Allen-Bradley 1747-SN User Manual page 159

A–6 Specifications
Publication 1747 6.6 - July 1996
Discrete I/O Throughput with Block Transfers (T
The information in this section is used to calculate the discrete
throughput of the 1747-SN 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 (T
determine your throughput. See page A–3.
The formula to calculate discrete I/O throughput with BTs present is:
T = 2T + 2T
dm–bt ps RIO
T = The maximum discrete throughput with BTs in milliseconds
dm–bt
(ms)
To calculate T throughput, substitute values for the variables in
dm–bt
the formula above. Locate these values in the following documents:
Variable Variable Description
The total processor scan time
T
ps
(ms)
T The total RIO scan time (ms)
RIO
Additional time due to sending
T
btx
any BT data on the RIO link.
The adapter throughput delay.
T For a 1747 ASB, this is two
adp
ASB backplane scan times.
Scanner output delay time with
T
SNo–bt
BTs present
The scanner module input
T
SNi
delay time (ms)
The input module delay time
T
id
(ms)
The output module delay time
T
od
(ms)
) Present section to
dm–nbt
+ 2T + T + T + T
btx adp SNo–bt
APS reference manual
see the section RIO Scan Time
Calculation (T
A-4
see the section Determining
T on page A-7
btx
adapter user manual
see the section Determining
T
SNo-bt
5 ms (constant value for all
formulas in this appendix)
I/O product data and I/O
instruction sheets
I/O product data and I/O
instruction sheets
) Present
dm-bt
+ T + T
SNi id od
Location of Variable
) on page
RIO
on page A-7