Re: [foxboro] Configuration of Function Blocks for MODBUS I/O
- From: Kevin Fitzgerrell <fitzgerrell@xxxxxxxxx>
- To: "foxboro@xxxxxxxxxxxxx" <foxboro@xxxxxxxxxxxxx>
- Date: Tue, 30 Apr 2013 14:59:09 +0800
Quay,
As Bruce has noted, you're correct, the blocks that directly reference the
MDSCAN data must be in that compound. My preference is to have the
compounds with MDSCAN blocks as interface compounds with only the
MAIN/MCIN/MCOUT/AOUT blocks required for mapping the data, putting any
control logic in equipment or plant area compounds, often in a CP rather
than in the INT30 (especially where I have some I/O from FBMs and some from
INT30s in that area). With INT30s (and especially with COM10s) you've got
some real limitations for communications processing - takes some careful
balancing and phasing of interface compounds to keep block processing and
I/O loading within guidelines. If you do put significant extra logic in
the MDSCAN compounds, watch your loading carefully.
The MAIN/MCIN/MCOUT/AOUT blocks in the MDSCAN compound may also have been
used to help document the mapping for maintainability. If the I/O block
names match the register or coil numbers in the PLC or 3rd party device, it
is easy to follow connections from the control logic blocks that reference
those I/O blocks through to the Modbus device.
Cheers,
Kevin
On Mon, Apr 29, 2013 at 3:15 PM, Quay B. Finefrock <qbfinefrock@xxxxxxxxx>wrote:
> All,
> I have a question with respect to location of function blocks used to
> access
> a serial dataset defined by a MDSCAN block. Per my interpretation of the
> Integrators for Modbus and Modbus Plus Devices document, function blocks
> that access the serial data must be configured in the same compound as the
> MDSCAN block. Is this correct?
>
> In the database that I am reviewing, the MCIN and MAIN function blocks are
> located in the same compound with the MDSCAN block and then AIN/CIN
> function
> blocks in other compounds reference the MCIN/MAIN blocks. I want to
> determine if the MCIN/MAIN function blocks are necessary or were just
> preferred by the configuration engineer.
>
> I would prefer to MCIN/MAIN blocks and let the AIN/CIN function blocks
> directly reference the serial dataset defined by the MDSCAN block.
> However,
> if my interpretation of the documentation is correct, it would not be
> possible to do so unless all of the AIN/CIN blocks are places within the
> Integrator compound.
>
> Regards,
>
> Quay
>
>
> Quay B. Finefrock
> Singapore Phone: +65 9 327 2923
> Brunei Phone: +673 883 1480
> Philippines Phone: +63 921 400 2886
> Malaysia Phone: +60 17 820 6900
> Email: qbfinefrock@xxxxxxxxx
>
>
>
>
>
>
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