Rockwell Automation 1747-SN Remote I/O Scanner - Manual (Page 109)

Publication 1747-UM013B-EN-P - January 2005
Specifications A-13
RIO Scanner Output Delay Time (TSNo) Tables
The tables provided in this section show the maximum scanner output
delay time (TSNo) for specific applications. TSNo is dependent on the
following:
• processor scan time, or time between immediate outputs (if no
BTs are present)
• number of logical racks configured
• whether normal or complementary I/O mode is selected
• RIO baud rate (if complementary I/O is selected)
The following variables are used in the TSNo tables on page A-14:
TSNo increases if the interval between Tupd decreases to the time
threshold (Thold). If Tupd is less than Thold, then the larger TSNo
number must be used. Otherwise, either number may be used.
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
Variable Variable Description
T
SNo
The maximum scanner output delay time
T
upd
The time between SLC processor output
scan updates or immediate output updates
T
hold
A constant time threshold that is dependent
on your configuration. Refer to the tables on
page A-14.
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.