Profibus I/O in Control Logix

[chavak]

Hi,

I started to work with my first project using Profibus in Control Logix PLC [L61] using a Proface MV156 PDPMV1 card in slot 2. I had configured the PLC and MV156 + the slaves in the field. I was using the sample program as a guide from the Proface site.

I am getting responses from the field devices correctly on the tags of MV156 which is of SINT data types.

My devices are all integer data types. Do I have to copy each of the 2 tags to a int tag to get it combined? Is this the usual practice? Usually I use Alias the I/O tags to a more readable tags in my programs and use that tag name as my wiring labels. For example -
Local:2:I.Data[0] to I_2_0 which gives me I_2_0.0, I_2_0.1, etc as digital entities.

But I am facing difficulties for MV156 to Alias to an int tags as the base tag is SINT. Is there any better way to do this, rather than copying 2 SINT to an INT tag.

I can't use the Local:2:I.Data[0] tags where the Profibus Card is residing, because the values in it is blinking [going on/Off] - not sure why is it so? Any idea?

Thankyou
Best Regards
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[jdbrandt]

Check the individual device's .gsd file, or other documentation, to see which bytes are what.
On -PA devices, there are four 8-bit (SINT) elements for sensor data, and one 8-bit (SINT) element for status information.

 

[Ken Roach]

First, a couple of corrections about the vendor. The company is ProSoft, and the module is an MVI56-PDPMV1. The correct spelling and part number will be important if people are searching for information.

http://www.prosoft-technology.com/content/view/full/8109

The Profibus module presents data to the ControlLogix as SINT data types because Profibus is fundamentally an eight-bit data bus, and because it's actually easiest to copy SINT -> INT, DINT, or REAL because the array always begins on a byte boundary.

The conventional method to use the data from the Profibus module is to use the COP or CPS instructions to place data into your own Tags. If you have a large number of INT data types, you might use a larger COP instruction to put the SINT's into an array of INTs, then create individual Alias tags that point to members of that INT array.

Profibus data is exchanged with the module using the MVI56PDPMV1_ProfibusData.Input and .Output array tags only.

The slot-defined "Local:2:Input" tags are part of the "mailbox" system for getting configuration and data into and out of the module, which is why you see the data in them "flashing on and off" as different data blocks are moved through.

 

[chavak]

Thankyou jdbrandt and Ken for the replies.

Oops, "Proface" - the brand got mixed up during typing, as I use both in my projects.

It is clear now which data tags to be used in project. So COP or CPS is the way to go. And thankyou very much for clearing the concern on flashing tags. I was wondering "what did I do wrong to make them blink"

Thank You
Best Regards
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