Experimental Physics and
Industrial Control System

John Dobbins <[email protected]> · Fri, 18 Dec 2009 14:25:26 -0500

I would add that various manufacturers sell remote I/O designed to be

connected to an Allen-Bradley PLC in connected mode., e.g. Opto22,

SMC Pneumatics,... Device support for connected mode would allow use of

these products without the PLC.

John Dobbisn

David Dudley wrote:

In the "unconnected" mode, that is correct.  One of the reasons I am working
toward modifying the driver to work in "connected" mode is to be able to get
around those limitations.

Going through the setup of a "connected" mode channel basically gets you a
'handle-id', which directly interacts with the selected remote data.

According to Rockwell, once the channel is formed, you no longer use one of
the 'unconnected' CIP channels, which eliminates the overhead of retrieving
data using TagNames.  Also, once the CIP channel is formed, the remote
device can be set to report data to the host on the 'RPI' (Report Periodic
Interval, as memory serves), or when the data changes.

David

On 12/18/09 1:05 AM, "John William Sinclair" <[email protected]> wrote:

Note that ControlLogix communications (multicast with tcp messaging)
includes a fairly severe penalty for using the
tag names. There are a limited number of cip resources (255 is common).
Each module consumes several and each IOC access
by tag name consumes one. As a result, we always use arrays and end up
in the same old boat of having to do lots of name
mapping to array position. In principle the tag names are very nice; in
practice they are not too useful.

John Sinclair

David Dudley wrote:

For NSLS-2, all configuration and logic is planned to be incorporated
into the IRMIS system, as a single database layout.

In addition, I should have initially mentioned that one of the primary
reasons for the A-B choice is that it uses a communications format
named ŒCIP¹, and its internal memory configuration is entirely driven
by TAGNames.

In tne ControlLogix platform, you do not do programming or
configuration by having to remember or know things like ³...
ŒB-703:R-E5<OTB>T-1¹  is wired to terminal IW102... (That¹s Building
703, Room E5, Optical Testing Lab, Temperature 1)² .

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System