Datasheet

Overview
The I/O devices of a process station is configured by creating objects in the Proview database. The
objects are divided in two trees, the Plant hierarchy and the Node hierarchy.
The Plant hierarchy describes how the plant is structured in various process parts, motors, pumps,
fans etc. Here you find signal objects that represents the values that are fetched from various
sensors and switches, or values that are put out to motors, actuators etc. Signal objects are of the
classes Di, Do, Ai, Ao, Ii, Io, Co or Po.
The node hierarchy describes the configuration of the process station, with server processes and I/O
system. The I/O system is configured by a tree of agent, rack, card and channel objects. The channel
objects represent an I/O signal attached to the computer at a channel of an I/O card (or via a
distributed bus system). The channel objects are of the classes ChanDi, ChanDo, ChanAi, ChanAo,
ChanIi, ChanIo and ChanCo. Each signalobject in the plant hierarchy points to a channel object in
the node hierarchy. The connection corresponds to the physical link between the sensor and the
channel of a I/O unit.
Levels
The I/O objects in a process station are configured in a tree structure with four levels: Agent, Rack,
Card and Channel. The Channel objects can be configured as individual objects, or reside as
internal attributes in a Card object.
Configuration
When configuring an I/O system on the local bus, often the Rack and Card-levels are sufficient. A
configuration can look like this. A Rack object is placed below the $Node object, and below this a
Card object for each I/O card that i installed in the rack. The cardobjects contains channelobjects for
the channels on the cards. The channelobjects are connected to signalobjects in the plant hierarchy.
The Channels for analog signals contains attributes for measurement ranges, and the card objects
contains attributes for addresses.
The configuration of a distributed I/O system is a bit different. Still the levels Agent, Rack, Card
and Channel are used, but the levels has another meaning. If we take Profibus as an example, the
agentlevel consist of an object for the master card that is mounted on the computer. The racklevel
consist of slave objects, that represent the profibus slaves that are connected to the Profibus circuit.
The cardlevel consist of module objects that represent modules handled by the slaves. The Channel
objects represent data sent on the bus from the mastercard to the modules or vice versa.