Rockwell Automation 1747-SN Remote I/O Scanner - Manual (Page 100)

Publication 1747-UM013B-EN-P - January 2005
A-4 Specifications
To calculate Tdm-nbt throughput, substitute values for the variables in
the formula above. Locate these values in the following documents:
RIO Scan Time Calculation (TRIO)
The RIO scan time is calculated by identifying the baud rate and
image size of each logical device on the RIO link. Locate the
corresponding time value in the following table. If you are using
multiple logical devices, add the time values together to determine the
total RIO scan time (TRIO).
Variable Variable Description Location of Variable
T
ps
The total processor scan
time (ms) Measured or estimated
T
RIO
The total RIO scan time (ms) see the section RIO Scan
Time Calculation (TRIO) on
page A-4
T
adp
The adapter throughput
delay. For a 1747-ASB, this
is two ASB backplane scan
times. adapter user manual
T
SNo
The scanner module output
delay time (ms) see the section RIO Scanner
Output Delay Time (TSNo)
on page A-13
T
SNi
The scanner module input
delay time (ms) 5 ms (constant value for all
formulas in this appendix)
T
id
The input module delay time
(ms) I/O product data and I/O
instruction sheets
T
od
The output module delay
time (ms) I/O product data and I/O
instruction sheets
RIO Scan TImes for Adapters
Adapter Size Baud Rate
57.6K 115.2K 230.4K
1/4 logical rack 6.0 ms 3.5 ms 2.5 ms
1/2 logical rack 6.5 ms 4.0 ms 2.75 ms
3/4 logical rack 7.5 ms 4.5 ms 3.0 ms
Full logical rack 9.5 ms 5.5 ms 3.5 ms
T
RIO
T
adapter1
T
adapter2
T
adapter3
+ + =