Datasheet

Modbus TCP Server
With the Modbus TCP Server it is possible for external SCADA and storage systems to fetch data
from a Proview system via Modbus TCP. It can also be used to exchange data between Proview
systems
The server is configured with a Modbus_TCP_Server object in the node hierarchy, and below this
with a Modbus_TCP_ServerModule object.
Data areas
The Modbus_TCP_ServerModule object handles two data areas. One area for reading, from which
the clients can read at specified offsets, and one for writing, where clients can write data. Each area
has a logical start address, which is stated in attributes in the Modbus_TCP_ServerModule object.
ReadAddress is the start address for the read area, and WriteAddress is the start address for the
write area. To perform a read or write operation, the client has to specify an address, and this
address it the sum of the startaddress and the offset to the channel that is to be written or read. The
start address makes it possible not to have overlaping address space for the read and write areas,
which might cause confusion on the client side.
The data area are configured with channel objects below the server module. The Representation
attributes in the channel objects states the size of each channel and how the data shoud be
interpreted. The normal representation for Di and Do channels are Bit8, where the Number
attributes specifies the bit number for the channel, and the normal representation for integer and
analog channels are Int16.
Unit id
Serveral modules can be configured in a node, by creating one Modbus_TCP_ServerModule object
for each module. Every module object has to have a unique unit identity, which is stated in the
UnitId attribute. This identity is used by the clients to addess a specific module.
Port
By default, the Modbus TCP communication uses the port 502.
If you, for example, want to use Modbus TCP for communication between two Proview systems,
another port can be stated in the Port attribute of the Modbus_TCP_Server object. The same port
also has to be specified in the slave object in the client node.