1747-6.22, Backup Scanner User Manual

Physical and Logical RIO Link Specifications
Overview 1-25
The maximum number of adapters with which your scanner can
communicate is determined by the scanner’s and adapter’s physical
and logical specifications, as described below:
• Physical Specifications are the maximum number of adapters
that can be connected to the scanner. For more information, see
Extended Node Capability below.
• Logical Specifications for the scanner are the maximum number
of logical racks the scanner can address, how the logical racks
can be assigned, and whether the scanner can perform block
transfers.
Extended Node Capability
Extended node functionality allows you to connect up to 32 physical
devices on an RIO link. You must use 82 Ohm termination resistors in
an extended node configuration. You can only use extended node if
all RIO link devices have extended node capability. (Refer to the
Compatible Devices table at the end of this chapter, or to the
specifications of your device.) The 1747-BSN Scanner has extended
node capability. However, the smallest logical rack division is 1/4
logical rack and the scanner image size is 4 logical racks. Therefore,
the scanner is limited to 16 devices unless complementary I/O is used.
Refer to the following section for more information on
complementary I/O.
Complementary I/O
Complementary I/O is very useful when portions of your input and
output images are unused because it allows the images of two
adapters to overlap each other in the scanner’s I/O image. To use
complementary I/O, the I/O image from one adapter must be the
mirror (complement) of the other. This means that if there is an input
module in the primary chassis, there must be an output module in the
same slot of the complementary chassis. This enables total use of the
scanner’s 32 input and 32 output word image for I/O addressing of up
to 1024 discrete points.
!
ATTENTION: Because the primary and
complementary chassis images overlap, input and
specialty combination I/O modules must never share
the same image location. Inputs received by the scanner
may be incorrect and RIO block transfers will not be
serviced properly.
If an output module shares its output image with another output
module, both output modules receive the same output information.
Publication 1747-6.22