Rockwell Automation 1747-BSN Backup Scanner Module - Manual (Page 171)

Publication 1747-UM010B-EN-P - September 2003
Specifications A-7
Discrete I/O Throughput with Block Transfers (T
dm-bt
) Present
The information in this section is used to calculate the discrete
throughput of the 1747-BSN Backup Scanner if there are BTs
occurring on the RIO link to any chassis.
If BTs are not present on the RIO link, you must use the Discrete I/O
Throughput without Block Transfers (Tdm-nbt) Present section to
determine your throughput. See page B-3.
The formula to calculate discrete I/O throughput with BTs present is:
T
dm-bt
= 2T
ps +
2T
RIO +
2T
btx +
T
adp +
T
SNo-bt +
T
SNi +
T
id +
T
od
T
dm-bt
= The maximum discrete throughput with BTs in
milliseconds (ms)
To calculate T
dm-bt
throughput, substitute values for the variables in
the formula above. Locate these values in the following documents:
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 (T
RIO
) on page A-5
T
btx
Additional time due to sending
any BT data on the RIO link. see the section Determining T
btx
on page
A-8
T
adp
The adapter throughput delay. For
a 1747-ASB, this is two ASB
backplane scan times. adapter user manual
T
SNo-bt
Backup scanner output delay time
with BTs present see the section Determining T
SNo-bt
on
page A-8
T
SNi
The backup 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