Publication 1747-UM006B-EN-P - June 2003
A-4 Specifications
Calculating Throughput
The 1747-ASB module throughput is determined by more than the
1747-ASB module itself. The input and output module delays, scanner
scan time, and processor scan time contribute to throughput as well.
Discrete I/O Throughput without Block Transfers Present
The information in this section is used to calculate the discrete
throughput of the 1747-ASB module if both conditions are true:
• There are no block transfer mapped I/O modules in the
1747-ASB chassis.
• There are no RIO block transfers occurring on the RIO link to
any chassis.
If RIO block transfers are present on the RIO link or if the 1747-ASB
chassis has block transfer mapped I/O modules, you must use the
Discrete I/O Throughput with Block Transfers Present section.
The formula to calculate the maximum 1747-ASB module discrete I/O
throughput without block transfers present is:
T
dm-nbt
= 2T
ps
+ 2T
RIO
+ 2T
bp
+ T
SNo
+ T
SNi
+ T
id
+ T
od
+ 10ms
(1)
T
dm-nbt
= The maximum 1747-ASB module discrete throughput
without block transfers in milliseconds (ms)
To calculate throughput, substitute values for the variables in the
formula above. Locate these values in the following documents:
(1) The value of 10ms is for PLC-5/11, -5/20, -5/30, -5/40, and -5/60 processors only. For all other processors the
value is not used.
Variable Variable Description Location of Variable
T
ps
The total processor scan time (ms) PLC or SLC programming manual
T
SNi
The scanner module input delay time (ms)
(only if scanner is a separate module,
otherwise value is 0)
scanner user manual
T
SNo
The scanner module output delay time (ms)
(only if scanner is a separate module,
otherwise value is 0)
scanner user manual
T
id
The input delay time (ms) SLC I/O technical data and I/O
instruction sheets
T
od
The output delay time (ms) SLC I/O technical data and I/O
installation instructions
T
RIO
The total RIO scan time (ms) page A-5 of this manual
T
bp
1747-ASB module backplane scan time (ms) page A-6 of this manual
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