Rockwell Automation 1747-BSN Backup Scanner Module - Manual (Page 172)

Publication 1747-UM010B-EN-P - September 2003
A-8 Specifications
Determining T
SNo-bt
Use the following table to find T
SNo-bt
for your particular
configuration.
Determining T
btx
Before determining (T
btx
), you need to establish the maximum BT
write or read length that is to be processed by each logical rack on the
RIO link. RIO scan time is increased each time an BT is sent to any
logical device on the RIO network. The scan time increase depends
on the number of words sent in the BT and the selected baud rate.
RIO link protocol allows for a maximum of one BT to be sent to each
logical rack on the RIO link during any single RIO scan. Therefore, if
multiple BTs are sent to devices within the same logical rack, only the
longest BT to that logical rack needs to be considered to determine
your maximum throughput. The RIO scan time increase (T
ri
) for each
logical rack is:
IMPORTANT
The times shown are, to the best of our knowledge,
the maximum delay times of the backup 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.
Number of
Logical Racks
Configured Normal Mode Complementary Mode
All Baud Rates 57.6K baud 115.2K baud 230.4K baud
1 Logical Rack 16.0 19.0 24.0 32.0
2 Logical Racks 19.0 23.0 27.0 36.0
3 Logical Racks 22.0 26.0 30.0 39.0
4 Logical Racks 25.0 28.0 34.0 42.0
Baud Rate RIO Scan Time Increase (T
ri
)
57.6K baud 0.300 x BT length + 5.0 ms
115.2K baud 0.150 x BT length + 3.5 ms
230.4K baud 0.075 x BT length + 2.0 ms