Interesting. Did you get any reasons why this is the case?
I've only used OPC for reading so far, and not on an I/A system yet. It
seems to work OK for that. We're interested in it in the future as an
integration tool, but even then it would still be a read-only mode (pulling
data from an SIS logic solver).
On the other hand, I have always felt that relying on OPC for a control
system's central communications infrastructure was a mistake. A lot of
automation vendors claim that their customers want Windoze-based solutions
(which is funny, since I have personally never met anyone who likes this
idea). To make their job easier (I presume), they bastardized COM/DCOM for
control uses and call it OPC. But the underlying protocols are still not
really designed for real-time applications. What's worse, they have no
control over COM/DCOM's direction (as Microsoft has proven by pushing aside
COM/DCOM for .Net). I am surprised there isn't more concern about these
drawbacks than there is; maybe we've been brainwashed by the Microsoft
"newspeak". I only hope that OS-independent, open protocols that are
designed for control applications become more popular, e.g., Ethernet/IP,
Fieldbus Foundation HSE, etc.
Corey
|---------+---------------------------->
| | Glen Bounds |
| | <gbounds@bellsout|
| | h.net> |
| | Sent by: |
| | foxboro-bounce@fr|
| | eelists.org |
| | |
| | |
| | 08/19/2002 11:36 |
| | AM |
| | Please respond to|
| | foxboro |
| | |
|---------+---------------------------->
>-------------------------------------------------------------------------------------------------------------------------------|
|
|
| To: foxboro
|
| cc:
|
| Subject: 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
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