Tuesday, October 5, 2010

SCADAServer Address Space

The SCADAServer address space consists of all Modbus registers in all controllers that can be accessed by the server, on all communication connections. An Item ID and optional Access Path specify the registers associated with each item in a group.

The Item ID is the unique identifier of each variable in the server address space. ID specifies the controller station number, the register address and the register format. Strings in the following form describe the Item ID. Note that the format and access path parameters are optional.

station : register : [format] [@accessPath]

The server supports standard an extended Modbus addressing. If standard addressing is configured the server allows station numbers from 1 to 255. If extended addressing is configured the server allows station numbers from 1 to 65534.

Each station can have the following register addresses.
register addresses
The optional format parameter defines how input and holding registers are read. Each analog register in the controller address space is a 16-bit register. The server allows two consecutive registers to be read as a single 32-bit value. This provides maximum flexibility for OPC clients.
optional format parameter
The optional Access Path parameter is used with OPC Clients that don’t support access paths. In most cases it is not required. If the parameter is used, add the character @ followed by the Access Path to the end of the Item ID.


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