Re: [foxboro] Foxboro and Allen Bradley SLC 504

Nope, what I call bi-directional data transfers (same data point being
activated on by both PLC and I/A) do not consistently work with any
and all OPC systems.  Trust me, I've tried!  Even Matrikon gave up.
It's the nature of the beast.

I completely agree about the limitations of the Int30's.  You can very
easily overload it.  We have eleven connected to the same PLC for
batching purposes just for that reason.

Glen Bounds
Corn Products International


----- Original Message -----
From: "Corey R Clingo" <clingoc@xxxxxxxxxxxxx>
To: <foxboro@xxxxxxxxxxxxx>
Sent: Monday, August 19, 2002 11:49 AM
Subject: Re: [foxboro] Foxboro and Allen Bradley SLC 504


>
>
> Hmmm...I've never experienced the master wantonly writing over the slave's
> data unless there was a configuration problem, on either I/A or brand H
> systems.  Once you understand that there are two possible sources of
> changes to a given register in the slave (the master and the slave's own
> programming), that the slave's programming typically runs many times
faster
> than the master's, and that the master typically reads back the actual
> slave register on writes to update displays etc., you can make it work.
>
> Having said that, we have "lost" data with Integrator 30s as well.  We
> found out, after a day spent with an Invensys application engineer, that
an
> Integrator 30 does not have a lot of horsepower, and that certain
> configurations carry a lot of overhead that can bury it.  We hope to get
an
> opportunity to optimize our configuration and fix these problems on one of
> our I30s.  If this does not work, we will probably look at the AW70 w/OPC
> client.  We don't use 70-series boxes, but since this will be a
> single-function machine, we are amenable to trying it.  It's capacity is
> vastly greater than an I30's; its only real disadvantage is that it is not
> redundant, but that will not be a huge drawback in our application.
>
> I'd love to see an Integrator 60, or better yet a RISC- or Pentium
> 3/4-powered Integrator(and CP :) as well; that's ultimately the most
robust
> solution.  But I'd think you could do bidirectional communication with an
> AW70 just fine, if redundancy was not critical.
>
> Corey Clingo
> Sr. Engineer
> BASF Corp.
>
>
>
> |---------+---------------------------->
> |         |           Glen Bounds      |
> |         |           <gbounds@bellsout|
> |         |           h.net>           |
> |         |           Sent by:         |
> |         |           foxboro-bounce@fr|
> |         |           eelists.org      |
> |         |                            |
> |         |                            |
> |         |           08/15/2002 01:54 |
> |         |           PM               |
> |         |           Please respond to|
> |         |           foxboro          |
> |         |                            |
> |---------+---------------------------->
>
>---------------------------------------------------------------------------
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>   |
|
>   |               To:  foxboro
|
>   |        cc:
|
>   |        Subject: Re: [foxboro] Foxboro and Allen Bradley SLC 504
|
>
>---------------------------------------------------------------------------
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>
>
>
>
>
> The whole issue of Allen Bradley "communicating" with I/A has been
> a dark spot on Foxboro since the inception of I/A.  And OPC does
> nothing to brighten this tarnish.  By definition, OPC requires a Server
> and a client, Master and Slave, or whatever the designers want to call
> it.  But to communicate with a PLC, you must have a seamless, bi-
> directional communication.  You can get fairly close with OPC, but the
> possibility of loosing data that was sent from the "slave" is great.  The
> Master will write over the slave's data as if it had never changed.
> Whether you make the I/A the server, or the PLC, you WILL loose
> data if you need to have bi-directional communications using OPC.
> The I/A gateway (Integrator 30, etc) is the only way to go if you have
> the need for bi-directional communication.  Period.
>
> Life is too short not to have an Integrator 60!
> Glen Bounds
> Corn Products International


 
 
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