Rockwell Automation 1747-BSN Backup Scanner Module - Manual (Page 68)

Publication 1747-UM010B-EN-P - September 2003
5-6 Configuration and Programming
Rules for Configuring the
Scanner General
•
The smallest portion of the scanner’s I/O image that can be
allocated to a single RIO device is two logical groups (1/4
logical rack).
•
If a device is configured in word 1, there must be image
allocated to it in word 2. This rule also applies to words 3 and 4
with the following exception: if word 3 = 1 and word 4 = 0, the
complementary mode is selected even though no
complementary devices are configured.
•
A logical device’s starting group must begin at even group
numbers (0, 2, 4, or 6). Each bit in words 2 and 4 represent an
even logical group number.
Concerning Complementary I/O
•
It is valid for you to have a complementary device configured
even if no associated primary device exists. Also,
complementary devices do not have to be the same logical
image size as the primary device.
•
G file words 1 and 2 can both be zero (no primary devices).
However, in this case there must be at least one complementary
device configured in G file words 3 and 4.
•
If there is at least one primary device configured in G file words
1 and 2, then words 3 and 4 can both be zero, or the G file size
can be set to 3 (complementary mode not selected).
•
The starting group of the primary and complementary chassis
should be the same if they share the same image space. If the
starting group is not the same, the image of the complementary
device must not “cross over” into the space of a primary device.
For example, if a primary device exists at Logical Rack 1, Logical
Group 4, the maximum size of a complementary device at
Logical Rack 9, Logical Group 0 is a half logical rack. The image
does not cross over into Logical Group 4.
•
A complementary device cannot be configured at locations
where primary devices are configured unless they both start at
the same location.