are not configurable, and are selected to be outside the normal operating range but
inside the linear hardware operational range (before the hardware reaches saturation).
Diagnostic messages for hardware limit checks and all other hardware diagnostics
for the board can be accessed with the software maintenance tools. A composite
diagnostic alarm state is provided in the database for each I/O pack, and a separate
logic state is provided to indicate a high/low (hardware) limit fault of any analog
input or the associated communications for that signal.
Diagnostic and system (process) alarms are time-stamped in the controller(s) and
transmitted to operator and maintenance stations. Communication links to a plantdistributed control system (DCS) can contain both the software (system) diagnostics
and composite hardware diagnostics.
Diagnostic LEDs are provided on I/O packs as previously shown for the Analog I/O
pack. Standard LEDs indicate: power status, attention (abnormality detected),
Ethernet link connected, and Ethernet link communicating. LEDs on discrete I/O
packs also indicate the status of each point. All boards feature an electronic ID that
contains the board name, revision, and a unique serial number. When power is
applied to the I/O processor, it reads the ID of the terminal board, application board,
and itself. It then uses this information for a start permissive, diagnostics, and system
asset management. Since the terminal boards can be mounted remote at the
equipment, local temperature sensors monitor the temperature at each I/O pack.
Excessive temperature causes an alarm message. The alarm state and current
temperature value are available for display and for use in the application software

Plant level control systems integrate the diagnostic data from the individual turbine
and generator controls with the overall plant. This allows maintenance personnel to
quickly identify the defective control node, switch, or station and locate the
particular device needing service.

Network Diagnostics for:
z Operator Stations
z Maintenance Stations
z Engineers Stations
z Switches on:
- Plant Data Highway
- Unit Data Highway
- IONet
z Control Nodes
- Boards Within Nodes
- I/O Packs