Allen-Bradley 1747-SN - Example Discrete I;O Throughput with Block Transfers Present

SpecificationsA–8
Publication 17476.6 - July 1996
Example Discrete I/O Throughput with Block Transfers Present
An SLC 5/03 is using a scanner to control a 115.2K baud RIO link
that has 3 adapters and 4 logical devices.
Adapter #1 (1747-ASB module):
• starting logical rack 0, logical group 0
• 12 logical groups (1 1/2 logical racks)
• one 8 word and two 4 word BT write/read modules in logical rack 0
• one 2 word BT write/read module in logical rack 1
Adapter #2 (1771-ASB module):
• starting logical rack 2, logical group 0
• 2 logical groups (1/4 logical rack)
• one 64 word BT write/read module
Adapter #3 (1771-ASB module):
• starting logical rack 2, logical group 2
• 2 logical groups (1/4 logical rack)
• one 32 word BT write/read module
1. Use the throughput formula to calculate the maximum throughput
of the 1747-ASB module.
T
dm–bt
= 2T
ps
+ 2T
RIO
+ 2T
btx
+ T
adp
+ T
SNo–bt
+ T
SNi
+ T
id
+ T
od
T
ps
= 25.0 ms, which is from the APS reference manual (assume for
example)
T
RIO
= The total RIO scan time (ms)
T
btx
= Additional time due to sending any BT data on the RIO link
T
adp
= Two 1747-ASB module backplane scan times (calculated from
ASB
manual) = 2(4.5) = 9.0 ms
T
SNo–bt
= 22.0 ms from the table on page A–13, T
SNo
with Block
Transfers
(Normal Mode). There are 3 logical racks configured.
T
SNi
= 5.0 ms
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–bt
= 2(25.0) + 2T
RIO
+ 2T
btx
+ 9.0 + 22.0 + 5.0 + 10.0 + 1.0