Rockwell Automation 1747-DCM,D17476.8 Direct Communication Module - Manual (Page 18)

Chapter 1
Overview
1–4
Extended Node Capability
Both scanners and adapters can have extended node capability. Extended
node capability allows you to have up to 32 adapters on the RIO link using
an 82 Ohm termination resistor at both ends of the RIO link for all baud
rates.
Extended node capability can only be used if the scanner and all adapters on
the RIO link have extended node capability. The DCM has extended node
capability.
The scanner allows each adapter to use a fixed amount (user defined) of its
input and output image.
The scanner image is divided into logical racks and further divided into
logical groups. A full logical rack consists of eight input and eight output
image words. A logical group consists of one input and one output word in a
logical rack. Each logical group is assigned a number from 0–7. The
number of racks available for data and I/O transfer depends on the scanner
you are using.
Processor I/O Image Scanner I/O Image Adapter
Image
Logical Group 7
Local I/O
Remote I/O
(Scanner Image)
Logical Rack 2
Logical Rack 1
Logical Rack 0
Logical Rack 3
Logical Group 0
The scanner image also contains the image of each adapter on the RIO link.
The adapter is assigned a portion of the scanner image, which is referred to
as the adapter image.
Scanner Image Division