Allen-Bradley 1747-SN - Discrete I;O Throughput with Block Transfers (Tdm-bt) Present

SpecificationsA–6
Publication 17476.6 - July 1996
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-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
dm–nbt
) Present section to
determine your throughput. See page A–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)
APS reference manual
T
RIO
The total RIO scan time (ms)
see the section RIO Scan Time
Calculation (T
RIO
) on page
A-4
T
btx
Additional time due to sending
any BT data on the RIO link.
see the section Determining
T
btx
on page A-7
T
adp
The adapter throughput delay.
For a 1747ASB, this is two
ASB backplane scan times.
adapter user manual
T
SNo–bt
Scanner output delay time with
BTs present
see the section Determining
T
SNo-bt
on page A-7
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