Re: [foxboro] Operator interface question

Stan your best solution to do this with Foxboro is to look at the new
bi-directional write-once and read all the time blocks available since
release 6.21 in the integrators and Micro IA. These blocks are designed
for exactly this purpose. The blocks you want to look at are the ROUT or
MROUT, typically running them in manual so and having the Foxboro
displays write the values from the ramp buttons to the output parameter.
When a chance is made from the Foxboro display these blocks will only do
a one shot write, not continuous like the older IO blocks, and read back
every scan in case the value is changed at the PLC. These blocks allow
you to not need different blocks to read and write to the PLC or logic
to sync. Them.

Rick de la Cierva
DLC SOLUTIONS CORP.
Phone:    203-207-9917
Fax:      203-207-9896
Cell:     203-722-3048
Email:    rcierva@xxxxxxxxxxxxxxxx



-----Original Message-----
From: foxboro-bounce@xxxxxxxxxxxxx [mailto:foxboro-bounce@xxxxxxxxxxxxx]
On Behalf Of stan
Sent: Saturday, May 11, 2002 1:59 PM
To: foxboro@xxxxxxxxxxxxx
Subject: [foxboro] Operator interface question


We are in the process of migrating one process units worth of controls
operator interface from a "application enabler" to a Foxboro system.

The existing controls are AB PLC5 based, and will stay that way for this
migration. There are some fairly simple PID loops in this unit which
are controlled by PID instructions in the PLC's.

The existing operator interface for this has an "input field", and a 
"read back field" for each of the analog values for these loops that can

be set by the operator (SP and CV). In addition it has some 
"increment/decrement" buttons, but they are implemented by sending a bit

down to the PLC's and doing the actual change of value there. This part
of 
the existing interface design does not work particularly well, and we
plan 
on changing it to use the more tradition Foxboro "look and feel". 
That is having the buttons increment and decrement a variable in the
Foxboro itself.

In addition we plan on implementing a field located CRT operator
station, 
which will communicate directly with he PLC's. This station should also
be 
able to modify the analog values, and of course there is always the
possibility 
of changing them from the PLC programming system.

The problem we are having with this design is that we see problems with
timing 
races here. The Foxboro needs to track, say the CV, as it is changed 
within the PLC, but yet the Foxboro needs to be able to read the current

value, increment, or decrement it, and write it back to the PLC.  As you

can see this is fraught with timing issues.

I thought I would seek the collective wisdom of this group, and see if 
anyone else had implemented something similar to this? If so how did you

do it, and how well has it worked out?  Any thoughts on this would be 
greatly appreciated.


-- 
"They that would give up essential liberty for temporary safety deserve
neither liberty nor safety."
                                                -- Benjamin Franklin
 
 
_______________________________________________________________________
This mailing list is neither sponsored nor endorsed by Invensys Process
Systems (formerly The Foxboro Company). Use the info you obtain here at
your own risks. Read http://www.thecassandraproject.org/disclaimer.html
 
foxboro mailing list:             http://www.freelists.org/list/foxboro
to subscribe:         mailto:foxboro-request@xxxxxxxxxxxxx?subject=join
to unsubscribe:      mailto:foxboro-request@xxxxxxxxxxxxx?subject=leave
 


 
 
_______________________________________________________________________
This mailing list is neither sponsored nor endorsed by Invensys Process
Systems (formerly The Foxboro Company). Use the info you obtain here at
your own risks. Read http://www.thecassandraproject.org/disclaimer.html
 
foxboro mailing list:             http://www.freelists.org/list/foxboro
to subscribe:         mailto:foxboro-request@xxxxxxxxxxxxx?subject=join
to unsubscribe:      mailto:foxboro-request@xxxxxxxxxxxxx?subject=leave

Other related posts: