Experimental Physics and Industrial Control System

If you use the EtherIP driver, see
  http://ics-web1.sns.ornl.gov/~kasemir/etherip/index.html
you'll notice that it's much more efficient for it
to access array tags.
I just noticed that Bob beat me in stating this ;-)

So the situation is typically like this:
You might have records with great looking names like
  ThingyXY1_Voltage
and
  ThingyXY1_Current
which both read data from PLC tags.

Those PLC tags, however, are meaningless array tags like
  ANA_XFER_RD[10]
and
  ANA_XFER_RD[11]
Well, the only meaning is:
ANA_XFER_RD=analog data transfer array, meant to be read by IOC.

To beautify your PLC code, you can create aliases in RSLogix:
  ThingyXY1_Voltage = alias for ANA_XFER_RD[10]
  ThingyXY1_Current = alias for ANA_XFER_RD[11].
That way, you have somewhat readable ladder logic,
while the data still resides in the array elements,
and can be transferred in a single array 'read' request.

Now one could rephrase your question as:
How well do your alias tags and the EPICS record names match?

In the systems that I've been somewhat involved with,
they didn't because
a) There were several instances of the same PLC code,
   duplicated on different PLCs.
   So on each PLC, you'll find the same tag names,
   but of course their associated EPICS record names
   needed to be unique.
b) The PLC programmer was free to pick any names.
   The only interface with him were the transfer array names,
   which of course don't carry any signal meaning.

ControlLogix Users,

I am wondering what folks do about ControlLogix Tag names when it comes to naming conventions.

1) As I understand it ControlLogix Tags names may contain underscores, letters, and numbers. Most naming systems include other separators such as hyphens, colons, periods. So what happens when these two meet?

2) Many times a ControlLogix tag has a corresponding EPICS database record. How do you distinguish these names, i.e. the Record name and the Tag name? Or are they the same and distinguished by context?

Thanks,

John Dobbins
Lab for Elementary Particle Physics
Cornell University

References:

Naming Conventions and Control Logix John Dobbins

Navigate by Date:

Prev: Re: Naming Conventions and Control Logix Rolf Keitel

Next: Fw: epics base compile fails Bob Soliday

Index: 1994  1995  1996  1997  1998  1999  2000  2001  2002  2003  2004  2005  <2006>  2007  2008  2009  2010  2011  2012  2013  2014  2015  2016  2017  2018  2019  2020  2021  2022  2023  2024 

Navigate by Thread:

Prev: Re: Naming Conventions and Control Logix Rolf Keitel

Next: RE: Naming Conventions and Control Logix Dalesio, Leo `Bob`

Index: 1994  1995  1996  1997  1998  1999  2000  2001  2002  2003  2004  2005  <2006>  2007  2008  2009  2010  2011  2012  2013  2014  2015  2016  2017  2018  2019  2020  2021  2022  2023  2024