Re: [foxboro] FOXAPI Configuration for Foxhistory Ver 2.0

On Wed, Dec 11, 2002 at 10:34:10AM -0500, Johnson, Alex (Foxboro) wrote:
> 
> Re: Now, I'm wondering if this was a waste of time? It appears that the
> fastest_rsr parameter will override anything we do. Is this correct?  
> 
> 

Thanks for all the useful information.

If you don't mind, in the interest of further educating myself, I'd like to
pursue this a bit further. 

It appears that I have a basic misunderstanding of how this whole thing
works. let me describe how _I thought_ it worked, and you can use that as a
basis for correcting my misconception(s0.

I thought that a given data object (C:B:P) was "owned" by a piece of
hardware (typically a CP for instance). Then this "owner" would broadcast
the value of this data object, based upon the delta from the last time it
was broadcast. In other words if the configuration called for a delta of 1%
and the object's scale was, say 0 ->100, and the last broadcast value was
56%, then a new broadcast would be sent when the value changed beyond 55% or
57%.

Then I thought that various "data consumers" (for example FoxAPI, simply
listened for these broadcasts. In the case of FoxAPI these changes would be
used to update a shared memory copy of tag/value pairs. Other "downstream
data consumers", such as PI could then poll FoxAPI at whatever rate they
wanted to, and get the these value from the shared memory copy.

Having said all of the above, there is no place in such a design for a
parameter such as fastest_rsr to impact anything.

Where am I going wrong?
-- 
"They that would give up essential liberty for temporary safety deserve
neither liberty nor safety."
                                                -- Benjamin Franklin
 
 
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