Publication 1747-UM013B-EN-P - January 2005
1-10
Overview
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 there must be an
input module in the primary chassis and 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.
If you want to use complementary I/O, two adapters that support this
function are required (e.g., 1747-ASB modules). One adapter is
configured (via its DIP switches) as a primary chassis, the other as a
complementary chassis. If a primary chassis exists, it is scanned first.
Primary and complementary chassis cannot have the same logical rack
number. The logical rack numbers must be assigned to the primary
and complementary racks as shown below:
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.
Primary Chassis Logical
Rack Number
Complementary Chassis Logical Rack Number
Decimal
Octal
0
8
10
1
9
11
2
10
12
3
11
13
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