On Wed, 3 May 2000 12:27:36 -0400 (EDT) Stan Brown wrote...
>>
>>Stan,
>>We are using 6 AB Stations rather than Integrator 30s at my plant. I
don't
>>have a basis for comparison, but I can certainly tell you a little about
our
>>AB Stations.
>>
>>The main reason to go with these for us was to keep setup fairly simple
--
>>setup and continuing work on the stations is exactly like the same work
on
>>CP30s. Response time is (can be anyway) faster as a result of only
having
>>one network for a piece of information to negotiate (we are using DH+
with
>>our PLC5s, probably would have needed to go to ControlNet if we had used
>>Integrators).
>
> Why do you say that? Number of connectors on the AB PLC's?
Number of connections and DH+ loading. However, we may
have had other alternatives.
>
>>Disadvantages are fairly serious with the AB Stations. You can't have a
>>redundant processor in your PLC when you have an AB Station in place.
You
>>must adhere to the Foxboro's maximum data table size limitations when
>>setting up the PLC5s -- if any data table exceeds Foxboro's size limits
it
>>will not read any of that table. You do not have the option of having
>>blocks being change driven -- every block evaluates every scheduled
cycle.
>>This can result in limiting the number of blocks you can use on an AB
>>Station, or can result in needing to run the blocks at slower periods
with
>>phasing implemented.
>
> So you are saying on data table file in the PLC (at all not just
> communication files) can be larger than this maximim.
> What is the maximum? PLC5/s have an inherent maximum file size
> per DT file of 1000 PLC words anywy.
Yes. Many of our timer and counter files at the PLC
were set up as 400 entries (1200 words), while the
AB Station will not read a file larger than 333 entries
(999 words). The issue also exists with floating point
files, however that has not been a problem here.
On boot, our AB Stations report an error like:
ABGRND - 00032 - Error Defining DTL Handle - PLC File C12
>
> Are you saying that all points in teh Inegrator 30 must run at the
same
> BPC? I can't have some at say 0.5 sec, and others at say 2 sec.?
The points in the AB Station can certainly run at
different periods so long as you don't exceed about
200 blocks per second. Just have AB Station bpc at 0.5
and run the blocks at whatever period you desire. I'm
not sure about the Integrator 30s. It is my
understanding we could have effectively had more
throughput with an Integrator 30 in event driven mode.
With our AB Stations, although we are processing
200 blocks per second, none of the parameters are
normally changing. Even during shut-down or start-up
we may only have 10-20 parameters changing per second
so much of the processing potential of the AB Station is
being unused.
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