[foxboro] FW: FDSI FBM230/231/232/233 Modbus Device Driver Product Enhancement Request

Let's try this one more time. Sorry for all that UUENCODE'd gibberish earlier.


List Members,
I recently heard back from TAC on my request for being able to have the 
FDSI Modbus device driver make separate, non-optimized queries (needed 
to read Modbus registers in a FireEye Flame Monitor/BMS). The response 
was that the product can't do this function today, but could be 
modified to do so. So,... it was recommended that I put in a Product 
Enhancement Request (PER).

If any of you feel as I do, that this is an enhancement worth having, 
then please take the time to submit your own PER on the CSC website. I 
think the FDSI concept for the FBM230/231/232/233 is really cool. Just 
my luck, the first application I tried one on didn't work out. Still, 
I'm likely to use one when I can.

Thanks,
Dave


DESCRIPTION OF PRODUCT CHANGE/ENHANCEMENT

The FDSI FBMs 230/231/232/233 using Modbus Device Driver 1.02 need to 
be able to do the following:

 > Create non-optimized or user definable Modbus queries.
Reason: Many Modbus capable devices do not support the reading of 
multiple contiguous registers.

 > Allow the user to define the scan rate for each query.
Reason: Many Modbus devices operate at very slow speeds, and could 
benefit from the ability to limit the scan rate of individual queries.

 > If non-optimized or user definable Modbus queries are not provided 
as an enhancement, please provide in the user documentation the rules 
by which queries are created.
Reason: With this information the user may be able to formulate 
requests from DCI blocks which produce separate queries by the Modbus 
device driver.


REASON/BENENFIT STATEMENT

The FBM224 Modbus Comm Module allows the user to configure the 
following for each device transaction:
* the frequency at which the transaction is to be executed;
* the function code to be used;
* the starting address of the data to be accessed;
* the number of data to be accessed, starting at the specified starting 
address.

The Integrators for Modbus used a scan block to define which data and 
when the data is read from a device. The information configured for a 
scan block included:
* Identification of the device from which to read data (PC_ID)
* The type of data to be read (DATYPE)
* The location of the first datum to read (RDADDR)
* The amount of (contiguous) data to read starting at the specified 
location (PCINPS)
* The time to read the data (PERIOD and PHASE)

The FDSI FBMs 230/231/232/233 Modbus Master driver operations include 
the creation of scan query request messages based on contiguous DCI 
input block PNT_NO addresses. Up to 124 registers (16-bit) can be read in one
Modbus message transaction. The queries are optimized such that a read 
of 40001 and 40016 will produce a single query of 16 registers 
beginning at 40001. This causes problems for some Modbus devices.

For the FDSI FBMs 230/231 (serial) the Port Configuration File defines 
the scan rate. For the FDSI FBMs 232/233 (Ethernet) the ECB201 defines 
the scan rate. In either case, it is not possible to scan some 
registers from a given device at a different frequency than others. For 
the FBM230/231 all queries are performed at the scan rate defined for 
the port (I think, I have not personally verified this). Therefore, all 
devices attached to that port will be scanned at the same rate. For the 
FBM232/233 all queries to a device will be initiated at the scan rate 
defined for that device (this I'm sure of).

As you can see, the FDSI Modbus device driver offers less flexibility 
than its predecessors (FBM224 and Integrator for Modbus). The product 
is lacking functionality many customers may need in order to integrate 
their Modbus devices. Making this enhancement to the FDSI Modbus device 
driver will allow more customers the option of using FDSI when 
integrating Modbus devices, and will position the FDSI as a viable 
replacement for FBM224 and Modicon Gateways (which it is not yet today).

 
 
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