Determining The Number Of Logical Racks Configured - Allen-Bradley 1747-SN User Manual

A–12 Specifications
Publication 1747 6.6 - July 1996
The following variables are used in the T
Variable Variable Description
The maximum scanner output
T
SNo
delay time
The time between SLC
T
processor output scan updates
upd
or immediate output updates
A constant time threshold that
is dependent on your
T
hold
configuration. Refer to the
tables on page A-13.
T increases if the interval between T
SNo
threshold (T ). If T
hold upd
number must be used. Otherwise, either number may be used.
Important:
The times shown in this section are, to the best of our
knowledge, the maximum delay times of the scanner.
However, in instances that throughput is an important
consideration, test the application thoroughly first to
ensure proper operation. Note that in most situations
the average throughput is much better than the
calculated maximum throughput.

Determining the Number of Logical Racks Configured

The number of logical racks configured is determined by the number
of racks that contain configured devices. For example, if there are
four 1/4 rack devices in logical rack 0 and one full rack device in
logical rack 3, there would be two logical racks configured. Note
that the number of logical devices on the RIO network affects only
T , and only affects T
RIO
When complementary mode is selected, the number of configured
racks is also determined by the number of primary or complementary
racks configured, but not by both. (The maximum number of
configured racks
is 4.) That is, if there is a primary rack configured with a
corresponding complementary rack, that is considered one logical
rack. If there is a primary rack configured without a complementary
rack (or vice versa), that also is considered one logical rack.
tables on page A–13:
SNo
decreases to the time
upd
is less than T , then the larger T
hold
when additional logical racks are used.
SNo
SNo