way of un-swapping the complete Array Thanks, Conor

[Ken Roach 194]

The FOR instruction in ControlLogix is like an "indexed JSR", so you could use a For/Next Loop if you want this to happen in the background. If you want to do it all at once, I say write a subroutine with a hundred SWPB instructions and call it when the Input data updates. That will be much faster than a FOR/NEXT loop because you won't have the time required to jump to the subroutine and back. Doesn't the Profibus module for CompactLogix include a "swap bytes" configuration setting ? Edited 11 Dec 2012 by Ken Roach

[Conor 4]

Not sure about that setting Ken. I am off tomorrow, but will check on Thurs when back in Thanks for your advise Edited 11 Dec 2012 by Conor

[Ken Roach 194]

In the Prosoft Configuration Builder software's Profibus configuration, when you go to a Slave Node's properties and select the third tab "Tags", there will be a set of Data Swap selections; Word, Byte, Both, or None. That's where I would do the data swapping; it will all be done at a low level and very rapidly by the Prosoft module, without any delay or complication in your ladder logic.