Re: [foxboro] AB30 TO FBM231
- From: arbysmith@xxxxxxxxxxx
- To: foxboro@xxxxxxxxxxxxx
- Date: Thu, 03 May 2007 19:30:15 +0000
We have just replaced an AB30 with a FBM230 FDSI. For your MCIN's and MCOUT's,
you can make a pretty seamless transition. Where they currently have an IOMOPT
of 1 and point to the ABSCAN block, you just change the IOMOPT to 0, and
connect a PAKIN block's PAKCIN parameter to the MCIN's INPUTS parameter.
Everything upstream of the MCIN (graphics, historians, etc.) are none the
wiser. The MCOUT and PAKOUT can be similarly paired. You can similary tie
MAIN's and AIN's to RIN's.
However, not all is rosey. We have a number of unresolved problems for which
there is a CAR. For one example, we read a lot of floating point data from a
single AB file. With the ABSCAN block, we had to create 4 compounds to
maintain the limit on the number of bytes that can be transfered in a single
read. However, you have no control over how communications are structured with
the FDSI. You can split the RIN's up into multiple compounds, but as of right
now, you can't read more that 56 floats from any single file. We had to
reprogram our PLC to put the floats in multiple files so we can read them. You
also have no real control over the rate of communication. With the ABSCAN, you
could have some executing at a higher rate than others so high priority data
could be read faster. With the FDSI, the block execution rate has nothing to
do with the communications and it appears that all communications has the same
priority. Afterall, the blocks are in the CP and the commu
nicati
ons is in the FBM. Unlike with the FBM224, where you build the device
definition files that are basically replacements for the MDSCAN or ABSCAN, the
FDSI software builds the communications and you don't even know what it is. As
others have pointed out, if you are reading two addresses that are not
adjacent, the FDSI may read them and all the data in between in a single read.
In some cases, that is a problem if you are talking to a "pseudo" device that
does not recognize those in between addresses. It's not generally a problem
talking to a standard PLC, but there is overhead in reading the extra data.
The problem here is the total lack of control in crafting the communications.
It would be nice if the FDSI exposed its communitions structure and allowed one
to massage it if desired.
I think its going to be a great device, but it has a ways to go and it remains
to be seen if Invensys will develop what I would like to see. I also miss the
Message Pass Through functionality of the Int30.
Roger B. Smith
City of Atlanta
Watershed Management
-------------- Original message --------------
From: Ricky.Cash@xxxxxxxxx
> I have several AB30 gateways communicating with PLC5 processors in my
> system. I am making plans to upgrade to the mesh system which would
> include FBM231 comm modules to replace these gateways. The FBM231 doesn't
> support the MCIN and MCOUT blocks that I now use, it looks like I would
> have to use PAKIN and PAKOUT blocks. Has anyone on the list been through
> this upgrade? I really don't want to do a complete rebuild of the gateway.
> Thanks for any help you can provide,
>
> Ricky Cash
> Process Control Engineer
> Greif Inc.
> Amherst VA
>
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