Communications

Omnicomm is the communication process responsible for controlling and managing the transfer of data between the RealTime database (RTDB) and remote devices such as Remote Terminal Units (RTUs). An Omnicomm process manages all connections between remotes and the host computer. The process also initiates all queries and moderates communications.

An Omnicomm process runs on the host computer to control a group of remotes and their connections. Omnicomm interprets packets of data according to predefined protocols. A protocol defines the interpretation of data during polling and the commanding of field devices. Each remote uses a specific protocol to communicate with the host computer.

The protocol-specific configuration of a remote record establishes the aspects of communication that are distinct to a given protocol/remote combination. Several standard protocols can be supplied with all systems, including Open Platform Communications (OPC).

Other records in the RTDB, such as analog records, reference logical data input/ output coordinates. The protocol driver maps protocol-specific entities to the appropriate coordinates when it processes the data into the RTDB:

• The Omnicomm process requests data from each remote, and transfers it to the appropriate RTDB table (analog, rate, or status).

• An Omnicomm process runs against a grouping of remotes and their connections.

• Omnicomm treats all connections generically, independent of the process using the connection. Thus, connections with different attributes (dial, network) and needs (for example, modems for dial connections) are all handled by the same Omnicomm process. A dial connection is unique in that it can lock a modem if a relevant modem is available; hence, it requires a combined connection and modem record, whereas other connections (for example, network) do not.

• Modems are dynamically allocated from the modem bank.