Re: [foxboro] Operator interface question
- From: Corey R Clingo <clingoc@xxxxxxxxxxxxx>
- To: foxboro@xxxxxxxxxxxxx
- Date: Tue, 14 May 2002 08:43:44 -0500
One characteristic of most DCS PLC gateways is that the output values are
silently read back behind the scenes so the operator is able to see exactly
what is in that PLC. This causes confusion sometimes (i.e., when operator
actions have no effect because the PLC logic obliterated their change), but
is a reflection of the real world, and helps in situations like this. I
believe the Integrator 30 at least behaves in this manner.
Expanding on Roger's "this station has control" bit theme, when the I/A's
"have control" bit is set, the PLC takes data from the I/A's buffer area in
the PLC and moves it to the blocks/registers in the PLC that actually
manipulate the process. When the I/S's "have control" bit is cleared,
these block/register values are moved into the I/A's buffer area. The
gateway's read-back function then shows you those actual values in the
I/A's outputs.
Corey
stan <stanb@xxxxxxxx>@freelists.org on 05/14/2002 07:18:08 AM
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To: foxboro
cc: "Hehn; Chris S."
Subject: Re: [foxboro] Operator interface question
Thanks for both of your suggestions.
Roger I like your approach, _but_ I don't think it will solve the problem
of letting us use the increment/decrement buttons on the Foxboro. Or if it
will I'm missing something in how to implement it.
To increment/decrement we need to start from a known value. In this case it
should be the actual working value for the PLC (not the last Foxboro
written
value). I can't quite get a handle on how to read this value, increment it,
write it back, and set the "accept new Foxboro value" digital bit.
This is probably because I'm just coming to grips with configuring the
Foxboro ate all. I'm comfortable with how to program the PLC side of this,
but I don't see how to configure the Foxboro system to do this
Can anyone provide insight as to how to do this?
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