Rockwell Automation 1747-ASB Remote I/O Adapter - Manual (Page 135)

Publication 1747-UM006B-EN-P - June 2003
Specifications A-7
Discrete I/O Throughput without Block Transfers Present Example
A PLC 5/40 is controlling an RIO link running at 115.2K baud that has
the following adapters:
•
One 1747-ASB module configured as 1/2 logical rack with 1-slot
addressing and discrete specialty I/O mode
– slot 1 - 1746-IB16, 16-point input module
– slot 2 - 1746-OB16, 16-point output module
– slot 3 - 1746-NIO4I, 2 input/ 2 output analog module
•
Two adapters, each configured as a full logical rack
•
Three adapters, each configured as a 1/4 logical rack
1. Use the throughput formula to calculate the maximum
throughput.
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)
T
ps
= 25.0 ms, which is from the PLC 5/40 programming manual
T
RIO
= The total RIO scan time (ms)
T
bp
= 1747-ASB module backplane scan time (ms)
T
SNo
= 0 since you are using a PLC processor with a built in scanner
T
SNi
= 0 since you are using a PLC processor with a built in scanner
T
id
= 10.0 ms, which is from I/O module instruction sheets
T
od
= 1.0 ms, which is from I/O module instruction sheets
T
dm-nbt
= 2(25) + 2T
RIO
+ 2T
bp
+ 0 + 0 + 10.0 + 1.0 + 10ms
(1)
2. Since there are two unknown values, continue with steps three
through seven on the following page.
3. Calculate the 1747-ASB module backplane scan time (T
bp
).
Determine the backplane scan time for each module in slots
one, two, and three.
slot 1 - 1747-IB16, 16-point input module = 0.325ms
slot 2 - 1747-OB16, 16-point output module = 0.273ms
slot 3 - 1746-NIO4I, 2 input/ 2 output analog module = input =
0.625ms output = .620ms
(2)
(1) The value of 10 ms is for PLC-5/11, -5/20, -5/30, -5/40, and -5/60 processors only. For all other PLC-5
processors the value is not required.
(2) Since the 1746-NIO4I has both input and output image, each amount is needed to calculate base backplane
scan time (T
b
).