[foxboro] Use of FBM232 to communicate with 20 devices via one IP address
- From: "Ahmed K. Sayed" <a.sayed@xxxxxxxxxx>
- To: <foxboro@xxxxxxxxxxxxx>
- Date: Wed, 29 Apr 2009 08:17:40 +0300
Dear Gents,
First of all, I wish you are fine and healthy.
I would like to ask about something regarding our FDSI - MODBUS TCP/IP
communication.
We have an HVAC system that is supposed to be linked to our DCS via
FDSI, as a MODBUS TCP/IP link on a single mode FBM232.
The HVAC system itself includes multiple RTUs that are connected
together via MODBUS RS-485 link, this also includes one converter
RS485-RS232 to connect to the HVAC computer (normal PC with a MODBUS
processing application). This HVAC computer then is connected to my
FBM232 via a normal RJ45 Ethernet cable.
Typically, I assigned an IP address for that computer (within the same
domain of my FBM IP), configured one ECB201 as a MODBUS device with that
IP.
The problem is that this HVAC application is not sending a combined
memory map for all the points collected over its MODBUS RS-485 link, but
it sends the data individually for each device considering that the
MODBUS device address will be used then to distinguish between these
data.
An example is:
RTU1 MODBUS address = 50 >> TI0001 on address 30001 and TI0002 on
address 30002
RTU2 MODBUS address = 60 >> TI0003 on address 30001 and TI0004 on
address 30002
.
.
etc.
As we see here, we shall then configure different device for each RTU to
include that different addresses and have the ability to use the similar
register allocation.
The problem then will be is that I still have one computer which is
assigned one IP address, and if I try to configure another device in the
system (same IP with different MODBUS address), the system gives the
error (duplicate connection) and disables the actions for "ENABLE
COMMUNICATION".
In my understanding, such a configuration can be connected to DCS via
only MODBUS Serial link not MODBUS Ethernet link (making use only of
MODBUS devices addresses and not TCP/IP).
The vendor has one MODBUS Scanner software (3rd party application), and
he used it to connect to his computer (in the place of my FBM) and then
it communicates very fine and was able to read the data from all his
devices directly with no problem.
Please advice
Ahmed Khaled
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