NotaTech 8000SeriesI/O - Manual (Page 5)

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Node Architecture
An 8000 Series node comprises single or redundant
Ethernet Bus Inter-face Modules, up to 64 I/O modules,
field terminals, and associated power supplies.
A schematic node architecture is shown below. In-
formation from the I/O modules is transferred to and
from the communication module (EBIM) via the Rail-
bus. The Railbus is a fast, serial data bus with parallel
module addressing and extends over the full length of
the node. The parallel address architecture means that
each I/O module position has a unique address which
eliminates the need to ‘train’ modules during installa-
tion.
Power for the node is provided by integrated power
supply modules; these convert the locally available
power source into a regulated internal supply rail. This
rail energizes the EBIM and all Railbus communication
between the EBIM and I/O modules.
For some I/O module types—such as those with
low-power and intrinsically safe field circuits—it also
provides power for the field wiring. Where additional
power is required for field devices (such as high cur-
rent AC circuits), power can be provided by means
of cabled connections from each module to external
relays. This Bussed Field Power facility reduces instal-
lation time by removing the need to make daisy chain
wiring connections at the field terminals of each I/O
module.
Node Operation
A typical request for data from the field might happen
as follows:
The D/3® PAS requires the temperature from a par-
ticular thermocouple input at a particular node and
transmits a signal on the I/O LAN. There are several
Series 8000 nodes on the I/O LAN, but the EBIM at the
chosen node recognizes its own node address, and
acknowledges the request.
At each node, the input modules constantly monitor,
linearize and digitize their respective field signals,
and make them available to scanning on the node’s
internal bus (Railbus).
The EBIM continually scans the I/O modules via the
Railbus, and builds up a map of the values of the input
variables, ready for the PCM to read. These are con-
verted into the LAN protocol and placed on the LAN
by the EBIM, together with acknowledgement signals.
The D/3 then interprets the signal and reconstructs
the temperature reading.
8000 Series I/O
®
Product Catalog
8000 Series I/O