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[User Guide]
Input Output Executive
is responsible
for NTMC communications, including those between subsystems, as
well as those with remote units. Execution of this core component is
transparent, operators interact with it only when reconfiguring or debugging
system communications. The sections below summarize the program’s most
important activities.
Communication Protocols
IOEX supports
industry standard protocols such as MODBUS RTU and DNP 3.0, as well as a host of
native protocols. Any protocol that a
customer may need can be added as long as protocol specification is publicly
available, or agreement can be reached with the vendor of proprietary protocol.
Subsystem Communications
The program
manages all interactions between NTMC components even when not all
of them are hosted by the same computer. For example, MCEX knows about RUEX
status by polling the later via IOEX. Or, when a remote client connects to the
local system via a network, remote operator interacts with the local system via
IOEX components on the respective hosts.
Remote Unit Communications
IOEX manages all communications between NTMC and
remote units. The latter can be switches, RTUs, PLCs, NTMC remote
clients, or full NTMC control systems. For example, when RUEX polls
an RTU the command first goes from RUEX to IOEX. The latter strips the message
of internal protocol wrapper, then sends it out to the RTU using the protocol
the RTU can understand. The reply is then returned via IOEX to RUEX for
processing.
Remote Clients
Above services are
based on the client - server model. When a remote client needs to contact the
system a local server has to be put in place. When that client wants to
initialize interaction, such a server has to be able to accept the connection,
authenticate the client, receive commands, and forward them to the relevant NTMC components.
For example, an external caller can connect with NTMC via a
telephone line, and reconfigure some of the load management parameters. Another
example is quiescent (unsolicited) reports from remote units.
More Details
IOEX performs other behind
the scenes tasks, including communications timing and synchronization, channel
sharing, automatic connects and disconnects, protocol management, event logging,
etc.
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